Changes in smoking status, amount of smoking and their relation to the risk of microvascular complications in men with diabetes mellitus

Background: Smoking is a definite risk factor for macrovascular complications in diabetes mellitus (DM). However, the effect of smoking on microvascular complications is inconclusive.Method: Study participants were 26,673 diabetic men who received health check-up both in 2003-2004 and 2009, excluding women. Assessing smoking status (never, quitting and current) at 2003-2004 and 2009, changes in smoking status were categorised into 7 groups (never - never, never - quitting, never - current, quitting-quitting, quitting-current, current-quitting and current-current). Smoking amount was categorised into never, light (0-10 pack years), moderate (10-20 pack years), and heavy smoking (>20 pack years) based on 2009 data. They were followed-up until 2013 to identify incident microvascular complications. We calculated the adjusted hazard ratios (HR) and 95% confidence interval (CI) (adjusted HR [95% CI]) for incident microvascular complications according to changes in smoking status and smoking amount.Results: Current-quitting (1.271 [1.050-1.538]), current-current (1.243 [1.070-1.444]) and heavy smoking (1.238 [1.078-1.422]) were associated with an increased risk of overall microvascular complications. The risk of nephropathy increased in current-current smoking (1.429 [1.098-1.860]) and heavy smoking (1.357 [1.061-1.734]). An increased risk of neuropathy was observed in current-quitting smoking (1.360 [1.076-1.719]), current-current smoking (1.237 [1.025-1.492]) and heavy smoking (1.246 [1.048-1.481]). However, we couldn't see the interpretable findings for the association between smoking and retinopathy.Conclusions: Lasting and heavy smoking increases the risk of microvascular complications, including nephropathy and neuropathy. Quitting smoking and reducing smoking amount are imperative in preventing microvascular complications in DM patients.

Automated summary

Long-term and heavy smoking increases the risk of microvascular complications, including nephropathy and neuropathy, in patients with diabetes mellitus. Quitting smoking and reducing smoking amount are crucial in preventing microvascular complications in diabetic patients.