Smoking habits and prevalence of clinical diabetic microangiopathy in insulin-dependent diabetics.

All patients having insulin-dependent diabetes with onset before 30 years of age and a duration of disease of 12-40 years who visited a diabetes centre within one year were registered. 97% (n = 668) answered a WHO questionnaire on cigarette smoking. The smoking habits were compared to the frequency of proliferative retinopathy and/or diabetic nephropathy (persistent proteinuria). The prevalence of diabetic nephropathy was significantly higher among heavy smokers (greater than 10 cigarettes a day for more than one year) than among non-heavy smokers, 19.2% versus 12.1% (p less than 0.02). An increasing frequency of nephropathy was found with increasing cigarette consumption (p less than 0.01). No difference in the prevalence of proliferative retinopathy was found between smokers and non-smokers. It is concluded that cigarette smoking is a risk factor for the development of nephropathy in insulin-dependent diabetics.