Cross-sectional and longitudinal associations of DXA-measured body composition with lung function in middle-aged Australians: The Busselton Healthy Ageing Study.

Background: Limited data are available on the association of body composition and lung function in middle-aged adults. We investigated the cross-sectional and longitudinal associations in participants of the Busselton Healthy Ageing Study.

Methods: At baseline (n = 4857, aged 46-70 years) and 6-year follow-up (n = 3436), body mass index (BMI), fat and lean mass index (FMI and LMI) and abdominal visceral adipose tissue (VAT) using dual-energy x-ray absorptiometry (DXA), forced expiratory volume in one second (FEV1 % predicted) and forced vital capacity (FVC % predicted) were assessed. Relationships were examined using linear regression, adjusted for age, lifestyle factors and comorbidities.

Results: At baseline, the reduction in FEV1 % and FVC% for each additional 1 kg/m2 of FMI was twice greater than that of BMI (men: 1.5-1.9 vs 0.4-0.7; women: 1.0-1.2 vs 0.3-0.5); in contrast each additional 1 kg/m2 of LMI was associated with 1.3-1.6 units increment in FEV1 % and FVC%. In the longitudinal analysis, ∆FEV1 % and ∆FVC% per 1 kg/m2 increment in ∆FMI were -2.2 and -2.3 in men and -1.0 and -1.1 in women, in comparison with -1.8 and -1.9 in men and -0.8 and -0.9 in women for ∆BMI. The range of change in LMI over time was narrow, and ∆LMI had little impact on ∆FEV1 % and ∆FVC%. Higher baseline VAT and greater increase over time were associated with lower lung function, but not totally independent of FMI.

Conclusions: In middle-aged adults, increased fat mass is a driver for lung function deterioration, whereas higher baseline lean mass may have a protective effect.