Impact of diabetes duration and cardiovascular risk factors on mortality in type 2 diabetes: the Hoorn Study

Background Several studies have reported differences in the mortality risk between diabetic subjects detected by screening and known diabetic patients. We studied mortality in relation to diabetes duration, and the contribution of other cardiovascular risk factors to the elevated risk. Materials and methods Participants were type 2 diabetic subjects (n = 174) of a population-based cohort study. Of these, 95 were diagnosed by screening. Known diabetic subjects were grouped into two categories of diabetes duration, with a median duration of 2.4 and 11.2 years, respectively. We assessed the contribution of classical cardiovascular risk factors (dyslipidaemia, hypertension, and prior myocardial infarction), and of new cardiovascular risk factors (microalbuminuria, von Willebrand factor, sVCAM-1 and C-reactive protein) to the mortality risk during nearly 10 years of follow up. Cox's proportional hazards model was used to study the association of diabetes duration and mortality. Results The age- and sex-adjusted relative risks of mortality were 2.06 (95% C.I. 1.04-4.10) and 3.19 (1.64-6.20) for the patients with short- and long-term diabetes compared with the screening-detected diabetic subjects, respectively. Adjustment for cardiovascular risk factors resulted in a reduction of mortality risk in both groups: 1.13 (0.51-2.50) and 2.39 (1.18-4.83), respectively. Mortality risk significantly increased with increasing diabetes duration, even after multiple adjustment (P-value for trend ranged from < 0.001-0.018). Conclusions Mortality risk increased with increasing diabetes duration. In subjects with short diabetes duration the mortality risk could largely be attributed to other risk factors. In subjects with a longer diabetes duration, however, the elevated mortality risk was independent of these cardiovascular risk factors.