Longitudinal Associations Between Walking Frequency and Depressive Symptoms in Older Adults: Results from the VoisiNuAge Study Dominic Julien, PhD,* Lise Gauvin, PhD,†‡§ Lucie Richard, PhD,*§¶** Yan Kestens, PhD,†‡§ and He´lene Payette, PhD††‡‡

BACKGROUND: Cross-sectional studies show that walking is associated with depression among older adults, but longitudinal associations have rarely been examined. The aim of this study was to investigate longitudinal associations between walking frequency and depressive symptoms in older adults to determine which variable is the stronger prospective predictor of the other. DESIGN: Longitudinal; four repeated measures over 5 years. SETTING: Population-based sample of urban-dwelling older adults living in the Montreal metropolitan area. PARTICIPANTS: Participants from the VoisiNuAge study aged 68 to 84 (N = 498). MEASUREMENTS: Main exposures: depressive symptoms (Geriatric Depression Scale) and number of walking days in previous week (Physical Activity Scale for the Elderly). Covariates: age, education, and number of chronic illnesses. Cross-lagged panel analyses were performed in the entire sample and in sex-stratified subsamples. RESULTS: Depressive symptoms predicted walking frequency at subsequent time points (and more precisely, higher depressive symptoms were related to fewer walking days), but walking frequency did not predict depressive symptoms at subsequent time points. Stratified analyses

From the *Institut de Recherche en Sante´ Publique de l’Universite´ de Montre´al, †Centre de Recherche du Centre Hospitalier de l’Universite´ de Montre´al, ‡De´partement de Me´decine Sociale et Pre´ventive, §Centre de Recherche Le´a-Roback sur les Ine´galite´s Sociales de Sante´ de Montre´al, ¶ Faculte´ des Sciences Infirmieres,**Centre de Recherche de l’Institut Universitaire de Ge´riatrie de Montre´al, Universite´ de Montre´al, Montre´al, Que´bec, ††Centre de Recherche sur le Vieillissement, Centre de Sante´ et des Services Sociaux, Institut Universitaire de Ge´riatrie de Sherbrooke, and ‡‡ De´partement des Sciences de la Sante´ Communautaire, Faculte´ de Me´decine et des Sciences de la Sante´, Universite´ de Sherbrooke, Sherbrooke, Que´bec, Canada. Address correspondence to Dominic Julien, Direction de Sante´ Publique de l’Agence de la Sante´ et des Services Sociaux de Montre´al, 1301, Sherbrooke East, Montreal, Quebec, Canada, H2L 1M3. E-mail: dominic. [email protected] DOI: 10.1111/jgs.12546

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revealed that prospective associations were statistically significant in women but not men. CONCLUSION: The longitudinal association between walking frequency and depressive symptoms is one in which depressive symptoms predict reduced walking frequency later. Higher depressive symptoms are more likely a cause of reduced walking because of time precedence than vice versa. Future research on longitudinal relationships between meeting physical activity recommendations and depression are warranted. J Am Geriatr Soc 61:2072– 2078, 2013.

Key words: depression; walking; motor activity; aged; longitudinal studies

D

epression is frequent in older adults, affecting between 1% and 5% of people aged 65 and older.1 Depression is associated with mental suffering; risk of suicide; and poor physical, cognitive, and social functioning.2 Older adults with depression use health and medical services two to three times as often as those without depression.3 With the aging of the global population, it is important to identify factors that may alleviate depressive symptoms in elderly people.4 Cross-sectional studies have reported significant associations between walking and depression in older adults5–7 but do not provide any information on the direction of the causality. To the knowledge of the authors of the current study, three longitudinal studies have examined prospective relationships between walking and depression in older adults, and results were mixed. In one study, walking was not associated with future depression,8 whereas in another, walking distance predicted future depression.9 In a third study, walking was not associated with future depression, but depression was related to future walking habits.10 One of these studies focused on older Japanese-American men9 and another on older Hispanic adults,10 so results may not generalize to other populations of older adults. Two of

