Abstract Body: Introduction: Higher amounts of physical activity (PA) have been shown to be associated with lower risk of Alzheimer’s disease related dementias (ADRD), however few studies have prospectively examined accelerometer measures of PA and sitting with ADRD and specifically vascular dementias (VD) among older diverse women.

Methods: Older postmenopausal women (n=5417; mean age=78 ± 7 years; 33% Black, 17% Hispanic) in the Objective Physical Activity and Cardiovascular Health Study without prior ADRD wore accelerometers for 7 days in May 2012-April 2014 and were followed through December 31, 2021. Incident ADRD was classified using Medicare Claims data, allowing for identification of events among older Black, Hispanic or Latina, and White women. Multivariable Cox models estimated hazard ratios (HR) and 95% confidence intervals (CI) for total PA, light PA (LPA), moderate-to-vigorous intensity PA (MVPA), steps/day, total sitting time, and mean sitting bout duration (MSBD) with ADRD and VD adjusting for age, race and ethnicity, education, alcohol, smoking, hypertension, diabetes, physical functioning, and body mass index (BMI). We additionally carried out stratified analysis across covariates.

Results: There were 1143 ADRD events, including 187 VD events, during a median follow-up of 8.6 years. The HR (95% CI; P-trend) for ADRD and VD for each 1 standard deviation (SD) increment was 0.83 (0.69-1.00; 0.04) and 0.77 (0.48-1.25; 0.70) for total PA (SD=90 minutes/day), 0.58 (0.48-0.71; <0.001) and 0.61 (0.38-0.99; 0.02) for MVPA (SD=34 minutes/day), 0.53 (0.43-0.65; <0.001) and 0.57 (0.34-0.97; 0.01) for steps/day (SD=2051 steps/day), and 1.15 (0.95-1.38; 0.03) and 0.84 (0.52-1.37; 0.72) total sitting time (SD=102 minutes/day). Associations for steps with ADRD were similar among Black (HR=0.69, 95% CI=0.57-0.85), White (HR=0.70, 95% CI=0.61-0.81) and Hispanic or Latina women (HR=0.80, 95% CI=0.63-1.01, P-interaction=0.32). LPA and MSBD were not associated with ADRD or VD.

Conclusions: Higher MVPA and steps/day were associated with lower ADRD and VD risk while higher total sitting time was associated with higher ADRD risk, supporting interventions aimed at increasing PA and reducing SB for ADRD prevention in diverse populations.