Prognostic impact of abdominal fat distribution and cardiorespiratory fitness in asymptomatic type 2 diabetics

Background Impaired cardiorespiratory fitness (CRF) is a potent risk factor for mortality in diabetes, and may modify the relation between adiposity and mortality. We evaluated the interaction between CRF and abdominal adiposity distribution with all-cause mortality, myocardial infarction or stroke in patients with diabetes. Methods We studied 294 type 2 diabetics without known coronary artery disease. CRF was quantified in metabolic equivalents by maximal treadmill testing, and categorized as low CRF (first tertile) or high CRF (second and third tertiles). Abdominal fat was quantified as subcutaneous or visceral adipose tissue from non-enhanced computed tomography scans. Association of CRF, adiposity distribution and their interaction with all-cause mortality, myocardial infarction or stroke was assessed by Cox proportional-hazard models. Results There were 31 (11%) events during 62 ± 12 months. Low CRF was significantly associated with event risk before and after adjustment for each measure of adiposity (hazard ratio 3.79, 95% confidence interval 1.79-8.01, p < 0.001). CRF level was inversely correlated with subcutaneous (r =≤circ;'0.44, p < 0.001) but not visceral adipose tissue (r =≤circ;'0.06, p = 0.31). Absolute event rates increased progressively across visceral adipose tissue tertiles, but decreased across subcutaneous tertiles. However, within each tertile of both adiposity measures, increased events were observed in the low compared with the high CRF group; this trend was also observed in an adjusted multivariate proportional hazards model. Conclusions Although subcutaneous and visceral adipose tissues differed in their association with CRF levels and absolute event rates, lower baseline CRF in type 2 diabetics was significantly associated with higher risk of all-cause mortality, myocardial infarction or stroke, regardless of abdominal adiposity pattern.