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these studies8,9 used regression analyses, which may not be well suited to the study of phenomena that change across time. Cross-lagged panel analysis is a better approach to investigating longitudinal associations between two variables than regression analysis because it allows for examining prospective associations between variables at multiple time points in a single analysis. Moreover, although cross-lagged panel analyses are not intended to determine causality per se, they examine prospective relationships in a way that establishes which variable is the stronger prospective predictor of the other, thereby suggesting which variable is a more likely cause of the other because of time precedence11 (the cause occurring before the effect). Prospective associations between walking and depression in older adults have not been extensively examined, so additional research is needed to clarify the plausible direction of associations. Uncovering these associations is important for health promotion professionals, clinical psychologists, physicians, and nurses. For example, if walking habits predict future depression, with more walking being associated with lower depression, then promoting walking may be an effective strategy for preventing depression in elderly adults. In contrast, if walking is a consequence of depression, poor mental health may interfere with walking and therefore negatively affect physical health. Thus, helping to alleviate depressive symptoms may also affect physical health. The aim of this study was to investigate longitudinal associations between walking and depressive symptoms in a population-based sample of urban-dwelling older adults in an effort to determine which variable is the stronger prospective predictor of the other.

METHODS Participants and Procedure Participants were taken from the VoisiNuAge Study, which investigates relationships between neighborhood environments and health-related behaviors such as walking and social participation in older adults. The VoisiNuAge database was created from the merging of two existing datasets: the Que´bec Longitudinal Study on Nutrition and Successful Aging (NuAge), a 5-year observational study on nutrition and successful aging,12,13 and Montreal Epidemiological and Geographic Analysis of Population Health Outcomes and Neighbourhood Effect (MEGAPHONE), a database for health research derived from geographic information systems, allowing for geocoding of VoisiNuAge participants at the address level.14 The NuAge cohort (N = 1,793) is an age- and sexstratified random sample for the regions of Montreal, Laval, and Sherbrooke in the province of Quebec, Canada. Inclusion criteria for the NuAge cohort were aged 68 to 84, free of activity of daily living disabilities (bathing and showering, cooking, dressing), without cognitive impairment (Modified Mini-Mental State Examination score >79), able to walk one block or climb a flight of stairs without rest, willing to commit to a 5-year study, and French or English speaking. Those reporting heart failure (≥ New York Heart Association Class II); chronic obstructive pulmonary disease

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requiring oxygen therapy or oral corticosteroids; inflammatory digestive diseases; or cancer treated using radiation therapy, chemotherapy, or surgery in the past 5 years were excluded. Global participation rate (sample studied/total eligible subjects) was 58.6%. Participants were followed four times over 5 years (2003–2008; T1 (baseline), T2, T3, and T4) and underwent a series of nutritional, functional, medical, biological, and social computer-assisted interviews (William, Multispectra, Montreal, Canada) conducted by trained research dieticians and nurses following standardized procedures.13 The VoisiNuAge study focused on participants who resided in the Montreal metropolitan area (n = 848). The sample was limited to those who were still in the cohort at T4 (n = 725), meaning drop-outs (n = 102) and participants who died (n = 21) were excluded. Participants with incomplete data on the variables described below were also excluded from analyses (n = 227), leaving a sample of 498 participants. A flowchart of participant inclusion appears in Figure 1.

Measures Depressive Symptoms The Geriatric Depression Scale (GDS)15 was used to assess depressive symptoms. The GDS is a 30-item questionnaire with a yes–no response format; scores from 11 to 20 suggest mild depression and scores of 21 and higher suggest

NuAge, a study on nutrition and successful aging N = 1,793 Participants living in Montreal,

MEGAPHONE, a database for

Laval, and Sherbrooke (Canada)

health research

VoisiNuAge, a study on neighborhood environments and Excluded participants healthy aging n = 945 n = 848 Participants not living in Participants living in Montreal Montreal metropolitan area metropolitan area (Montreal and Laval)

VoisiNuAge participants still in

Excluded participants

the cohort at T4

n = 102 dropouts

n = 725

n = 21 deceased

Participants in the current study

Excluded participants

n = 498

n = 227 for incomplete data

Figure 1. Flowchart of participant inclusion.

