Meeting World Health Organization recommendations for levels of physical activity reduces the odds of prevalent depression by 40%, according to a study of more than 4,000 adults aged 50 years and older.
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“To [our] knowledge, this is the first prospective cohort study to examine the protective effect of meeting [moderate to vigorous physical activity] guidelines, and different volumes of walking, on depression among a sample of adults,” Cillian P. McDowell, of the University of Limerick (Ireland), and his associates wrote in Experimental Gerontology.
The study drew on data from The Irish Longitudinal Study of Ageing and included 4,556 individuals, 56.7% of whom were female. The investigators created “dose categories” based on how much exercise participants performed each week. For moderate to vigorous physical activity, they assigned participants to low (0 to less than 600 metabolic equivalent [MET]–minutes per week), moderate (600 to less than 1,200 MET-min/week), and high (1,200 or more MET-min/week) categories. For walking, investigators divided participants among tertiles of minutes performed (0-110 min/week, 120-400 min/week, and 420 or more min/week). Symptoms of depression were assessed using the Center for Epidemiologic Studies Depression Scale, reported Mr. McDowell and his associates.
The odds of prevalent depression were 40% lower (odds ratio, 0.60; 95% confidence interval, 0.48-0.76) among participants who met the physical activity guidelines, 23% lower (OR, 0.77, 95% confidence interval, 0.49-1.21) among those who were in the moderate and high categories, and 43% lower (OR, 0.57; 95% CI, 0.45-0.73) among those who were in the moderate and high categories, Mr. McDowell and his associates wrote.
The study was not conducted to explore possible mechanisms underlying the ties between physical activity and depression. However, Mr. McDowell and his associates speculated that exercise training has both brain monoaminergic and neurotropic effects and might lower “inflammatory and oxidant markers. Further, physical activity may be associated with depression through psychological factors such as self-esteem.”
Mr. McDowell and his associates wrote. “Recent evidence has shown that people with [major depressive disorder] engage in higher levels of sedentary behavior, and that cross-sectionally sedentary behavior, is positively associated with depression,” they added. “Meeting WHO recommended [physical activity] levels could be recommended ... to prevent the onset of depression.”
The investigators pointed out that one of the major limitations of the study was that participants’ depression and activity were self-reported, which could predispose results to over- or underreporting. They also pointed out that a strength of the study was its large sample size.
Mr. McDowell and his associates reported no conflicts of interest. The sponsors of The Irish Longitudinal Study of Ageing played no role in this study’s design, methods, subject recruitment, data collection, analysis, or preparation.
SOURCE: McDowell CP et al. Exp Gerontol. 2018 Oct 2;112:68-75.