Accepted Manuscript

Life-Space Assessment and Physical Activity Scale for the Elderly: Validity of ProxyInformant Responses

James T. Cavanaugh, PT, PhD Kelley Crawford, PT, DPT

PII: S0003-9993(14)00268-8

DOI: 10.1016/j.apmr.2014.03.027

Reference: YAPMR 55798

To appear in: ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION

Received Date: 21 October 2013

Revised Date: 7 March 2014

Accepted Date: 25 March 2014

Please cite this article as: Cavanaugh JT, Crawford K, Life-Space Assessment and Physical ActivityScale for the Elderly: Validity of Proxy Informant Responses, ARCHIVES OF PHYSICAL MEDICINEAND REHABILITATION (2014), doi: 10.1016/j.apmr.2014.03.027.

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Running Head: Validity of Proxy Informant Responses

Title: Life-Space Assessment and Physical Activity Scale for the Elderly: Validity of Proxy

Informant Responses

Authors: James T. Cavanaugh, PT, PhD1 and Kelley Crawford, PT, DPT2

1Department of Physical Therapy, University of New England, Portland, ME (USA)

2Department of Rehabilitation Medicine, Maine Medical Center, Portland, ME (USA)

Study Location: University of New England, Portland, ME (USA)

Acknowledgements:

• The work was sponsored by the Department of Physical Therapy of the University of

New England, Portland, ME (USA).

• The authors declare no competing financial interests.

Corresponding Author Contact Information:

J.T. Cavanaugh, PT, PhD, University of New England / Department of Physical Therapy,

716 Stevens Ave., Portland, ME 04103. Tel: 1-207-221-4595. jcavanaugh@une.edu. Reprints

not available.

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Title: Life-Space Assessment and Physical Activity Scale for the Elderly: Validity of 1

Proxy Informant Responses 2

3

ABSTRACT 4

Objective: To validate the administration of the Life-space Assessment (LSA) and 5

Physical Activity Scale for the Elderly (PASE) surveys to proxy informants, as would be 6

necessary when measuring long-term outcomes in acutely ill, hospitalized older adults 7

who are initially incapacitated but eventually return to the community. 8

Design: Cross-sectional study. 9

Setting: General community. 10

Participants: Convenience sample of 40 dyads comprised of an ambulatory older adult 11

and a familiar companion. 12

Interventions: Dyads completed the LSA and PASE surveys on one occasion. 13

Companions based their responses on the recent mobility and physical activity of the 14

older adult. 15

Main Outcome Measures: Paired total scores for each instrument. 16

Results: At a group level, the difference between older adult and companion mean scores 17

for each instrument was not significant (p > 0.05). Standardized mean difference values 18

were small (d < 0.1). Paired scores were significantly yet moderately associated (ICC (1, 19

1) = 0.84 - 0.88, p < 0.01). Difference in scores was not associated with time spent 20

together (p > 0.05) or older adult gait speed (p > 0.05). At an individual level, older 21

adults and companions agreed more closely on the LSA than the PASE. However, 22

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disagreement in excess of estimated measurement error occurred in 40% of dyads for the 23

LSA and in none of the dyads for the PASE. 24

Conclusions: Older adults and companions collectively provided similar responses on 25

each instrument. Nonetheless, varying levels of agreement within individual dyads 26

suggested that proxy responses should be considered carefully. Implications for clinical 27

research and practice research are discussed. 28

29

KEY WORDS: Geriatrics; Motor activity; Outcome assessment (health care) 30

31

ABBREVIATIONS 32

CI: Confidence interval 33

ICU: Intensive care unit 34

ICC: Intraclass correlation coefficient 35

LSA: Life Space Assessment 36

MDD: Minimum detectable difference 37

PASE: Physical Activity Scale for the Elderly 38

PRO: Patient reported outcome 39

SDD: Smallest detectable difference 40

41

42

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The Life-Space Assessment (LSA)1 and the Physical Activity Scale for the 43

Elderly (PASE)a, 2 represent patient-reported outcome (PRO) measures that quantify, 44

respectively, an elderly respondent’s recent mobility and physical activity. Both represent 45

the “participation” domain of the International Classification of Functioning, Disability, 46

and Health,3 and accordingly, are well-suited for capturing community-level mobility and 47

physical activity clinical outcomes. Importantly, however, the collection of baseline (i.e., 48

pre-admission) PRO data from acutely ill, hospitalized older adults involves important 49

methodological considerations.4,5 One central issue is how to collect reliable and accurate 50

baseline data from familiar proxy informants (e.g., family member, caregiver, or close 51

companion) in circumstances when patients are mechanically ventilated, sedated, and / or 52

present with communication, cognitive, or other severe impairment that prevents them 53

from responding on their own behalf. Neither the LSA nor the PASE survey has been 54

validated in this regard. 55

The broad purpose of this study was to examine the validity of administering the 56

