Abstract MP01: Association of Objectively-measured Physical Activity with Cardiovascular Risk in Mobility-limited Older Adults

Abstract

Introduction: In middle-aged adults, time spent being sedentary is associated with cardiovascular (CV) health risks independent of structured physical activity (PA). However, data are sparse regarding the impact of sedentary behavior on CV risk in older adults. The extent to which the absolute duration or intensity of daily PA reduces CV risk in older adults is also unknown. Objectives: Our objective was to examine the cross-sectional association between objectively-measured sedentary behavior and predicted CV risk among older adults in the Lifestyle Interventions and Independence for Elders (LIFE) study. The secondary objective was to evaluate associations between the duration/intensity of daily PA and predicted CV risk. Methods: LIFE is a randomized clinical trial to determine if regular PA prevents mobility disability among mobility-limited older adults. Activity data were collected by hip-worn accelerometer at baseline prior to participation in study interventions. Only participants with at least three days of accelerometry data (≥ 10 hrs wear time) were included. Unadjusted and adjusted linear regression was used to model the relationship between accelerometry measures and predicted 10-year Framingham risk of Hard Coronary Heart Disease (HCHD; i.e. myocardial infarction or coronary death). Adjusted models included demographic confounders (e.g. education, race, income) and health parameters (e.g. depression, cognition, arthritis) not in the risk score. Accelerometry cut-points were (in counts/min): sedentary behavior: < 100; low-intensity activity: 100-499; higher intensity activity: > 500. Results: Participants (n = 1170; 78.7 ± [SD] 5.3 years; 66.1% female) had a median HCHD risk of 10.3% (25 th -75 th %: 5.7-18.6). Over a mean accelerometer wear time of 8.1 ± 3.2 days, participants spent 77.0 ± 8.2% of their time sedentary. They also spent 16.6 ± 5.0% of their time in low-intensity PA and 6.4 ± 4.4% in higher-intensity PA. For all PA performed (> 100 counts/min), participants achieved a median of 393.4 (337.8-473.5) counts/min. In the unadjusted model, time spent sedentary (β = 2.41; 95% CI : 1.94, 2.89), in low-intensity PA (-2.56; -3.03, -2.08), and in higher-intensity PA (-1.60; -2.09, -1.11) were all associated with HCHD risk (all p’s < 0.001). These associations remained significant after adjustment. The mean intensity of daily PA was not significantly associated with HCHD risk in any model (p > 0.05). Conclusions: Daily time spent being sedentary is positively associated with predicted 10-year HCHD risk among mobility-limited older adults. Duration, but not mean intensity, of daily PA is inversely associated with HCHD risk score in this population.