Evidence summary (Updated 2022)
A meta-analysis of prospective studies has reported a protective effect for physical activity in all-cause dementia – incidence of dementia was reduced by 21% in those who undertook high levels of physical activity, and by 24% with moderate levels. Greater benefit was seen in Alzheimer’s Disease (37% risk reduction with high levels of activity, 29% with moderate levels), but no protective effect was observed in vascular dementia (although this finding may have been limited by a smaller sample size) . Another systematic review reported that physical activity conveys a mild positive effect on cognition but was not able to observe a dose-response relationship . This finding has not always been observed in the oldest age groups – a population-based cohort study of over-75s demonstrated no significant effect of physical inactivity and risk of severe cognitive impairment or dementia . Physical activity in mid-life has been associated with positive ageing outcomes, including the absence of cognitive impairment or mental health limitations .
A retrospective study of individuals with a family history of Alzheimer’s Disease (≥1 affected relative), showed greater cognitive function in those who met recommended physical activity guidelines, compared to those who were inactive . There is increasing evidence that higher levels of physical activity may be associated with reduced risk of cognitive decline, but such conclusions are limited by a large variability in study design, differences in assessment of cognition/definitions of dementia and use of self-reported levels of physical activity.
In recently updated evidence, further studies report that physical activity reduces the risk of all-cause dementia and Alzheimer’s disease  There is evidence of a strong association between moderate or high levels of physical activity and improved cognitive performance later in life (even after multivariate adjustment), particularly in women who engaged in higher physical activity in earlier years . The exact dose- response relationship is however uncertain, with evidence that even ‘minor’ physical activity is connected to a lower dementia risk and inactivity is a risk factor for dementia . A recent systematic review assessing interventions to prevent dementia and reduce cognitive decline concluded that twice weekly aerobic exercise for 16 weeks had a moderate effect on global cognition. They also reported that resistance training for less than four months was ineffective at improving cognition .
Quality of Evidence
Strength of recommendation
Physical activity should be strongly encouraged in order to prevent cognitive decline and may be effective in reducing the likelihood of dementia.
 Impact of Physical Activity on Cognitive Decline, Dementia, and Its Subtypes: Meta-Analysis of Prospective Studies. Biomed Res Int. 2017;2017:9016924. Epub 2017 Feb 7.
 Physical Activity in Community Dwelling Older People: A Systematic Review of Reviews of Interventions and Context. PLoS One. 2016 Dec 20;11(12):e0168614.
 Lack of associations between modifiable risk factors and dementia in the very old: findings from the Cambridge City over-75s cohort study. Aging Ment Health. 2017 Feb 2:1-7. [Epub ahead of print]
 Behavioural Risk Factors in Mid-Life Associated with Successful Ageing, Disability, Dementia and Frailty in Later Life: A Rapid Systematic Review. PLoS One. 2016 Feb 4;11(2):e0144405. eCollection 2016.
 Physical activity is associated with higher cognitive function among adults at risk for Alzheimer’s disease. Complement Ther Med. 2018 Feb;36:46-49. Epub 2017 Nov 24.
 Brini S, Sohrabi HR, Peiffer JJ et al. (2018) Physical Activity in Preventing Alzheimer’s Disease and Cognitive Decline: A Narrative Review. Sports Med 48, 29–44.
 Yu J-T, Xu W, Tan C-C et al. (2020) Evidence-based prevention of Alzheimer’s disease: systematic review and meta-analysis of 243 observational prospective studies and 153 randomised controlled trials J Neurol Neurosurg Psychiatry 2020;91:1201–1209. doi:10.1136/jnnp-2019-321913.
 Hussenoeder FS, Riedel-Heller SG. (2018) Primary prevention of dementia: from modifiable risk factors to a public brain health agenda? Soc Psychiatry Psychiatr Epidemiol. Dec;53(12):1289-1301. doi: 10.1007/s00127-018-1598-7. Epub 2018 Sep 25. PMID: 30255384
 Whitty E, Mansour H, Aguirre E, et al (2020) Efficacy of lifestyle and psychosocial interventions in reducing cognitive decline in older people: Systematic review. Ageing Res Rev. 2020 Sep;62:101113. doi: 10.1016/j.arr.2020.101113. Epub 2020 Jun 10. PMID: 32534025.