Associations Among Self-reported Physical Activity, Coronary Artery Calcium Scores, and Mortality Risk in Older Adults

OBJECTIVE: To assess whether self-reported physical activity during daily life reduces the mortality risk associated with atherosclerotic burden, as measured by coronary artery calcium (CAC) scanning. METHODS: We assessed 2318 patients aged 65 to 84 years who underwent CAC scanning from August 31, 1998, through November 16, 2016, and had daily life physical activity assessed by a single-item question that was used to divide patients by low, moderate, and high physical activity levels. Patients were followed for a mean ± SD of 10.6±4.9 years for the occurrence of all-cause mortality. RESULTS: The results indicated a graded relationship between the magnitude of CAC abnormality and mortality and an inverse relationship between physical activity and mortality. Of patients with low CAC scores (0-99), those with low, moderate, and high physical activity levels had similarly low mortality rates. Of patients with high CAC scores (≥400), however, there was a stepwise increase in mortality with decreasing physical activity. Patients with CAC scores of 400 or greater but reporting high physical activity had a mortality rate that was similar vs that observed in patients with CAC scores of only 0 to 99 and low physical activity (19.9 vs 16.3 per 1000 person-years; P=.60). CONCLUSION: Combining CAC score with self-reported physical activity level provides a synergistic means for predicting clinical risk in older patients, with high physical activity level substantially attenuating the mortality risk associated with elevated CAC scores. Moreover, the useful prognostic information afforded by just a single-item physical activity questionnaire supports current initiatives to make such assessments into a “fifth vital sign.”