Background: Coronary artery calcification (CAC) is a strong predictor of cardiovascular disease. We investigated the independent and joint effects of cardiorespiratory fitness (CRF) and CAC on all-cause mortality, myocardial infarction (MI) or stroke in patients with diabetes.
Methods: We studied 600 type 2 diabetics aged 55-74 years without known coronary heart disease. CRF was quantified in metabolic equivalents by maximal treadmill testing and categorized as low (1st tertile) or high (2nd and 3rd tertiles) CRF. CAC score was calculated by non-enhanced computed tomography scans. CAC score
Results: There were 72 (12%) events during follow-up. Low CRF was independently associated with event risk after adjustment for traditional risk factors and CAC (HR 2.04, 95% CI 1.28-3.23, p=0.003). Low versus high CRF allowed further outcome discrimination amongst diabetics with low CAC scores (10% vs 1.4% event rate) and amongst diabetics with high CAC score (22% versus 13% event rate), Fig. 1. The addition of CRF to the UKPDS + CAC scores improved the area under the curve for event prediction from 0.66 to 0.71, p=0.03.
Conclusions: CRF provided independent prognostic information which was additive to CAC. Low CRF may identify asymptomatic diabetic subjects at higher risk for all-cause mortality, MI or stroke, despite low CAC.
