Short-Term Trajectories of Depressive Symptoms in Stroke Survivors and Their Family Caregivers

Rahul Malhotra, MBBS, MD, MPH,*† Choy-Lye Chei, PhD,* Edward Menon, FAMS (Rehab Med),‡ Wai Leng Chow, MBBS, GDFM,§ Stella Quah, PhD,* Angelique Chan, PhD,*† and David Bruce Matchar, MD*

Goal: We utilize group-based trajectory modeling (GBTM) to delineate depressive symptom trajectories among stroke survivor–caregiver dyads, to identify predic- tors of the delineated trajectories, and to assess the influence of time-varying covariates (stroke survivor depressive symptoms and functional disability, caregiver depres- sive symptoms, and foreign domestic worker [FDW] assistance) on the level of the depressive symptom trajectories. Methods: Data on 172 stroke survivor–caregiver dyads in Singapore, for whom depressive symptoms were assessed thrice (baseline/3 months/6 months), were utilized. GBTM was applied to delineate depressive symptom trajectories, and to identify their predictors and time-varying covariates. Findings: Three stroke survivor depressive symptom trajectories (low and decreas- ing [47.6%], low and increasing [43.1%], and high and increasing [9.3%]) and 2 caregiver depressive symptom trajectories (low and stable [71.5%] and high and decreasing [28.5%]) were delineated. Caregivers with chronic diseases were more likely (odds ratio [95% confidence interval]: 8.09[2.04-32.07]) and those caring for older stroke sur- vivors (0.94[0.90-0.98]) were less likely to follow the high and decreasing than the low and stable depressive symptom trajectory. An increase in stroke survivor func- tional disability and caregiver depressive symptoms led to a rise (~worsening) in stroke survivor depressive symptom trajectories. Whereas an increase in stroke survivor depressive symptoms led to a rise in caregiver depressive symptom tra- jectories, FDW assistance led to a decline (~improvement). Conclusion: Care professionals should be mindful of heterogeneity in depressive symptom pat- terns over time among stroke survivor–caregiver dyads. Reciprocal association of depressive symptoms in the stroke survivor–caregiver dyad suggests that ad- dressing mood problems in 1 member may benefit the other member, and calls for dyadic mental health interventions. Key Words: Stroke—depression—caregivers— longitudinal studies—Singapore. © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.

From the *Health Services and Systems Research, Duke-NUS Graduate Medical School, Singapore; †Centre for Ageing Research and Ed- ucation, Duke-NUS Graduate Medical School, Singapore; ‡Saint Andrew’s Community Hospital, Singapore; and §Health Services Research, Eastern Health Alliance, Singapore. Received July 21, 2015; revision received September 4, 2015; accepted September 15, 2015. Grant support: Supported by Singapore Ministry of Social and Family Development’s Family Research Fund grant titled “Study of the Impact of Caring for Stroke Survivors on Family Structure and the Mental Health of Caregivers” (FRF-2008-5) and Singapore Ministry of Health’s National Medical Research Council under its Singapore Translational Research Investigator Award (NMRC/STaR/0005/2009) as part of the project “Establishing a Practical and Theoretical Foundation for Comprehensive and Integrated Community, Policy and Academic Efforts to Improve Dementia Care in Singapore.” The content including the methods, findings and results are solely the authors’ responsibility and do not represent the endorsement and views of the grant administering organizations. Department and institution where the work was performed: Health Services and Systems Research, Duke-NUS Graduate Medical School, Singapore. Address correspondence to Rahul Malhotra, MBBS, MD, MPH, Health Services and Systems Research, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857. E-mail: [email protected]. 1052-3057/$ - see front matter © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2015.09.012

