Journal of Affective Disorders 138 (2012) 34–40

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Journal of Affective Disorders

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Research report

A nationwide survey on the prevalence and risk factors of late life depressionin South Korea

Joon Hyuk Park a, Ki Woong Kim b,⁎, Myoung-Hee Kim c, Moon Doo Kim a, Bong-Jo Kim d,Shin-Kyum Kim e, Jeong Lan Kim f, Seok Woo Moon g, Jae Nam Bae h, Jong Inn Woo i,Seung-Ho Ryu j, Jong Chul Yoon k, Nam-Jin Lee l, Dong Young Lee i, Dong Woo Lee m,Seok Bum Lee n, Jung Jae Lee o, Jun-Young Lee p, Chang-Uk Lee q, Sung Man Chang o,Jin Hyeong Jhoo r, Maeng Je Cho i

a Department of Psychiatry, Jeju National University School of Medicine and Jeju National University Hospital, Jejudo, Republic of Koreab Department of Psychiatry, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Gyeonggido, Republic of Koreac Health Equity Research Center, People's Health Institute, Seoul, Republic of Koread Department of Psychiatry, Gyeongsang National University College of Medicine and Gyeongsang National University Hospital, Gyeongsangnamdo, Republic of Koreae Department of Neuropsychiatry, Gwangju Inkwang Dementia Hospital, Gwangju, Republic of Koreaf Department of Psychiatry, Chungnam National University College of Medicine and Chungnam National University Hospital, Chungcheongnamdo, Republic of Koreag Department of Psychiatry, Konkuk University College of Medicine and Konkuk University Chungju hospital, Chungcheongbukdo, Republic of Koreah Department of Psychiatry, Inha University College of Medicine and Inha University Hospital, Incheon, Republic of Koreai Department of Psychiatry, Seoul National University College of Medicine and Seoul National University Hospital, Seoul, Republic of Koreaj Department of Neuropsychiatry, Konkuk University College of Medicine and Konkuk University Hospital, Seoul, Republic of Koreak Department of Neuropsychiatry, Kyunggi Provincial Hospital for the Elderly, Gyeonggido, Republic of Koreal Department of Psychiatry, Jeonju City Welfare Hospital for the Elderly, Jeollabukdo, Republic of Koream Department of Neuropsychiatry, Inje University College of Medicine and Inje University Snaggye Paik Hospital, Seoul, Republic of Korean Department of Psychiatry, Dankook University College of Medicine and Dankook University Hospital, Chungcheongbukdo, Republic of Koreao Department of Psychiatry, Kyungbook National University College of Medicine and Kyungbook National University Hospital, Daegu, Republic of Koreap Department of Psychiatry, Seoul National University College of Medicine and Seoul National University Boramae Hospital, Seoul, Republic of Koreaq Department of Psychiatry, College of Medicine and Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korear Department of Neuropsychiatry, Kangwon National University College of Medicine and Kangwon National University Hospital, Kangwondo, Republic of Korea

a r t i c l e i n f o

⁎ Corresponding author at: Department of Neuropsy(463-707), Republic of Korea. Tel.: +82 31 787 7432;

E-mail address: kwkimmd@snu.ac.kr (K.W. Kim).

0165-0327/$ – see front matter © 2011 Elsevier B.V. Adoi:10.1016/j.jad.2011.12.038

a b s t r a c t

Article history:Received 6 October 2011Received in revised form 15 November 2011Accepted 14 December 2011Available online 26 January 2012

Objective: This study aimed to estimate prevalence rates and risk factors of LLD among a largenationwide sample of Korean elders in South Korea.Method: Of 8199 randomly sampled Koreans aged 65 years or more, 6018 participated (re-sponse rate=73.4%). Using the Korean version of the short form Geriatric Depression Scale(SGDS-K), we classified individual scoring 8 or 9 as having possible depression and those scor-ing≥10 as having probable depression.Results: The age-, gender-, education-, and urbanicity-standardized prevalences were 10.1%(95% CI=9.3–10.8) for possible depression, 17.8% (95% CI=16.8–8.7) for probable depression,and 27.8% (95% CI=26.7–29.0) for overall depression. Poverty, living alone, low education, il-literacy, smoking, history of head trauma, and low Mini Mental Status Examination score wereassociated with greater risk of depression, while mild alcohol use and moderate to heavy ex-ercise were associated with lower risk of depression. However gender difference in the riskof depression was not found.

