Journal of Occupational Health Psychology Copyright 2000 by the Educational Publishing Foundation 2000, Vol. 5, No. 3, 374-385 1076-8998/00/$5.00 DOI: 10.1037//1076-8998.5.3.374

The Relationships Among Objective and Subjective Environmental Stress Levels and Serum Uric Acid: The Moderating

Effect of Perceived Control

A_rie Shirom Tel Aviv University

Samuel Melamed Loewenstein Hospital

Merav Nir-Dotan Tel Aviv University

This study was designed to investigate the effects of objective and subjective stress levels and perceived control on serum uric acid (SUA). Respondents were 2,504 male and 1,176 female manufacturing employees. Objective job-related stress was assessed by the Ergonomic Stress Level (ESL) inventory (S. Melamed, D. Yekutieli, P. Froom, E. Kristal-Boneh, & J. Ribak, 1999). As expected, ESL was positively associated with SUA, but among male respondents only. The measure of subjective stress, environmental annoyance, was negatively related with SUA for male respondents, thus not confirming the hypothesis. Perceived control was not found to have a direct effect on SUA, after controlling for the ESL measure. For male respondents only, perceived control moderated the relationship between ESL and SUA: This relationship was negative for those reporting above-average control and positive for those reporting below-average control.

From the early 1970s, it was evident to researchers that serum uric levels change in response to socially and psychologically stressful situations and achieve- ment-related behaviors (Mueller & French, 1974; Mueller, Kasl, Brooks, & Cobb, 1970). However, with few exceptions (e.g., Najem, Seebode, Samady, Feuerman, & Friedman, 1997; Zorbas, Yaroshenko, & Federenko, 1996), this pattern of associations has remained relatively unexplored by behavioral science researchers. This is all the more striking in view of the epidemiological evidence implicating elevated levels of serum uric acid in the pathogenic processes leading to coronary atherosclerosis (e.g., Lee, Spar- row, Vokonas, Landsberg, & Weiss, 1995) and cor- onary heart disease (e.g., Brand, McGee, & Kannel, 1985; Cappuccio, Strazzullo, Farinaro, & Trevisan, 1993; Frohlich, 1993). There are exceptions to the above pattern of results, including studies in which uric acid did not predict coronary artery morbidity or mortality (e.g., Menotti, Spagnolo, Scanga, & Dima, 1992). Elevated levels of serum uric acid carry an

Arie Shirom and Merav Nir-Dotan, Faculty of Manage- ment, Tel Aviv University, Tel Aviv, Israel; Samuel Mel- amed, Occupational Health and Rehabilitation Institute, Loewenstein Hospital, Raanana, Israel.

Correspondence concerning this article should be ad- dressed to Arie Shirom, Faculty of Management, Tel Aviv University, P.O. Box 39010, Tel Aviv 69978, Israel. Elec- tronic mail may be sent to ashirom@ccsg.tau.ac.il.

increased risk of gouty arthritis or renal stones (Kelly & Palella, 1987) and may be toxic to the central nervous system's activity (Muller et al., 1970).

Muller et al. (1970) noted that the possible mech- anisms that link stress with central nervous system activity and with body production of serum uric acid might include metabolic precursors of serum uric acid. Twin studies conducted in the United Kingdom and United States (Boyle et al., 1967; Jensen, Blan- kenhorn, Chin, Sturgeon, & Ware, 1965) have indi- cated that environmental factors are considerably more important than genetic factors in explaining concentrations of serum uric acid. More specifically, it has been shown that exposure to objective stress, like a critical job event or a natural disaster, can produce arousal of the pituitary adrenal system and might cause elevated levels of serum uric acid (Eden, 1982; Lee et al., 1995; Trevisan et al., 1997).

On the basis of the above evidence, it is likely that adverse work and environmental conditions that may be prevalent in a typical industry might affect serum uric acid levels. To our knowledge, this possibility has not been addressed by past research. Workers in a typical industry are likely to be simultaneously exposed to safety hazards, overcrowding, cognitive and physical demands, and environmental stressors (Melamed, Yekutieli, Froom, Kristal-Boneh, & Ribak, 1999). There is evidence to support the con- tention that combined exposure to these factors, ex- pressed as the ergonomic stress level (ESL), was

374

ENVIRONMENTAL STRESS AND URIC ACID 375

associated with the stress-related outcomes, such as the outcome of occupational injuries (Melamed, Luz, Najenson, Jucha, & Green, 1989).

The research model guiding our study (see Fig- ure 1) follows the theoretical framework to the study of stress in organizations developed by Kahn and Byosiere (1992), which posits that objective and subjective environmental stress may lead to physiological response. Specifically, we designed the present study to test the hypothesis that objec- tive and subjective environmental stress affect se- rum uric acid concentrations.

We have conceptualized objective environmental stress as a summary measure of several facets of objective stress at work. These facets included active safety hazards (such as lack of protection, lack of hazard warnings, and constricted escape routes), physical effort, physical discomfort, overcrowding, climate discomfort, exposure to noise, poor lighting, and vibration. Subjective stress refers to environmen-

tal annoyance, defined as the extent to which a per- son is disturbed by physical stressors in the work environment, such as noise, high or low ambient temperature, vibration, dust, and noxious odors (Mel- amed et al., 1989; Stansfeld, Clark, Jenkins, & Tar- nopolsky, 1985). Certain components of environmen- tal annoyance, such as noise annoyance, were found to predict physiological outcomes independent of ob- jective environmental stress (e.g., Melamed, Luz, &

Green, 1992). In one of our studies, both noise an- noyance and noise exposure levels were found to have an additive effect on cholesterol levels in men and women (Melamed, Froom, Kristal-Boneh, Gofer, & Ribak, 1997).

In Figure 1, these relationships were represented as moderated by perceived control, a key property of the organizational situation. Perceived control refers to the employee's ability to make decisions concerning the job (see Kushnir & Melamed, 1991), which cor- responded to decision authority in Karasek's de- mand-control model (Karasek & Theorell, 1990).

