Concurrent associations between visit-to-visit changes in actigraphy-based physical activity and cognitive aging in older adults.

Within-person increases in daily step count were significantly associated with within-person increases in executive functioning.

• Standardized β = 0.128, 95% CI [0.056, 0.200], p ≤ 0.001
• Association was examined using linear mixed-effects models with visit-to-visit PA as a predictor
• Models controlled for time (years since baseline), baseline age, sex, and education
• 107 older adults were included, completing neuropsychological testing and brain MRI followed by 30-day Fitbit monitoring at two or more annual study visits

Within-person increases in daily step count were significantly associated with within-person decreases in depressive symptoms.

• Standardized β = -0.201, 95% CI [-0.284, -0.119], p ≤ 0.001
• This was described as one of the strongest associations observed in the study
• The association was concurrent, measured at the same study visit as the PA assessment
• PA was objectively measured via Fitbit actigraphy over 30-day monitoring periods

Longitudinal associations between within-person changes in PA and memory did not reach statistical significance.

• Memory was assessed as part of neuropsychological testing at each annual study visit
• Linear mixed-effects models were used to examine memory as a function of visit-to-visit PA
• The non-significant finding was in contrast to the significant executive function association
• Models included covariates of time, baseline age, sex, and education

Longitudinal associations between within-person changes in PA and hippocampal volumes did not reach statistical significance.

• Hippocampal volumes were measured via brain MRI at each annual study visit
• Neuroimaging models additionally included total intracranial volume as a covariate
• 107 older adults completed both neuropsychological testing and brain MRI followed by Fitbit monitoring
• The absence of a significant hippocampal association contrasts with cross-sectional literature linking PA to hippocampal structure

Longitudinal associations between within-person changes in PA and white matter hyperintensities (WMH) did not reach statistical significance.

• WMH were measured via brain MRI at each annual study visit
• Neuroimaging models included total intracranial volume as an additional covariate
• Linear mixed-effects models examined WMH as a function of visit-to-visit average daily step count
• The non-significant WMH finding was grouped with hippocampal volumes as outcomes not reaching statistical significance

The study used a longitudinal within-person design with objectively measured PA via actigraphy in older adults at the UCSF Memory and Aging Center.

• 107 older adults completed neuropsychological testing and brain MRI followed by 30-day Fitbit monitoring at two or more annual study visits
• PA was measured as average daily step count over 30-day Fitbit monitoring periods
• Visits were annual, and time was modeled as years since baseline
• Outcomes included memory, executive function, hippocampal volumes, WMH, and depressive symptoms
• Linear mixed-effects models were used to examine concurrent visit-to-visit associations between changes in PA and changes in each outcome

Real-world actigraphy-based monitoring of movement may be sensitive to early and subtle aspects of neurobehavioral declines with aging.

• Authors interpret the significant PA-executive function and PA-depressive symptom associations as evidence of this sensitivity
• The concurrent nature of the associations suggests PA tracks with real-time neurobehavioral status rather than only long-term structural brain changes
• The authors note that few prior studies have examined objectively measured PA with concurrently measured brain and cognitive aging outcomes longitudinally
• The findings are described as suggesting 'within-person changes in PA may reduce real-time risk of cognitive decline'