Longitudinal changes of body mass index, spirometry, and diffusion in general population

Aim of this study was to evaluate the effects of BMI changes, over an eight-year follow-up, on longitudinal changes of VC, FVC, FEV1, and DLCO indices in a general population sample of North Italy.To avoid including weight changes possibly related to physical growth, only the 1426 (46% males) adults (over 24 years) with complete follow-up were selected. Median linear regression models were applied to estimate the medians of changes (computed as follow-up minus baseline values) of VC, FVC, FEV1, and DLCO indices as functions of changes of BMI over follow-up period, separately by gender, after considering several potential confounders and effect modifiers. The extent of lung function loss tended to be higher among those who, at baseline, reported greater BMI values. Males experienced larger losses than females (20 and 16 ml FEV1 median reduction for a BMI unit increase in males and females, respectively). Conversely, longitudinal changes of BMI caused a slight and non-significant increase in DLCO values in both sexes. Over an eight-year follow-up, the detrimental effect of gaining weight might be reversible for many adults as most of those who reduced their BMI values also increased their lung function. Overweight patients with ventilatory impairment should be routinely encouraged to lose weight for improving their lung function.