Trajectory classes of depressive symptoms in a community sample of older adults

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<ul><li><p>Trajectory classes of depressive symptomsin a community sample of older adults</p><p>Introduction</p><p>Our focus is on a little-studied area the naturalhistory of depressive symptomatology in oldercommunity residents. There are many studies of</p><p>the prevalence, but fewer of the incidence ofdepression in the elderly. They tend to agree thatdepression is less prevalent in older than inyounger groups, but may increase in the oldestold (13). There is inconsistent agreement with</p><p>Kuchibhatla MN, Fillenbaum GG, Hybels CF, Blazer DG. Trajectoryclasses of depressive symptoms in a community sample of older adults.</p><p>Objective: To identify trajectories of depressive symptoms in oldercommunity residents.Method: Depressive symptomatology, based on a modied Center forEpidemiological StudiesDepression scale, was obtained at years 0, 3,6, and 10, in the Duke Established Populations for EpidemiologicStudies of the Elderly (n = 4162). Generalized growth mixture modelsidentied the latent class trajectories present. Baseline demographic,health, and social characteristics distinguishing the classes wereidentied using multinomial logistic regression.Results: Four latent class trajectories were identied. Class 1 stablelow depressive symptomatology (76.6% of the sample); class 2 initially low depressive symptomatology, increasing to thesubsyndromal level (10.0%); class 3 stable high depressivesymptomatology (5.4%); class 4 high depressive symptomatologyimproving over 6 years before reverting somewhat (8.0%). Class 1 wasyounger, male gender, with better education, health, and socialresources, in contrast to class 3. Class 2 had poorer cognitivefunctioning and higher death rate. Class 4 had better health and socialresources.Conclusion: Reduction in high depressive symptomatology isassociated with more education, better health, fewer stressful events,and a larger social network. Increasing depressive symptomatology isaccompanied by poorer physical and cognitive health, more stressfullife events, and greater risk of death.</p><p>M. N. Kuchibhatla1,2,G. G. Fillenbaum1,3, C. F. Hybels1,4,D. G. Blazer1,41Center for the Study of Aging and HumanDevelopment, Duke University Medical Center, Durham,NC, 2Department of Biostatics and Bioinformatics, DukeUniversity Medical Center, Durham, NC, 3GeriatricsResearch, Education, and Clinical Center, VeteransAdministration Medical Center, Durham, NC and4Department of Psychiatry and Behavioral Sciences,Duke University Medical Center, Durham, NC, USA</p><p>Key words: depressive symptomatology; trajectories;community sample; longitudinal; elderly</p><p>Maragatha N. Kuchibhatla, Box 3003, Center for theStudy of Aging and Human Development, Duke Uni-versity Medical Center, Durham, NC 27710, USA.E-mail: mnk@geri.duke.edu</p><p>An earlier version of this paper was presented at theannual scientific meeting of the Gerontological Societyof America, New Orleans, November 21, 2010.</p><p>Accepted for publication October 21, 2011</p><p>Significant outcomes</p><p> Over a 10 year period, depressive symptoms remained stable for 82% of the sample (few symptomsfor 77%, many symptoms for 5%).</p><p> The 10% whose depressive symptoms increased had poorer cognitive functioning, possibly indicativeof a developing dementing disorder.</p><p> The 8% whose depressive symptoms declined had better health and social resources.</p><p>Limitations</p><p> Limited sample size for some trajectories, and high mortality restricted ability to take interveningevents into account.</p><p> Our measure is of depressive symptomatology; although well accepted in epidemiological studies, it isnot a measure of clinical depression.</p><p>Acta Psychiatr Scand 2012: 125: 492501All rights reservedDOI: 10.1111/j.1600-0447.2011.01801.x</p><p> 2011 John Wiley &amp; Sons A/SACTA PSYCHIATRICA</p><p>SCANDINAVICA</p><p>492</p></li><li><p>respect to the demographic characteristics withwhich depression is associated (age, gender, edu-cation, income, race ethnicity), and whetherdepression is a risk factor for or a consequence ofcertain physical and mental health conditions andfunctional diculty (1, 2, 414). There is, however,good agreement that social ties and stressful lifeevents are associated with depression (6, 1519),that comorbid medical conditions may portend apoorer outcome, and that depressive symptoms arecostly to the health system and may increase risk ofdeath (2022).To date, the history of depression in older adults</p><p>has focused primarily on those already depressed,and determining the course of their disease (2327).The main patterns of the natural history ofdepressive symptoms their increase and decline have rarely been examined (6), and in an olderpopulation are barely known (10, 17).Cui et al. (17) used longitudinal cluster analysis</p><p>to examine the course of depression over 2 years inprimary care patients present throughout(n = 319, 81.4% of the initial sample; non-compl-eters excluded). They argued that such patientswere representative of persons their age, since