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moderate to severe depression, but continuous GDS scores were used in the cross-lagged panel analyses. Higher scores on the GDS indicate higher levels of depressive symptoms. The mean Cronbach alpha across different measurement times in the VoisiNuAge sample (n = 848) was 0.83 (range 0.82–0.83), indicating high internal consistency of the measure.

Walking One question taken from the Physical Activity Scale for the Elderly (PASE)16 was used to assess the number of days that walking episodes occurred over the past week: “Over the past 7 days, how often did you walk outside your home or yard for any reason? For example, for fun or exercise, walking to work, walking the dog, etc.?” (never (0 days), seldom (1–2 days), sometimes (3–4 days), and often (5–7 days); recoded as 0, 1.5, 3.5, and 6 days). Although there are no validity data on the PASE item assessing frequency of walking episodes, the item shares considerable resemblance with a validated question from the International Physical Activity Questionnaire17 and thus shows face validity. This single PASE item has been used in other studies5,18 to assess walking. The PASE showed good test–retest reliability (correlation coefficient = 0.75) and satisfactory convergent validity with health, strength, and balance.16

Sociodemographic and Health Characteristics Covariates were sex, age, years of education, and number of chronic illnesses based on a list of 23 reported medical conditions (Table 1).

Study Design The current study used a longitudinal design. Age and years of education were collected at T1; GDS scores, walking, and number of chronic illnesses were collected at each time point. The ethics committees of the University Geriatrics Institutes in Montreal and Sherbrooke approved the research, and respondents signed an informed consent form.

Statistical Analysis Group differences between included and excluded VoisiNuAge participants were tested on variables of interest. Descriptive analyses were conducted to characterize respondents included in the final sample (n = 498). Using a procedure described elsewhere,19 scores for change from T2 to T1, T3 to T1, and T4 to T1 were computed for depressive symptoms and walking frequency, respectively, to exclude the possibility that a small proportion of participants who experienced change drove cross-lagged panel analyses results. Average proportions of participants presenting increase, decrease, or unchanged depressive symptoms or number of walking days were computed, as were standard deviations for change scores. Then cross-lagged panel analyses were conducted to estimate prospective associations between walking frequency and depressive symptoms at the four measurement times. Four models were created following previously

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Table 1. Characteristics of VoisiNuAge Participants Included in the Analyses Characteristic

Entire Sample, n = 498

Women, n = 262

Age at inception, 74.64  4.08 74.86  4.18 mean  SD Education, years, 12.96  4.58 12.35  3.99 mean  SD Number of chronic illnesses, mean  SDa T1 3.45  2.43 3.85  2.62 T2 3.18  2.05 3.39  2.25 T3 3.47  2.11 3.73  2.25 T4 3.64  2.23 3.90  2.33 Potentially clinically depressed (GDS ≥11), n (%) T1 40 (8.0) 28 (10.7) T2 48 (9.6) 32 (12.2) T3 55 (11.0) 32 (12.2) T4 52 (10.4) 34 (13.0) GDS score, mean  SD T1 4.49  4.05 4.95  4.40 T2 4.65  4.22 5.17  4.70 T3 4.67  4.24 4.95  4.47 T4 4.75  4.36 5.15  4.52 Days of walking in previous week, mean  SD T1 3.77  2.35 3.67  2.38 T2 3.14  2.45 2.98  2.40 T3 3.53  2.45 3.32  2.46 T4 3.52  2.49 3.37  2.47

Men, n = 236

74.40  3.97 13.63  5.07 3.00 2.95 3.19 3.35 12 16 23 18

   

2.11 1.77 1.90 2.09

(5.1) (6.8) (9.7) (7.6)

3.99 4.08 4.36 4.30

   

3.55 3.53 3.95 4.12

3.88 3.31 3.75 3.68

   

2.32 2.49 2.43 2.50

SD = standard deviation; GDS = Geriatric Depression Scale. a Arthritis/rheumatism, glaucoma/ocular disease, edema, asthma, emphysema/chronic bronchitis, high blood pressure, heart trouble, circulatory problems in arms or legs, diabetes mellitus, ulcers (of the digestive systems), other digestive problems (vomiting, constipation, diverticulosis), liver or gallbladder disease, kidney disease, urinary problems (prostate), osteoporosis, cancer, anemia, thrombosis/cerebral hemorrhage/cerebrovascular accident, Parkinson’s disease, thyroid and gland problems, skin disorders, epilepsy, other diseases (specified).

