Aim of this paper was to evaluate the effects of changes in obesity status on lung function decline over an 8-year follow-up.

Adults over 24 years (n=1212) from the general population, who participated in both Po River Delta first (PD1, 1980–1982) and second (PD2, 1988–1991) epidemiological surveys, were stratified as “never obese” (BMI<30Kg/m² at both PD1 and PD2), “becoming obese” (BMI<30Kg/m² at PD1 and ≥30Kg/m² at PD2), “always obese” (BMI≥30Kg/m² at both PD1 and PD2), and “becoming non-obese” (BMI≥30Kg/m² at PD1 and <30Kg/m² at PD2). Linear regression models for changes in FEV₁, FVC, and VC (computed as absolute differences between the values at PD2 and those at PD1) with longitudinal categories of obesity, gender, age, and baseline smoking habits as covariates were applied.

The “becoming obese” and “always obese” categories had a significantly greater decline of lung function than “never obese” group; in the “always obese” group, this was true for vital capacities but not FEV₁. Conversely, in the “becoming non-obese” group lung function was at PD2 improved with respect to PD1. Compared with “Never obese” the mean increase in lung function was of 93, 180, and 48mL for FEV₁, FVC, and VC, respectively.

In this general population sample, remaining or becoming obese increases the decline in lung function over 8 years, while becoming non-obese decreases it.