LSA and PASE instruments to familiar proxy informants. To do so, we administered each 57

survey to community-dwelling older adult-companion dyads, who were asked to base 58

their responses on the mobility and physical activity of the older adult participant. Our 59

primary aim was to examine the agreement between paired scores. Based on previous 60

elder-proxy studies using physical function measures,6-9 we hypothesized that older adult 61

and companion respondents would provide similar information on each survey. Our 62

secondary aim was to examine the extent to which older adult-companion agreement 63

might be biased by (a) the number of hours per week the pair spent together and (b) the 64

ambulatory capability of the older adult. Based on a previous study,8 we hypothesized 65

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that closer agreement would be associated with more hours spent together. In contrast, 66

given a lack of previous research, we conservatively hypothesized that no relationship 67

would exist between the amount of agreement and older adult ambulatory capability. 68

69

70

METHODS 71

Design and Participants 72

The study employed a cross-sectional design in which dyads formed by a 73

community-dwelling older adult and his or her close companion were recruited as a 74

sample of convenience. Older adult participants were at least 60 years of age and 75

identified their companion as “someone who they have spent at least 7 hours per week 76

with during the last month.” Study candidates were recruited by advertisement and word 77

of mouth. In promoting the study (e.g., at local retirement communities), every effort was 78

made to recruit a range of companion types; that is, those who shared a residence with the 79

older adult participant (e.g., spouse; partner; sibling) and those who did not (e.g., 80

extended family; friend). Dyads were screened by the primary investigator (JTC) over the 81

phone and excluded if either individual (1) was unable to speak English, (2) reported 82

cognitive, memory, or communication impairments that limited his / her ability to 83

complete surveys, or (3) if the targeted older adult participant was non-ambulatory. The 84

Institutional Review Board for the Protection of Human Subjects at the University of 85

New England approved the study. 86

87

Measures 88

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Descriptive Measures: We recorded the age and gender of each participant, 89

whether or not dyad members shared a residence, the type of relationship (e.g., spouse, 90

friend, family member, caregiver), and the reported number of hours / week spent 91

together during the previous month. To characterize older adult ambulatory mobility, we 92

collected 2 trials of self-selected gait speed over a 3m distance; assistive devices were 93

allowed as needed.10 94

Life-Space Assessment: The LSA is a brief survey that asks respondents to reflect 95

on their mobility activities during the preceding month.1 Mobility is categorized in terms 96

of five increasingly broader “life-space” levels, ranging from within their home to 97

beyond their town. Respondents indicate (1) whether or not they have been to each life 98

space in the past four weeks, (2) if so, how many days per week, and (3) if so, whether or 99

not they used equipment or needed help from another person. A composite score is 100

calculated based on highest level of life-space achieved, frequency of attaining each 101

level, and degree of independence at each level. Scores range from 0-120, with higher 102

scores indicating greater mobility. Previous investigations have supported the construct 103

and concurrent validity of the LSA in older adult populations,1, 11 its test-retest reliability 104

(Intraclass correlation coefficient (ICC) = 0.96),1 and its utility as an outcome measure in 105

clinical trials.12-14 We administered the LSA to both dyad members, asking each to focus 106

on the recent mobility of the older adult participant and thereby generating a LSAOlder Adult 107

and LSACompanion score. 108

Physical Activity Scale for the Elderly: The PASE is a brief survey designed to 109

measure the physical activity of older adults during leisure, household, and occupational 110

activities occurring over the previous 7 day period.2 PASE item scores are calculated by 111

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multiplying either time spent (hours / week) or participation in (yes / no) each activity 112

with empirically derived item weights. The PASE total score represents the sum of 113

individual item scores and ranges from 0 to over 400. Higher scores correspond to greater 114

physical activity. The PASE has been validated for use in elderly populations,2,15 and its 115

test-retest reliability has been reported (r = 0.75).2 We administered the PASE to both 116

dyad members, asking each to focus on the recent physical activity of the older adult 117

participant and thereby generating a PASEOlder Adult and PASECompanion score. 118