mostolder people do seek primary care, but few olderpersons with signicant depression go to a special-ist. Diagnosis and severity were based on theStructured Clinical Interview for DSM-III-R(SCID), and the Hamilton Rating Scale forDepression. Importantly, patients ranged fromthose with no depression to those with majordepressive disorder. Six longitudinal clusters bestdescribed the ndings. Three clusters were constantover the 2 years: cluster 1, consistently non-depressed (48.6%); cluster 3, consistently at asubsyndromal level (21.6%); and cluster 5, consis-tently at a depressed level (4.7%). Of the threeremaining clusters, two indicated increased depres-sion: cluster 4 (11.9%), started as non-depressed,but became subsyndromal; cluster 6 (5.6%) declin-ing from the subsyndromal level to major depres-sion. One cluster improved from minor depressionto subsyndromal non-depressed (cluster 2, 7.5%).The only characteristics that distinguished theclusters in multivariate analysis were score on theCumulative Illness Rating Scale, the Hamiltondepression rating scale, and functional status.Lincoln and Takeuchi (10) used data gathered</p><p>on four occasions over 16 years in the AmericansChanging Lives Study (n = 3482 African-Ameri-cans and Whites age 25 and over at baseline, 34%age 65+). Depressive symptomatology was deter-mined by an 11-item Center for EpidemiologicalStudies-Depression (CES-D) scale (28). Informa-tion on subjects who dropped out during the study</p><p>was included to the extent that it was present. Fourtrajectories of depressive symptomatology wereidentied using growth mixture modeling. Twotrajectories were stable, one of low symptomatol-ogy (68.4% of the sample), and one of highsymptomatology (4.8%). Two trajectories showedchange: initially high symptoms in which symp-toms improved (15.4%), and initially low symp-toms, in which symptoms increased (11.4%).Although there is good agreement between thesetwo studies, information from additional represen-tative samples of older community residents isdesirable.</p><p>Aims of the study</p><p>The present study identies 10-year latent classtrajectories of depressive symptomatology in anolder community-representative sample, and deter-mines whether these trajectories can be distin-guished at baseline by their demographiccharacteristics, health status, social factors, andby risk of death. We also examine potentialpredictors of risk for and improvement fromdepressive symptoms.</p><p>Material and methods</p><p>Sample</p><p>Data came from sample members of the DukeEstablished Populations for Epidemiologic Studiesof the Elderly (Duke EPESE) residing in oneurban, and four rural counties in the north-centralPiedmont of North Carolina (29, 30). Of the 5221persons age 65 and over who were selected usingstratied random household sampling, 4162 (80%)were successfully interviewed. Of these, 2261 (54%)were African-American, who were deliberatelyover-sampled to improve statistical precision forthis group. African-Americans represent 35% ofthe older population in the geographical area. Ofthe remainder, 1875 (45%) were White, and 26were of other race ethnicity; 35% were of malegender. Roughly half came from the urban andhalf from the rural counties. Sample members wereinterviewed in person at home at baseline(1986 1987), and 3, 6, and 10 years later, withtelephone contact at follow-up years 1, 2, 4, and 5.Information on depressive symptomatology wasobtained only at the in-person interviews. Attritionfor reasons other than death was minimal. Annualresponse rates of survivors ranged from 93.7% to98.7% through the rst seven waves, and 92.3%(n = 1767) at the nal wave. For the current studywe excluded the sample members of other race,</p><p>Trajectory classes of depressive symptoms</p><p>493</p></li><li><p>and those who provided no information ondepressive symptomatology at baseline (162proxy respondents, 3 others), yielding an analysissample of 3973 persons. This study was carried outwith permission from the Duke InstitutionalReview Board. All participants provided signedconsent.</p><p>Data gathered</p><p>Information on depressive symptomatology wasobtained using a modied version of the 20-itemCenter for Epidemiological Studies-Depression(CES-D) scale (28). Response on each item wason a 2-point rather than a 4-point scale, indicatingpresence or absence of the symptom in the pastweek. Where relevant, items were reverse coded, sothat the sum of the responses indicated the numberof depressive symptoms endorsed. A value of nineor greater on this modied CES-D (from a possiblerange of 020) has been found to be equivalentto a score of 16 or greater on the originalscale, indicating clinically relevant depressivesymptomatology (29).