A major methodological shortcoming in the re- search literature is the paucity of attempts to compare objective with subjective measures of environmental stress in the prediction of health outcomes. In many survey-based studies, environmental stress was de- fined exclusively by the participants' descriptions of their work (see Karasek, & Theorell, 1990). This precludes the possibility to disentangle the respective effects of objective exposure and subjective appraisal of this exposure. An intervention designed to reduce exposure to objective environmental stress might be entirely inadequate for ameliorating employees' stress assessments (see Kasl, 1984). We hypothesized that both pathways, leading respectively from the objective environmental and subjective stress to the physiological strain, do coexist. To illustrate, a num- ber of studies focusing on objective work conditions

C o n t r o l Variables

• Age

• Sport Activity

• Obesity

• Illness

Subjective Stress

Envi ronmen ta l

A n n o y a n c e

I

Perceived ~ Control

Imlo

Objective Stress [ESLI ~ , e~.

Ergonomic Stress Level --41 I~

Figure 1. The research model. ESL = ergonomic stress level.

376 SHIROM, MELAMED, AND NIR-DOTAN

have demonstrated high physiological stress reac- tions, as well as a high prevalence of ill-health symp- toms (cf. Karasek & Theorell, 1990; Melamed, Ben- Avi, Luz, & Green, 1995). The objective work conditions included assembly-line work, piecework, and monitoring (e.g., French, Caplan, & van Harri- son, 1982; Johansson, Aronsson, & Lindstrom, 1978; Lundberg, Granqvist, Hansson, Magnusson, & Wal- lin, 1989). Employees' appraisals of their work con- ditions appear to mediate these stress outcomes (e.g., Cox, 1985; Lundberg et al., 1989; Shirom, Westman, & Melamed, 1999). The present study was designed to address the above methodological issues by col- lecting data from a large sample of male and female blue-collar workers on objective work conditions, subjective stress appraisals of the same work condi- tions, and an objective stress outcome measure, se- rum uric acid.

Object ive Stress and Serum Uric Acid

Kahn and Byosiere's (1992) theoretical framework posits that physical stress in organizations, including noise, light, and vibration, may have direct impact on physiological strain. It follows that ESL could di- rectly impact serum uric acid. Most past research of the stress-serum uric acid association in real work situations (excluding laboratory research or non- working participants) was conducted on event-based stresses like being exposed to a critical job event (Eden, 1982). A study that reported a change in serum uric acid in response to an objective stress was Kasl, Cobb, and Brooks's (1968) investigation of employees who underwent job loss as a result of permanent plan shutdown. They found high levels of serum uric acid on the first measurement, during anticipation of the closing down of the company for which the employees had worked an average of 18 years. Serum uric acid dropped sharply back to nor- mal among those employees who were quickly reem- ployed but remained high for the rest, returning to normal only when they were on a new job. The employees' subjective reports of the severity and duration of the job loss experienced were related to the amount of change in uric acid level. However, chronic stress, either objective or subjective, was not measured in this study.

In a series of studies on underwater demolition training, Rahe and colleagues (Rahe & Arthur, 1967, 1968; Rahe, Rubin, & Gunderson, 1972) found that serum uric acid concentrations rise significantly when the trainees anticipated arduous training activ- ity that they encountered as a challenge, that is, with

optimism and expectations of success. The levels of serum uric acid declined significantly when the train- ees experienced overload and were unsure of suc- cessfully completing the mission. These findings are in accord with an earlier study of Brooks and Mueller (1966), who reported that among university profes- sors, worries and feelings of being overburdened were negatively associated whereas achievement ori- entation was positively associated with serum uric acid. The series of studies of Rahe and his colleagues were summarized in Rahe, Rubin, and Arthur (1974) as indicating that serum uric acid levels rise above baseline when people expect a challenging physical or psychological stress. However, in this series of studies, the researchers did not measure self-reported stress or success expectations, rather they inferred these relationships from their observations of the trainees. Therefore, the steep rise and decline of serum uric acid could be associated with the different types of objective stress faced by the trainees during the different phases of the 4-month-long training period.

There are very few studies of chronic stress-uric acid relationships. Trevisan and his colleagues (Trevisan et al., 1997) studied the physiological consequences of long-term exposure to a natural disaster among employees. They reported that short-term (about 2 weeks) exposure to a major earthquake was associated with a decrease in uric acid levels. They interpreted this finding as due to overwhelming loss of control in the immediate aftermath of the disaster. Trevisan et al. also re- ported that long-term exposure (about 5 years) to the natural disaster was associated with an increase in the levels of uric acid. Following this line of evidence, we hypothesized (Hypothesis 1) that ob- jective stress would be positively associated with serum uric acid levels.

Subject ive Stress and Serum Uric Acid

Baron (1994) suggested that a person's perception of physical stress in the work environment might be both an independent predictor of psychological and physiological strain and a mediator of the effects of physical stress on these strains. Employees' percep- tion of physical stress at work could be regarded as an indicator of their sensitivity to this environmental stress. In this study, we referred to the perceived environmental stress as environmental annoyance (cf. Melamed et al., 1989; Stanfeld et al., 1985). A possible pathway leading from subjective stress (in this study, environmental annoyance) to serum uric

ENVIRONMENTAL STRESS AND URIC ACID 377

acid is through the impact of the former on the sympathetic nervous system. Perceived stress may lead to the activation of the sympathetic nervous system, whose arousal may be associated with an increase in the production of serum uric acid (Ferris & Gordon, 1968). We are not aware of past research that linked chronic perceived stress with serum uric acid. However, several empirical studies provide in- direct support to this line of reasoning.

House, McMichael, Wells, Kaplan, and Lander- man (1979) found that the perceived occupational stress of factory workers exacerbated the deleterious effect of exposure to physical stress on these work- ers' health. Conrad (1973) reported that physiologi- cal strain reaction was elevated among people who were annoyed by environmental noise irrespective of the level of their exposure to it. Melamed et al. (1989) found that factory workers' reported subjec- tive annoyance predicted risk of involvement in ac- cidents. Noise annoyance, which tends to be posi- tively correlated with environmental annoyance (Stansfeld, 1992), was found to be related to serum lipid levels (Melamed et al., 1997) and blood pres- sure (Lercher, Hortnagal, & Kofler, 1993). Therefore, we formulated the second hypothesis (Hypothesis 2) thus to expect a positive relationship between envi- ronmental annoyance and levels of serum uric acid, even after controlling for the effects of objective stress.