172 Journal of Stroke and Cerebrovascular Diseases, Vol. 25, No. 1 (January), 2016: pp 172–181 DEPRESSIVE SYMPTOM TRAJECTORIES 173 Introduction depressive symptom trajectories in various population and patient groups. For example, distinct depressive symptom Depressive symptoms, well-documented among stroke trajectories are reported among the elderly,27 new mothers,28 survivors and their family caregivers,1,2 are associated with and women with acute cardiac events.29 Among caregiv- poorer stroke survivor functional outcomes3,4 and affect ers, distinct depressive symptom trajectories are described caregiver health and quality of life.5,6 Further, the mental in mothers of children with epilepsy,30 spousal demen- health status of stroke survivors and their caregivers is tia caregivers,31 and caregivers of mechanically ventilated mutually associated: stroke survivor distress influences adults.32 In fact, a study comparing growth curve mod- caregiver emotional state,2,7,8 and caregiver depressive symp- eling and GBTM for charting depressive symptoms over toms are in turn associated with poststroke depression.9,10 time favored GBTM.30 Depressive symptoms among stroke survivors and their Using GBTM to delineate distinct depressive symptom caregivers are not static but evolve over time. While in- trajectories among stroke survivors and their caregivers cidence of depression among stroke survivors is highest is beneficial for identifying at-risk individuals. This will in the first month poststroke,11 emergent cases are re- help channel limited resources toward those most likely ported thereafter.11,12 While 1 study observed depressive to follow trajectories indicating increasing depressive symp- symptoms in caregivers to decrease in the first year fol- toms. To our knowledge, no study has utilized GBTM lowing their care recipients’ stroke,13 a longitudinal study for describing stroke caregiver outcomes and only a few of spousal caregivers reported both positive and nega- recent studies have applied it among stroke survivors to tive psychological well-being changes poststroke.7 Given describe trajectories of disability status,33 apathy,34 and psy- the dynamicity of depressive symptoms, it is important chological symptoms.35 The latter 2 studies do focus on to describe their longitudinal pattern for the benefit of mental health constructs but not exclusively on depres- not only care professionals and researchers managing stroke sive symptoms. Further, they do not provide concurrent survivors and their families but also stroke survivors them- trajectories of the outcome among stroke caregivers. A selves and their families. dyadic focus, concurrently considering both stroke sur- Most longitudinal studies on depressive symptoms or vivors and their caregivers, has been called for to expand depression among stroke survivors and their caregivers the horizon of poststroke depression research.36 determine the incidence or baseline predictors of depres- We addresses the limitations of the extant literature, sive symptoms or depression.11,12,14-20 Others, somewhat outlined above, by applying GBTM to longitudinal data simplistically, report average depressive symptoms or from 172 stroke survivors and their family caregivers in changes in average depressive symptoms or proportion Singapore, in whom depressive symptoms were as- with (or without) depression or depressive symptoms above sessed at 3 time points. Singapore is a multiethnic Southeast some threshold at various time points poststroke.7,11,13,15,18,19,21,22 Asian island state, where stroke was the fourth most Relatively few studies detail the longitudinal pattern common cause of death in 2013 and the third most of depressive symptoms.8,14 A 2010 review of studies common cause of overall disease burden in 2010.37 The on stroke caregiving highlighted that only 2 of the 63 study’s objectives were to (1) delineate short-term de- included longitudinal studies described the pattern of pressive symptom trajectories among stroke survivors and caregiver depressive symptoms.14 Further, the review their caregivers, (2) identify stroke survivor and care- commented on infrequent application of complex longi- giver characteristics predictive of trajectory group tudinal data analysis approaches, which take full advantage membership, and (3) assess the influence of time- of longitudinal data, as a key limitation of the extant varying covariates (stroke survivor functional disability literature.14 level, stroke survivor depressive symptoms, caregiver de- When used, the most common longitudinal data anal- pressive