Abstract
Studies have demonstrated the adverse effects of smoking on the risk of microvascular complications; however, few have also examined the potential mediating effects of glycemic control. Using data from the Diabetes Control and Complications Trial (DCCT 1983–1993), we describe the acute and long-term risks of smoking on glycemic control and microvascular complications in a well-characterized cohort of participants with type 1 diabetes. The DCCT recorded self-reported smoking behaviors, glycemic exposure based on HbA1c, and complications status. Generalized linear mixed models were used to assess whether time-dependent measurements of smoking predict HbA1c levels. Cox proportional hazard models were used to assess time-dependent smoking exposures as predictors of retinopathy and nephropathy. During a mean of 6.5 years of follow-up, current smokers had consistently higher HbA1c values and were at a higher risk of retinopathy and nephropathy compared with former and never smokers. These risk differences were attenuated after adjusting for HbA1c suggesting that the negative association of smoking on glycemic control is partially responsible for the adverse association of smoking on the risk of complications in type 1 diabetes. These findings support the potential for a beneficial effect of smoking cessation on complications in type 1 diabetes.
Highlights
The Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study have demonstrated that improved metabolic control can prevent or delay longterm morbidity and mortality in individuals with diabetes [1, 2]
The prevalence of diabetes continues to increase worldwide [3, 4] and despite advances in treatment, it is estimated that approximately one third of all individuals with diabetes are affected by diabetic retinopathy and nephropathy [5,6,7]
There were no differences in DCCT treatment group, cohort assignment, or duration of diabetes between current, former, and never smokers at baseline
Summary
The Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study have demonstrated that improved metabolic control can prevent or delay longterm morbidity and mortality in individuals with diabetes [1, 2]. The prevalence of diabetes continues to increase worldwide [3, 4] and despite advances in treatment, it is estimated that approximately one third of all individuals with diabetes are affected by diabetic retinopathy and nephropathy [5,6,7]. Minimizing the risk of long-term complications and premature mortality has become a global priority. Cigarette smoking is associated with a heightened risk of morbidity and mortality in individuals with diabetes [8,9,10,11]. Smoking has been shown to worsen diabetes-related.
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