outlined guidelines.11 Model 1 is a base model examining simultaneously whether walking frequency predicted itself at subsequent time points (walking frequency at T1 predicting walking frequency at T2, T3, and T4; walking frequency at T2 predicting walking frequency at T3 and T4; walking frequency at T3 predicting walking frequency at T4) and whether depressive symptoms predict themselves at subsequent time points. Model 2 investigated whether walking frequency predicted future depressive symptoms and consisted of the base model with the addition of constraints for walking frequency predicting depressive symptoms at subsequent time points (walking frequency at T1 predicting depressive symptoms at T2, walking frequency at T2 predicting depressive symptoms at T3, and walking frequency at T3 predicting depressive symptoms at T4). Model 3 investigated whether depressive symptoms predicted future walking frequency. It also consisted of the base model with the addition of constraints for depressive symptoms predicting walking frequency at subsequent time points. Model 4 investigated bidirectional associations between walking frequency and depressive symptoms. It also consisted of the base model with the addition of constraints for walking frequency and depressive symptoms predicting each other at subsequent time points.

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The overarching objective of the cross-lagged panel analyses was to determine whether Model 2, 3, or 4 provided a significantly better fit of the data than the base model or either of Model 2 or 3 in the case of Model 4 (see below). A chi-square difference test (D v2) was used to establish fit improvement. Models 2 and 3 were compared with the base model (Model 1), and Model 4 was compared with the base model if Models 2 and 3 did not significantly improve the fit of the data or Models 2 or 3 if either of these models provided significantly improved fit over the base model. Thus, if Model 2 provided significant fit improvement, walking frequency would be thought to predict future depressive symptoms. If Model 3 provided significant fit improvement, then depressive symptoms would be thought to predict future walking frequency. If Model 4 provided significant fit improvement, then walking frequency and depressive symptoms would both be thought to have effects on the other variable (bidirectional relationship) at subsequent time points. In addition, data fit was considered good if the models met the following criteria: ratio of v2 to degrees of freedom (df) of less than 2.0, Comparative Fix Index (CFI) greater than 0.95, Normed Fit Index (NFI) greater than 0.95, Root Mean Square Error of Approximation (RMSEA) of 0.06 or less,20 and Tucker-Lewis Index (TLI) of 0.95 or greater.21 Path coefficients (from walking frequency predicting subsequent depressive symptoms or depressive symptoms predicting subsequent walking frequency) were also examined in models that significantly improved fit. These path coefficients are comparable with regression analysis coefficients such that the direction and statistical significance can be interpreted in the same way. Walking frequency and depressive symptoms were adjusted for age and education at T1 and for chronic illnesses at every time point. Walking frequency and depressive symptom error terms were allowed to covary at every time point. Analyses were performed in the entire sample and sex-stratified subsamples. All analyses were performed using PASW statistical software (version 18, SPSS Inc., Chicago, IL) and AMOS 19 (Arbuckle, JL, IBM SPSS, Chicago, IL).

RESULTS Participant Characteristics When comparing VoisiNuAge participants who had dropped out, died, and other VoisiNuAge respondents, those who died were significantly older (P = .04) and walked less often outside their home (P = .047) than those dropping out, and those who dropped out reported significantly more depressive symptoms at T1 than the remaining VoisiNuAge participants (P = .02). Of the remaining participants, those who were excluded from the analyses because of incomplete data were significantly older (P < .001); reported more chronic illnesses at T1 (P < .001), T2 (P = .001), and T3 (P = .04); had higher depression scores at the four measurement points (P ≤ .001); and walked less often outside their home at T1 (P = .01) and T3 (P = .01) than those included in the analyses. Characteristics of respondents included in the analyses are shown in Table 1. The mean age of participants at

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cohort inception was 74.6  4.1 (range 68–84). Women represented 52.6% of the final sample. The number of chronic illnesses reported increased slightly over time (with the exception of T2). Table 1 also presents participant characteristics stratified according to sex. Women reported more chronic illnesses and depressive symptoms but fewer days of walking at every time point than men (t-tests not computed).