symptoms, and foreign domestic worker [FDW] ysis approach in studies of depressive symptoms among assistance) on the level of the delineated depressive stroke survivors or their caregivers is growth curve symptom trajectories. Given the heterogeneity in depres- modeling,8,14 which assumes the presence of a single sive symptom trajectories in other populations,27-32 we “average” depressive symptom trajectory. However, this hypothesized the presence of at least 2 distinct depres- may be inaccurate when there is theoretical or empiri- sive symptom trajectories among stroke survivors and cal support for the presence of population subgroups that among their caregivers. Further, given the reciprocity of vary with respect to the variable of interest over time.23 mental health among stroke survivors and their An alternate approach, group-based trajectory model- caregivers,2,7-10 the association between stroke survivor func- ing (GBTM), assumes the presence of and identifies latent tional disability and psychological outcomes among stroke groups of individuals sharing distinct developmental tra- survivors and their caregivers,2,4,38-40 and the beneficial jectories of the variable of interest, thereby allowing a impact of FDW assistance on family caregivers in better understanding of its longitudinal pattern.24-26 In the Singapore,41 we hypothesized that FDW assistance leads context of the course of depressive symptoms, several to a downward shift (~improvement of depressive symp- studies use GBTM and support the presence of discrete toms) and the rest of the time-varying covariates lead to 174 R. MALHOTRA ET AL. an upward shift (~worsening of depressive symptoms) be established at trajectory initiation,47 baseline inter- in the level of delineated depressive symptom trajectories. view information was used. Predictors considered for stroke survivors were stroke survivor age (years), gender, eth- Materials and Methods nicity (Chinese/non-Chinese), education (no formal or primary/secondary and above), housing (1-3 rooms Study Design and Participants public/4 rooms or more public or private; socioeconom- Participants comprised stroke survivors, admitted to ic status indicator48), chronic disease status (no/yes [self- a community hospital between November 2010 and De- reported high blood pressure/cataract/diabetes/kidney cember 2012 for in-patient rehabilitation subsequent to disease]), and stroke survivor–caregiver relationship acute stroke, and their family caregivers. Of a total of (spouse/child or others). For caregivers, considered pre- 353 stroke survivors meeting the inclusion criteria, 105 dictors were caregiver age, gender, ethnicity, education, were excluded (noncommunicative: 47, no caregiver: 20, housing, chronic disease status (no/yes [self-reported ar- cognitive impairment: 13, could not be contacted within thritis or rheumatism/asthma/cancer or leukemia/ 6 weeks of stroke: 14, supervening event: 11). Further, cataract/diabetes/stroke/heart problems/high blood in 57 (23.0%) of the 248 eligible stroke survivor– pressure/kidney disease]), stroke survivor–caregiver re- caregiver dyads, 1 or both members refused participation. lationship, and stroke survivor age. Thus, at baseline, which on average was 4.7 weeks (range: 0-54.5) poststroke, 191 stroke survivor–caregiver dyads Time-Varying Covariates were interviewed at the community hospital. Subse- Stroke survivor functional disability is associated with quently, the dyads were interviewed twice at their home: the mental health of stroke survivors and their first follow-up, on average 15.4 weeks (9.5-30.3) poststroke caregivers.2,4,38-40 Further, there is evidence of a recipro- (146 dyads interviewed at home) and second follow-up, cal association of mental health between stroke survivors on average 28.5 weeks (23.7-47.4) poststroke (134 dyads and their caregivers.2,7-10 Assistance from an FDW (hiring interviewed at home). The study was approved by the of live-in FDWs, mostly women from neighboring low- institutional review board of National University of Sin- income countries, to help in household chores and assist gapore. Written informed consent was obtained from all family caregivers is common in Singapore) in caring for participants. an older person is reported