Cigarette smoking is a risk factor for nephropathy and its progression in type 2 diabetes mellitus.

Cigarette smoking is a risk factor for diabetic nephropathy in Type 1 diabetes (T1DM); a few reports support this possibility in Type 2 diabetes (T2DM) as well. Since heterogeneity among populations could exist, we investigated the association of cigarette smoking and nephropathy, and progression of nephropathy in Italian T2DM patients. A retrospective study was conducted in 273 long-duration T2DM subjects with a 3-year follow-up in the out-patient clinic, and at least one access per year. Albumin excretion rate, serum creatinine, and a number of other parameters implicated in the development of diabetic renal disease were evaluated. Progression of nephropathy was defined as the passage from different stages of renal involvement (no renal derangement, microalbuminuria, proteinuric disease or severe nephropathy). At baseline, 13.2% of the subjects had microalbuminuria, and 3.7% proteinuric disease. Microalbuminuria and proteinuric disease were more frequent in actual smokers than in non- and former smokers (chi2=8.35; p=0.015). Progression of nephropathy was less common in non- and former smokers than in smokers (31 of 134, 23%, and 15 of 67, 22%, and 30 of 72, 42%, respectively; chi2=9.32;p=0.009). From logistic regression analysis, smoking (p=0.0012) emerged as the most important factor associated with progression of nephropathy, followed by packyears (p=0.011), HbA1c mean value at follow-up (p=0.024), and total cholesterol (p=0.038). In conclusion, cigarette smoking is a risk factor for progression of nephropathy also in Italian T2DM patients; reducing or quitting smoking should be part of the therapy or of the preventive measures in these patients and their relatives.