The Effec ts o f Contro l on Se rum Uric Ac id

The stress literature has identified a number of situational features that moderate the impact of stress on strain, in addition to their direct effects on psy- chological and physiological strain. Perceived con- trol has often been investigated as a situational char- acteristic with considerable impact on strain and as a moderator of the effects of stress on strain. In part, this is due to the influence of Karasek's job demands- control model (Karasek, 1979). The demand-control model posits that stress and control interact in pre- dicting strain and ill health. According to this model, a combination of high demands and low control produces the most adverse physiological and psycho- logical outcomes (Baker, 1985). Karasek and Theo- rell (1990) presented data supporting the contention that the lower the control over the work process, the more pronounced the effects of physical and psycho- logical stress on strain, including risk factors for cardiovascular heart disease (e.g., Alfredsson, Karasek, & Theorell, 1982; Karasek, Baker, Marxer, Ahlbom, & Theorell, 1981). Frese (1989) argued that

both additive and interactive effects of perceived control on health should be investigated, suggesting two major mechanisms for these two types of effects. Because control implies that one can change envi- ronmental condition, certain physical stresses can be reduced or even abolished, leading in turn to a re- duction of physiological strain and ill health. This mechanism has been referred to as the main effect model of control, which is viewed as directly asso- ciated with increased well-being (Barling & Kello- way, 1996). Support for the main effect of control was found in many studies (Spector, 1986).

Control may also interact with physical stress in predicting physiological outcomes. This interaction may occur because job control enables employees to modify the stressful environment, thus making it more suitable to their psychophysical prerequisites (Frese, 1989). This mechanism has been referred to as the interactive effect model of control, and it implies that the person can develop effective coping strategies with physical stress that buffer its effects on physiological stress. Evidence for the interactive model 's robustness with regard to physiological out- comes has been mixed (Fletcher & Jones, 1993; Spector, 1986, 1987). We were not able to find any study involving perceived control and serum uric acid. However, following the above theoretical mod- els and past research, we expected control to have a direct negative effect on serum uric acid (Hypothesis 3), thus representing the main effect model. In addi- tion, we expected perceived control, in accordance with the interactive effect model, to reduce the del- eterious impact of objective and subjective stress on serum uric acid (Hypotheses 4 and 5).

Certain physiological variables, including age and body weight (Lee et al., 1995; Mueller et al., 1970) and sport activity (Yano, Rohads, & Kagan, 1977), are known to be associated with nigher levels of serum uric acid and therefore were used as control variables in this study. We also controlled for diabe- tes and certain types of medications known to have an impact on the levels of serum uric acid (Nakanishi, Suzuki, Kawashimo, Nakamura, & Tatara, 1999). The literature on uric acid depicts consistent male- female differences in concentrations of serum uric acid across the life span (e.g., Mikkelsen, Dodge, & Valkenberg, 1965; Nakanishi et al., 1999). Therefore, the hypotheses were tested separately for male and female workers. A similar decision was taken by other investigators of stress-uric acid relationships (Thomas, Goodwin, & Goodwin, 1985).

378 SHIROM, MELAMED, AND NtR-DOTAN

M e t h o d

S a m p l e

The design of the present investigation is a cross-sec- tional study of a fairly large sample of employees in man- ufacturing industry. Participants were 3,680 blue-collar workers (2,504 men and 1,176 women) in the CORDIS (Cardiovascular Occupational Risk Factors Determination in Israel) study. This is a multidisciplinary, cross-sectional, and longitudinal epidemiological project aimed at identify- ing occupational risk factors for cardiovascular disease. The screening was offered free of charge on company time and was accepted by roughly 60% of the employees. The data collected for each participant covered a multitude of med- ical, biochemical, ergonomic, environmental, and psycho- logical variables. The present study was based on data collected during Phase I of the project (1985-1987) in 21 manufacturing plants. A detailed description of the types of plants sampled, the definition of blue-collar work, the re- spondents who were excluded from the final sample, and the characteristics of those excluded was presented elsewhere (Melamed et al., 1995). In addition to those employees who did not complete the questionnaires (mainly because of language difficulties or because they were absent at the time of administration), we excluded from the sample those who self-reported gout as a chronic illness. Gout is a rheumatic disease, definitively diagnosed by observing crystals of so- dium monourate in synovial fluid or in the tissues, often marked by abnormally high amount of serum uric acid, whose prevalence rises with age (Sturrock, 2000). Although idiopathic hyperuricaemia occurs more often than clinical gout (Sturrock, 2000), we excluded those with gout to avoid reverse causation and the confounding effects of antigout medications these respondents took.

P r o c e d u r e

All test procedures, including medical examinations, blood tests, assessments of the ergonomic stress levels by experienced judges, interviews, and questionnaires, were conducted at the work site. The psychological question- naires were presented as part of the overall medical data- gathering process and were administered individually. Two experienced observers performed the work environment evaluation, using the ESL inventory (described below) to assess the 640 workstations of the 21 plants in which the study participants were employed. The work environment evaluation was conducted independently of the psycholog- ical questionnaire and the cardiovascular disease risk factors screening, by visiting each plant several times, checking observations and measurements, and verifying their stability over the period of the study.

M e a s u r e s

Concentrations of serum uric acid are considered elevated in an absolute sense when they exceed the upper limit of an arbitrary normal range (indicating solubility of monosodium urate in serum), which in most studies is 7.0 and 6.0 mg/dL for men and women, respectively (Kelly & Palella, 1987). In this study, the concentration of uric acid in the serum was

assessed by a modification of the phosphotungstate method (Sigma, New York City, NY). Blood tests were performed on venous blood samples drawn in vacuum tubes without additives between 7 and 9 a.m. in the morning, with the participants seated and after fasting of 9-11 hr. Serum was separated from the whole blood within 2 hr of being drawn. Blood tests were carried out on fresh serum with an Abbott VP autoanalyzer (Abbott Park, IL). Internal and external quality control were used throughout. The data analysis was carried out separately for male and female respondents. Serum uric acid increases in men more than in women, perhaps influenced by the levels of estrogens and andro- gens; values in women are known to be constant from about age 20 through 40 but rise steeply after menopause (Kelly & Palella, 1987). These well-known differences among men and women led us to run separate regression analyses on male and female respondents.

