Pulmonary function tests in type 2 diabetes: a meta-analysis

OBJECTIVES: The aim of this study was to determine the association between type 2 diabetes (T2D) and pulmonary function tests. METHODS: After conducting an exhaustive literature search, we performed a meta-analysis. We employed the inverse variance method with a random-effects model to calculate the effect estimate as the mean difference (MD) and 95% confidence interval (CI). We calculated the heterogeneity with the I(2) statistic and performed a meta-regression analysis by sex, body mass index (BMI), smoking and geographical region. We also conducted a sensitivity analysis according to the studies’ publication date, size of the T2D group and the study quality, excluding the study with the greatest weight in the effect. RESULTS: The meta-analysis included 66 studies (one longitudinal, two case–control and 63 cross-sectional), with 11 134 patients with T2D and 48 377 control participants. The pooled MD (95% CI) for the predicted percentage of forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), forced expiratory flow at 25–75% of FVC, peak expiratory flow, and diffusing capacity of the lung for carbon monoxide were −7.15 (95% CI −8.27, −6.03; p<0.001), −9.21 (95% CI −11.15, −7.26; p<0.001), −9.89 (95% CI −14.42, −5.36; p<0.001), −9.79 (95% CI −13.42, −6.15; p<0.001) and −7.13 (95% CI −10.62, −3.64; p<0.001), respectively. There was no difference in the ratio of FEV(1)/FVC (95% CI −0.27; −1.63, 1.08; p=0.69). In all cases, there was considerable heterogeneity. The meta-regression analysis showed that between studies heterogeneity was not explained by patient sex, BMI, smoking or geographical region. The findings were consistent in the sensitivity analysis. CONCLUSIONS: T2D is associated with impaired pulmonary function, independently of sex, smoking, BMI and geographical region. Longitudinal studies are needed to investigate outcomes for patients with T2D and impaired pulmonary function.