119

Procedures 120

Trained research personnel collected descriptive data and administered the LSA 121

and PASE to each older adult and companion dyad in a place convenient to them (e.g. the 122

older adult’s home). Participants were sequestered from one another when completing the 123

surveys to avoid influencing each other’s responses. 124

125

Data Analysis 126

Data were analyzed using SPSS version 20.b Descriptive statistics were used to 127

characterize the sample. To account for the possibility of recall error by either participant, 128

time spent together was characterized using the average reported value. Gait speed was 129

calculated as the mean of 2 trials. 130

Our analysis was based partly on the approach used in a previous investigation.16 131

At a group level, we analyzed agreement of scores using the dependent samples t-test (α 132

= 0.05), standardized mean difference (d),17 and ICC (1,1). At an individual level, we 133

calculated difference values between paired scores, constructed Bland-Altman plots,18 134

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and determined the 95% limits of agreement. Finally, we analyzed the relationship 135

between difference in paired scores and (a) time spent together and (b) mean gait speed 136

using appropriate parametric or non-parametric correlation coefficients (α = 0.05). 137

To facilitate the interpretation of individual-level results, we compared one 138

instrument to the other by normalizing the raw difference scores as percent difference 139

values (= 100* [(older adult score – companion score) / mean of paired scores]). We also 140

used previous literature to provide estimates of measurement error against which the 141

agreement for each instrument could be compared. Because LSA measurement error 142

values had not been published previously, we used standard formulas19 and information 143

contained in the original LSA publication1 to calculate a Minimum Detectable Difference 144

(MDD) value based on a 95% confidence interval (MDD95% = 13.7 using ICC = 0.96 and 145

Standard Error of Measurement = 4.94.) For the PASE, we lacked sufficient information 146

from previous literature to produce an analogous measurement error estimate. Thus, we 147

selected instead the only available PASE measurement error value available, the Smallest 148

Detectable Difference (SDD) based on a 95% confidence interval from a recent study of 149

adult patients with cancer (SDD95% = 84).20 150

151

152

RESULTS 153

Forty-five dyads were screened initially. None were rejected due to language, 154

cognitive, or physical limitations. Four dyads were unable to participate in data collection 155

due to scheduling conflicts. Data from one dyad were incomplete and therefore not 156

included in the analysis. 157

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The final sample contained 22 female and 18 male older adult participants (mean 158

age ± SD of 80.7 ± 7.5 years.) Mean gait speed ± SD was 0.82 ± 0.26 m/s. Companions 159

included 33 females and 7 males (mean age ± SD of 69.2 ± 14.4 years.) Two companions 160

did not report their age. Twenty-five companions reported living with the older adult. 161

Mean time spent per week together ± SD was 90.7 ± 62.3 hours, with 19 dyads reporting 162

spending more than 100 hours per week together. Companions included 21 spouses, 11 163

children, 6 friends, and 2 unrelated caregivers. Additional characteristics of the sample 164

have been reported elsewhere.21 165

166

Life-Space Assessment 167

Older adults as a group reported a moderate level of life-space mobility (mean 168

LSAOlder Adult = 71.1, 95% confidence interval (CI) = 61.8 – 80.3), similar to the collective 169

report provided by their companions (mean LSACompanion = 68.5, 95% CI = 59.8 – 77.2). 170

The difference between group mean scores was not significant (mean difference = 2.54, 171

95% CI = - 1.77 to 6.84, t (39) = 1.19, p = 0.24), and the standardized mean difference 172

was small (d = 0.09). The 2 sets of scores were significantly yet moderately associated 173

(ICC (1,1) = 0.88, 95% CI = 0.79 - 0.94, p < 0.001). Difference in LSA scores was not 174

associated with time spent together (Spearman rho = -0.26, p = 0.11) or older adult gait 175

speed (Pearson r = 0.06, p = 0.70). Family members (n = 32) were relatively more 176

accurate in their characterization of older adult life-space mobility than friends or 177

caregivers (n = 8) (Figure 1). At an individual level, the mean percent difference between 178

paired LSA scores was 18.1% (95% CI = 13.5 – 22.7). Seven dyads had ≤ 5% difference 179

in scores, 15 dyads had ≤ 10% difference in scores, and 22 dyads had ≤ 20% difference in 180

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scores (Figure 2). For all dyads, the percent difference in paired LSA scores was ≤ 60%. 181

