Smoking and microalbuminuria: a case-control study in African-Americans with type 2 diabetes.

African-Americans are at increased risk of diabetic nephropathy (1,2). Cigarette smoking has been shown to increase the risk of microalbuminuria in Caucasian populations with type 1 and type 2 diabetes (3,4,5,6). In contrast, despite their high risk of nephropathy, the association between cigarette smoking and microalbuminuria in African-Americans with diabetes has not previously been assessed. We conducted a case-control study to examine the association between lifetime cigarette smoking history and risk of prevalent microalbuminuria in patients with recently diagnosed type 2 diabetes. Our study population was African-American patients with type 2 diabetes duration ≤2 years who had an initial visit to the Grady Diabetes Clinic in Atlanta, Georgia, between January 1994 and December 1996. The present study is partially based on secondary data from a cross-sectional analysis of this study population, which has been previously described in detail (7). We excluded patients missing urine albumin and/or urine creatinine measurements and patients with clinical nephropathy (urine albumin-to-creatine [Alb/Cr] ratio >250 μg/mg). Serum and urine creatinine were measured in a random morning urine specimen at the first clinic visit. Patients were divided into two groups based on Alb/Cr ratios: normoalbuminuria (Alb/Cr <25 μg/mg) or microalbuminuria (Alb/Cr from 25 to 250 μg/mg) (8). All 246 microalbuminuric patients were case subjects; based on a priori power calculations, 506 control subjects were randomly sampled from …