The Role of Active and Passive Smoking in Chronic Obstructive Pulmonary Disease and Systemic Inflammation: A 12-year Prospective Study in China

Abstract Background There is no consensus on the cause and effect of systemic chronic inflammation (SCI) regarding chronic obstructive pulmonary disease (COPD). The impact of second-hand smoke (SHS) on COPD has reached inconsistent conclusions. Methods The China Kadoorie Biobank cohort was followed up from the 2004–08 baseline survey to 31 December 2018. Among the selected 445,523 participants in the final analysis, Cox and linear regressions were performed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of tobacco exposure with COPD risk and baseline levels of log-transformed inflammatory factors [βs (95% CIs)], respectively. Results Participants were followed up for a median of 12.1 years and 11,825 incident COPD events were documented. Ever-smokers were associated with a higher risk of COPD than non-smokers with non-weekly SHS exposure. A younger age to start smoking, a greater amount of daily tobacco consumption, and deeper inhalation were associated with increased risk of COPD and correlated with elevated levels of plasma high-sensitivity C-reactive protein (hs-CRP, all P trend