Reduced lung function predicts risk of incident type 2 diabetes: insights from a meta-analysis of prospective studies

Epidemiological studies have repeatedly investigated the association between reduced pulmonary function and incident type 2 diabetes mellitus (T2DM). However, the results have been inconsistent. This meta-analysis aimed to clarify this association with prospective cohort studies. We searched PubMed, Web of Science (ISI), and Google Scholar for all studies (in English) reporting reduced lung function with a risk of T2DM. The measures of lung function included percentage of forced vital capacity for predicted values (FVC_%pre), percentage of forced expiratory volume in the first second after expiration for predicted values (FEV_1%pre) and FEV₁-to-FVC ratio%. Summary risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using fixed-effects or random-effects meta-analyses. A total of 5,480 incident T2DM patients among 88,799 individuals were identified from nine prospective cohort studies. Compared to the highest category of FVC_%pre and FEV_1%pre, the lowest category of FVC_%pre and FEV_1%pre were significantly associated with increased incident T2DM risk (FVC_%pre: RR = 1.49, 95% CI: 1.39-1.59; FEV_1%pre: RR = 1.52, 95% CI: 1.42-1.62). However, no significant relationship was found between the FEV₁/FVC ratio and incident T2DM risk (RR = 1.01, 95% CI: 0.91-1.13). Current evidence suggests that restrictive rather than obstructive impairment of lung function is significantly associated with the incidence of T2DM. Further research is warranted to explore potential mediators of this relationship.