Effects of exercise on improving depression, cognitive function, and sleep in older adults

Abstract

Facing the drastically increasing number of older population and prevalence rates of non-communicable diseases worldwide, exercise has been proposed as a non-pharmacological approach for the management of various aging-related diseases, including depression, mild cognitive impairment (MCI) and chronic insomnia. Two pilot randomized controlled trials, one systematic review and network meta-analysis and one non-inferiority randomized controlled trial were conducted to 1) evaluate the effects of walking exercise interventions following the World Health Organization physical activity guidelines and explore the role of exercise intensity and exercise frequency on alleviating depression and improving cognitive function in older adults; and 2) compare the treatment effectiveness and long-term effects of Tai Chi to the common treatment approaches for chronic insomnia - cognitive behavioral therapy for insomnia (CBT-I) and pharmacotherapy on improving sleep in older adults.

The first study investigated the effects of a 12-week walking exercise intervention and explored the role of exercise intensity on alleviating depression in older adults with clinical depression. Participants were randomized to usual care control (n=11), moderate-intensity walking exercise (n=13) and vigorous-intensity walking exercise groups (n=11). The moderate- and vigorous-intensity walking exercise significantly and similarly improved depression compared to the control group. The second study investigated the effects of a 12-week walking exercise intervention on improving cognitive function in older adults with MCI. Participants were randomly allocated to the stretching exercise control (n=10), once-a-week moderate-intensity walking exercise (n=10), thrice-a-week moderate-intensity walking exercise (n=10), once-a-week vigorous-intensity walking exercise (n=10) and thrice-a-week vigorous-intensity walking groups (n=10). Participants in four walking groups demonstrated significant improvements in global cognitive function compared to the stretching exercise control group.

The third study comparatively investigated the long-term (≥ 6 months after the interventions ended) effectiveness of exercise, CBT-I and pharmacotherapy on improving sleep in chronic insomniacs using a systematic review and network meta-analytical approach. The findings showed that at the end of the follow-up period, both exercise and CBT-I were superior in improving sleep compared to control, while pharmacotherapy did not show sustained benefits. In addition, no significant differences were found between exercise and CBT-I.

The fourth study investigated whether 1) 3 months of Tai Chi (experimental) is non-inferior to 3 months of CBT-I (the first-line non-pharmacological treatment of insomnia) in treating chronic insomnia in older adults and 2) whether Tai Chi is non-inferior to CBT-I in maintaining sleep quality after a 12-month follow-up. The detailed study protocol was presented in the chapter 5 and the preliminary results were reported in the chapter 6. Older adults with chronic insomnia were randomized to Tai Chi (n=37) and CBT-I (n=39) groups. The results showed that both Tai Chi and CBT-I significantly improved sleep after the 3-month intervention. And after the 12-month follow up, Tai Chi was non-inferior to CBT-I on improving sleep.

Collectively, the present work demonstrated that walking exercise and Tai Chi conferred promising beneficial effects on improving depression, cognitive function and sleep in older adults, which highlights the importance of promoting regular exercise among older adults to combat the tidal wave of non-communicable diseases.