Keywords:PrevalenceRiskLate life depression (LLD)South Korea

chiatry, Seoul National University Bundang Hospital, 300 Gumidong, Bundanggu, Seongnamsi, Gyeonggidofax: +82 31 787 4058.

ll rights reserved.

35J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

Conclusion: LLD is decidedly common in South Korea. It was associated with various sociode-mographic and clinical factors, some of which are amendable through policy actions. Thisstudy was limited by use of the SGDS-K rather than a standardized clinical interview.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

Late life depression (LLD) is likely to become one of themost significant public health problems in Asian countries,including in Korea, where the numbers of elderly personsare increasing at a remarkable rate. Although depression isone of the most common and treatable mental illnesses, LLDoften goes under-recognized and undertreated due to its sub-syndromal features and complicated etiologies. The burdenof inadequately treated LLD is substantial since LLD, even ifsubsyndromal, is as detrimental to well-being, and as dis-abling, as major depressive disorder (MDD) is (Beekman etal., 1997). Recently, researchers and clinicians have been pay-ing more attention to LLD due to a steep rise in the suiciderate among elderly Koreans. Recent statistics show SouthKorea has the highest suicide rate among Organization forEconomic Cooperation and Development (OECD) membernations (KNSO, 2010).

One estimate gave the prevalence of MDD among the el-derly as 5.37% in Korea, higher than the prevalences in mostWestern countries and in other Asian countries (Park et al.,2010). MDD, however, might be just the tip of the iceberg,since a considerable proportion of the elderly people withclinically significant depressive symptoms do not meet therigorous MDD diagnostic criteria of the Diagnostic and Statis-tical Manual of Mental Disorders, Fourth Edition (DSM-IV).Although no agreement exists on a gold standard for definingthis clinically-significant but subsyndromal depression, re-searchers and clinicians have often used self-rating question-naires for depressive symptoms, such as the GeriatricDepression Scale (GDS) (Yesavage et al., 1982), its shortform (SGDS) (Sheikh et al., 1986), and the Center for Epide-miologic Studies Depression Scale (CES-D), to capture sub-syndromal and syndromal depression for individuals inlater life.

In Korea, LLD that encompasses MDD and subsyndromaldepression has rarely been studied. Two studies using eitherthe GDS or the SGDS (Cho et al., 1998; Kim et al., 2002) esti-mated the prevalence of LLD as 13.4% and 15.8%, respectively.However, these studies were conducted over 10 years ago ona small regional sample. In the present study, we investigatedthe prevalence and risk factors of LLD, as defined by SGDSscore, among a large nationwide sample of Korean elders.

2. Methods

2.1. Subjects

This study was conducted as part of the Nationwide Sur-vey on Dementia in Korea (NaSDeK) (Kim et al., 2011). Themethod of estimating sample size was described in detail inour previous work (Kim et al., 2011). To capture national var-iations, we selected 15 districts across the country. Withinthese, 13 hospitals had the responsibility of conducting the

survey in their nearby districts. The hospitals randomly se-lected villages within their corresponding districts so as tocover about 5000 residents (except for one large, mixedurban/rural district covering about 10,000 residents) aged65 years or more and selected 10% of these as participantsthrough systematic random sampling, based on the residen-tial rosters. Finally, we sampled 8199 elderly Koreans livingindependently in communities or living in institutions, suchas nursing homes and hospitals.