Change in Depression and Walking over Time The number of participants categorized as potentially clinically depressed according to GDS cutoff scores was fairly stable across time, as were mean depression scores (Table 1), although 38.4% of participants reported a decrease in depressive symptoms at time points after T1 (40.7% of women, 35.9% of men), 41.9% of participants showed an increase (41.6% of women, 42.1% of men), and 19.8% of participants reported no change (17.7% of women, 22.0% of men). The average standard deviation in depressive symptom change was 3.0 (3.1 in women, 2.9 in men). On average, 30.6% of participants reported a decrease in walking frequency after T1 (31.9% of women, 29.1% of men), 20.6% of participants reported an increase (20.9% of women, 20.2% of men), and 48.9% of participants reported no change (47.2% of women, 50.7% of men). The average standard deviation in change in walking frequency was 2.4 (2.5 in women, 2.4 in men). These results suggest that a substantial proportion of participants reported change in depressive symptoms and walking frequency over time, indicating that a small proportion of participants did not drive the cross-lagged panel analyses results.

Cross-Lagged Panel Analysis Results Square root transformations were applied to depressive symptom scores, years of education, and number of chronic illnesses to improve the normality of distributions. Table 2 presents fit indices for the entire and sex-stratified subsamples. In the entire sample, overall fit of the base model (Model 1) was excellent (v2/df = 1.54, CFI = 0.99, NFI = 0.98, RMSEA = 0.03, TLI = 0.99). The model in which depressive symptoms predicted walking frequency at subsequent time points (Model 3) provided a significantly better fit of the data than the base model (D v2 (3) = 15.13, P  .002). For Model 3, the fit indices were v2/df = 1.34, CFI = 1.00, NFI = 0.98, RMSEA = 0.03, and TLI = 0.99 (Table 2). Path coefficients from depressive symptoms T2 to walking frequency T3 and from depressive symptoms T3 to walking frequency T4 were statistically significant and negative (b = 0.23, P = .008 and b = 0.19, P = .02, respectively), and a trend toward significant associations was observed from depressive symptoms T1 to walking frequency T2 (b = 0.17, P = .07) (Figure 2). Overall, this model supports the idea that more depressive symptoms were related to fewer days of walking in the future. An increase of 1 point on the square rooted depressive symptom scale (which corresponds to an increase of approximately 5.5 points on the original scale) was associated with a 21% decrease

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Table 2. Cross-Lagged Panel Analyses Results Examining Longitudinal Associations Between Walking Frequency and Depressive Symptoms in VoisiNuAge Participants Included in the Analyses

Model

Total (n = 498) Model 1: Base model Model 2: Walking frequency predicting depressive symptoms Model 3: Depressive symptoms predicting walking frequency Model 4: Bidirectional Women (n = 262) Model 1: Base model Model 2: Walking frequency predicting depressive symptoms Model 3: Depressive symptoms predicting walking frequency Model 4: Bidirectional Men (n = 236) Model 1: Base model Model 2: Walking frequency predicting depressive symptoms Model 3: Depressive symptoms predicting walking frequency Model 4: Bidirectional

v2 (df)

v2/ df

Comparative Fix Index

Normed Fit Index

Root Mean Square Error of Approximation

TuckerLewis Index

Model Comparisons

v2 Difference Test (df)

83.40 (54) 82.01 (51)

1.54 1.61

0.99 0.99

0.98 0.98

0.03 0.04

0.99 0.98

– 2 vs 1

– 1.39 (3)

68.27 (51)

1.34

1.00

0.98

0.03

0.99

3 vs 1

15.13 (3)a

66.83 (48)

1.39

1.00

0.98

0.03

0.99

4 vs 3

1.44 (3)

77.85 (54) 73.95 (51)

1.44 1.45

0.99 0.99

0.96 0.96

0.04 0.04

0.98 0.98

– 2 vs 1

– 3.90 (3)