For all multi-item indexes, described in this section, a respondent's score represented the mean of his or her re- sponses to the items in that index. The perceived control measure was based on Quinn and Stains (1979) and con- sisted of six items, each scored on a 6-point scale ranging from 1 (very little) to 6 (very much). Sample items included the following: (a) To what extent are you free to determine the pace of your work? (b) To what extent are you able to initiate various things in your job? and (c) To what extent are you free to determine how to perform you work? Cron- bach's alpha for this index was .82. This measure was found to be associated with both psychological distress symptoms (Kushnir & Melamed, 1991) and ambulatory blood pressure levels at work (Melamed, Kristal-Boneh, Harari, Froom, & Ribak, 1998).

Environmental annoyance was measured by a five-item index. Respondents indicated on a 5-point scale, ranging from 5 (very disturbed) to 1 (not disturbed at all), the extent to which they were bothered by noise, heat, humidity, and unpleasant odors. Cronbach's alpha for this index was .79. A detailed description of the construction of the ESL inven- tory and construct validation of the ESL measure is avail- able elsewhere (Melamed et al., 1999). The ESL measure constructed was assessed on a 4-point scale, ranging from 1 (very adequate environmental conditions) to 4 (very inade- quate environmental conditions). It comprised 62 items that covered a multitude of adverse work and environmental conditions. The major clusters of these adverse environmen- tal conditions were active hazards, falling hazards, passive hazards, poor control and safety guards, lack of protection, lack of hazard warning, physical effort, physical discomfort, overcrowding, need for sustained attention, noise distur- bance, climate discomfort, lighting problems, exposure to dust, exposure to fumes, and vibration (Melamed et al., 1999). Items were transformed into normal scores to over- come the uneven distribution of item rankings across the workstations. The internal consistency reliability of the en- tire inventory was .95, and the value of the interobserver agreement coefficient was .97. The convergent validity of the observers' rating and those obtained by asking employ- ees and their supervisors to evaluate the same workstations was evaluated in pilot studies. For additional details on the above convergent validity and on the consistency of the ratings across time, see Melamed et al. (1999).

The demographic variables of age, gender, and sport activity (coded as a dichotomy, with 1 = engaged in regular sport activity and 0 = not engaged in regular sport activity)

ENVIRONMENTAL STRESS AND URIC ACID 379

were collected in the questionnaire. Body mass index was calculated using the formula: body mass index = weight in kg/(height in m) 2. This index is also referred to as the Quetelet's index. Illness, another control variable used in this study, was scored as 1 for male employees who reported having diabetes or taking any of the following medications, including oral antidiabetics, insulin use, antihypertensive drugs, diuretics, and medication for angina pectoris, or it was scored as 0 otherwise. For female employees, the same dichotomous variable was scored as 1 for one or more of the above, plus oral contraceptive use.

Analytic Methods

In the multivariate analysis, we controlled for the con- founding variables of age and body mass index, represent- ing obesity, in a manner similar to that of French et al. (1982, pp. 26-27). Hypotheses 4 and 5 were tested by moderated multiple regressions (Aiken & West, 1991, pp. 9-10). A recent review by Aguinis, Petersen, and Pierce (1999) has revealed that moderated multiple regression is the method of choice for estimating moderating effects in applied psychology. In the regression runs, we first entered the control variables, followed by the main effects of ESL and environmental annoyance, and then perceived control. In the fourth step, we entered the multiplicative terms that were hypothesized. To reduce the possibility of multicollinearity among the product terms of the interactions and their compo- nent predictors, we centered the predictors (Aiken & West, 1992, pp. 28-35; Jaccard, Turrisi, & Wan, 1990).

R e s u l t s

Table 1 represents, for each variable used in the analyses, the means for female and male respondents .

As expected f rom previous reports in the literature (e.g., Mikkelsen et al., 1965), the concentrat ion o f serum uric acid was significantly higher among the men compared with the w o m e n in the study. With the except ion of environmental annoyance, the means o f all other predictors were found to be significantly higher for male compared with female respondents , in accordance with previous findings reported by Melamed et al. (1995). This finding lends credence to the content ion o f Martocchio and O 'Lea ry (1989), who reported in their meta-analysis that there is no evidence for sex differences in the stress exper ienced by employees but argued that sex differences might emerge if stress could be measured more objectively.

Table 2 represents the matrix of intercorrelations among the study's variables. Objective (ESL) and sub- jective (environmental annoyance) stress were signifi- cantly correlated among male (r = .16, p < .05) but not female employees. The measure of objective stress was negatively correlated with perceived control for both female and male employees (r = - .15, p < .05). Among the control variables, sport activity was not correlated with serum uric acid for either female or male respondents and also was not a significant predictor in the regression runs. Therefore, this control variable was omitted from Table 3.

Table 3 represents the results o f the two regression runs o f serum uric acid on the predictors for female and male respondents . The squared multiple correla- tion coefficients (adjusted for degrees o f f reedom)

Table 1 Descriptive Data on the Study's Measures for Male and Female Respondents

Female employees Male employees (n = 1,172) (n = 2,493)

Measure M SD M SD

Criterion Uric acid 3.85 1.06 5.19" 1.15

Predictors Ergonomic stress level 1.31 0.28 1.54" 0.45 Environmental annoyance 2.60 0.79 2.62 0.81 Perceived control 3.91 1.23 4.21 * 1.17

Control variables Age 35.9 11.2 41.10" 11.96 Sport activity 0.14 0.35 0.27* 0.44 Body mass index 24.9 4.98 25.5* 3.63 Illness a 0.16 0.36 0.18" 0.38

a Illness: for male employees, one or more of the following--diabetes, oral antidiabetics, insulin use, antihypertensive drugs, diuretics, medication for lowering uric acid, and medi- cation for angina pectoris; for female employees, one or more of the above, plus oral contraceptive use. * p < .05 for the significance of the difference between the respective two row means.

