Dementia Risk in Older Women Reduced with More Vigorous Physical Activity, More Daily Steps

Increasing daily step count and adding minutes of moderate-to-vigorous exercise reduced the risk of mild cognitive impairment (MCI) or dementia among women aged ≥65 years in one of the few studies to measure physical activity using research-grade accelerometers.

According to the study authors from the Herbert Wertheim School of Public Health and Human Longevity Science at University of California San Diego (UCSD), physical activity has been established as 1 of the 3 most promising ways to lower an individual’s risk of dementia and Alzheimer disease.

“However, because few large studies have examined device measures of movement and sitting in relation to mild cognitive impairment and dementia, much of the published research on the associations of physical activity and sedentary behavior with cognitive decline and dementia is based on self-reported measures,” said first author, Steve Nguyen, PhD, MPH, postdoctoral scholar at the Herbert Wertheim School of Public Health, in a statement from UCSD. Accelerometry more accurately and more completely captures ambulatory movement, the authors write, and particularly light intensity activity and sedentary behavior patterns among older adults.

Accelerometry more accurately and more completely captures ambulatory movement, and particularly light intensity activity and sedentary behavior patterns among older adults.

For this study, the authors hypothesized that higher amounts of physical activity and lower amounts of sitting measured by accelerometer would be associated with lower risk of MCI and probable dementia, that the associations would be linear, and that magnitude would be consistent across relevant variables including age, body mass index (BMI), physical functioning, and CVD risk factor profile.

Published online January 25, 2023, in Alzheimer’s & Dementia, the study found that among more than 1000 women participating in 2 Women’s Health Initiative (WHI) ancillary studies, each additional 1-standard deviation (SD) increment (31 minutes/day) of moderate-to-vigorous physical activity (MVPA) was associated with a 21% lower risk of developing MCI or dementia. With each additional 1865 steps/day, the risk dropped by 33%.

The researchers sampled data from 1277 women enrolled in both the WHI Memory Study and the Objective Physical Activity and Cardiovascular Health study. The median age among participants was 82 ± 6 years.

Investigators gave each participant a research-grade accelerometer and instructed them to pursue regular daily activities for up to 7 days to register accurate measures of the full range of physical activity as well as sitting. For purposes of the analysis, light physical activity could include housework, gardening, or walking. MVPA could include brisk walking.

Investigators then examined the associations of the accelerometer measures with incident MCI/probable dementia.

FINDINGS

When they analyzed accelerometer data the investigators found that on a daily basis the women averaged:

• 3,216 steps
• 276 minutes in light physical activities
• 45.5 minutes of moderate-to-vigorous physical activity
• 10.5 hours of sitting

During a median follow-up of 4.2 years, the Wertheim School team observed 167 (13%) incident MCI, 161 (12%) incident dementia, and 267 (21%) combined cases of MCI/probable dementia.

Higher MVPA and steps/day were associated with lower adjusted risks of incident MCI, probable dementia, and MCI/probable dementia.

MVPA associations

Compared to women with <23 MVPA min/day, those with at least 61 min/day had a 36% lower risk of incident MCI ( 95% CI 0.36 to 1.13; P_trend=.047), 21% lower risk of probable dementia (95% CI 0.45 to 1.37; P_trend=.189), and 31% lower risk of MCI/probable dementia (95% CI 0.45 to 1.06; P_trend.009), all independent of relevant covariates including physical functioning, BMI, and CVD risk.

Steps/day associations

The associations for steps/day were stronger than for MVPA min/day, according to the study. Compared to women with <1867 steps/day, those with at least 4050 steps/day had a 64% lower risk of MCI (95% CI 0.20 to 0.66; P_trend =.006), 52% lower risk of probable dementia (95% CI 0.26 to 0.87; P_trend=.008), and 63% lower risk of MCI/probable dementia (95% CI 0.23 to 0.61; P_trend< .001) independent of covariates.

The HR (95% CI) for each 1-SD increment in MVPA (31 min/day) was 0.79 (95% CI 0.67 to 0.94) and for steps/day (1865) 0.67 (95% CI 0.54 to 0.82).

Perhaps counterintuitively, the authors report that higher amounts of sitting and prolonged sitting were not associated with a higher risk of MCI/probable dementia.

Larger studies, more diversity

The authors state that their findings compare favorably with those of several large cohort studies that have analyzed accelerometer-measured data, including 2 in the UK Biobank. However, they say that "larger studies with accelerometer measures, adjudicated cognitive outcomes, and long follow-up periods are needed” to further investigate and clarify associations between physical activity, sedentary behavior, and bidirectional associations that may mediate physical activity and brain aging. Future research should also include more diverse populations that include men

"Overall, the present study contributes important novel information on device-measured PA and sitting in relation to MCI and probable dementia among older women, which is desperately needed as part of an evolving evidence-base aimed at delaying or preventing (Alzheimer's disease and related dementias ) in an aging society.

The authors said further research is needed among large diverse populations that include men.

Reference: Nguyen S, LaCroix AZ, Hayden KM, et al. Accelerometer-measured physical activity and sitting with incident mild cognitive impairment or probable dementia among older women. Alzheimers Dement. Published online January 25, 2023. doi:10.1002/alz.12908