63.45 (51)

1.24

0.99

0.97

0.03

0.99

3 vs 1

14.40 (3)a

59.45 (48)

1.24

0.99

0.97

0.03

0.99

4 vs 3

4.00 (3)

75.53 (54) 74.66 (51)

1.40 1.46

0.99 0.99

0.96 0.96

0.04 0.04

0.98 0.97

– 2 vs 1

– 0.87 (3)

71.08 (51)

1.39

0.99

0.96

0.04

0.98

3 vs 1

4.45 (3)

70.22 (48)

1.46

0.99

0.96

0.04

0.97

4 vs 1

5.31 (6)

Df = degrees of freedom; v2 = chi-square. Models control for age and education measured at T1 and for number of chronic illnesses at every time point. a P < .01.

(mean of significant path coefficients) in walking frequency 1 year later. The models in which walking frequency predicted depressive symptoms at subsequent time points

Walking

Walking

Walking

Walking

T1

T2

T3

T4

–.17 a

–.19b

–.23c

Depression

Depression

Depression

Depression

T1

T2

T3

T4

Figure 2. Best-fitting model (Model 3) for the cross-lagged panel analyses results among 498 older adults from the VoisiNuAge Study. For greater ease of presentation, associations between walking at T1 and T3, T1 and T4, and T2 and T4 and associations between depressive symptoms at T1 and T3, T1 and T4, and T2 and T4 are not shown. Models control for age and education measured at T1 and for chronic illnesses at every time point (not shown). Walking refers to walking frequency, and depression refers to depressive symptoms. P < a.10, b.05, c.01. Full graphs for all models are available from the first author upon request.

(Model 2) and the bidirectional model (Model 4) did not provide significant fit improvement (Table 2). Further analyses were performed in women and men separately. In women, the overall fit of the base model (Model 1) was excellent (v2/df = 1.44, CFI = 0.99, NFI = 0.96, RMSEA = 0.04, TLI = 0.99) (Table 2). The model in which depressive symptoms predicted walking frequency at subsequent time points (Model 3) provided a significant fit improvement over the base model (D v2 (3) = 14.40, P  .002) (Table 2). The fit indices were v2/ df = 1.24, CFI = 0.99, NFI = 0.97, RMSEA = 0.03, and TLI = 0.99 (Table 2). The path coefficient from depressive symptoms T3 to walking frequency T4 was statistically significant (b = 0.34, P = .004), and a trend toward significant associations was found from depressive symptoms T1 to walking frequency T2 (b = 0.24, P = .06) (for the path from depressive symptoms T2 to walking frequency T3, b = 0.19, P = .10) (Figure 3). This model suggests that an increase of approximately 5.5 points on the original depressive symptom scale is associated with a 34% decrease in walking frequency from T3 to T4. Models 2 and 4 did not provide significantly better fit (Table 2). In men, the overall fit of the base model (Model 1) was excellent (v2/df = 1.40, CFI = 0.99, NFI = 0.96, RMSEA = 0.04, TLI = 0.98), but none of the other models provided significant fit improvement (Table 2).

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LONGITUDINAL ASSOCIATIONS WALKING AND DEPRESSION

Walking

Walking

Walking

Walking

T1

T2

T3

T4

–.24 a

–.34 b

–.19

Depression

Depression

Depression

Depression

T1

T2

T3

T4

Figure 3. Best-fitting model (Model 3) for the cross-lagged panel analyses results in a subsample of 262 women in the VoisiNuAge Study. For greater ease of presentation, associations between walking at T1 and T3, T1 and T4, and T2 and T4 and associations between depressive symptoms at T1 and T3, T1 and T4, and T2 and T4 are not shown. Model controls for age and education measured at T1 and for chronic illnesses at every time point (not shown). Walking refers to walking frequency, and depression refers to depressive symptoms. P < a.10, b.01.

