Is smoking a risk factor for proliferative diabetic retinopathy in type 1 diabetes?

The aim was to evaluate if smoking was a risk factor for proliferative retinopathy (PDR) in a 25-year follow-up study.

201 persons from a population-based cohort of Danish type 1 diabetic patients were examined at baseline and again 25 years later. At both examinations the patients were asked about their smoking habits. The level of retinopathy was evaluated by ophthalmoscopy at baseline and by nine 45-degree colour field fundus photos at the follow-up.

In multivariate analyses there was a trend that current smokers at baseline were more likely to develop PDR at the follow-up (odds ratio 1.90, 95% confidence interval 0.88-4.11, p = 0.10). Neither smoking status at the follow-up nor pack-years of smoking were associated with PDR.

We found neither a beneficial nor a harmful effect of smoking on long-term incidence. Selective mortality among smokers and patients with PDR at baseline might provide at least part of the explanation for this.