Healthy diet is associated with better lung function, especially in individuals with COPD: findings from the Lifelines cohort study.

OBJECTIVE: To investigate whether the association between diet and lung function (LF) differs according to asthma or COPD status in the Lifelines cohort study. METHODS: We included adults from Lifelines with valid dietary and spirometry data. Dietary quality was calculated at baseline using the Lifelines diet score (LLDS) (range 0-48, where higher scores indicate a healthier diet). LF was assessed via pre-bronchodilator spirometry (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC) at baseline and two follow-ups (∼10 years). Cross-sectional associations between diet and LF were examined using linear regression and longitudinal associations with linear mixed-effects models. Interactions between diet and asthma or COPD were included. RESULTS: Higher LLDS was associated with higher LF and slower decline. In cross-sectional analyses (n=83 460, 59% female, mean age 44±13 years), higher LLDS was associated with higher FEV1 and FEV1/FVC levels in participants with asthma (FEV1 βinteraction (βint)=2.48 mL, 95% CI 0.68-4.27; FEV1/FVC βint=0.027%, 0.003-0.052) and COPD (FEV1 βint=8.31 mL, 6.93-9.69; FEV1/FVC βint= 0.094%, 0.079-0.109) compared with those without asthma or COPD. In longitudinal analyses (n=37 752, 59% female, age 46±11 years) in COPD-patients higher LLDS was associated with slower FEV1 decline (βint=0.18 mL·yr-1, 0.04-0.33), FVC (βint=0.23 mL·yr-1, 0.04-0.41) and FEV1/FVC (βint=0.002%·yr-1, 0.000-0.005) compared with those without COPD. CONCLUSIONS: Higher diet quality was associated with better LF, particularly in those with asthma or COPD, and with slower decline in participants with COPD. These findings suggest that diet may be a modifiable factor in respiratory health.