Individuals with the highest risk for chronic obstructive pulmonary disease (COPD) have a mixed obstructive and restrictive lung function pattern that is characterized by a low forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio and low FVC trajectories. This is among study findings published in The Lancet Respiratory Medicine.
Researchers sought to assess lifetime trajectories in individuals with COPD for FEV1/FVC ratio, FVC, and their combinations. The investigators also sought to correlate the combined trajectory groups with static lung volume and gas transfer measurements, and to evaluate the risk factors and consequences for these combined trajectory groups.
The prospective cohort study included data from 6 phases of the Tasmanian Longitudinal Health Study (TAHS) from childhood to middle age. Group-based trajectory modeling was used to identify unique groups of individuals whose measurements had a similar pattern for pre-bronchodilator FEV1/FVC ratio and FVC z scores at 7, 13, 18, 45, 50, and 53 years. The FEV1/FVC ratio was combined with the FVC trajectories to assess overlapping lifetime spirometry patterns.
Of the original TAHS cohort, 2422 (28%) of 8583 individuals had lung function data available at 7 years and 53 years and were included in the analysis. The best-fitting models identified 5 FVC trajectories and 6 FEV1/FVC ratio trajectories.
The study authors then identified 4 patterns of lifetime spirometry. The low FEV1/FVC ratio only group (obstructive-only; n=626 [25.8%]; 50% male) included individuals in 1 of the 3 low FEV1/FVC ratio trajectory groups without a co-existent low FVC trajectory. Low FVC only (restrictive-only; n=253 [10.5%]; 55% male) included individuals in the low FVC trajectory group without a co-existent low FEV1/FVC ratio trajectory. Low FEV1/FVC ratio and low FVC (mixed; n=84 [3.5%]; 56% male) included individuals in 1 of the 3 low FEV1/FVC and low FVC trajectory groups. The reference group (n=1459 [60.2%]; 46% male) included individuals with neither a low FEV1/FVC ratio trajectory nor a low FVC trajectory group.
The prevalence of bronchodilator reversibility at age 45 years was 8.5% in the obstructive-only pattern group, 5.4% in the restrictive-only pattern, 22.2% in the mixed pattern, and 1.9% in the reference pattern. At age 53 years, the prevalence of bronchodilator reversibility in these patterns was 9.2%, 4.9%, 18.0%, and 0.6%, respectively.
The prevalence of COPD at age 53 years was significantly higher in individuals with mixed (37%) and obstructive-only patterns (22%). The prevalence of asthma, other respiratory symptoms, and respiratory medication use was significantly increased among individuals in all 3 subnormal patterns, although those with the mixed pattern had the highest prevalence of these markers. Individuals with the mixed pattern also had a significantly higher rate of diagnosed depression, and those with the restrictive-only pattern had a significantly higher rate of multiple comorbidities.
Participants with the mixed pattern had the highest prevalence of other respiratory symptoms at age 53 years, parental asthma, childhood illnesses, increased C-reactive protein level, and lung injury. The restrictive-only pattern group had decreased static lung volumes, increased childhood illnesses, and increased C-reactive protein levels.
Study limitations include insufficient lung function data from about 18 years of age; a possible healthy survivor bias; a study sample of largely White participants; and lack of data on the effects on daily life.
“These findings could be incorporated into clinical algorithms designed to identify those at a high risk of developing COPD (pre-COPD) and those with established but as yet undiagnosed COPD,” stated the researchers. “Such approaches could be used to aggressively target the high prevalence of comorbidities in the longitudinal restrictive lung function pattern. Overall, our findings highlight the untapped opportunities for tackling disease burden that result from tracking early lung function deficits.”
Disclosure: Some of study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Dharmage SC, Bui DS, Walters EH, et al. Lifetime spirometry patterns of obstruction and restriction, and their risk factors and outcomes: a prospective cohort study. Lancet Respir Med. Published online October 13, 2022. doi:10.1016/S2213-2600(22)00364-2