Study ties sedentary lifestyle to dementia risk
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Key takeaways:
- The incidence of dementia increased as more time was spent being sedentary.
- Research is still needed to determine whether the relationship between sedentary time and dementia is causal.
Among older adults, more time spent being sedentary was significantly associated with a higher incidence of dementia, a study published in JAMA found.
“Half of U.S. adults spend more than 9.5 hours of their day sitting, including more than 80% of their leisure time,” David A. Raichlen, PhD, a professor of biological sciences and anthropology at the University of Southern California, and colleagues wrote. “Previous work has detailed the potential links between sedentary behaviors and a range of health risks, including associations with both cognitive and structural brain aging.”
The researchers analyzed data from a U.K. Biobank cohort of 49,841 adults, aged 60 years and older who did not have a diagnosis of dementia at baseline. The researchers accounted for participants’ mean daily sedentary behavior time, mean daily sedentary bout length, maximum daily sedentary bout length and the mean number of daily sedentary bouts — all measured using wrist-worn accelerometers. The study’s primary outcome was incident all-cause dementia diagnosis, based on inpatient hospital records and death registry data.
Participants were followed for a mean of 6.72 years.
Overall, 414 participants were diagnosed with dementia. Raichlen and colleagues found that HRs for dementia, relative to 9.27 hours of sedentary behavior a day, were:
- 1.08 (95% CI, 1.04-1.12) for 10 hours of sedentary time a day;
- 1.63 (95% CI, 1.35-1.97) for 12 hours of sedentary time a day; and
- 3.21 (95% CI, 2.05-5.04) for 15 hours of sedentary time a day.
Meanwhile, the adjusted incidence rate of dementia per 1,000 person-years was:
- 7.49 (95% CI, 7.48-7.49) for 9.27 hours of sedentary time a day;
- 8.06 (95% CI, 7.76-8.36) for 10 hours of sedentary time a day;
- 12 (95% CI, 10-14.36) for 12 hours of sedentary time a day; and
- 22.74 (95% CI, 14.92-34.11) for 15 hours of sedentary time a day.
Both mean daily sedentary bout length (HR = 1.53; 95% CI, 1.03-2.27) and maximum daily sedentary bout length (HR = 1.15; 95% CI, 1.02-1.31) were significantly associated with a higher risk for dementia, although these associations were no longer significant when the researchers accounted for mean daily sedentary behavior time.
Raichlen and colleagues noted the mean daily sedentary time of 9.5 hours in the U.S. “falls close to the level when the risk of dementia began to increase in this study.”
“Similar to the results for mortality, the links between high levels of sedentary behavior and incident dementia remain strong when adjusting for time spent engaged in moderate to vigorous intensity physical activity,” they wrote.
The researchers concluded that future research is warranted “to determine whether the association between sedentary behavior and risk of dementia is causal.”