Aim: The influence of lifetime body mass index (BMI) trajectories on adult lung function (LF) deficits and chronic obstructive pulmonary disease (COPD) has not previously been investigated. We have analysed associations between BMI trajectories from childhood to mid-adulthood and LF patterns and COPD in the TAHS.

Methods: BMI trajectories from 5 to 43 years of age were developed previously for 4194  participants. We analysed post-bronchodilator (BD) spirometry from ages 45 and 53 years. LF patterns and COPD were defined using spirometry. Associations were assessed with multivariable regression.

Results: We identified five distinct BMI trajectories and analysed them compared to the average trajectory. Belonging to the child average-increasing trajectory was associated with a more significant FVC decline from 45 to 53 years (?=-178ml, p <0·005) and lower FVC at 53 years (?=-227ml, p<0·001). The consistently high trajectory was associated with restrictive LF (OR=6·95, p<0·002). Both these trajectories were associated with decreased TLC, ERV and FRC at age 45, and increased TLco at 45 and 53 years. The consistently low trajectory was associated with lower FEV1 (?= -124ml, p<0·001), FVC (?=-91ml, p<0·03), FEV1/FVC (?=-1·2%, p<0·02, and increased ERV at 45 years with a similar pattern at 53 years. No associations were observed for spirometrically defined COPD.

Conclusion: Participants belonging to the high BMI trajectories were at greater risk of restrictive LF pattern, and those with low trajectories were at risk of an obstructive LF pattern. This novel finding highlights the respiratory advantages of maintaining a normal weight throughout life.