Very low level of microalbuminuria is associated with increased risk of death in subjects with cardiovascular or cerebrovascular diseases

BACKGROUND: The original definition of microalbuminuria (20-200 microg min-1 or 15-150 microg min-1 overnight) is based on studies of patients with diabetes, in whom microalbuminuria was associated with increased risk of chronic renal failure. In a recent report an overnight urinary albumin excretion (UAE) above only 5 microg min-1 was strongly predictive of coronary heart disease and death in the general population. The aim of the present study was to investigate if this cut-off level also has prognostic value in a population with cardiovascular or cerebrovascular disease. METHODS AND RESULTS: In The Third Copenhagen City Heart Study in 1992-1994, 491 men and women aged 30-80 years with a history of coronary heart disease or stroke delivered a timed overnight urine sample. They were followed by registers with respect to vital status until 2004. During follow-up, 141 of the 491 participants died. The relative risk of death in subjects with UAE above 5 microg min-1 compared with subjects with lower UAE was 2.0 (1.4-2.8; P<0.001). It was unaffected [RR 1.9 (1.3-2.7); P<0.005] by adjustment for age, sex, blood pressure, diabetes, lipoproteins, renal creatinine clearance, smoking and body mass index. CONCLUSIONS: Subjects with cardiovascular or cerebrovascular disease have about 100% higher risk of death if microalbuminuria defined as UAE above 5 microg min-1 is present. Measurements of UAE should be included in the risk assessment in subjects with cardiovascular or cerebrovascular disease. This study supports the definition of microalbuminuria as UAE above 5 microg min-1.