Altered respiratory function is associated with increased metabolic risk, independently of adiposity, fitness and physical activity

Aims Reduced lung function is associated with an adverse metabolic risk profile, even after adjusting for body fatness. However, previous observations may have been confounded by aerobic fitness and physical activity. This study aimed to examine the association between lung function and both metabolic risk and insulin resistance in a cohort of White British adults with a family history of Type 2 diabetes, and to explore the extent to which these associations are independent of body fatness, aerobic fitness (VO_2max) and objectively measured physical activity. Methods Adults (n = 320, mean age 40.4 ± 6.0 years) underwent measurement of physical activity energy expenditure (PAEE), spirometry [forced expiratory volume in 1 s (FEV₁)] and forced vital capacity (FVC), aerobic fitness (predicted VO_2max), and anthropometric and metabolic status at baseline and again after 1 year (n = 257) in the ProActive trial. Clustered metabolic risk was calculated by summing standardized values for triglycerides, fasting insulin, fasting glucose, blood pressure and the inverse of high-density lipoprotein-cholesterol. A cross-sectional analysis using linear regression with repeated measures was performed. Results Both FEV₁ and FVC were inversely and statistically significantly associated with metabolic risk and insulin resistance after adjusting for age, sex, smoking status, height, PAEE and fitness. The associations with metabolic risk remained significant after adjusting for measures of body fatness, but those with insulin resistance did not. Conclusions Reduced lung function was associated with increased metabolic risk in this cohort of carefully characterized at-risk individuals. This association was independent of overall and central body fatness, objectively measured physical activity and aerobic fitness.