DISCUSSION The aim of this study was to investigate longitudinal associations between walking frequency and depressive symptoms in older adults in an effort to determine which variable is the stronger prospective predictor of the other. In the entire sample and in the subsample of women, the models in which depressive symptoms predicted walking frequency at subsequent time points provided significant fit improvement over the base model; higher depressive scores were or tended to be related to fewer walking days at subsequent time points. An increase of approximately 5.5 points on the original depressive symptom scale was associated with a 21% decrease in walking frequency 1 year later (for T2–T3 and T3–T4) in the entire sample and with a 34% decrease in walking frequency 1 year later (for T3–T4) in the subsample of women. These associations were independent of age, education, and number of chronic illnesses and were not driven by a small subset of participants reporting change in depressive symptoms or walking frequency across time. The models in which walking frequency predicted depressive symptoms at subsequent time points and the bidirectional models did not significantly improve fit, so it was concluded that the longitudinal association between walking frequency and depressive symptoms is one in which greater depressive symptoms predict reduced walking frequency later on and therefore that depressive symptoms are a plausible cause of walking frequency because of time precedence rather than vice versa. This causal effect seems more prominent in women than men. Because no fit improvement or significant associations were found in the subsample of men, it was also concluded that findings observed in women mainly explained the results in the entire sample. Underreported depressive symptoms in men, who are traditionally less likely to disclose having mental health problems, may explain the sex differences. Alternatively, negative life events or depressive mood may affect women’s health behaviors such as walking more than men.

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Results pertaining to prospective associations between depressive symptoms and walking frequency in the entire sample are consistent with a study reporting that walking was not a significant predictor of future depression.8 Similarly, another study reported that walking did not predict future depressive symptoms but that depressive symptoms predicted subsequent walking.10 Conversely, another study reported that walking predicted future depression in older Japanese-American men,9 which differences in samples or assessment of walking (distance vs frequency) might explain. In the current analyses, path coefficients between depressive symptoms and future walking frequency were statistically significant or close to statistical significance in the entire sample and the subsample of women. A lack of power due to smaller sample size may explain trends, so results should be replicated in larger samples, and sex differences should be further investigated. Strengths of this study include its longitudinal design and the use of cross-lagged panel analyses that allowed for insights into the direction of associations between variables. One limitation of the current study is that respondents may not be representative of the overall population of older adults because they lived in urban areas and appeared to be more educated and wealthier than the general population of older adults. Participants included in the analyses reported fewer depressive symptoms than those excluded, and average depression scores were low, so the strength of the associations reported may be underestimated in comparison with the general population of older adults. Atypical external (and personal) conditions such as weather and health might have affected walking frequency in the previous week.22 Finally, walking frequency was focused on without taking into account duration of walking episodes because, in the response options for the measure of walking, the shortest duration category was 1 hour per day, which was too broad within the context of a population survey for older adults to adequately ascertain different durations of walking. Replication of results with a more-sensitive assessment of walking activity is warranted. In conclusion, although significant associations between walking frequency and subsequent depressive symptoms were not found, it seems premature to conclude that promoting walking is not a relevant strategy to protect against depressive symptoms. There are also ample data to recommend walking for physical health reasons. Future research could investigate prospective associations between meeting recommendations for physical activity levels and depressive symptoms in older people.

ACKNOWLEDGMENTS Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. This work was supported by a postdoctoral fellowship from the Institut de Recherche en Sante´ Publique de l’Universite´ de Montre´al to DJ, the Canadian Institutes of Health Research (Grants MOP-173669 and MOP-62842), and the Fonds de la Recherche en Sante´ du Que´bec

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(Grants 16207 to LR and 20328 to YK). LG holds a Canadian Institutes of Health Research/Centre de Recherche en Prevention de l’Obe´site´ Applied Public Health Chair on Neighbourhoods, Lifestyle, and Healthy Body Weight. Author Contributions: All authors: conception, design, analyses, interpretation of data, drafting of the manuscript or revising it critically for important intellectual content. Sponsor’s Role: The sponsors had no role in conception, design, analyses, interpretation of data, or in the drafting, review, or approval of the manuscript.

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Longitudinal associations between walking frequency and depressive symptoms in older adults: results from the VoisiNuAge study.

Cross-sectional studies show that walking is associated with depression among older adults, but longitudinal associations have rarely been examined. T...
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