Microalbuminuria in type 2 diabetes: An independent predictor of cardiovascular mortality

Background: Microalbuminuria has been shown to be associated with cardiovascular mortality in type 2 diabetic subjects. It is unclear to what extent this is due to the increased prevalence of other cardiac risk factors. Aims: To examine the relationship of urine albumin excretion to cardiovascular mortality and to determine its status as an independent risk factor. Methods: In a prospective longitudinal study from 1986-1993 we followed 666 type 2 diabetic subjects from a diabetes outpatient service. Cardiovascular risk factors including urine albumin concentration were measured at study entry. Cox proportional hazards regression was used to determine risk factors for mortality. The hazard ratios of microalbuminuria and macroalbuminuria for all cause, cardiovascular and coronary heart disease mortality were determined after accounting for other cardiac risk factors including blood pressure, glycated haemoglobin, total cholesterol, HDL cholesterol, triglycerides, urea, smoking, body mass index, patient age and disease duration. Results: The prevalence of urine albumin of 30-300 mg/L at study entry was 31.7%. A total of 167 deaths occurred (80 from cardiovascular disease). Mortality hazard ratios in subjects with urine albumin of 30-300 mg/L as compared to <30 mg/L, adjusted for age, sex and other cardiovascular risk factors were 1.77 (95% CI 1.22-2.57, p=0.002) for all causes, 2.34 (95% CI 1.38-3.99, p=0.002) for cardiovascular and 1.78 (95% CI 0.97-3.26, p=0.061) for coronary heart disease (CHD) mortality. Other factors significantly associated with cardiovascular mortality included diastolic blood pressure, HDL cholesterol and glycated haemoglobin. Total cholesterol and log triglyceride were significantly associated with CHD mortality. Disease duration, age at diagnosis, smoking and body mass index were not related to cardiovascular or CHD mortality. Conclusions: We confirm microalbuminuria as an independent predictor of mortality in type 2 diabetes despite its association with a number of conventional cardiovascular risk factors.