380 SHIROM, MELAMED, AND NIR-DOTAN

Table 2 Correlations for the Study Variables for Female (Above Diagonal) and Male (Below Diagonal) Employees

Variable 1 2 3 4 5 6 7 8

1. Age - - - .08* .44* - .01 .03 - .08* .19" .21" 2. Sport activity - . 16" - - - .12" - .17" .04 .11" .01 - .02 3. Body mass index .28* - .06* - - .03 - . 00 - . 10" .15" .30* 4. Ergonomic stress level .04* - .05* .06* - - .05 - . 15" - .01 - .04 5. Environmental annoyance .05* - .03 .03 .16" - - - .03 .04 - .04 6. Perceived control - . 0 0 .10" .01 - .15" - .05 - - .01 - .06* 7. Illness a .35* - .06* .17" - . 02 .06* - .01 - - .12" 8. Uric acid .04* - .01 .28* .03 - . 04 .02 - -

Note. ns = 1,176 and 2,504 for female and male respondents, respectively. a See Table 1 for explanation of illness. * p < .05.

were .11 and .10, respectively, for female and male respondents . These two regressions provide only par- tial support for the Hypothes is 1. ESL was found to be a posi t ive predictor o f serum uric acid, as expected by Hypothes is 1, but for male employees only. Also not in accord with the hypothesis formulated in this regard was the finding that the measure of subjective stress, environmental annoyance, was not a signifi- cant predictor o f serum uric acid for female employ- ees and was negatively associated with the criterion for the group of male employees .

In the regression runs, perceived control was not a significant predictor o f serum uric acid, thus discon-

firming Hypothesis 3 in this regard. Out of the two interactive terms that expressed the hypothesis re- garding the moderat ing effect o f perceived control on s t ress -se rum uric acid relationships, a significant in- teraction was found. The effect o f ESL on serum uric acid was modera ted by perceived control, in accor- dance with the hypothesis , but only for male employ- ees. As can be seen f rom Figure 2 , which depicts the interaction found, for those reporting high levels o f control, the higher the level o f ESL, the lower the level o f serum uric acid. For those reporting low level o f control, the higher the ESL, the higher the level o f serum uric acid.

Table 3

Summary of Hierarchical Multiple Regressions of Serum Uric Acid on Control Variables, Objective and Subjective Environmental Stress, and Perceived Control for Female and Male Employees

Female employees (n = 1,172) Male employees (n = 2,493)

Variable B SEB [3 AR" B SEB /3 A R 2

S~p 1: Control variables Age .01" .00 .09 - .01 .00 - . 06 Body mass index .05* .01 .25 .09* .01 .28 Illness a .17" .08 .06 .16" .07 .05

.10" .08* Step 2: Main effects

Ergonomic stress level (ESL) - .18 .10 - .05 .08* .03 .03 Environmental annoyance - .05 .03 - . 04 - .07* .03 - .05 Perceived control - .03 .02 - . 04 - .02 .02 - .02

Step 3: Moderating effects of control ESL × Perceived Control

.01" .01"

- . 11" .04 - .05 .01 *

Note. The symbols B and/3 represent the unstandardized and standardized partial regression coefficients, respectively, and SEB stands for the standard error of the former. The symbol AR 2 stands for the incremental squared multiple correlation coefficient, adjusted for degrees of freedom, for the respective step of the regression. Only statistically significant interactive terms are presented. a See Table 1 for explanation of illness. * p < .05.

ENVIRONMENTAL STRESS AND URIC ACID 381

A 5.5 m

C~ 5.25

E 5

(J 4.75

U ":" 4.5

E 4.25

¢~ 4 u'j

Control

~ H i g h Control

I I L o w High

Ergonomic Stress Level Figure 2. The interaction between ergonornic stress level and job and perceived control in the prediction of serum uric acid for male respondents.

Discuss ion

Several results seem to stand out in the regression runs, after we controlled for the effects of age, taking certain medications, and obesity. First, for male em- ployees but not for female employees, the objective stress measure of ESL was positively correlated with serum uric acid. This finding provides some support for Hypothesis 1. Second, in contrast with our hy- pothesis, perceived control did not predict serum uric acid for either male or female employees. It is clear that the disordinal interaction that described the me- diating effects of perceived control on ESL-uric acid relations for male employees explains the lack of support for the hypothesized main effect of control in this case. Third, after the effects of the measure of objective stress were controlled for, the measure of subjective stress (environmental annoyance) was not a significant predictor of the criterion for female employees and was a negative predictor of the crite- rion among male employees, again not confirming Hypothesis 2. Lastly, perceived control moderated the effects of ESL on the criterion for male employ- ees, providing some support to the hypothesis that expected a moderating effect of control on stress- serum uric acid linkages.

There may be several reasons for the lack of sup- port to our hypotheses that concerned the direct ef- fects of ESL and environmental annoyance on serum

uric acid among female employees. Female employ- ees in our sample were less likely to be employed in workstations that were physically demanding and that had heavy workloads. Therefore, for female em- ployees, ESL may have been less salient and proba- bly tapped to a lesser extent potential threats as compared with male employees. Still, for female employees the hypothesis that expected environmen- tal annoyance to predict serum uric acid was not confirmed. A possible explanation may concern the specific effects of objective versus subjective stress on serum uric acid for men as compared with women. Eden (1982), in a multiple interrupted time series study, found that the 39 first-year nursing students, all women, in his sample responded physiologically to the objective transient stress events that he had investigated, in terms of rising and then falling serum uric acid levels in four out of five measurement spells. However, these nursing students responded to the critical job event studied without reporting higher levels of subjective stress. In Eden's study, the ob- jective stress measure used was highly relevant and salient to the female respondents. This may account for the fact that in the present study, we failed to replicate the finding that concerned objective stress effects in Eden's study. Indirect evidence supporting this interpretation comes from the study of Thomas et al. (1985), who found that in a sample of 256 healthy

382 SHIROM, MELAMED, AND NIR-DOTAN

elderly persons above the age of 61, social support was not correlated with serum uric acid for men in their sample, whereas it was correlated - .20 with uric acid for women in their sample. Thomas et al. argued that this may be due to the greater sensitivity of women to relationships with significant others. Other researchers (e.g., Caplan & Jones, 1975) similarly found changes in physiological strain without the predicted antecedent changes in subjective stress.

