Abstract 13762: Sedentary Behavior and Physical Activity Are Differentially Associated with Fat Deposition in Older Adults

Abstract

Background: Physical activity is robustly cardioprotective. Recent studies, however, suggest that sedentary behavior, specifically time spent sitting, predicts greater cardiovascular morbidity and mortality, and does so independently of physical activity levels. This association is only partially explained by BMI and body composition, suggesting mechanisms other than general increased adiposity, such as location of fat deposition, may be involved. Objective: To explore the independent associations of physical activity and sedentary behavior with fat deposition among older community-dwelling adults in the Rancho Bernardo study.

Methods: Participants were 504 adults (26% Caucasian men, 32% Caucasian women, 23% African American women, and 19% Filipino women) with a mean age of 65 years. Weekly physical activity hours and daily sitting hours were measured by self-report. Areas of pericardial, intra-thoracic, visceral, and intermuscular fat were measured using computed tomography (CT) scans of abdominal and chest regions. Reported physical activity and sitting hours were entered simultaneously into multivariate regression models to determine independent associations with each area of fat deposition.

Results: After adjusting for age, sex, race/ethnicity, BMI, and cardiovascular risk factors, each additional hour of weekly physical activity predicted 2.54 cm2 less visceral fat and 0.34 cm2 less intermuscular fat (for both p < .05). Physical activity was not significantly associated with pericardial or intra-thoracic fat. In contrast, each additional hour of daily sitting was associated with 2.73 cm3 more pericardial fat (p < .05), but was not significantly associated with visceral, intra-thoracic, or intermuscular fat. Adjusting for inflammatory markers (IL-6, TNF-α, leptin, adiponectin) did not materially change the results. There were no significant interactions by sex or race/ethnicity.

Conclusions: Sitting time and physical activity have distinct, independent associations with the location of fat deposition in older adults. Common inflammatory markers did not mediate these associations. The positive association between sitting and pericardial fat could partially explain the link between sitting and coronary heart disease.