Physical inactivity does not increase dementia odds except in cardiometabolic disease
Physical inactivity in adults was not associated with all-cause Alzheimer’s disease or dementia, but a signal of elevated risk for dementia was observed in physically inactive adults who developed cardiometabolic disease, according to findings of a meta-analysis published in The BMJ.
Mika Kivimäki, PhD, and colleagues sought to determine whether physical activity was a risk factor for dementia, with attention to the role of cardiometabolic disease in the association and reverse causation bias arising from physical inactivity in the preclinical phase of dementia.
“Randomized controlled trials have linked physical activity to better cognitive performance, but they have not shown reduced risk of dementia or Alzheimer’s disease,” Kivimäki, a professor in the department of epidemiology and public health at the University College of London and the University of Helsinki, and colleagues wrote.
Kivimäki and colleagues identified 404,840 participants in the study population (mean age, 45 years; 58% women) without dementia, who had a measurement of physical inactivity at study entry and were linked to electronic health records.
In 6 million person-years at risk, 2,044 incident cases of all-cause dementia were recorded, the researchers wrote.
Incident cases of Alzheimer’s disease were 1,602 in 5.2 million person-years, according to data found in studies with information on dementia subtype, Kivimäki and colleagues wrote.
When measured with less than 10 years before dementia diagnosis, physical inactivity was associated with increased incidence of all-cause dementia (HR = 1.4; 95% CI 1.23-1.71) and Alzheimer’s disease (HR = 1.36; 95% CI, 1.12-1.65), the researchers wrote.
Kivimäki and colleagues wrote that when reverse causations were minimized through assessing physical activity 10 or more years before dementia onset, there was no difference in risk for dementia between people who were physically inactive and those who were physically active.
According to the researchers, physical inactivity was consistently associated with increased risk for incident diabetes (HR = 1.42; 95% CI, 1.25-1.61) and CHD (HR = 1.24; 95% CI, 1.13-1.36). Stroke was also associated with physical inactivity (HR = 1.16; 95% CI, 1.05-1.27).
Among participants with cardiometabolic diseases that preceded dementia, physical inactivity was nonsignificantly associated with dementia (HR for physical activity assessed > 10 years before dementia onset = 1.3; 95% CI, 0.79-2.14), the researchers wrote.
Future large-scale studies should assess cumulative physical activity using repetitive measures including wearing accelerometers while extending dementia follow-up until old age or death, Kivimäki and colleagues wrote.
“Physical activity is promoted as a simple, widely applicable, low-cost strategy that could reduce the burden of diabetes, coronary heart disease and stroke. Our findings support this basic tenet of prevention in public health,” Kivimäki and colleagues wrote. “However, there was little evidence that targeting physical inactivity alone would prevent dementia or Alzheimer’s disease.” – by Earl Holland Jr.
Disclosures: The authors report no relevant financial disclosures.