The Association of Multiparity with Lung Function and Chronic Obstructive Pulmonary Disease-Related Phenotypes

Background: Apparent increased female susceptibility to chronic obstructive pulmonary disease (COPD) suggests sex hormones modulate disease pathogenesis. Little is known about associations between multiparity and lung function in smokers.

Research question: We hypothesized that multiparity is associated with lung function and measures of emphysema and airway disease.

Study design and methods: Utilizing female participants from the 5-year follow up of the COPD Genetic Epidemiology (COPDGene^®) study we performed multivariable linear regressions to assess the effect of multiparity and number of pregnancies on forced expiratory volume in 1 second (FEV₁) percentage of predicted (% predicted), FEV₁/forced vital capacity (FVC), percent emphysema on computed tomography (CT) scans, and Pi10, a measure of airway thickening. We sampled never smokers and those with lower smoking exposure from the National Health and Nutrition Examination Survey (NHANES) 2011-2012 dataset.

Results: We included 1820 participants from COPDGene^® and 418 participants from NHANES (321 never smokers, 97 ever smokers). In COPDGene^®, multiparity (beta coefficient [β] = -3.8, 95% confidence interval [CI]: [-6.5, -1.1], p = 0.005) and higher number of pregnancies were associated with lower FEV₁ % predicted. Multiparity was not associated with percent emphysema or Pi10. In individuals with no or mild obstruction, multiparity was associated with lower FEV₁ % predicted. There was an interaction with multiparity and age on FEV₁ % predicted (p = 0.025). In NHANES, there was no association between multiparity and FEV₁ % predicted in never smokers or the lower smoking exposure group.

Interpretation: Multiparity was associated with lower FEV₁ % predicted in current and former smokers in COPDGene^® study participants. These preliminary results emphasize the importance of smoking abstinence in women of child-bearing age.