2.2. Assessments

The current study employed a single-stage design to esti-mate the prevalence of depression. We conducted this surveyfrom May 2008 through October 2008. We instructed the re-search nurses to invite all subjects to take part in the studyvia a home visit and to administer a semi-structured inter-view to each subject. This interview consisted of the Koreanversion of the SGDS (SGDS-K) (Bae and Cho, 2004), the Kore-an version of the Mini-Mental State Examination (MMSE-KC)(Lee et al., 2002), questions on demographic characteristics,and checklists for risk factors. We determined the meandaily alcohol consumption for those subjects indicating they“drank alcohol within the last year,” with one drink beingequivalent to a glass of wine, a half pint of beer, or a singleounce of spirits. We evaluated the amount of exercise usingthe metabolic equivalent of task (MET) by determining themean daily hours of light, moderate, and vigorous exercisein the past year. If the participant alone could not giveenough information, we interviewed reliable informants(spouse, children, other relatives, or close friends, in des-cending order), as well.

An earlier research has shown the SGDS-K (Sheikh andYesavage, 1986) to be valid and reliable for identifyingMDD among Korean elders (Bae and Cho, 2004). Althoughthe SGDS-K is a self-questionnaire, the research nurses readit, without comment, for the illiterate participants. Since theSGDS-K's optimal cutoff score for MDD in Korean elders is10 (sensitivity=0.7419, specificity=0.8587), we defined in-dividuals having scores≥10 as “probably having clinicallysignificant depressive symptoms (probable depression).”We defined those having scores of 8 or 9 as “possibly havingclinically significant depressive symptoms (possible depres-sion).” At a cutoff score of ≥8, the SGDS-K's sensitivity andspecificity for MDD are 0.8548 and 0.6957, respectively, inKorean elders (Bae and Cho, 2004). The Institutional ReviewBoard of Seoul National University Hospital, Korea, approvedthis study protocol, and all participants or their family mem-bers provided informed consent.

2.3. Statistical analyses

We estimated prevalences of possible and probable de-pression by age (65–69 years, 70–74 years, 75–79 years,

36 J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

80–84 years, and≥85 years), gender, education (unedu-cated, 1–6 years, and ≥7 years of schooling) and urbanicity(rural and urban), calculating 95% confidence intervals (CIs)for each prevalence estimate using the Wald method. Forcells that contained less than 100 subjects, we derived bino-mial parameter CIs using the Clopper–Pearson method.

We estimated standardized prevalence rates for elderlyKoreans using the direct standardization method, whereinwe adjusted prevalence rates by age and gender to the totalKorean population, based on the 2005 national census. In ad-dition, we calculated descriptive statistics, to determine thesociodemographic and clinical characteristics of participantswith possible and with probable depression. To comparesociodemographic and clinical characteristics among the sub-jects with possible and with probable depression to those ofpersons without depression, we used analyses of variance(ANOVAs), with Bonferroni post hoc comparisons, or chi-square tests. To identify factors associating with the risk ofLLD, we employed polytomous logistic regression models,

Table 1Characteristics of participants.

Variable Level Normal (N=4355)

Age (years) 65–69, % 35.1170–74, % 30.7775–79, % 18.6580–84, % 9.7185+, % 5.76Mean (SD) 72.97 (6.15)

Gender Men, % 42.89Women, % 57.11

Education (years) None, % 25.691–6, % 38.307+, % 36.00Mean (SD) 6.20 (5.28)

Illiteracy No, % 10.48Yes, % 89.52

Residence Rural, % 33.43Urban, % 66.57

Marital status Married, % 61.60Bereaved and others, % 38.40

Cohabitants No, % 17.76Yes, % 82.24

Economic status Not disadvantaged, % 92.86Disadvantageda, % 7.14

Smoking No, % 87.07Yes, % 12.93

Alcohol (SU)b 0, % 72.18≤1, % 16.19≤2, % 3.80≥3, % 7.83

Exercise (MET)c Mild, % 35.13Moderate, % 33.24Heavy, % 31.63Mean (SD) 3302.87 (4432.50)

