A six-year follow-up study of smoking habits and microvascular complications in young adults with type 1 diabetes.

One hundred insulin-dependent diabetic patients (age < 45 years, 53 smokers) were followed for six years. The age, duration of diabetes and mean glycated haemoglobin levels, were comparable between the smokers and non-smokers. Microvascular complications (retinopathy and increased urine albumin excretion) were commoner and more severe in the smoking group at six years, particularly in heavy smokers. Of the 45 original smokers reviewed at six years, 12 (27%) had stopped, six of whom had developed microvascular complications. Only two of the 'heavy' initial smokers, likely to be at most risk, had stopped smoking, and three original non-smokers had started smoking.