The Role of Smoking as a Modifiable Risk Factor in Diabetic Nephropathy.

OBJECTIVE To study the relation of smoking and abnormal renal function in type 2 diabetes mellitus by estimating urine protein- creatinine ratio, blood urea, serum creatinine, glomerular filtration rate and serum lipid profile in selected subjects. METHODS Diabetic patients who attended the Diabetic Clinic, Medical College, Kozhikode were enrolled in the study. The study duration was 6 months, from July 2008 to December 2008. It was conducted in four groups of 40 subjects: diabetic smokers, diabetic non-smokers, non-diabetic smokers and non-diabetic non-smokers. The parameters assayed were: Blood urea, Serum creatinine, Fasting Blood Glucose and Serum Lipid Profile. The parameters assayed in the different groups were compared. Logistic regression analysis was done to study the effect of smoking on renal function. RESULTS The mean difference of Urine protein- creatinine ratio between diabetic smokers and non-diabetic smokers is statistically significant (0.46±0.21 vs 0.24±0.14, p<0.001). The mean differences of Blood Urea between all the groups are statistically significant. The mean difference of Serum Creatinine of diabetic smokers with non-diabetic smokers is statistically significant (1.2±0.5 vs 0.96±0.2, p<0.05). The mean differences of Total Cholesterol, Triglycerides, HDL, LDL and VLDL between all the study groups is statistically significant. In the regression analysis, it was found that 12.9% of the alteration of renal function can be explained by smoking alone. (R2 = 0.129). CONCLUSIONS Smoking is an independent risk factor for progression of diabetic nephropathy. 24.8% of deterioration of renal function can be explained by smoking, obesity, hypertension and dyslipidemia and 12.9% of the alteration of renal function by smoking alone.