Head traumad No, % 91.32Yes, % 8.68

MMSE (z score)e ≥−1.0, % 65.40−1.0 to −1.5, % 13.82b−1.5, % 20.78Mean (SD) 22.94 (4.85)

a Subjects who were covered by the National Medical Aid program.b Standard unit.c Metabolic Equivalent of Task (MET).d Presence of previous head trauma, with loss of consciousness exceeding 10 mie z Score of Mini Mental Status Exam (MMSE) calculated using an age-, gender-

assuming that the outcome variable (normal vs. possible de-pression vs. probable depression) is the ordinal scale. All sta-tistical analyses were performed using the SPSS 15.0statistical package.

3. Results

3.1. Demographical characteristics of respondents

6018 subjects (age=73.41±6.27 years; female=60.00%)participated in the study (response rate=73.4%). The responserate was higher in rural areas than in urban regions (77.6% ver-sus 71.4%, Pb0.001). Responders and non-responders had nosignificant differences in gender or age distributions (P=0.52for gender, P=0.56 for age). Of the 6018 participants, 1054had probable depression, and 609had possible depression. Par-ticipants with possible or probable depression were older, lesseducated (Pb0.001 for both, ANOVA) and more likely to bewomen (Pb0.001, chi-square test). Overall, depression (both

Possible depression (N=609) Probable depression (N=1054)

26.11 26.0029.72 29.0321.84 23.7211.66 12.6210.67 8.6374.57 (6.61) 75.54 (6.33)34.15 31.5065.85 68.5039.90 46.3940.23 37.7619.87 15.844.06 (4.34) 3.37 (4.07)17.72 24.8182.28 75.1934.65 37.1065.35 62.9046.13 44.7253.87 55.2827.14 30.9672.86 69.0486.17 81.7113.83 18.2984.38 83.5415.63 16.4676.32 80.3613.65 9.822.30 2.867.73 6.9644.74 48.8130.76 26.9824.51 24.212647.03 (4215.80) 2478.88 (4014.83)88.96 83.6211.04 16.3852.87 51.9915.11 15.0932.02 32.9221.54 (5.03) 20.67 (5.21)

n.and education-adjusted norms of Korean elders.

Table 2Estimated prevalence rates of depression.

Prevalence rates (95% confidential Intervals)

Possible depression Probable depression Overall depression

Age 65–69 8.1 (6.9–9.3) 14.0 (12.4–15.5) 22.1 (20.2–23.9)70–74 9.9 (8.5–11.3) 16.7(15–18.5) 26.7 (24.6–28.7)75–79 11.1 (9.3–12.9) 20.9 (18.6–23.2) 32.1 (29.4–34.7)80–84 11.3 (8.8–13.8) 21.2 (18–24.4) 32.5 (28.9–36.2)85+ 16.0 (12.4–19.5) 22.4 (18.3–26.4) 38.6 (33.8–43.3)

Gender Men 14.3 (7.4–21.2) 13.8 (12.4. 15.2) 22.4 (20.8–24.1)Women 16.5 (12.4–20.6) 20.0 (18.7–21.3) 31.1 (29.6–32.7)

Education None 13.1 (11.6–14.7) 26.4 (24.4–28.4) 39.6 (37.4–41.8)1–6 years 10.6 (9.3–11.9) 17.2 (15.7–18.8) 27.8 (26.0–29.7)7+ years 10.3 (8.9–11.6) 9.0 (7.7–10.3) 15.5 (13.9–17.2)

Urbanicity Rural 10.3 (8.9–11.6) 19.0 (17.3–20.7) 29.3 (27.3–31.3)Urban 10.1 (9.1–11.0) 16.7 (15.6–17.9) 26.8 (25.4–28.2)

Crude prevalence 10.1 (9.4–10.9) 17.5 (16.6–18.5) 27.7 (26.5–28.8)Adjusted prevalencea 10.1 (9.3–10.8) 17.8 (16.8–18.7) 27.8 (26.7–29.0)

a Age, gender, education, and urbanicity adjusted based on the 2005 National Census.