to benefit family caregivers.41 In the current study, stroke survivor functional disabil- Trajectory Variable: Depressive Symptoms ity, stroke survivor and caregiver depressive symptoms, The 20-item Center for Epidemiologic Studies Depres- and FDW assistance (yes/no) evolved over time. In the sion scale (CES-D)42 was administered to the stroke context of GBTM, such variables are considered as time- survivors and caregivers at the 3 interviews. The CES- varying covariates influencing the level of a trajectory (i.e., D, validated in Singapore,43 has been used among stroke upward or downward shift). Thus, these variables were survivors and their caregivers.44,45 Individual CES-D items evaluated as time-varying covariates, as appropriate: stroke (score 0 [rarely/none] to 3 [most/all the time], depend- survivor functional disability and caregiver depressive ing on how often the respondent felt during the past week) symptoms as time-varying covariates of stroke survivor were added to arrive at total depressive symptoms; higher depressive symptom trajectories, stroke survivor func- values indicate higher level of depressive symptoms. Total tional disability and depressive symptoms, and FDW depressive symptoms were prorated for those missing re- assistance as time-varying covariates of caregiver depres- sponses on 1 or 2 items (stroke survivors: n = 49 at baseline, sive symptom trajectories. Stroke survivor functional 3 at first, and 1 at second follow-up; caregivers: n = 17 disability was assessed using the modified Barthel Index,49 at baseline and 1 at first follow-up) and were treated as which measures degree of independence from any as- missing for those missing responses on more than 2 items sistance in 10 domains of functioning. It provides a total (stroke survivors and caregivers: n = 5 at baseline). Across score ranging from 0 (fully dependent) to 100 (fully in- the 3 interviews, depressive symptoms ranged from 0 to dependent). For our analysis, we reversed the modified 55 for stroke survivors and from 0 to 42 for caregivers. Barthel Index score to a functional disability score—a higher Depressive symptoms of 16 or above denote clinically sig- score indicates greater functional disability. nificant depressive symptoms (CSDS).46 Analysis Cohort Predictors of Trajectory Group Membership The “time” variable for defining depressive symptom Variables considered or reported to be associated with trajectories was weeks poststroke. GBTM necessitates the depression/depressive symptoms among stroke survi- “time” pertaining to each point constituting a trajectory vors and/or caregivers38,39 and deemed to be constant over to be exclusive. Thus, 3 mutually exclusive trajectory time time were evaluated as predictors of depressive symptom points, 0-10 weeks (T0), 11-22 weeks (T1), and 23-47 weeks trajectory group membership. Since such predictors should (T2) poststroke, corresponding closely with the timing of DEPRESSIVE SYMPTOM TRAJECTORIES 175 the 3 interviews, were used for developing the trajecto- trajectories were identified similarly. All analyses were ries. A total of 12 dyads were deleted as the timing of performed using SAS for Windows Version 9.3 (SAS In- one or more of their 3 interviews disallowed inclusion stitute Inc.). in the specified trajectory time points. Further, 7 dyads In the sensitivity analysis, determination of the best- for which stroke survivor/caregiver depressive symp- fitting GBTM model and significant covariates, for stroke toms (4 dyads) or stroke survivor functional disability survivors and for caregivers, was done only among the (3 dyads) was unavailable at any of the 3 time points 129 dyads contributing to all 3 trajectory time points. were excluded. Thus, the analysis cohort comprised 172 stroke survivor–caregiver dyads, which had informa- Results tion on depressive symptoms for both members at least at 1 trajectory time point. While 167 dyads contributed The distribution of predictors and time-varying covariates to T0, 135 and 129 dyads contributed to T1 and T2, re- is presented in Tables 1 and 2, respectively. While average spectively; 129 dyads contributed to all the 3 time points. depressive symptoms remained relatively stable over time There was no significant difference in values of