The significance of physical activity to brain health has been investigated extensively. Studies have provided indications of the protective effect of physical activity on the health of the brain, but findings have been partially contradictory.
In a meta-analysis conducted collaboratively by the University of Helsinki and the University of Jyväskylä, prior research findings on the link between physical activity and the risk of developing a memory disorder were collected and analysed together. The study encompassed 58 research articles, in which a total of more than 250,000 individuals from around the world had been studied.
The findings published in the British Journal of Sports Medicine demonstrate that the risk of developing a range of memory disorders is reduced in people who engage in physical activity. Physically active individuals have a lower risk of developing both Alzheimer's disease and vascular dementia.
In the meta-analysis, the effect of the level of physical activity on the risk of developing a memory disorder was also assessed.
“Based on our analyses, exercising even just a little was particularly important,” says Postdoctoral Researcher Paula Iso-Markku from the University of Helsinki.
The researchers also sought to determine whether the research design, such as the follow-up duration or the age of the study subjects, has an impact on the connection between physical activity and memory disorders.
The development of a memory disorder can take as long as over 20 years. In many of the studies examined now, the follow-up period had been short, and data on physical activity had been collected for only a few years preceding the related memory tests.
“In such research designs, a developing memory disorder could be seen as reduced physical activity, in which case this reduction would actually be caused by the memory disorder. However, our meta-analysis indicates that the protective role of physical activity also emerges in longer follow-ups and already in middle age,” says Iso-Markku.
The researchers also investigated the effect of hereditary risk on the link between physical activity and memory disorders.
Roughly one-third of Finns carry the ApoE4 gene variant, which predisposes them to Alzheimer's disease as well as cardiovascular diseases. This gene type has previously also been thought to have an effect on the connection between physical activity and memory disorders.
“Based on our research, physical exercise reduces the risk of memory disorders regardless of the genetic risk associated with the ApoE4 allele,” says Katja Waller from the University of Jyväskylä.
According to the researchers, it should be noted that causalities cannot be verified with the follow-up studies that have now been analysed. Further research on the topic is also needed, since studies where no connection between physical activity and memory disorders is found may remain unpublished. However, this meta-analysis lends support to the role of physical activity in maintaining brain health.
The study, which was published in the British Journal of Sports Medicine, is openly available. The project received funding from the Juho Vainio Foundation and the Academy of Finland.
Original publication: Paula Iso-Markku, Urho Kujala, Knittle Keegan, Juho Polet, Eero Vuoksimaa, Katja Waller. Physical activity as a protective factor for dementia and Alzheimer’s disease: systematic review, meta-analysis, and quality assessment of cohort and case-control studies. British Journal of Sports Medicine 2022. Online First: 17 March 2022. http://dx.doi.org/10.1136/bjsports-2021-104981
Paula Iso-Markku, MD, postdoctoral researcher, Institute for Molecular Medicine Finland (FIMM), HiLIFE, University of Helsinki
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Katja Waller, PhD (Health Sciences), university lecturer, Faculty of Sport and Health Sciences, University of Jyväskylä
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