Twenty-four dyads had raw difference values less than MDD95% = 13.7. 182

INSERT FIGURE 1 ABOUT HERE 183

INSERT FIGURE 2 ABOUT HERE 184

Figure 3A features a Bland-Altman plot,18 in which the mean of the paired scores 185

(x-axis) was plotted against difference in paired LSA scores (y-axis). There was 1 case of 186

exact agreement. Positive differences (n = 23) indicated cases in which older adults 187

reported greater life-space mobility than their companion (mean difference = 11.8, 95% 188

CI = 8.1 – 15.4). Negative differences (n = 16) indicated cases in which companions 189

reported greater life-space mobility of the older adult than the older adult reported about 190

his or herself (mean difference = - 10.6, 95% CI = - 14.4 to - 6.8). The maximum paired 191

difference (=26.0) was less than 26.9, the 95% limits of agreement. 192

INSERT FIGURE 3 ABOUT HERE 193

194

Physical Activity Scale for the Elderly 195

Physical activity levels reported by older adults as a group were relatively low 196

(mean PASEOlder Adult score = 81.7, 95% CI = 63.4 – 100.0) and slightly less than the 197

collective report of the companions about the older adults (mean PASECompanion = 82.4, 198

95% CI = 64.6 – 100.1). The difference between group mean scores was not significant 199

(mean difference = - 0.70, 95% CI = - 11.77 to 9.71, t (39) = 0.14, p = 0.89), and the 200

standardized mean difference between scores was small (d = 0.01). The 2 sets of scores 201

were significantly yet moderately associated (ICC (1,1) = 0.84, 95% CI = 0.71 - 0.91, p < 202

0.001). Difference in PASE scores was not associated with time spent together (rho = -203

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0.22, p = 0.18) or older adult gait speed (r = 0.08, p = 0.61). Similar to the LSA results, 204

family members (n = 32) were relatively more accurate in their characterization of older 205

adult life-space mobility than friends or caregivers (n = 8) (Figure 1). At an individual 206

level, the mean percent difference between paired PASE scores was 43.2% (95%CI = 207

28.5 – 58.0), with 6 dyads having ≤ 5% difference in scores, 8 dyads having ≤ 10% 208

difference in scores, 14 dyads having ≤ 20% difference in scores (Figure 2). Unlike LSA 209

scores, the percent difference in PASE scores exceeded 60% for 8 dyads. Four dyads had 210

percent differences in PASE scores in excess of 100%. All dyads had raw difference 211

values less than SDD95% = 84. 212

Figure 3B features a Bland-Altman plot of the PASE scores.18 There were 2 cases 213

of exact agreement. Positive differences (n = 19) indicated cases in which older adults 214

reported greater physical activity than their companion (mean difference = 26.2, 95% CI 215

= 16.2 – 36.2). Negative differences (n = 19) indicated cases in which companions 216

reported greater physical activity of the older adult than the older adult reported about his 217

or herself (mean difference = - 27.7, 95% CI = - 36.4 to - 19.0). One paired difference (= 218

69.7) was greater than 65.14, the 95% limits of agreement. 219

220

221

DISCUSSION 222

Agreement 223

Consistent with previous studies of proxy agreement on measures of physical 224

function,6-9 our hypothesis that older adults and their familiar companions would provide 225

similar responses on each survey was generally supported. At a group level, there was no 226

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statistical difference for either instrument between mean older adult and mean companion 227

scores, their standardized mean difference was very small,17 and older adult scores were 228

strongly and significantly associated with companion scores. Also consistent with 229

previous literature,6 family members tended to agree more closely with their respective 230

older adult than non-family members (Figure 1). Unlike the latter study, however, in 231

which proxy respondents tended to over estimate disability relative to elderly patients 232

with a hip fracture, our data revealed no substantial evidence of systematic bias in 233

companion ratings (Figure 3). Furthermore, the extent of agreement in our data did not 234

appear to depend on time spent together or on the ambulatory capability of the older 235

adult. 236

A key question, which has been raised previously,9 is how strong measures of 237

agreement need to be before one can conclude that the agreement is satisfactory. To our 238

knowledge, no relevant guidelines exist for interpreting the agreement of patient-proxy 239

scores at an individual level for physical function instruments like the LSA and PASE. 240

