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 (R)) 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 (R) and 418 participants from NHANES (321 never smokers, 97 ever smokers). In COPDGene (R), multiparity (beta coefficient [beta] = -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 (R) study participants. These preliminary results emphasize the importance of smoking abstinence in women of child-bearing age.