Moderate exercise doses gave the most reliable cognitive gains in MCI

Design

Bayesian dose-response network meta-analysis of 38 randomised trials

Population

Adults aged ≥60 with mild cognitive impairment

Primary outcome

Working memory, cognitive flexibility and inhibitory control

Effect

Most reliable gains at about 300–1,000 MET-min/week; plateau at higher doses

This Bayesian dose-response network meta-analysis pooled 38 randomised trials of repeated exercise programmes in adults aged 60 and over with mild cognitive impairment, measuring working memory, cognitive flexibility and inhibitory control. Dose was standardised as MET-minutes per week.

Gains in all three executive domains followed a curve rather than a straight line. The most reliable benefit came at about 300–1,000 MET-minutes per week, with plateaus or small declines above that. Combined exercise and cognitive training gave the most consistent working-memory gains, while multicomponent training and walking were steadier for flexibility and inhibition. Certainty was low to moderate.

In practical terms, 300–1,000 MET-minutes is roughly 75 to 250 minutes a week of brisk walking. That is achievable for many older adults and argues against pushing frail patients towards very high volumes. The trials measured cognitive test scores, not dementia or independence.

• Advise older adults with MCI to aim for roughly 75–250 minutes a week of moderate activity such as brisk walking.
• Consider combining exercise with cognitive tasks, such as dual-task training, for working memory.
• Multicomponent programmes and walking suit most patients and are easy to start.
• There is no evidence here that higher volumes help more; build up gradually in frail patients.
• Screen for falls risk and cardiovascular limits before increasing activity.

Why it matters

It suggests a realistic target rather than 'as much as possible' for patients worried about memory.

Don't overread it

Improvements were in executive-function test scores; the analysis does not show that exercise prevents dementia.

The statistics, in plain English

A dose-response curve shows how benefit changes with the amount of exercise. A plateau means extra exercise adds little. 'Low to moderate certainty' means the true dose window may differ, and the outcomes are test scores, which may not translate into daily function.

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