predic- for stroke survivors, they declined over time for caregivers. tor variables or T0 value of time-varying covariates, The best-fitting stroke survivor GBTM model was the − including stroke survivor and caregiver depressive symp- one specifying 3 trajectory groups. Its BIC value ( 1635.0) − toms, among the 129 dyads contributing to all 3 time points was closer to 0 than those specifying 2 ( 1639.9) or 4 − and 43 dyads contributing to only 1 or 2 time points. ( 1638.7) groups. The average posterior probability value of all 3 groups exceeded .80. Based on their trajectories (Fig 1), the distinct stroke survivor depressive symptom Statistical Analysis trajectory groups were labeled low and decreasing, low and GBTM,24 operationalized through Proc Traj in SAS (SAS increasing, and high and increasing. The low and decreas- Institute Inc., Cary, NC),25,47 was used to delineate the de- ing group depressive symptom trajectory, comprising 47.6% pressive symptom trajectory groups. GBTM identifies stroke survivors, sloped down over time, starting just above groups of individuals who follow a similar pattern of an outcome/behavior (trajectory variable) over time. Em- Table 1. Distribution of predictor variables* ploying maximum likelihood methods for parameter 25,47 estimation, GBTM allows for inclusion of individu- Stroke survivors Caregivers als who have trajectory variable data for even 1 trajectory (N = 172) (N = 172) time point. Variable % or mean ± SD % or mean ± SD Determination of the appropriate number of trajecto- ± ± ry groups was done by considering model fit statistics Age (years) 71.6 12.2 49.9 12.4 (Bayesian information criteria [BIC]: value closer to 0 is Gender Male 48.8 38.4 better), leaning toward parsimony in the number of tra- Ethnicity jectory groups. Models were fit separately for stroke Chinese 79.2 79.7 survivors and for caregivers, consecutively increasing the Non-Chinese 20.8 20.3 number of specified trajectory groups. The functional form Education (linear or polynomial) of the trajectory for each group No formal 76.7 24.4 was based on significance of polynomial terms, starting education or with a cubic (up to time3) specification, then iteratively primary dropping nonsignificant (P value > .05) polynomial terms; Secondary and 23.3 75.6 linear terms were retained irrespective of significance. If above specification of an additional trajectory group resulted Housing in an increase in BIC, then the more parsimonious model 1-3 rooms, public 32.0 27.9 4 rooms or more, 68.0 72.1 (without the additional trajectory group) was chosen. In- public or private ternal reliability was assessed by comparing the average Chronic diseases predicted posterior probability of membership against a One or more 87.8† 34.9‡ 26 threshold of .70. Caregiver is the stroke survivor’s. . . Potential covariates were assessed once the best- Spouse — 22.7 fitting GBTM models were determined. For stroke survivor Child or others — 77.3 depressive symptom trajectories, each applicable poten- tial predictor and time-varying covariate was first added Abbreviation: SD, standard deviation. to the best-fitting model on its own (~bivariate analy- *Values correspond to those elicited in the baseline interview (~tra- ≤ jectory time point T1). sis). Those significant (P value .05) were then considered †High blood pressure/cataract/diabetes/kidney disease. in a multivariate model. Significant predictors and time- ‡Arthritis or rheumatism/asthma/cancer or leukemia/cataract/ varying covariates for caregiver depressive symptom diabetes/stroke/heart problems/high blood pressure/kidney disease. 176 R. MALHOTRA ET AL. Table 2. Distribution of time-varying covariates Table 3. Time-varying covariates influencing level of the trajectory of the 3 stroke survivor depressive symptom Variable % or mean ± SD trajectory groups: multivariate analysis*

