Association between diabetes and asthma: Evidence from a nationwide Korean study

Type 2 diabetes and asthma share a common pathophysiology: "chronic inflammation." However, it is unclear whether patients with type 2 diabetes are at increased risk of asthma.

To investigate the effect of type 2 diabetes on asthma using data from a large population-based study in Korea.

Data from the Korean National Health Insurance Service identified 13,154,348 participants who underwent regular health checkups from 2005 to 2008. Subjects were classified according to status of diabetes mellitus (DM) and diabetic retinopathy (DR), and followed until the date of asthma development, death, or December 31, 2013. Cox proportional hazard regression analysis was used to evaluate the effect of diabetes, with or without retinopathy, on asthma development.

The incidences of asthma in the non-DM, DM without DR, and DR groups were 27.1, 30.1, and 38.4 per 1,000 person-years, respectively. Cox proportional hazard multiple regression models revealed that diabetic patients without retinopathy had a significantly lower risk of developing asthma than non-DM subjects (hazard ratio, 0.943; 95% confidence interval, 0.939-0.948). By contrast, diabetic patients with retinopathy had a higher risk of developing asthma (hazard ratio, 1.067; 95% confidence interval, 1.053-1.081).

Type 2 diabetes without retinopathy is not a risk factor for asthma development. However, patients with DR are at a greater risk of incident asthma, supporting the notion that the lung is a target organ for diabetic injury. Future studies will address whether proper glycemic control mitigates the risk of asthma.