Abstract P160: Cross-sectional and Longitudinal Associations of Objective Sedentary Time, Physical Activity, and Obesity: The CARDIA Study

Abstract

Higher sedentary time (ST) and lower moderate-to-vigorous intensity physical activity (MVPA) have been independently associated with obesity, but most available studies are cross-sectional and measure ST and MVPA by self-report. It has also been suggested that obesity may predict future ST rather than ST leading to future obesity. Objective: To investigate whether objective ST and MVPA were associated with current and 5-year changes in body mass index (BMI) and waist circumference (WC). Methods: We analyzed 1,963 CARDIA participants (aged 38-50 years, 57% female, 41% black) with accelerometry data (≥4 days with ≥10 hr/day) in 2005-2006. BMI and WC were assessed concurrently and 5 years later. Linear regression evaluated cross-sectional and longitudinal associations between ST and MVPA with BMI and WC across all participants and in race/gender groups due to the presence of interactions. Standardized coefficients (β std ) reflect differences per each 1.7 hr/day increase in ST and each time MVPA increases by a factor of 2. Results: Average ST was 8.1 ± 1.7 hr/day and 21% met MVPA guidelines of 150 min/wk. During the 5 year follow-up, BMI and WC increased in all groups (Table, all p<0.01). Cross-sectionally, in the combined cohort, higher ST and lower MVPA were each independently related to higher BMI and WC (Table). After stratification, lower MVPA was associated with higher BMI in white women and higher WC in white women and men. Higher ST was directly related to BMI in black men and WC in white and black men. Baseline ST and MVPA did not predict 5-year changes in BMI or WC in the full cohort; higher MVPA predicted a smaller BMI increase only in white men (Table). Conclusions: ST and MVPA were each associated with general and abdominal obesity cross-sectionally, but mostly did not predict 5-year changes in these outcomes. These findings do not support that lower ST and higher MVPA will curtail unfavorable gains in general and abdominal obesity over 5 years, but could result from a relationship where greater obesity leads to higher ST and inactivity.