Depression is a worldwide problem and is projected to be the second leading cause of disability worldwide in 2020 (Whiteford et al., 2013). In particular, late life depression (LLD) is one of the most prevalent mental disorders in older adults, with prevalence estimates ranging from 4.6 to 9.3% (Luppa et al., 2012). LDD is associated with increased health care costs, increased morbidity and suicidal risks, impairments in physical, social, and cognitive functioning, and increased dementia (Georgakis et al., 2016).
Despite its prevalence and clinical significance, however, LLD is underrecognized and undertreated due to its complicated etiologies, and often being viewed as an inevitable part of the aging process.
Antidepressants, such as selective serotonin re-uptake inhibitors, have been the most common treatment choice (Allan and Ebmeier, 2018). However, the pharma-cologic options are unfortunately often accompanied by many side effects, including falls, cardiovascular events, fractures, epilepsy, hyponatremia, and increased risk of all-cause mortality (Stubbs, 2015). Hence, alternative strategies for treatment of LLD are needed.
Whether exercise improves depressive symptoms in older populations has not been consistently demonstrated in trials; some have been positive (Williams and Lord, 1997), whereas others have yielded null effects (Jette et al., 1996). In a cluster-randomized controlled trial, for example, Underwood et al. found that a moderately intense exercise program did not reduce depressive symptoms in 65 years or older residents in care homes (Underwood et al., 2013). In a meta-analysis of seven exercise intervention studies, Bridle and his colleagues found a small to moderate effect (standardized mean difference = -0.34, 95% confidence interval -0.52 to -0.17) of exercise on depression in older adults (Biddle et al., 2015). Conversely, exercise may have beneficial effects as an adjunctive treatment for older adults who partially respond to antidepressant medications (Mura and Carta, 2013).
The lack of consistent results from exercise trials in patients with LLD appears multifactorial. In particular, previous research has shown positive effects of exercise on depression but studies have mainly focused on the short-term effects; few have examined the long-term effects (Helgadottir et al., 2017). In this study, therefore, we report the beneficial effects of a long-term exercise intervention on depressive symptoms in older Korean women.
Overall study design is illustrated in Figure 1. At baseline, a total of 30 older women were recruited from local retirement centers via flyers and advertisement. Study participants attended an orientation session where they received an explanation regarding the study and underwent a screening for study participation.
Eligibility criteria were: (a) age of 75 years or older; (b) having clinically significant depressive symptoms but not taking anti-depressants; (d) no pain in the knee(s) on most days of the month; or (e) no difficulty with the following due to knee pain: walking one-quarter mile; climbing stairs; getting in and out of a car, bath, or bed; rising from a chair; or performing shopping, cleaning, or self-care activities. Exclusion criteria were: (a) presence of a medical condition that precluded participation in a safe exercise program (e.g., recent myocardial infarction or stroke, severe chronic obstructive pulmonary disease, congestive heart failure); (b) inflammatory arthritis; (c) regular participation in exercise (more than once a week for at least 20 minutes); or (d) inability to walk without assistance.
Afterward, participants completed baseline assessments including depressive symptoms, physical fitness capacity, and body composition. Participants were then assigned to either control (n = 15, mean age of 78.6 [+ or -] 3.2 years) or exercise (n = 15, mean age of 80.8 [+ or -] 3.6 years) group (p value for age = 0.120). The sample size for each group was determined so that the study would be sufficiently powered to detect group differences in the primary outcome of depressive symptoms in this study. Based on our preliminary data, we calculated that a sample size of 12 participants per group would provide 85% power with probability of alpha error of 0.05 for detecting a statistically significant difference in the primary outcome between the two groups.
Individuals in the exercise group underwent a 6-month exercise program, while individuals in the control group maintained their sedentary lifestyles. Then, participants had post-intervention assessments using the same procedures as at baseline. Two participants in the exercise group refused to participate in the exercise intervention due to personal reasons, and three participants in the control group refused post-intervention assessment. Consequently, data obtained from 13 (retention rate of 90%) and 12 participants (retention rate of 85%) out of the exercise and control groups, respectively, were used for statistical analyses.
Informed consent was obtained from all participants prior to study participation. The Institutional Review Board, in accordance with the World Medical Association Declaration of Helsinki, reviewed and approved the study protocol (SKKU 2017-06-009).
Assessment of depressive symptoms
The Korean version of the Short form of the Geriatric Depression Scale (SGDS-K) was administered as a screening measure for depression...