Stroke survivor functional disability Shift in trajectory = ± At T0 (n 166) 57.0 25.2 per unit change in = ± At T1 (n 133) 36.2 25.2 Time-varying time-varying = ± At T2 (n 129) 31.8 23.6 covariate covariate (95% CI)† P value Assistance from an FDW—yes At T0 (n = 172) 30.8 Stroke survivor functional disability At T1 (n = 139) 46.8 Low and .05 (−.01, .11) .130 At T2 (n = 125) 60.8 decreasing group Stroke survivor depressive symptoms Low and .27 (.05, .49) .015 At T0 (n = 167) 21.3 ± 10.0 increasing group At T1 (n = 135) 23.4 ± 12.1 High and .14 (−.003, .28) .055 At T2 (n = 129) 21.3 ± 12.0 increasing group Caregiver depressive symptoms Caregiver depressive symptoms At T0 (n = 167) 15.7 ± 10.5 Low and .42 (.30, .54) <.001 At T1 (n = 135) 9.6 ± 7.6 decreasing group At T2 (n = 129) 8.9 ± 8.2 Low and .57 (.13, 1.01) .012 increasing group Abbreviations: FDW, foreign domestic worker; SD, standard High and .55 (.17, .92) .004 deviation. increasing group

Abbreviation: CI, confidence interval. the CSDS threshold and moving below it by T1. The low *Only predictors and time-varying covariates significant in the bi- and increasing group trajectory, comprising 43.1% stroke variate analysis were included. survivors, was curvilinear with depressive symptoms being †Positive values indicate an upward shift and negative values in- highest at T1. The lowest proportion (9.3%) was classi- dicate a downward shift. fied into the high and increasing group, whose trajectory started high and sloped up over time. No predictor for stroke survivor depressive symptom survivor functional disability was associated with a sig- trajectory group membership was significant. The 2 time- nificant upward shift of the depressive symptom trajectory varying covariates, however, had a significant influence of the low and increasing group (Table 3). on the trajectory level of 1 or more groups. In the mul- For caregivers, the model specifying 2 trajectory groups, tivariate analysis, at a given trajectory time point, each with curvilinear specification for both, had the best fit unit increase in caregiver depressive symptoms was as- (Fig 2;BIC:−1513.5 versus −1536.4 [1 group] and −1520.1 sociated with a significant upward shift (~worsening [3 groups]). The average posterior probability value of depressive symptoms) in the depressive symptom tra- both groups exceeded .85. The depressive symptom tra- jectory in all 3 groups. And each unit increase in stroke jectory of the low and stable group, comprising 71.5% of

Figure 1. Stroke survivor depressive symptom trajectories (solid lines), with 95% confidence in- tervals (dashed lines). Note: The dotted line indicates the threshold value (16) for clinically significant depressive symptoms. DEPRESSIVE SYMPTOM TRAJECTORIES 177

Figure 2. Caregiver depressive symptom trajec- tories (solid lines), with 95% confidence intervals (dashed lines). Note: The dotted line indicates the threshold value (16) for clinically significant de- pressive symptoms.

the caregivers, started and remained below the CSDS [.90, .98]). Two of the three considered time-varying threshold throughout the follow-up period. On the other covariates significantly influenced the trajectory level of hand, the trajectory of the high and decreasing group, com- 1 or both groups: at a given trajectory time point, each prising 28.5% caregivers, started high then declined sharply unit increase in stroke survivor depressive symptoms was from T0 to T1 and gradually thereafter, falling below the associated with a significant upward shift of the trajec- CSDS threshold by T2. tory in both groups and FDW assistance was associated In bivariate analysis, caregiver education and chronic with a significant downward shift (~improving depres- disease status, stroke survivor–caregiver relationship, and sive symptoms) of the high and decreasing group trajectory stroke survivor age were predictive of caregiver depres- (Table 4). sive symptom trajectory group membership. In multivariate Sensitivity analysis results (not presented), conducted analysis, only caregiver chronic disease status and stroke among the 129 dyads contributing to all 3 trajectory time survivor age remained significant: the odds for the high points, were similar in terms of the number of trajecto- and decreasing group versus the low and stable group were ry groups and the shape of depressive symptom trajectories significantly higher for caregivers with chronic diseases therein, as well as covariates significantly associated with (odds ratio [95% confidence interval]: 8.09 [2.04, 32.07]) trajectory group membership and level of depressive and lower for caregivers of older stroke survivors (.94 symptom trajectories.

