Abstract
BACKGROUND: Coronary artery calcium (CAC) and physical performance have been shown to be associated with mortality, but it is not clear whether one of them modifies the association. We investigated the association between the extent of CAC and physical performance among older individuals and explored these individual and combined effects on cardiovascular disease (CVD) mortality and non-CVD mortality. METHODS: We studied 4074 participants of the AGES-Reykjavik Study who were free from coronary heart disease, had a CAC score calculated from computed tomography scans and had data on mobility limitations and gait speed at baseline in 2002-2006 at a mean age of 76 years. Register-based mortality was available until 2009. RESULTS: Odds for mobility limitation and slow gait increased according to the extent of CAC. Altogether 645 persons died during the follow-up. High CAC, mobility limitation and slow gait were independent predictors of CVD mortality and non-CVD mortality. The joint effect of CAC and gait speed on non-CVD mortality was synergistic, i.e. compared to having low CAC and normal gait, the joint effect of high CAC and slow gait exceeded the additive effect of these individual exposures on non-CVD mortality. For CVD mortality, the effect was additive i.e. the joint effect of high CAC and slow gait did not exceed the sum of the individual exposures. CONCLUSIONS: The extent of CAC and decreased physical performance were independent predictors of mortality and the joint presence of these risk factors increased the risk of non-CVD mortality above and beyond the individual effects.