Higher level of physical activity decreases risk of disabling dementia

Moderate to vigorous physical activity was associated with decreased risk of disabling dementia in men, according to a study published in JAMA Network Open.

“This cohort study examined associations of daily total physical activity and total [moderate to vigorous physical activity (MVPA)] with risk of disabling dementia,” Hikaru Ihira, PT, PhD, a researcher for the epidemiology division in the Center for Public Health Sciences at the National Cancer Center in Japan, and colleagues wrote. “The findings suggest that a high level of leisure-time MVPA was associated with decreased risk of disabling dementia in men.”

Ihira and colleagues conducted a data analysis between February 2019 and July 2021 of the Japan Public Health Center-based Prospective Disabling Dementia Study of two cohorts, which was segmented into quarters based on physical activity. Cohort one launched in 1990, and cohort two launched in 1993, with data collection taking place between 2000 and 2003 and between 2006 and 2016.

Of 43,896 participants (mean age, 61; 53.9% women), the authors discovered risk of dementia decreased in the second quarter (adjusted HR = 0.73; 95% CI, 0.65-0.82), third quarter (aHR = 0.69; 95% CI, 0.61-0.78) and fourth quarter (aHR = 0.75; 95% CI, 0.66-0.8) with increased physical activity for men, as well as women in the second (aHR = 0.76; 95% CI, 0.69-0.84), third (aHR = 0.73; 95% CI, 0.66-0.81) and fourth quarters (aHR = 0.75; 95% CI, 0.67-0.84), compared with the first quarter of daily total physical activity.

“After excluding participants diagnosed within 7 years from the starting point in men and within 8 years in women, the inverse associations of daily total physical activity and total MVPA with risk of disabling dementia incidence disappeared,” the researchers wrote.

Participants with high daily total physical activity level were younger, had a lower BMI, were likely to never smoke, likely to drink, unlikely to be unemployed and had a lower prevalence of diabetes and hypertension.

However, an inverse effect associated with leisure time and disabling dementia risk remained in men in the fourth quarter of observation (aHR = 0.72; 95% CI, 0.56-0.92) but not in women.

“To our knowledge, this is the first prospective cohort study to suggest a potential for reverse causation bias between daily total physical activity and total MVPA and dementia,” the researchers concluded. “In contrast, a higher level of leisure-time MVPA was associated with reduced risk of disabling dementia in men.”