- Design
- Bayesian network dose-response meta-analysis of 28 randomised trials
- Population
- 2,262 adults aged 50 or over with mild cognitive impairment
- Primary outcome
- Depressive symptoms and peripheral BDNF
- Effect
- Depression: largest predicted effect 0.38 (95% CrI 0.15 to 0.67) at 670 MET-min/week
A Bayesian network meta-analysis in PLOS ONE (7 October) pooled 28 randomised trials of exercise in 2,262 adults aged 50 and over with mild cognitive impairment, modelling how the type and weekly amount of exercise related to depressive symptoms and blood BDNF.
Exercise was associated with improved depressive symptoms, with the largest predicted effect at about 670 MET-minutes per week (effect size 0.38, 95% credible interval 0.15 to 0.67), roughly two and a half hours of moderate activity. Dancing and multicomponent programmes looked most favourable; estimates for tai chi, walking and yoga were less precise. Different statistical models placed the best dose differently.
Depression is common in mild cognitive impairment and medication options carry anticholinergic and falls risks. Structured exercise is a low-risk option to recommend. The specific best dose is a modelling estimate, not a proven target.
- Recommend regular structured exercise for older adults with mild cognitive impairment, including those with low mood.
- Consider dancing or multicomponent programmes combining aerobic, strength and balance work.
- Aim for around two to three hours of moderate activity a week as a practical goal, adjusted for fitness.
- Screen for depression in people with mild cognitive impairment.
Why it matters
It supports a safe, non-drug option for depression in a group at high risk from psychotropic side effects.
Don't overread it
The 'best dose' figures are model predictions that changed with the statistical model, not established targets.
The statistics, in plain English
A posterior mean of 0.38 is a small-to-moderate effect, and the credible interval (0.15 to 0.67) excludes no effect. A network meta-analysis compares exercise types indirectly, so rankings between them are less certain than the overall benefit.
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