General population-based lung function trajectories over the life course: an accelerated cohort study

Abstract

Background Lung function is a key determinant of health, but current knowledge on lung function growth and decline over the life course is based on fragmented, potentially biased data. We aimed to empirically derive general population-based life course lung function trajectories, and to identify breakpoints and plateaus. Methods We created an accelerated cohort by pooling data from eight general population-based child and adult cohort studies from Europe and Australia. We included all participants with information on lung function, smoking status, BMI, and asthma diagnosis status from at least two visits. We used cross-classified three-level linear mixed models to derive sex-specific life course trajectories of FEV1, forced vital capacity (FVC), and FEV1/FVC ratio based on observations at ages 4–80 years, and Bayesian time-series decomposition to identify breakpoints and plateaus. We repeated sex-specific analyses with separate stratification for asthma status (never had asthma vs persistent asthma, where persistent was defined as the risk factor being present at all participant visits) and smoking status (never smoker vs persistent smoker). Findings The accelerated cohort included 30 438 participants born between 1901 and 2006 (15 703 [51·6%] female and 14 735 [48·4%] male; mean age 26 [SD 16] years), who provided a total of 87 666 observations (range 2–8 observations per participant). In female participants, FEV1 increased non-linearly in two phases, at a mean of 234 (95% CI 223 to 245) mL/year until age 13 (95% credible interval [CrI] 12 to 15) years, then at 99 (76 to 122) mL/year until a peak at age 20 (18 to 22) years, and subsequently decreased throughout the rest of adulthood (−26 [−27 to −25] mL/year). In male participants, the pattern was similar, with an increase in FEV1 of 271 (263 to 280) mL/year until age 16 (14 to 18) years, which slowed to 108 (93 to 124) mL/year until reaching a maximum at age 23 (21 to 25) years, decreasing thereafter (−38 [−39 to −37] mL/year), representing a later peak than in female participants. In female participants, FVC increased non-linearly in two phases, at 232 (95% CI 222 to 243) mL/year until age 14 (95% CrI 12 to 15) years, then at 77 (59 to 94) mL/year until peaking at age 20 (19 to 22) years, after which it decreased throughout the rest of adulthood (−26 [−27 to −25] mL/year). In male participants, FVC also increased in two phases, at 326 (315 to 337) mL/year until age 15 (13 to 17) years, then at 156 (144 to 168) mL/year until a peak at 23 (19 to 30) years, and subsequently declined in two phases (−22 [−29 to −14] mL/year until age 42 [38 to 50] years, then −36 [−38 to −34] mL/year thereafter). No plateau after the peak was observed for either lung function parameter in both sexes. FEV1/FVC ratio decreased throughout life from the starting age of 4 years in both sexes with some distinct patterns. Stratified analysis showed that persistent asthma (vs never had asthma) was related to an earlier FEV1 peak, lower FEV1 throughout adulthood, and lower FEV1/FVC ratio across the life course in both sexes. Persistent smoking (vs never smoking) was related to an accelerated decrease in FEV1 and FEV1/FVC ratio during adulthood in both sexes. No statistically significant plateau was observed in any lung function parameter across the strata of asthma or smoking status. Interpretation In both sexes, FEV1 and FVC increased in two phases, with a fast increase until around age 13–16 years, and then a slower increase until a peak. Neither parameter showed a plateau phase after the peak, and decreases started earlier than previously described. FEV1/FVC ratio decreased throughout life. These observations provide an essential, but previously unavailable, framework to assess and monitor lung health over the life course.