Cigarette smoking and urinary albumin excretion in insulin-treated diabetics without manifest nephropathy

The frequency of microalbuminuria and glomerular hyperfiltration in insulin-treated diabetics without manifest nephropathy was studied in 76 patients, 20-40 years of age and with a diabetes duration not exceeding 20 years. Clinical determinants of urinary albumin excretion (UAE) with regard to smoking were studied further in a sample of male diabetics (n = 49) without manifest nephropathy. All patients had an age-related glomerular filtration rate (GFR) exceeding -2 SD, and their diastolic blood pressure (DBP) did not exceed 90 mmHg. GFR was assessed by 51Cr-EDTA-clearance, and UAE was analysed using an immunochemical method. Diabetic smokers with a long diabetes duration (10-20 years) had a significantly higher UAE (39.5 +/- 2.4 mg 24 h-1 vs. 17.1 +/- 2.4 mg 24 h-1; P = 0.03), a higher mean arterial blood pressure (MAP) (97.9 +/- 7.5 mmHg vs. 91.5 +/- 6.3 mmHg; P = 0.02) and a higher frequency of micro-albuminuria (85.7% vs. 37%; P = 0.028) than non-smoking diabetics. Smokers with a short diabetes duration (0-10 years) had a significantly higher frequency of glomerular hyperfiltration (64% vs. 15%; P = 0.005) than non-smokers. The frequency of microalbuminuria or blood pressure did not differ significantly. In male non-smokers (n = 35) UAE was positively correlated with HbAlc and negatively correlated with age of onset. In male smokers (n = 14) regression analysis showed that UAE was positively correlated only with duration of smoking. We conclude that smoking is associated with two accepted risk factors for nephropathy in insulin-treated diabetics, namely hyperfiltration and microalbuminuria. A positive linear relationship between smoking parameters and UAE in male diabetics also supports the view that smoking may increase the risk of nephropathy development in insulin-treated diabetics.