Effect modification of glycemic control on association of lung function with all-cause and cardiovascular mortality in persons with type 2 diabetes - A retrospective cohort study

Background: Poor glucose control might deteriorate the impaired pulmonary function, which can ultimately lead to mortality. However, few studies have examined the effect modification of glucose control on the association between pulmonary function and mortality. This study aimed to examine the association of pulmonary function with mortality and determine the effect modification of glycemic level on the association of pulmonary function with mortality in persons with type 2 diabetes (T2DM). Methods: A retrospective cohort study included 3846 persons with T2DM with pulmonary function testing in Taiwan during 2002-2020. Expiratory volume in 1 s (FEV1) was measured as pulmonary function. Cox proportional hazards models were used and the effect modification of pulmonary function parameters and glucose control was assessed by their product terms. Results: There were 733 deaths during an average follow-up of 7.83 years. Significant associations of FEV1 and mortality were found (hazards ratio [HR] for FEV1 Z-scores of <0 to -1, <-1 to -2 and <-2: 1.47 [1.20, 1.80], 2.48 [1.95, 3.14] and 3.07 [1.74, 5.44] compared with participants with Z-score >= 0, respectively. All p for trend<0.001). Significant effect modifications were found and the association between FEV1 and mortality was stronger in persons with good glycemic control compared with poor glycemic control (FEV1-FPG effect modification, P = 0.01; FEV1-HbA1c effect modification, P = 0.03). Conclusion: Pulmonary function, measured by FEV1, is significantly associated with mortality in persons with T2DM. Significant effect modification of glucose control on the association between pulmonary function parameters and mortality was found.