New definition of microalbuminuria in hypertensive subjects: association with incident coronary heart disease and death

Microalbuminuria has so far been defined as urinary albumin excretion between 20 and 200 microg/min (or 15 to 150 microg/min overnight). In a recent report, an overnight urinary albumin excretion >5 microg/min was strongly predictive of coronary heart disease and death in the general population. The aim of the present study was to confirm this observation in a population of hypertensive individuals. In The Third Copenhagen City Heart Study in 1992 to 1994, 1734 men and women aged 30 to 70 years with hypertension, but no history of coronary heat disease, delivered a timed overnight urine sample. They were followed-up prospectively by registers until 2000 with respect to coronary heart disease, and until 2004 with respect to death. During follow-up, 123 incident cases of coronary heart disease and 308 deaths were traced. Incident coronary heart disease occurred in 11% of subjects with urinary albumin excretion > or =5 microg/min compared with 5% in subjects with urinary albumin excretion <5 microg/min (P<0.001). Similarly, the cumulative mortality was 28% versus 13% (P<0.001). The relative risks of coronary heart disease and death associated with urinary albumin excretion > or =5 microg/min were 2.0 (1.4 to 2.9; P<0.001) and 1.9 (1.5 to 2.3; P<0.001), respectively, after adjustment for age, sex, blood pressure level, antihypertensive drugs, diabetes, creatinine clearance, smoking, lipoproteins, and body mass index. In conclusion, our study supports the new definition of microalbuminuria as urinary albumin excretion >5 microg/min. In future risk assessment in hypertensive individuals, measurement of microalbuminuria has to be included.