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Introduction: Leisure-time physical activity (LTPA) has favorable effects on many risk factors for cardiovascular disease (CVD). Paradoxically, LTPA has also been associated with higher amounts of coronary artery calcium (CAC) in athletes. Recently, a higher density of CAC was shown to significantly mitigate the risk of CVD associated with a given volume of CAC. The effects of LTPA and non-LTPA on the density and volume components of CAC among individuals with calcified coronary atherosclerosis are unknown.Methods: We evaluated 3,398 participants from the Multi-Ethnic Study of Atherosclerosis with prevalent CAC (50% of cohort). CAC was assessed via cardiac computed tomography, while physical activity was assessed via questionnaire and categorized by quintiles of moderate and vigorous LTPA (e.g. exercise) and non-LTPA (e.g. work). Multiple linear regression with mutual adjustment for LTPA, non-LTPA, demographics, and CVD risk factors was performed.Results: Mean age of the sample was 66 years, 58% were male, 44% were Caucasian, 24% were African-American, 20% were Hispanic, and 12% were Chinese-American. Compared to the lower four quintiles, LTPA above the threshold of 2567 MET-minutes/week (quintile 5) was associated with 0.057 (0.008, 0.105) higher CAC density-units after full adjustment. LTPA at any level was not associated with CAC volume. Conversely, non-LTPA was associated with both lower CAC density and higher CAC volume in a stepwise fashion, with the highest quintile meeting statistical significance for both (see Table).Conclusions: The highest quintile of LTPA was associated with higher CAC density but not higher CAC volume, suggesting a possible explanation for high CAC scores in athletes with favorable CVD risk factor profiles. Non-LTPA was associated with a less favorable CAC composition after adjustment for LTPA, an unexpected finding that merits further investigation.