Psychiatrist.comPhysical Exercise and Health, 6: Sedentary Time, Independent of Health-Related Physical Activity, as a Risk Factor for Dementia in Older Adults

Unveiling the Connection Beyond Physical Activity

Recent research magnifies the significant impact of sedentary behavior on the risk of dementia among older adults, independent of their engagement in moderate to vigorous physical activity. With sedentariness ingrained in our daily lives, through activities such as sitting for prolonged periods, watching television, and using smartphones, its implications on cognitive health have become a focal point of study. This comprehensive analysis explores how sedentary lifestyles, distinct from low physical activity levels, contribute to an increased risk of dementia, highlighting the necessity for a shift in both public health messaging and individual lifestyle choices.

Key Points:

• Sedentary behavior, characterized by activities requiring less than 1.5 metabolic equivalents (METs) and common in everyday life, is now recognized as a distinct factor contributing to dementia risk, beyond the absence of moderate to vigorous physical activity.
• A dose-dependent relationship exists between sedentariness and the incidence of dementia; individuals with sedentary behavior exceeding 10 hours per day face significantly increased risk, with the adjusted 10-year risk of dementia rising from approximately 8% to 23% as daily sedentariness increases from 10 to 15 hours.
• This association remains significant even after adjusting for moderate to vigorous physical activity, suggesting that reducing sedentary time is crucial for dementia risk reduction, independent of physical activity levels.
• The findings from a recent cohort study utilizing the UK Biobank data indicate that even after excluding subjects who developed dementia within the first four years of follow-up, to account for reverse causation, a clear link between higher levels of sedentariness and increased dementia risk was observed.
• Despite limitations such as the potential for residual confounding and the absence of randomized controlled trials to provide direct guidance, the evidence suggests a prudent approach would be to encourage less sedentary behaviors, considering their association with other adverse health outcomes as well.

HCN Medical Memo
Moderate to vigorous physical activity reduces the risk of dementia, while sedentariness increases it, independent of physical activity levels, a relationship that remains robust even after accounting for reverse causation.

More on Exercise/Working Out