Physical Activity and Subclinical Measures of Atherosclerosis: Study Replication and Sensitivity Analysis

Abstract

Abstract Physical Activity and Subclinical Measures of Atherosclerosis: Study Replication and Sensitivity Analysis Julian Jonn Nilsson Whitford Chair of the Supervisory Committee: Lecturer Michelle Averill Environmental and Occupational Health Sciences Background: Atherosclerosis contributes greatly to morbidity and mortality in the United States. Prevention of incidence, and progression of atherosclerosis through lifestyle modification represents an opportunity to reduce the burden of this disease. Ankle brachial index (ABI) and coronary artery calcification (CAC) are subclinical measures of atherosclerosis. The effects of physical activity on such subclinical measures in unselected populations is not comprehensively described. Objective: To conduct a replication of the 2013 study by Delaney et al. and sensitivity analysis to examine whether higher physical activity has a protective effect on cardiovascular disease risk. Methods: The replication analyses were based on the methods of Delaney et al. Physical activity measures were used as predictive variables for incident coronary artery calcification and peripheral artery disease in Multi-Ethnic Study of Atherosclerosis (MESA) participants clinically free of cardiovascular disease. Physical activity predictors (intentional, sedentary, vigorous, moderate & vigorous, and conditioning) were as continuous variables and measured in Metabolic Equivalents of Task (MET) minutes per week. Additionally, progression of coronary artery calcification and peripheral artery function were determined. Results: The mean age of participants was 61.8 years, with mean body mass index of 28.2 kg/m2 and 48% of participants were male. Following adjustment for traditional risk factors for cardiovascular disease and socioeconomic factors, increased intentional activity (OR = 0.64, 95% CI 0.48,0.85) was found to be protective against progression to an ankle brachial index (ABI) of <0.90. Increased sedentary behavior was also observed to lower the odds (OR = 0.52, 95% CI 0.35,0.78) of low ABI progression. Additionally, increased sedentary behavior was associated with an increase in coronary artery calcification (CAC) progression (Coefficient = +0.062, 95% CI 0.014, 0.111). In sensitivity analyses, the associations between increased intentional activity and sedentary behaviors persisted. No significant relationships were consistently observed between other physical activity variables and subclinical measures of atherosclerosis. Conclusion: The key finding of Delaney et al. that intentional physical activity may be protective against progression to low ABI was consistent throughout the present replication and sensitivity analysis. A positive association between sedentary behavior and CAC progression was also found to be consistent. Exercise may be a low risk intervention to reduce mortality and morbidity due to progression of subclinical peripheral arterial disease to clinical disease.