Introduction: Smoking is known to be associated with the risk of nephropathy in patients with diabetes. However, the effect of smoking before or after the diagnosis of diabetes is not well known.
Hypothesis: The effect of cigarette smoking before and after the diagnosis of diabetes on the presence of diabetic nephropathy would be different.
Methods: We analyzed the 2011 - 2013 Korea National Health and Nutrition Examination Survey. Total 1,259 subjects diagnosed with diabetes were classified into 658 non-smokers, 247 smokers who did not smoked after the diagnosis of diabetes and 354 smokers who continued smoking after the diagnosis of diabetes. Diabetic nephropathy was defined as the presence of albuminuria (spot urine albumin/creatinine ratio ≥ 30 mg/g) or low estimated glomerular filtration rate (< 60 mL/min/1.73 m2). Multivariate logistic regression models were used to assess the independent association after adjusting for age, duration of diabetes, HbA1c, body mass index, blood pressure and dyslipidemia.
Results: Compared to non-smokers, male patients who continued smoking after diagnosis of diabetes had a significantly higher odds ratio (2.17, 95% CI 1.23 to 3.83) for the presence of diabetic nephropathy. The corresponding odds ratio for male patients who smoked before the diagnosis of diabetes but not after was 1.26 (95% CI, 0.70 to 2.29). However in female, we did not observed this association probably due to small number of smokers.
Conclusions: Smoking, especially smoking after the diagnosis of diabetes, is associated with the presence of diabetic nephropathy. Our findings reaffirm that smoking cessation should be strongly recommended to patients with diabetes who smoke.