Table 4. Predictors of trajectory group membership and time-varying covariates influencing the level of the trajectory of the 2 caregiver depressive symptom trajectory groups: multivariate analysis*

Odds (95% CI) of being in “high and decreasing group” Predictors versus “low and stable” group P value

Stroke survivor age (years) .94 (.90, .98) .006 Caregiver education—secondary and above .97 (.26, 3.62) .968 Caregiver chronic diseases—one or more 8.09 (2.04, 32.07) .003 Caregiver–stroke survivor relationship—spouse 2.68 (.59, 12.22) .203 Time-varying covariate Shift in trajectory per unit change in time-varying covariate P value (95% CI)† Stroke survivor depressive symptoms Low and stable group .14 (.02, .25) .026 High and decreasing group .42 (.27, .57) <.001 FDW assistance—yes Low and stable group −1.42 (−3.37, .54) .156 High and decreasing group −3.08 (−5.97, −.19) .037

Abbreviations: CI, confidence interval; FDW, foreign domestic worker. *Only predictors and time-varying covariates significant in the bivariate analysis were included. †Positive values indicate an upward shift and negative values indicate a downward shift. 178 R. MALHOTRA ET AL. Discussion detrimental influence on mood observed in the stroke survivor–caregiver dyad in our study is likely reflective We observed 3 stroke survivor depressive symptom tra- of the emotional contagion phenomenon, as proposed by jectories and 2 caregiver depressive symptom trajectories, Hatfield et al.53 It is defined as “the tendency to auto- confirming our hypothesis of heterogeneity of depres- matically mimic and synchronize expressions, vocalizations, sive symptoms over time among stroke survivor– postures and movements with those of another pe- caregiver dyads. Our finding adds to the growing literature rson’s and, consequently, to converge emotionally.”53 It describing diversity in depressive symptoms over time is proposed to act through various mechanisms includ- in various patient and population groups,27-32 and pro- ing “cognitive empathy” (mutual empathy among closely vides empirical support for GBTM as an analytical related dyad members) and “mimicry and feedback” approach to describe the natural history of depressive (neural afferent feedback through observing the other’s symptoms. facial, verbal and body movement, and direct cortical neural None of the considered stroke survivor depressive network activation from observing the other’s emo- symptom trajectory group membership predictors were tions) among care recipient–caregiver dyads.51,53 Our finding significant. This possibly results from many of the con- has 2 implications. First, interventions addressing mood sidered variables reported to be inconsistent risk factors in 1 member of the stroke survivor–caregiver dyad may for poststroke depressive symptoms/depression.40 Infor- benefit the other member’s mood; there is evidence of mation on more consistent risk factors such as prestroke an indirect benefit on stroke survivors’ mood from in- depressive symptoms/depression, family history of psy- tervention studies conducted among their caregivers.54 chiatric disorder, and severity of stroke38,40,50 was not Second, interventions that simultaneously address de- collected, precluding them from consideration. This is a pressive symptoms in both dyad members may be more key limitation of the present study. Similarly, lack of in- beneficial than those targeting 1 member. Evidence sup- formation on the characteristics of the brain lesion, such porting this stems from dyadic or family psychosocial as size and location, did not allow for their inclusion as interventions for addressing chronic diseases in general.55 potential risk factors. While brain lesion characteristics The few dyadic interventions conducted specifically among have not been reported consistently as risk factors for stroke survivor–caregiver dyads to date,54 however, do poststroke depressive symptoms/depression, they also have not capture mood outcomes among both dyad members been less studied as risk factors and have not been studied and/or do not include control groups targeting only 1 in the context of depressive symptom trajectories.38,40 Future dyad member to allow us to state or quantify such a longitudinal studies employing GBTM should consider benefit. Future dyadic interventions should address this all these risk factors, whether reported consistently or not issue. as risk factors in previous studies, in the context of de- Of the 2 other time-varying covariates considered for pressive symptom trajectories. caregiver depressive symptom trajectories, stroke survi- Nonetheless, both the time-varying covariates (stroke vor functional disability was not significant. Previous survivor functional disability and caregiver depressive studies also report an inconsistent association between symptoms) evaluated for stroke survivor depressive stroke survivor functional disability and caregiver de- symptom trajectories were significant, and were in the pressive symptoms.2 FDW assistance, however, as hypothesized direction. The increase in stroke survivor hypothesized, led to a downward shift (~improvement) functional disability over time was associated with an in both caregiver depressive symptom trajectories, and upward shift (~worsening) of the trajectory for all 3 groups, significantly so for the high and decreasing group