37J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

probable and possible) had a greater prevalence in rural areas(29.3%) than in urban areas (26.8%; P=0.04, chi-square test).Probable depression accounted for 63.4% of all depressioncases. Table 1 summarizes the participants' characteristics.

Table 3Factors associated with the risk of possible and probable depression from proportio

Variable Level Univaria

Odds ra

Age (years) 65–69 1.0070–74 1.2875–79 1.6680–84 1.70≥85 2.08

Gender Men 1.00Women 1.56

Residence Urban 1.00Rural 1.14

Marital status Spouse 1.00No spouse 1.92

Economic status Not disadvantaged 1.00Disadvantageda 2.60

Cohabitant Family 1Single 1.95

Education (years) ≥7 1.001–6 2.100 3.58

Illiteracy No 1.00Yes 2.48

Smoking No 1.00Yes 1.30

Alcohol (standard units/day) 0 1.00≤1 0.62≤2 0.65≥3 0.84

Exercise (MET) Mild 1.00Moderate 0.63Severe 0.57

Head traumab No 1.00Yes 1.83

MMSE Z score ≥−1.0 1.00−1.0bZ≤−1.5 1.36b−1.5 1.93

CI = confidence intervals; MET = Metabolic Equivalent of Task.a Covered by National Medical Aid.b Presence of previous head trauma with loss of consciousness longer than 10 m

3.2. Prevalence rates of LLD

As Table 2 shows, the estimated crude prevalence rateswere 10.1% (95% CI=9.4–10.9) for possible depression,

nal odds models.

te model Multivariate model

tio 95% CI Odds ratio 95% CI

– 1.00 –

(1.10–1.48) 1.17 (1.00–1.37)(1.42–1.95) 1.27 (1.07–1.51)(1.40–2.06) 1.12 (0.90–1.39)(1.66–2.60) 1.01 (0.78–1.31)– 1.00 –

(1.39–1.76) 1.07 (0.90–1.27)– 1.00 –

(1.01–1.28) 0.86 (0.75–0.98)1.00

(1.71–2.15) 1.14 (0.96–1.35)– 1.00 –

(2.19–3.07) 1.86 (1.55–2.24)1

(1.71–2.22) 1.38 (1.17–1.64)– 1.00 –

(1.80–2.45) 2.03 (1.72–2.41)(3.06–4.17) 2.85 (2.33–3.49)– 1.00 –

(2.14–2.87) 1.22 (1.02–1.48)1.00

(1.11–1.51) 1.44 (1.20–1.73)1.00

(0.52–0.74) 0.81 (0.67–0.98)(0.46–0.91) 0.86 (0.60–1.23)(0.68–1.04) 1.01 (0.79–1.30)

1.00(0.55–0.72) 0.66 (0.57–0.76)(0.50–0.66) 0.65 (0.56–0.76)– 1.00 –

(1.55–2.17) 1.67 (1.40–2.00)– 1.00 –

(1.15–1.60) 1.36 (1.14–1.62)(1.70–2.19) 2.01 (1.75–2.32)

in.

38 J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

17.5% (95% CI=16.6–18.5) for probable depression, and27.7% (95% CI=26.5–28.8%) for overall depression. The prev-alences of probable and possible depression were higher forolder, female, and less educated individuals. The estimatedage-, gender-, education-, and urbanicity-standardized prev-alences among Koreans aged 65 years or more were 10.1%(95% CI=9.3–10.8) for possible depression, 17.8% (95%CI=16.8–18.7) for probable depression, and 27.8% (95%CI=26.7–29.0) for overall depression.

