Asthma Does Not Explain A Decline In Post Bronchodilator Lung Function In Early Adult Life

RATIONALE: Using the Isle of Wight Birth Cohort (IOWBC), we investigated lung function deficits in young adults with asthma to identify whether airways obstruction in that group accounted for a decline in post-bronchodilator lung function within the overall population seen by 26-years.

METHODS: The IOWBC is a population based cohort (n=1456), recruited in 1989- 90 and assessed at birth, 1, 2, 4, 10, 18 and 26 years for asthma, allergic diseases and environmental exposures. Spirometric lung function tests were carried out using standardized methodology at 18 (n=839) and 26 years (n=555) before and after inhaled bronchodilator (salbutamol 400mcg). Forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), FEV₁/FVC ratio and mid-expiratory flows (FEF_25-75) at 26 years plus changes in these indices between 18 and 26 were assessed. Asthma was defined as physician diagnosis plus current wheeze and/or on treatment.

RESULTS: Pre-bronchodilator FEV₁, FEV₁/FVC, and FEF_25-75 were all significantly reduced (P<0.001) in those with asthma (3.52L, 0.73 and 3.11L) compared to those without asthma (3.90L, 0.73, and 3.89L). However, there was no significant difference in post-bronchodilator FEV₁, FEV₁/FVC, and FEF_25-75 between the two groups.

CONCLUSIONS: Airways obstruction at 26 years of age is usually fully reversible in most people with asthma. An observed decline in postbronchodilator FEV₁, FEV₁/FVC, and FEF_25-75 from 18 to 26 years in this cohort therefore does not appear to be accounted for by the influence of asthma.