INTRODUCTION:Increased sedentary behavior predicts greater cardiovascular morbidity and mortality and does so independently of physical activity (PA). This association is only partially explained by body mass index (BMI) and overall body fat, suggesting mechanisms besides general increased adiposity. The purpose of this study was to explore associations of self-reported leisure PA and sitting time with regional fat depositions and abdominal muscle among community-dwelling older adults. METHODS:Participants were 539 diverse adults (mean age = 65 yr) who completed a study visit in 2001-2002. Areas of pericardial, intrathoracic, subcutaneous, visceral, and intermuscular fat, as well as abdominal muscle, were measured using computed tomography. Leisure PA and sitting hours were entered simultaneously into multivariate regression models to determine associations with muscle and fat areas. RESULTS:After adjusting for demographics, smoking, diabetes, hypertension, triglycerides, and cholesterol, greater PA was associated with less intrathoracic, visceral, subcutaneous, and intermuscular fat (for all P < 0.05), while greater sedentary time was associated with greater pericardial and intrathoracic fat (for both P < 0.05). After further adjusting for BMI, each hour of weekly PA was associated with 1.85 cm less visceral fat (P < 0.01) but was not associated with other fat depositions. Conversely, each hour of daily sitting was associated with 2.39 cm more pericardial fat (P < 0.05) but was not associated with any other fat depositions. There were no associations with abdominal muscle area. Adjusting for common inflammatory markers had little effect. Associations between fat and PA were stronger for men. CONCLUSIONS:Sitting and PA have distinct associations with regional fat deposition in older adults. The association between sitting and pericardial fat could partially explain the link between sitting and coronary heart disease.

Objective: Body mass index (BMI) may not accurately or adequately reflect body composition or its role in the development of cardiovascular disease (CVD). Ectopic adipose depots may provide a more refined representation of the role of adiposity in CVD. Thus, the association of pericardial and intra-thoracic fat with coronary artery calcium (CAC) was examined.Design and Methods: Nearly 600 white men and women, as well as Filipina women and African-American women, all without known CVD, had abdominal and chest computed tomography (CT) scans at two time points about 4 years apart from which CAC presence, severity and progression, as well as pericardial and intrathoracic fat volumes were obtained. Logistic and linear regression models with staged adjustment were used to assess associations of pericardial and intra-thoracic fat with CAC presence, severity, and progression.Results: After adjustment for age, BMI, sex/ethnic group, ever smoking, and lipids, each standard deviation higher increment of intra-thoracic fat, but not pericardial fat, was significantly associated with 3.84-fold higher odds of prevalent CAC (95% CI (1.54, 9.58), P = 0.004) and a 38.4% higher CAC score (95% CI (3.5%, 90.0%), P = 0.03). Neither pericardial nor intrathoracic fat were associated with CAC progression.Conclusion: Contrary to previous reports, pericardial fat was not associated with the presence, severity or progression of CAC. However, a significant association between intrathoracic fat and both the presence and severity of CAC was demonstrated. Studies measuring fat in the thoracic cavity may consider defining intrathoracic fat as a separate entity from pericardial fat.

Background: Excess abdominal adipose tissue has been identified as an important factor in the development of type II diabetes. Lean muscle tissue also plays an important role in glucose regulation, yet research on the role of muscle in diabetes etiology is limited. Abdominal muscle mass could be particularly relevant for normal weight diabetics, for whom excessive abdominal adipose tissue may play less of a role. Objective: To explore the association between muscle-to-abdominal cavity area ratio and prevalent diabetes in older community-dwelling women in the Rancho Bernardo Study, UCSD Filipino Women’s Health Study, and the Health Assessment Study of African-American Women. Methods: Participants were 421 women (40% Caucasian, 28% Filipina, 32% African American) with a mean age of 64 (6.9) years. Abdominal muscle and fat areas were measured using computed tomography (CT) scans, and were used to compute a muscle-to-abdominal cavity area ratio (MACR). Based on body mass index (BMI), participants were classified as normal weight (18-24.9 kg/m2), overweight (25-29.9), or obese (30+). Prevalent diabetes was defined as self-report of physician diagnosis, anti-diabetes medication use, fasting morning glucose ≥ 126 mg/dL or 2 hour glucose ≥ 200mg/dL. MACR was modeled per standard deviation (SD) and logistic regression was used to examine the association with diabetes while adjusting for relevant covariates. Results: Prevalent diabetes was seen in 12.8% of the sample (54 of 421). In age and race/ethnicity adjusted models, each SD increase in MACR was associated with significant reduced odds of diabetes (OR = 0.62, CI: 0.43-0.89, p = 0.01), which remained significant after further adjustment for BMI category, smoking, physical activity, hypertension, anti-hypertensive drugs, and estrogen use (OR = 0.64, CI: 0.41-0.98, p = .041). The association was modestly attenuated after further adjusting for visceral fat area (OR = 0.70, CI: 0.44-1.10, p = 0.12). Normal weight women with diabetes had significantly less total muscle (p = 0.045) and smaller MACR’s (p = 0.001) than those without diabetes, while this was not seen for overweight or obese women with diabetes. Stratified by BMI category, MACR was significantly associated with lower odds of diabetes for normal weight women across all three models (fully adjusted OR = 0.37, CI: 0.15-0.90, p =.03), yet was not associated with diabetes in any models for women who were overweight or obese (all p > 0.50). Interactions of MACR with race/ethnicity were not significant. Conclusions: Muscle-to-abdominal cavity ratio is associated with reduced likelihood of type II diabetes in women. This association differs by BMI category, with muscle showing the greatest protection in normal weight women, and no effect in overweight or obese women. This highlights the potential role of low muscle mass as a risk factor for diabetes, particularly in women who may appear to be at low risk.

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 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.