trajec- and significantly so for the low and increasing group. This tory. Not much is known about the impact of instrumental was not surprising as a consistent positive relationship support from formal care sources on depressive symp- between the extent of functional disability and poststroke toms among family caregivers, especially stroke caregivers. depressive symptoms/depression is reported among stroke While a Canadian study found no association between survivors.38,40 community-based services received by stroke survivors There was strong support for the reciprocal associa- and caregiver depressive symptoms,8 a Singaporean study tion of depressive symptoms among both members of reported instrumental support from FDWs to elderly care the stroke survivor–caregiver dyad: an increase in care- recipients to moderate negative caregiver outcomes.41 Our giver depressive symptoms led to a significant upward study, also from Singapore, agrees with the latter. While shift in all 3 stroke survivor depressive symptom trajec- family caregivers likely benefit from FDWs, caring for tories, and both caregiver depressive symptom trajectories stroke survivors may have impacted the health status of demonstrated a significant upward shift with an in- the FDWs themselves. This information, not captured in crease in stroke survivor depressive symptoms. This finding the current study, should be explored in future studies. was in line with our hypothesis and with the extant lit- Our findings call for a greater focus on stroke care- erature on stroke survivor–caregiver dyads2,7-10 and on care givers with chronic diseases and those caring for younger recipient–caregiver dyads in general.51,52 The mutually stroke survivors. Both these characteristics increased the DEPRESSIVE SYMPTOM TRAJECTORIES 179 chance for caregivers to follow the higher depressive depressive symptom pattern over time among stroke sur- symptom trajectory. A previous study also suggested poor vivors and their caregivers. Use of GBTM also allowed health status to predict depression in stroke caregivers.56 for inclusion of variables that evolve over time, such as A possible explanation for our finding on stroke survi- stroke survivor functional disability, as time-varying vor age as a risk factor is that stroke in a younger, than covariates and not use them restrictively as fixed base- older, individual may be more disturbing for family line variables. The time-varying covariates we observed caregivers. to significantly influence the depressive symptom trajec- In addition to those outlined above, other limitations tories are themselves modifiable; thus they offer of our study are its sample size and short-term follow- characteristics of the stroke survivor (functional disabil- up, and the dyads were interviewed only thrice over ity and depressive symptoms) or caregiver (depressive time. When using GBTM, the number of respondents symptoms) or care environment (FDW assistance) that and, more importantly, the duration of follow-up influ- can be altered to improve the mood of the stroke survivor– ence the number of trajectory groups identified and the caregiver dyad. shape of trajectories therein.57 It is thus possible that In conclusion, more than half of stroke survivors ad- subsequent studies with larger number of respondents mitted to in-patient rehabilitation followed increasing and greater follow-up durations provide different results. depressive symptom trajectories that remained above the Nonetheless, we did delineate distinct and meaningful CSDS threshold for at least 8 months poststroke. These depressive symptom trajectories among stroke survi- included a subset (9.3%) that was especially at risk, fol- vors and their caregivers, and identified significant lowing a depressive symptom trajectory that started and predictors and/or time-varying covariates for the trajec- remained high. While depressive symptoms in the ma- tories. It may be contended that the study setting, jority (71.5%) of their caregivers followed a trajectory below in-patient rehabilitation, may have resulted in selection the CSDS threshold, in the rest (28.5%) the depressive of stroke survivors with greater frequency of depres- symptom trajectory suggested CSDS, at least in the im- sion, relative to population-based or hospital-based mediate few months poststroke. Health and social care recruitment. However, the frequency of poststroke de- professionals should be mindful of this heterogeneity in pression is reported to be consistent across recruitment depressive symptom patterns over time among stroke sur- settings.1 Nevertheless, as our sample was recruited vivors and their caregivers. The reciprocal association of from a single in-patient rehabilitation center, our find- depressive symptoms in the stroke survivor–caregiver dyad ings have limited generalizability to all stroke survivors suggests that addressing mood problems in 1 member and their caregivers. The interview location was differ- may benefit the other member, and calls for dyadic mental ent for the first (community hospital) and second and health interventions. third (home of the stroke survivors/family caregivers) interviews, which may have influenced the affective Acknowledgment: We would like to thank Nicloa Lew for state of caregivers and stroke survivors. 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