3.3. Risk factors of LLD

Table 3 shows the factors we found to be in associationwith LLD through our univariate and multivariate models ofestimated crude odds ratios (hereafter, ORs), including allcovariates' simultaneously estimated adjusted ORs. The uni-variate model showed older age, female gender, absence ofa spouse, poverty, living alone, low education, illiteracy,smoking, history of head trauma, and low MMSE associatedwith increased depression risk and that moderate alcoholuse and exercise associated with decreased depression risk.Among these factors, the multivariate model showed olderage, poverty, living alone, low education, illiteracy, smoking,history of head trauma, low MMSE score, exercise, and mod-erate alcohol use remained significant.

4. Discussion

This study estimates prevalence rates for possible andprobable depression in Korean elders as 10.1% and 17.8%, re-spectively. Although both possible and probable depressionincrease in prevalence at greater ages, this age-associated de-pression risk peaks at 75–79 years and decreases thereafter.Although both possible and probable depression were moreprevalent in women than in men, this female preponderancelacks statistical significance after we adjust for other risk fac-tors. Probable depression accounted for more of the depres-sion in the oldest-old group (85+ years old) than in theyoung-old group. In line with many previous studies, pover-ty, living alone, low education, illiteracy, smoking, history ofhead trauma, and cognitive impairment associate with in-creased risks of depression, whereas exercise and mild alco-hol use associate with decreased risks of depression.

Currently, researchers employ various depression ques-tionnaires for screening subjects in or out for a wide rangeof studies, including epidemiological studies, biological stud-ies, and clinical trials. The GDS, (Yesavage et al., 1982) one ofthe most widely-used screening instruments for LLD, is a 30-item, easy-to-administer inventory (Bae and Cho, 2004). Toshorten the screening procedure for depression, Sheikh andYesavage developed the SGDS, using the 15 items from theoriginal GDS that had the highest correlations with depres-sive symptoms. The SGDS takes an average of 5–7 min tocomplete (Sheikh and Yesavage, 1986). In previous studieson prevalence of geriatric depression, SGDS cut-off scoresfor defining clinically significant depression varied widely,from 5 to 11 (Chi et al., 2005; Garcia-Pena et al., 2008; Papa-dopoulos et al., 2005; Romero et al., 2005; Wada et al., 2004,2005), and researchers and clinicians conventionally use acutoff score of 6–8 to indicate significant current depressivesymptomatology, or “caseness.” However, the diagnostic

accuracy and optimal cut-off score of the SGDS for MDDmay vary widely between ethnicities and countries, sinceethno-cultural factors influence the manifestation of depres-sive symptoms and, thus, individuals' responses to depres-sion questionnaires (Lee et al., 2011). In elderly Koreans,the optimal cutoff score of the SGDS-K for MDD was 9/10(sensitivity=0.7419, specificity=0.8587), which was higherthan such scores are for Caucasian populations. According toour previous study, this high cutoff score for MDD in elderlyKoreans could be attributable to these individuals' culturallydetermined response styles, particularly to Koreans' reluc-tance to endorse positive feelings (Lee et al., 2011). One-third of the SGDS-K items are positive questions: “Are youbasically satisfied with your life?”; “Are you in good spiritsmost of the time?”; “Do you feel happy most of the time?”;“Do you think it is wonderful to be alive now?”; and “Doyou feel full of energy?”

Assuming that sensitivity and specificity of probable de-pression defined by the SGDS-K score of 10 or higher forMDD are 0.7419 and 0.8587 respectively according to Baeand Cho (2004), the number of MDD patients in our popula-tion was estimated to be 339 (crude prevalence=5.63%).This is quite comparable to the prevalence of MDD in an el-derly Korean population (5.37%) (Park et al., 2010) whichwas estimated using the Mini International NeuropsychiatricInterview (MINI) (Youu et al., 2006) according to the DSM-IVdiagnostic criteria. In previous epidemiologic studies usingthe SGDS, researchers estimate the prevalence rates of LLDto be 12.5–33.8% in Eastern countries(Chi et al., 2005; Wadaet al., 2004, 2005) and 5.4–27.0% in Western countries(Papadopoulos et al., 2005; Romero et al., 2005). This vari-ability in prevalence estimates between countries could beattributable to methodological differences, such as variationsamong study designs and cutoff scores for diagnosing clini-cally significant depression, or to true differences in popula-tion characteristics, such as incidences of depression,mortality after onset of depression, and/or the examined so-cieties' demographics.