</p><p>Explanatory variables</p><p>Since previous reports indicated that at least onelatent class was likely to represent a small per centof the sample (e.g. 5%), and analysis requiredmultiple comparisons, we were necessarily parsi-monious in selecting variables that, nevertheless,were expected to represent the three areas ofprimary interest: demographic, health, and social.Demographic characteristics the basic demo-</p><p>graphic information considered included age (con-tinuous), race, gender, and education (continuous,but capped at 17 years).Health was assessed by three items. Two items</p><p>were indicative of physical health: self-rated health[excellent (1), good, fair, poor (4)], and a functionalstatus measure based on the sum of basic activitiesof daily living [ADL; 5 items (31)], OARS instru-mental ADL items [7 items (32, 33)], and abbre-viated RosowBreslau scale [3 items, primarilymobility (32)], that could not be performed inde-pendently (possible range for the sum of the threemeasures: 015) (34). Cognitive status was assessedby number of errors on the 10-item Short PortableMental Stratus Questionnaire [SPMSQ (35), pos-sible range 010]. Error scores were not correctedfor race or education, since both of these variableswere included in the model.Social characteristics were assessed by the sum</p><p>of stressful life events, e.g. divorce; death of spouse,child or friend; nancial decline; relocation</p><p>[possible range 014 (36)]; a scale of social inter-action with others (summarizing ve variablesmeasuring frequency of contact with friends andrelatives, and membership in social organizations,possible range 039); and network size (summar-izing seven variables on number of relatives andclose friends, possible range 049).Survival status for all participants, survival</p><p>status through December 31, 1998 (12 years postbaseline) was determined by search of NationalDeath Index records.</p><p>Statistical analyses</p><p>Initial analyses included basic descriptive statistics.Statistical software, M-plus version 5.1 (37) wasused to identify distinct trajectories of CES-Dscores using generalized growth mixture models(GGMM). The analyses started with an interceptonly model, to which linear and quadratic growthfactors were added to determine the forms of thegrowth model. A piecewise linear model best t thedata. The number of latent classes was determinedby sequentially increasing the number of classes,and examining t statistics including Akaikeinformation criteria (AIC), Bayesian informationcriteria (BIC), sample size adjusted BIC (SSABIC),entropy and condition number. We also conductedsequential tests to determine if the decrease inlikelihood ratio with increase in classes was statis-tically signicant using the Lo-Mendell-Rubin test.Models were tested with a number of start valuesto ensure that proper solution was obtained. Inaddition, bootstrap-based testing, and theoreticaland other considerations were used to determinethe number of classes. The trajectories were iden-tied based on CES-D scores alone. Associationsbetween classes and categorical variables wereassessed using chi-squared tests, whereas associa-tions between classes and continuous variables weredetermined using non-parametric Wilcoxon tests.Multinomial logistic regression, with the most</p><p>prevalent class as the referent, was used to deter-mine the predictors of depressive symptomatologytrajectory classes. The three groups of potentialpredictor variables (demographic, health, andsocial characteristics) constituted three chunks.To control for type 1 error, the signicance ofeach group of variables was assessed separately in achunk test. If a chunk was signicant, the signif-icant variables in the chunk were included in a nalmodel. All three chunks were signicant. Althoughage was not signicant in the demographic chunk,we nevertheless included it because of its relevancein a study of older persons. The nal modelincluded gender, race, age and education; self-rated</p><p>Kuchibhatla et al.</p><p>494</p></li><li><p>health, functional status, and cognitive status; andstressful life events, social network, and socialinteraction. All data were run unweighted, sinceweighting methods were not available for allstatistical procedures. sas version 9.2 (SAS, Cary,NC, USA) was used for the logistic regression anddescriptive analyses.</p><p>Results</p><p>At baseline, the sample ranged in age from 65 to105 years, 54% were African-American, 35%(both African-Americans and Whites) were men.Over half had not gone beyond grade school.Health was rated between good and fair.A substantial proportion reported impairment inmobility and instrumental ADL, but few had anybasic ADL impairments. On average, cognitivestatus was in the unimpaired range. At baseline, amajority had experienced one stressful life event[mean (standard deviation) 0.67 (0.95)]; meannetwork size was 13.82 (7.10), and mean socialinteraction was 13.97 (6.76). The mean CES-Dscore was 3.2 (3.4), with 9.6% reporting nine ormore depressive symptoms. In the early yearsapproximately 5% of the sample died each year,the percentage dying each year increasing with theage of the study.A four class model best t the data. Participants</p><p>were assigned to the class to which they had thehighest probability of belonging. The four trajec-tory classes were a stable class with few depressivesymptoms (n = 3043; 76.6%); a stable class withmany depressive symptoms (n = 216; 5.4%),where stable indicates consistency in number ofdepressive symptoms (score on the CE...</p></li></ul>

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