To address this issue, we developed an analytical approach that provided a relative 241

comparison of one instrument to the other and a comparison of each instrument to an 242

external criterion. The result of this analysis was mixed. In the percent difference 243

comparison, older adults and their companions generally agreed more closely on the LSA 244

than on the PASE. The finding was evident not only in the relatively smaller mean 245

percent difference value of paired LSA scores, but also in the number of dyads in 246

relatively close agreement (Figure 2). In comparison to an external criterion, however, 2 247

out of 5 dyads using the LSA had raw difference values in excess of our measurement 248

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error estimate, where as all dyads using the PASE had raw difference values less than 249

measurement error. 250

251

Implications for Clinical Research and Practice 252

The LSA and PASE instruments each serve as an indicator of physical 253

functioning and are well suited for use with community-dwelling older adults. Both 254

instruments show promise as PRO measures for measuring clinical outcomes. Based on 255

our findings, both instruments also appear suitable, albeit with limitations, for 256

administration to familiar proxy informants in circumstances when an acutely ill, 257

hospitalized older adult is initially incapacitated but may eventually return to community. 258

The validity of instruments like these may be particularly important to researchers and 259

clinicians seeking to measure long-term outcomes associated with the early mobilization 260

of patients admitted to the intensive care unit,22-27 the impetus for which has become a 261

national research priority.28 262

The selection of either the LSA or the PASE as a PRO measure for use in clinical 263

research depends on a variety of factors. Each instrument has a distinct construct (i.e., 264

life-space mobility vs. physical activity). Though brief, both instruments seem too 265

complex for efficient self-administration by patients or their proxies. The PASE is 266

copyrighted and requires a user license agreement.29 Finally, both instruments present 267

tradeoffs when considering administration to proxy informants. The LSA appears to offer 268

the potential for relatively close agreement in the majority of cases, but at the risk of 269

some proxies providing inaccurate responses in excess of measurement error. Such 270

inaccuracy presumably would confound the interpretation of long-term outcome data. In 271

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contrast, there were more instances of relatively large disagreement on the PASE. 272

Overall, however, the errors appear more likely to be less than measurement error, which 273

would minimize their confounding potential in longitudinal studies. How these tradeoffs 274

are resolved is likely to depend on the specific circumstances of a given patient or 275

research study. 276

277

Study limitations 278

Our study was limited in several ways. The sample was relatively small and 279

restricted to older adults with an identified companion. Although companions as a group 280

represented a range of social relationship types, some companions may have been more 281

familiar with their older adult than others. Undetected cognitive impairments among 282

older adults and companions may have confounded the results. In addition, the LSA and 283

PASE were potentially prone to recall error. Finally, not only did we rely on estimates of 284

measurement error based on previous research, rather than on our own sample, the 285

estimates were derived using different methods. Thus, comparative differences between 286

the LSA and PASE should be interpreted with caution. Future investigations should 287

consider these limitations in their study designs. 288

289

290

CONCLUSION 291

Older adults and their familiar companions collectively provided similar 292

responses on the LSA and PASE instruments. Nonetheless, agreement within individual 293

older adult-companion dyads varied enough to warrant recommendations for thoughtful 294

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consideration of each instrument in the collection of proxy responses. Both instruments 295

show promise for collecting community-level clinical outcomes in circumstances when 296

an acutely ill, hospitalized older adult is unable to provide information about their pre-297

admission mobility and physical activity. 298

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29. New England Research Institute. Physical Activity Scale for the Elderly. Available at 378

http://www.neriscience.com/. Accessed September 26, 2013. 379

380

381

SUPPLIERS 382

a. New England Research Institute, 9 Galen St., Watertown, MA 02472. 383

b. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606. 384

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Figure Legend 385

Figure 1. Distribution of percent difference values according to the type of relationship 386

between older adults and their companion. 387

388

Figure 2. Distribution of percent difference values as a cumulative percentage of the 389

sample. 390

391

Figure 3. Bland Altman plots of the agreement between paired scores as a function of 392

their mean (n = 40). Plot 3A features LSA scores. Plot 3B features PASE scores. Positive 393

differences indicate cases in which older adults reported being more mobile or more 394

physically active than their companion reported about them. Negative differences 395

indicate cases in which companions reported the older adult to be more mobile or 396

physically active than the older adult reported about his or herself. Dashed lines indicate 397

95% limits of agreement. 398

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0  20  40  60  80  100  120  140  160  180  200  220  240  

LSA   PASE  

Mean  Percent  D

ifference  in  Paired  Scores  

Spouse  (n  =  21)   Child  (n  =  11)   Friend  (n  =  6)   Caregiver  (n  =  2)  

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