In our previous study, we found that MDD in late life wasmore prevalent in Korea than in most of the Western coun-tries and other Asian countries including Japan (Park et al.,2010). Although various cutoff points as well as cross-cultural and geographical variations precluded firm conclu-sions about the difference in the prevalence rates betweencountries, the prevalence of LLD using the SGDS also seemshigher in Korea than in other Eastern countries as well as inWestern countries. A large population-based study(N=5363) from Japan, employing the same SGDS cutoffscore for depression as our study, reported the prevalenceof LLD to be 11.3% (95% CI=8.4–12.0%) (Wada et al., 2004),which is much lower than that of the present study. If we de-fine LLD using an SGDS-K score of 9 or higher, giving a sensi-tivity (77%) and specificity (77%) for MDD comparable to thesensitivities (70–85%) and specificities (70–77%) of otherstudies' SGDS cutoff scores (Gerety et al., 1994; Lesher andBerryhill, 1994), we find an estimated LLD prevalence of22.4%, which is still higher than that in other countries(12.5–21.7%) (Chi et al., 2005; Garcia-Pena et al., 2008;Romero et al., 2005).

Korea might be transitioning from a low incidence-highrecognition to a high incidence-low recognition society with

39J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

regard to LLD. As we suggest in our earlier study, this highprevalence of LLD in Korean elders could possibly be attribut-able to the tremendous sociocultural, economic, and politicalchanges Korea has undergone during the past few decades(Park et al., 2010). The rapid shift from extended to nuclearfamily structures in Korea might have reduced the recogni-tion of LLD. Reportedly, only 7.4% of MDD patients in Koreapresently receive treatment with antidepressants (Ohayonand Hong, 2006). One study finds that community-basedscreening for depression in Japan reduced the suicide ratein the elderly (Oyama et al., 2010). Such screening mayhave even greater effectiveness in Korea, since the preva-lence of LLD in Korea is markedly higher than that in Japan.

In a previous study that was conducted on a regional ruralsample 12 years before the current study and employed theSGDS-K score of 9/10 as the cutoff for LLD as in currentstudy (Cho et al., 1998), the estimated prevalence of LLDwas 15.8%, which is lower than that in rural sample of currentstudy (19%). This suggests that the prevalence of LLD couldhave been increasing in Korean elders for a decade. The Kore-an Epidemiologic Catchment Area Studies, conducted in 2001and 2006 (Cho et al., 2004, 2009), also found the prevalenceof MDD in Korea increased 1.3% over the 5 years.

In accordance with previous studies, this study finds prev-alence rates of depression increase with advancing age,which could be attributable, at least in part, to the concomi-tant increase in physical morbidities. In our population, therisk of depression peaks at 75–79 years of age and decreasesthereafter. Either low survival rates or selection bias due tothe disabilities associated with physical comorbidities mightcontribute to lowering the risk of depression in the oldestgroup. In addition, adverse life events, such as the deaths ofone's spouse and friends, that could precipitate depressionmight be more common for Koreans in their late seventies,since Koreans' mean life expectancy is 79.4 years (OECD,2009).

