For older adults, a lack of exercise may put their risk of developing dementia on par with that of adults who are genetically predisposed to the disease, a Canadian study has found.
One of the biggest risk factors for Alzheimer’s disease is the apolipoprotein E (APOE) e4 gene and, the report says, according to the Alzheimer’s Association, adults who possess one copy of the APOE e4 gene are three times more likely to develop the disease than those without the gene, while those with two copies are 8-12 times more likely to develop Alzheimer’s.
However, the researchers of the new study that included Jennifer Heisz, an assistant professor in the department of kinesiology at McMaster University in Canada, suggest that the risk of dementia may be just as high for older adults exhibiting sedentary behaviour. For their study, Heisz and colleagues set out to investigate the association between physical activity and dementia risk among older adults with and without the APOE e4 gene.
The report says the researchers came to their findings by analysing the physical activity and dementia development of 1,646 older adults who were part of the Canadian Study of Health and Aging. All participants were free of dementia at study baseline and followed up for around 5 years.
Among adults who did not carry the APOE e4 gene, the researchers found that those who did not exercise were more likely to develop dementia than those who exercised.
For APOE e4 gene carriers, however, there was no significant difference in dementia risk between those who exercised and those who did not.
According to the researchers, these findings indicate that a lack of exercise may be just as risky for dementia development than carrying the APOE e4 gene. The study results also suggest that increasing physical activity may protect against the development of dementia in people without the APOE e4 gene.
“Although age is an important marker for dementia, there is more and more research showing the link between genetic and lifestyle factors,” says study co-author Parminder Raina, a professor in the department of health evidence and impact at McMaster. “This research shows that exercise can mitigate the risk of dementia for people without the variant of the apolipoprotein genotype,” he adds. “However, more research is needed to determine the implications from a public health perspective.”
Lead study author Barbara Fenesi, a postdoctoral fellow at McMaster, points out that further studies are needed in order to pinpoint the type of exercise that is most beneficial for brain health. “A physically active lifestyle helps the brain operate more effectively. However, if a physician were to ask us today what type of exercise to prescribe for a patient to reduce the risk of dementia, the honest answer is ‘we really don’t know,'” she says.
Genetics and lifestyle independently determine dementia risk, but the interaction is unclear. We assessed the interactive relationship of apolipoprotein E (APOE) genotype and physical exercise on dementia risk over a 5-year period in 1,646 older adults from the Canadian Study of Health and Aging who were dementia-free at baseline. Physical exercise moderated the relationship between genotype and dementia (p < 0.01). Specifically, for APOE ɛ4 non-carriers, the odds of developing dementia were higher in non-exercisers than exercisers (OR = 1.98, 95% CI = 1.44, 2.71, p < 0.001), whereas, for APOE ɛ4 carriers, the odds of developing dementia were not significantly different between non-exercisers and exercisers (OR = 0.71, 95% CI = 0.46, 1.31, p = 0.34). Given that most individuals are not at genetic risk, physical exercise may be an effective strategy for preventing dementia.
Fenesi, Barbara; Fang, Hanna; Kovacevic, Ana; Oremus, Mark; Raina, Parminder; Heisz, Jennifer J