To evaluate the effect of elevated fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) concentrations on lung dysfunction and to prospectively investigate whether reduced lung function would be independently predictive of diabetes.
Participants and Methods
From January 6, 1997, through December 22, 2008, we observed 5346 men with no history of diabetes or lung dysfunction. Hazard ratios (HRs) for incident diabetes (FPG ≥126 mg/dL, HbA1c ≥6.5%, or self-reported clinician-diagnosed diabetes) were estimated for spirometry indices as continuous and categorical variables.
Elevated HbA1c concentrations within the normal range were significantly and more strongly associated with reduced forced vital capacity and forced expiratory volume in the first second after expiration (FEV1) than were FPG concentrations. During a 4.0-year follow-up, diabetes developed in 214 individuals. A 10-point decrease in percentage of FEV1 predicted value was associated with an increased HR of 1.21 (95% confidence interval [CI], 1.09-1.34; P=.001) for diabetes after adjustment for demographic factors and body mass index. This association remained significant even after adjustment for metabolic factors, smoking status, and FPG or HbA1c concentrations but was attenuated substantially after adjustment for baseline HbA1c values (HR, 1.13; 95% CI, 1.01-1.26; P=.03). Lower quartile (Q) categories of percentage of FEV1 predicted value were associated with increased risk of diabetes independently of known predictors including HbA1c (HR, 1.73; 95% CI, 1.14-2.62 for Q1; and HR, 1.76; 95% CI, 1.15-2.69 for Q2).
Reduced lung function was significantly related to chronic glycemic exposure within a normal range. Relatively low pulmonary function was an independent risk factor for diabetes in apparently healthy Japanese men.