It is notable that there is no clear association betweengender and depression in this study. Both probable and pos-sible depression were more prevalent in women, but genderwas not a significant risk factor for depression, per the multi-variate analysis (OR=1.07, 95% CI=0.90–12.7), indicatingthat gender effect was mainly due to gender-related changesin risk factors rather than to gender itself. Researchers haveattributed gender differences in the risk of depression to dif-ferences between the genders in their socioeconomic status-es, physical functioning, and social roles with aging(Takkinen et al., 2004). Although many reports support theassociation between being female and the risk of depression(Djernes, 2006), this female preponderance has not beenconsistently replicated and decreased in the oldest popula-tions (Skoog et al., 1993). This discrepancy could be attribut-able to the differences in the risk factors that can confoundthe association between gender and depression, such as cog-nitive impairment, low socioeconomic status, living alone,widow/widower status, and social isolation (Papadopouloset al., 2005).

Consistent with our earlier observations (Shin et al.,2008), the present study found that lack of cohabitants asso-ciates with a higher risk of LLD. In our previous study, lack ofcohabitants associated strongly with poor social support, par-ticularly with lack of positive social support, which is a strong

risk factor for depression in elderly Koreans. Low educationalattainment and, possibly, illiteracy also correlated withpoorer social support. In the present study, Illiteracy was as-sociated with the risk of depression independently from loweducational attainment, indicating that illiteracy might con-fer a risk of depression beyond the influence of lack of formaleducation per se. Low self-efficacy, which is common in peo-ple with limited literacy, might contribute to the depressionrisk that is attributable to illiteracy (Weiss et al., 2006). Illit-erate persons might have little belief in their ability to takeactions that influence the events affecting their lives andthereby become prone to higher levels of depression. Recentstudies demonstrate that enhancing self-efficacy through im-proving literacy might improve depressive symptoms (Weisset al., 2006). Since illiteracy remains common among elderlyKoreans (13.7%, in the present study), interventions to im-prove literacy could help reduce the LLD prevalence in Korea.

History of head trauma and smoking was also associatedwith the risk of depression. Traumatic brain injury, evenwhen mild, can increase the risk of depression, particularlyin elderly individuals (Rao et al., 2010). Depression can man-ifest shortly after the injury or well into the future, and its'prevalence ranged widely, from 18.5% to 61.0% (Kim et al.,2007). Smoking is consistently associated with the risk of de-pression. Although the underlying mechanisms giving rise tosuch associations remain unclear, a unidirectional effect ofnicotine on neurotransmitters might underlie the increasedrisk of depression in smokers (Boden et al., 2010).

Mild alcohol use (less than 1 standard drink daily) andmoderate to intense exercise were associated with lowerrisks of depression in this study. Since the relationship be-tween depression and alcohol consumption is J-shaped orU-shaped, the rate of depression is lowest in light drinkers(Alati et al., 2005). Previous studies report that physical inac-tivity was associated with depression and that resumption ofphysical activity improved depression, (Farmer et al., 1988)indicating that changes in physical activity could relate to de-pression causally (Fukukawa et al., 2004).

This study has some strengths: a large representativesample of Koreans aged 65 years or older; a good participa-tion rate; and a sizeable sample over age 85. This study alsohas some limitations: LLD was defined by SGDS-K scores in-stead of a standardized clinical interview; non-responderscould be in poorer health than are responders, which mightresult in an underestimation of the prevalence of depression,and the failure to consider certain known depression risk fac-tors, such as history of MDD and comorbid cerebrovascular orcardiovascular diseases.

In conclusion, LLD seems more prevalent in Korea than inother countries, which may contribute to the highest suicidalrate of elderly Koreans in the world. In addition, gender dif-ference in the risk of depression was not evident in late life.

Role of funding sourceThis study was supported by a research grant from the Ministry of

Health, Welfare, and Family Affairs, Korea (Grant No. 07-2008-0270) and agrant of the Korean Health Technology R&D Project, Ministry for Health,Welfare, and Family Affairs, Republic of Korea (Grant No. A092077).

Conflict of interestThe authors have no conflicts of interest to report in relation to the re-

search presented in this manuscript.

40 J.H. Park et al. / Journal of Affective Disorders 138 (2012) 34–40

AcknowledgmentsWe thank all the participants who so generously gave us their time and

support.

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