How could the negative relationship between en- vironmental annoyance and serum uric acid among male respondents, found in this study, be accounted for? A possible explanation is that for male employ- ees, noise, heat, humidity, and unpleasant odors---~e types of physical stress tapped by this subjective measure--were perceived as externally determined and therefore led to a pattern of response of passive coping. Several past studies (Melamed, Kushnir, & Shirom, 1992; Rahe & Arthur, 1967; Trevisan et al., 1997) have reported that, under similar conditions, significantly lower levels of uric acid were found.

One of the limitations of the present study relates to the validity of the measure of environmental an- noyance. This measure of subjective stress was not a commensurate reflection of the ESL measures used here. This is due to the fact that environmental an- noyance did not tap employees' perceptions of most of the items included in the objective measure of ESL. To illustrate, environmental annoyance did not cover employees' perceptions of objective stresses such as safety hazards, overcrowding, and physical demands at work. Future research should attempt to construct more comprehensive subjective stress mea- sures corresponding to the breadth of work-related hazards captured by the ESL measure.

Yet another major limitation of the present study is the small amount of variance of serum uric acid explained by our stress and control predictors. We studied a fairly large and representative sample of manufacturing employees. Thus, conventional signif- icance testing procedures that were used in the re- gression analysis may provide an impoverished view of how seriously one can take the effects of stress and control on serum uric acid reported here. There are several arguments that can be made to support the importance of the small effects we have found. First, we used a cross-sectional design to investigate our hypotheses. In ongoing processes, even small effects may accumulate over time to become large effects. Future researchers using a longitudinal design could test this argument. Second, as explained earlier in the context of known physiological determinants of se- rum uric acid, its choice as a criterion limited in

advance the effect size that could have been found using stress and control variables. Third, several au- thors (e.g., Rosenthal & Rubin, 1983) have pointed out that even small effects may result in a person being moved by his or her physician from a category of "borderline" to the clinical category of "in need of medications therapy." Fourth, following Prentice and Miller (1992), we argue that what makes some effects seem important is not their magnitude but rather the methodologies of the studies that produced them. Our study used measures of objective and subjective stress and perceived control to predict a physiological strain. Lastly, the moderating effect of control belief on the relationship of environmental stress and serum uric acid, found in this study for male employees, does have theoretical importance, for two reasons.

First, the moderating effect of control beliefs on environmental stress-uric acid relationship provides support to the person-environment fit approach, as reformulated by Reich, Erdal, and Zautra (1997) to represent the interactions of control beliefs and health behaviors. According to their theoretical expectation, the interaction of control beliefs and stress accounts for a significant additional variance of health criteria over and above the main effects of stress and control (Reich et al., 1997). It is clear that male employees in our sample who held strong beliefs about possessed control were less susceptible to the physical dysfunc- tion of environmental stress as compared with those with below-average perceived control. A similar in- teraction of perceived control and stress was reported in another study in which the criterion was systolic ambulatory blood pressure (Melamed et al., 1998). Future research may address the specific mechanisms underlying these effects. These mechanisms may in- clude the possibility that those respondents with strong control beliefs adopted proactive coping strat- egies with respect to environmental stress, or sough t more health-related information, or assumed respon- sibility for their health habits compared with the group of male employees with below-average per- ceived control (see Rodin, 1986).

Second, our results on the relations between stress and uric acid may suggest that for some categories of respondents, highly relevant stress, like proximal en- vironmental stress, may involve raised levels of stim- ulation and arousal that lead subsequently to elevated levels of serum uric acid. It has been observed (Theo- rell et al., 1998; Theorell, Lind, Froberg, Karlsson, & Levi, 1972) that serum uric acid concentration reflect the general activation level in the sympathoadre- nomedullary system. This possibility needs to be addressed in future research.

ENVIRONMENTAL STRESS AND URIC ACID 383

In sum, in most manufactur ing jobs, physical stresses at work are very important for male employ- ees. A physiological pathway through which physical stress affects health may be through serum uric acid.

We offer this argument because it is possible that in the evolut ionary process, uric acid acted as an en- dogenous cortical st imulant (Muller et al., 1970). Our research suggested that male employees who exert themselves in their jobs , such as by bending over in awkward posit ions, and had little control over their work processes were at greater risk for high levels o f serum uric acid. Their coworkers who had high con- trol over their work processes were relatively pro- tected f rom the adverse effects o f physical stress on their job on serum uric acid.

R e f e r e n c e s

Aiken, L. A., & West, S. G. (1991). Multiple regression: Testing and interpreting interactions. Newbury Park, CA: Sage.

Aguinis, H., Petersen, S. A., & Pierce, C. A. (1999). Ap- praisal of the homogeneity of error variance assumption and alternatives to multiple regression for estimating moderating effects of categorical variables. Manuscript submitted for publication.

Alfredsson, L., Karasek, R. A., & Theorell, T. (1982). Myocardial infraction risk and psychological work envi- ronment: An analysis of the male Swedish working force. Social Science and Medicine, 16, 463-467.

Baker, D. B. (1985). The study of stress at work. Annual Review of Public Health, 6, 367-381.

Barling, J., & Kelloway, E. K. (1996). Job insecurity and health: The moderating role of workplace control. Stress Medicine, 12, 253-259.

Baron, R. A. (1994). The physical environment of work settings: Effects on task performance, interpersonal rela- tions and job satisfaction. Research in Organizational Behavior, 16, 1-46.

Boyle, J. A., Greig, W. R., Jasani, M. K., Duncan, A., Diver, M., & Buchanan, W. W. (1967). Relative roles of genetic and environmental factors in the control of serum uric acid levels in normouricaemic subjects. Annals of Rheu- matic Diseases, 26, 234-238.

Brand, F. N., McGee, D. L., & Kannel, W. B. (1985). Hyperuricemia as a risk factor of coronary heart disease: The Framingham Study. American Journal of Epidemi- ology, 121, 11-18.

Brooks, G. M., & Mueller, E. F. (1966). Serum urate con- centrations among university professors. Journal of the American Medical Association, 195, 415-418.

Caplan, R. D., & Jones, K. W. (1975). Effects of work load, role ambiguity, and personality Type A on anxiety, de- pression, and heart rate. Journal of Applied Psychology, 60, 713-719.

