Passive Measures of Physical Activity and Cadence as Early Indicators of Cognitive Impairment: Observational Study.

Background: Emerging research suggests that regular physical activity can reduce the risk of cognitive decline. However, most prior studies rely on self-reported measures, which are subject to recall bias, subjectivity, and limited temporal resolution. Objective: This study aims to investigate whether objectively measured physical activity, captured through passive accelerometry, is associated with incident cognitive impairment and neuropsychological test performance and to evaluate its potential as an early indicator of cognitive decline. Methods: We analyzed data from the Framingham Heart Study (FHS), a community-based cohort with longitudinal surveillance of cognitive impairment. Participants wore an Actical accelerometer for at least 3 days (excluding bathing). A total of 30 accelerometer-derived physical activity measures were categorized into intensity-specific durations, step and cadence summaries, and peak cadence. At FHS, diagnoses of cognitive impairment were established by a review committee based on established criteria. Cox proportional hazard models were used to examine the association with incident cognitive impairment, adjusting for age, gender, education, and accelerometer wear time. Time-dependent area under the receiver operating characteristic curves, derived from random survival forest models, were used to assess predictive performance. Linear regression models were used to evaluate the associations between physical activity measures and 18 neuropsychological test scores. Results: Among 1212 participants from the FHS Offspring cohort (age: mean 70, SD 8 y; women: 651/1212, 53.71%; follow-up period: mean 9, SD 2 y), 10 physical activity measures, including all peak cadence metrics, were nominally associated with incident cognitive impairment. Higher peak 1-minute cadence (steps/min) was significantly associated with lower risk (hazard ratio 0.82; 95% CI 0.69-0.97; P=.02). Incorporating peak 1-minute cadence into the base model (age, gender, education, and accelerometer wear time) improved the 8-year prediction area under the curve by 10.2%. Peak 1-minute cadence and total steps per day were also associated with better performance on trail making tests A and B. Conclusions: This study highlights significant associations between accelerometer-based physical activity metrics and both incident cognitive impairment and cognitive test performance. In particular, moderate-intensity movement, as reflected by cadence measures, may serve as a valuable marker for cognitive health and a potential target for early intervention.