The association between metabolic syndrome, microalbuminuria and impaired renal function in the general population: impact on cardiovascular disease and mortality.

OBJECTIVE: Microalbuminuria and metabolic syndrome are both associated with cardiovascular disease (CVD). The aim of this study was to determine the potential association between numbers of components in the metabolic syndrome, different levels of microalbuminuria and renal function. We also aimed to determine the risk of death and CVD at different levels of microalbuminuria and renal function and numbers of components in the metabolic syndrome. DESIGN: Population-based observational follow-up study. SETTING: Epidemiological research unit (Copenhagen City Heart Study). SUBJECTS: A total of 2,696 men and women, 30-70 years of age. BASELINE MEASURES: Urinary albumin excretion (UAE), creatinine clearance and metabolic risk factors were measured in 1992-1994. MAIN OUTCOME MEASUREMENTS: The participants were followed prospectively by registers until 1999-2000 with respect to CVD, and until 2004 with respect to death. RESULTS: We found a strong association between microalbuminuria and the metabolic syndrome: 2% with none and 18% with five metabolic risk factors had microalbuminuria (P < 0.001). No association between impaired renal function defined as creatinine clearance <60 mL min(-1) and the metabolic syndrome was found. Microalbuminuria was associated with increased risk of death and CVD to a similar extend as the metabolic syndrome, irrespective of concomitant presence of metabolic syndrome (RR approximately 2; P < 0.001). Impaired renal function was not associated with increased risk of death and CVD in subjects with the metabolic syndrome. CONCLUSIONS: Microalbuminuria (UAE >5 microg min(-1)) confers increased risk of death and CVD to a similar extent as the metabolic syndrome.

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.