Systemic inflammation and lung function in adulthood and their association with early life factors

Introduction Forced vital capacity (FVC) is a more powerful predictor of mortality than the ratio of forced expiratory volume in one second to FVC (Burney et al. Thorax 2011;66:49-54). Reduced FVC is associated with low birth weight (BW) and low grade inflammation and low BW is also associated with low grade inflammation. BW could therefore explain the association between FVC and inflammation. We tested this hypothesis in the Northern Finland 1966 birth cohort by examining the associations between FVC, systemic inflammation and BW. Methods Using linear regression we examined the association between FVC and BW and whether adjusting for early life factors (ELF) such as maternal smoking, maternal height and weight before pregnancy explain this association. We then used linear regression to determine the association between FVC and inflammatory markers and whether adjusting for BW and other ELF accounted for the association between FVC and inflammatory markers. Results FVC in adulthood increased by 92mL (95% confidence interval (CI): 56 to 130) for each kilogram increase in BW. Adjusting for ELF did not substantially change this association. As BW rose levels of C-reactive protein (CRP) and white blood cell count (WBC) in adulthood fell. One standard deviation (SD) increase of CRP was associated with a 53 mL reduction in FVC (95% CI: -71 to -35) and one SD increase of WBC was associated with a 24 mL reduction in FVC (95% CI: -42 to -5.8). Adjusting for BW did not substantially alter the associations between FVC and CRP or WBC. Conclusions FVC is independently associated with birth weight, CRP and WBC. However the association of FVC with CRP or WBC is not explained by variation in BW.