Cappuccio, F. P., Strazzullo, P., Farinaro, E., & Trevisan, M. (1993). Uric acid metabolism and tubular sodium handling: Results from a population-based study. Journal of the American Medical Association, 270, 354-359.

Conrad, D. W. (1973). The effects of intermittent noise on

human serial decoding performance and physiological response. Ergonomics, 16, 739-747.

Cox, T. (1985). Repetitive works: Occupational stress and health. In C. L. Cooper & M. Y. Smith (Eds.), Job stress and blue collar work (pp. 83-112). New York: Wiley.

Eden, D. (1982). Critical job events, acute stress, and strain: A multiple interrupted time series. Organizational Be- havior and Human Performance, 30, 312-329.

Ferris, T. F., & Gordon, P. (1968). Effect of angiotensin and norepinephrine upon urate clearance in man. American Journal of Medicine, 44, 359-365.

Fletcher, B., & Jones, F. (1993). A refutation of Karasek's demand-discretion model with a range of dependent measures. Journal of Organizational Behavior, 14, 219 - 330.

French, J. R. P., Caplan, R. D., & van Harrison, R. (1982). The mechanisms of job stress and strain. Chichester, England: Wiley.

Frese, M. (1989). Theoretical models of control and health. In S. I. Santer, J. J. Hurrell, Jr., & C. L. Cooper (Eds.), Job control and worker health (pp. 107-129). Chiches- ter, England: Wiley.

Frohlich, E. D. (1993). Uric acid: A risk factor for coronary heart disease. Journal of the American Medical Associ- ation, 270, 378-379.

House, J. S., McMichael, A. J., Wells, J., Kaplan, B. H., & Landerman, L. R. (1979). Occupational stress and health among factory workers. Journal of Health and Social Behavior, 20, 139-160.

Jaccard, J. J., Turrisi, R., & Wan, C. K. (1990). Interaction effects in multiple regression. Newbury Park, CA: Sage.

Jensen, J., Blankenhorn, D. H., Chin, H. P., Sturgeon, P., & Ware, A. G. (1965). Serum lipids and serum uric acid in human twins. Journal of Lipid Research, 6, 193-205.

Johansson, G., Aronsson, G., & Lindstrom, B. O. (1978). Social, psychological, and neuroendocrine stress reac- tions in highly mechanized work. Ergonomics, 21, 583- 599.

Kahn, R. L., & Byosiere, P. (1992). Stress in organizations. In M. D. Dunnette & L. M. Hough (Eds.), Handbook of industrial and organizational psychology (Vol. 3, 2nd ed., pp. 571-651). Palo Alto, CA: Consulting Psycholo- gists Press.

Karasek, R. A. (1979). Job demands, job decision latitude and mental strain: Implications for job redesign. Admin- istrative Science Quarterly, 24, 285-309.

Karasek, R. A., Baker, D., Marxer, F., Ahlbom, A., & Theorell, T. (1981). Job decision latitude, job demands and cardiovascular disease: A prospective study of Swed- ish men. American Journal of Public Health, 71, 694- 705.

Karasek, R. A., & Theorell, T. (1990). Healthy work: Stress, productivity and the reconstruction of work life. New York: Basic Books.

Kasl, S. V. (1984). Stress and health. Annual Review of Public Health, 5, 319-341

Kasl, S. V., Cobb, S., & Brooks, G. W. (1968). Changes in serum uric acid and cholesterol levels in men undergoing job loss. Journal of the American Medical Association, 206, 1500-1507.

Kelly, W. N., & Palella, T. D. (1987). Gout and other disorders of purine metabolism. In E. Braunwald, K. J. Isselbacher, & R. G. Petersdorf (Eds.), Harrison "s prin-

384 SHIROM, MELAMED, AND NIR-DOTAN

ciples of internal medicine (pp. 1623-1632). New York: McGraw-Hill.

Kushnir, T., & Melamed, S. (1991). Work and psycholog- ical distress in Type A/B industrial workers. Journal of Organizational Behavior, 12, 155-168.

Lee, J., Sparrow, D., Vokonas, P. S., Landsberg, L., & Weiss, S. T. (1995). Uric acid and coronary heart disease risk: Evidence for a role of uric acid in the obesity- insulin resistance syndrome. American Journal of Epide- miology, 142, 288-294.

Lercher, P., Hortnagal, J., & Kofler, W. W. (1993). Work noise annoyance and blood pressure: Combined effects with stressful working conditions. International Archives of Occupational and Environmental Health, 65, 23-28.

Lundberg, U., Granqvist, M., Hansson, T., Magnusson, M., & WaUin, L. (1989). Psychological and physiological stress responses during repetitive work at an assembly line. Work and Stress, 3, 143-153.

Martocchio, J. J., & O'Leary, A. M. (1989). Sex differences in occupational stress: A meta-analytic review. Journal of Applied Psychology, 74, 485-501.

Melamed, S., Ben-Avi, I., Luz, J., & Green, M. (1995). Objective and subjective work monotony: Effects on job satisfaction, psychological distress, and absenteeism in blue-collar workers. Journal of Applied Psychology, 80, 29-42.

Melamed, S., Froom, P., Kristal-Boneh, E., Gofer, D., & Ribak, J. (1997). Industrial noise exposure, noise annoy- ance, and serum lipid levels in blue-collar workers: The CORDIS Study. Archives of Environmental Health, 52, 292-298.

Melamed, S., Kristal-Boneh, E., Harari, G., Froom, P., & Ribak, J. (1998). Variation in the ambulatory blood pres- sure response to daily workload: The moderating role of job control. Scandinavian Journal of Work, Environment and Health, 24, 190-196.

Melamed, S., Kushnir, T., & Shirom, A. (1992). Burnout and risk factors for cardiovascular diseases. Behavioral Medicine, 18, 53-60.

Melamed, S., Luz, J., & Green, M. S. (1992). Noise expo- sure, noise annoyance, and their relation to psychological distress, accident and sickness absenteeism among blue collar workers: The CORDIS Study. Israel Journal of Medical Science, 28, 629-635.

Melamed, S., Luz, J., Najenson, E., Jucha, E., & Green, M. (1989). Ergonomic stress levels, personal characteristics, accident occurrence and sickness absence among factory workers. Ergonomics, 32, 1101-1110.

Melamed, S., Yekutieli, D., Froom, P., Kristal-Boneh, E., & Ribak, J. (1999). Adverse work and environmental con- ditions predict occupational injuries. The Cardiovascular Occupational Risk Factors Determination in Israel (CORDIS) Study. American Journal of Epidemiology, 150, 18-26.

Menotti, A., Spagnolo, A., Scanga, M., & Dima, F. (1992). Multivariate prediction of coronary deaths in a 10 year follow-up of an Italian occupational male cohort. Acta Cardilogica, 47, 311-370.

Mikkelsen, W. M., Dodge, H. J., & Valkenberg, H. A. (1965). The distribution of serum uric acid values in a population unselected as to gout or hyperuricemia: Tecumseh, Michigan, 1959-1960. American Journal of Medicine, 39, 242-251.

Mueller, E. F., & French, J. R. P. (1974). Uric acid and

achievement. Journal of Personality and Social Psychol- ogy, 30, 336-548.

Mueller, E. F., Kasl, S. V., Brooks, G. W., & Cobb, S. (1970). Psychosocial correlates of serum urate levels. Psychological Bulletin, 73, 238-257.

Najem, G. R., Seebode, J. J., Samedy, A. J., Feuerman, M., & Freidman, L. (1997). Stressful events and the risk of symptomatic kidney stones. International Journal of Ep- idemiology, 26, 1017-1023.

Nakanishi, N., Suzuki, K., Kawashimo, H., Nakamura, K., & Tatara, K. (1999). Serum uric acid: Correlations with biological, clinical, and behavioral factors in Japanese men. Journal of Epidemiology, 9, 99-106.

Prentice, D. A., & Miller, D. T. (1992). When small effects are impressive. Psychological Bulletin, 112, 160-164.

Quinn, R. P., & Stains, G. L. (1979). The 1977 Quality of Employment Survey. Ann Arbor: University of Michigan, Institute for Social Research.

Rahe, R. H., & Arthur, R. J. (1967). Stressful underwater demolition training, serum urate and cholesterol variabil- ity. Journal of the American Medical Association, 202, 1052-1054.

Rahe, R. H., & Arthur, R. J. (1968). Biochemical correlates of behavior. Diseases of the Nervous System, 29, 114- 117.

Rahe, R. H., Rubin, R. J., & Arthur, R. J. (1974). The three investigators study. Serum uric acid, cholesterol and cor- tisol variability during stresses of everyday life. Psycho- somatic Medicine, 36, 258-268.

Rahe, R. H., Rubin, R. T., & Gunderson, E. K. E. (1972). Measures of subjects' motivation and affect correlated with their serum uric acid, cholesterol and cortisol. Ar- chives of General Psychiatry, 26, 357-359.

Reich, J. W., Erdal, K. J., & Zautra, A. J. (1997). Belief about control and health behaviors. In D. S. Gochman (Ed.), Handbook of health behavior research: Vol. 1. Personal and social determinants (pp. 93-111). New York: Plenum Press.

Rodin, J. (1986). Health, control, and aging. In N. M. Baltes & P. B. Baltes (Eds.), The psychology of control and aging (pp. 139-163). Hillsdale, NJ: Erlbaum.

Rosenthal, R., & Rubin, D. (1983). A note on percent of variance explained as a measure of the importance of effects. Journal of Applied Social Psychology, 9, 395- 396.

Shirom, A. Westman, M., & Melamed, S. (1999). The effects of pay systems on blue collar employees emo- tional distress: The mediating effects of objective monot- ony and subjective work monotony. Human Relations, 52, 1077-1097.

Spector, E. P. (1986). Perceived control by employees: A meta-analysis of studies concerning autonomy and par- ticipation at work. Human Relations, 39, 1005-1016.

Spector, E. P. (1987). Interactive effects of perceived con- trol and job stressors on affective reaction and health outcome. Work and Stress, 1, 155-162.

Stansfeld, S. A. (1992). Noise, noise sensitivity and psychi- atric disorder." Epidemiological and psychophysiological studies. Cambridge, England: Cambridge University Press.

Stansfeld, S. A., Clark, C. R., Jenkins, L. M., & Tarnopol- sky, A. (1985). Sensitivity to noise in a community sample: I. Measurement of psychiatric disorder and per- sonality. Psychological Medicine, 15, 243-254.

ENVIRONMENTAL STRESS AND URIC ACID 385

Sturrock, R. D. (2000). Gout: Easy to misdiagnose. British Medical Journal 320, 132-133.

TheoreU, T., Konarski, K., Westerlund, H., Burell, A. M., Engstrom, R., Lagercrantz, A. M., Teszary, J., & Thulin, K. (1998). Treatment of patients with chronic symptoms by means of art psychotherapy: A process description. Psychotherapy and Psychosomatics, 67, 50-56.

Theorell, T., Lind, E., Froberg, J., Karlsson, C. G., & Levi, L. (1972). A longitudinal study of 21 subjects with cor- onary heart disease: Life changes, catecholamine excre- tion and related biochemical reactions. Psychosomatic Medicine, 34, 506-514.

Thomas, P. D., Goodwin, J. M., & Goodwin, J. S. (1985). Effects of social support on stress-related changes in cholesterol level, uric acid level, and immune function in elderly sample. American Journal of Psychiatry, 142, 735-737.

Trevisan, M., O'Leary, E., Farinaro, E., Jossa, F., Galasso,

R., Clentano, E., Scottoni, A., Fusco, G., & Panico, S. (1997). Short- and long-term association between uric acid and a natural disaster. Psychosomatic Medicine, 59, 109-113.

Yano, K., Rohads, G., & Kagan, A. (1977). Epidemiology of serum uric acid among 8000 Japanese-American men in Hawaii. Journal of Chronic Diseases, 30, 171- 184.

Zorbas, Y. G., Yaroshenko, Y. N., & Federenko, Y. F. (1996). Serum urate and cholesterol levels in endurance trained volunteers during acute and rigorous bed test conditions. Panminerva Medicine, 38, 223-228.

Received August 3, 1999 Revision received January 24, 2000

Accepted March 2, 2000 •