Mediating Effect of Tobacco Dependence on the Association Between Maternal Smoking During Pregnancy and Chronic Obstructive Pulmonary Disease: Case-Control Study
Authors: Li Jinxuan , Xu Jianying , Yang Lan , Xu Yongjian , Zhang Xiangyan , Bai Chunxue , Kang Jian , Ran Pixin , Shen Huahao , Wen Fuqiang , Huang Kewu , Yao Wanzhen , Sun Tieying , Shan Guangliang , Yang Ting , Lin Yingxiang , Zhu Jianguo , Wang Ruiying , Shi Zhihong , Zhao Jianping , Ye Xianwei , Song Yuanlin , Wang Qiuyue , Hou Gang , Zhou Yumin , Li Wen , Ding Liren , Wang Hao , Chen Yahong , Guo Yanfei , Xiao Fei , Lu Yong , Peng Xiaoxia , Zhang Biao , Wang Zuomin , Zhang Hong , Bu Xiaoning , Zhang Xiaolei , An Li , Zhang Shu , Cao Zhixin , Zhan Qingyuan , Yang Yuanhua , Liang Lirong , Cao Bin , Dai Huaping , Chung Kian Fan , Chen Zhengming , He Jiang , Wu Sinan , Xiao Dan , Wang Chen ,   China Pulmonary Health Study Group
Published: February 2024

Background
Maternal smoking during pregnancy (MSDP) is a known risk factor for offspring developing chronic obstructive pulmonary disease (COPD), but the underlying mechanism remains unclear.

Objective
This study aimed to explore whether the increased COPD risk associated with MSDP could be attributed to tobacco dependence (TD).

Methods
This case-control study used data from the nationwide cross-sectional China Pulmonary Health study, with controls matched for age, sex, and smoking status. TD was defined as smoking within 30 minutes of waking, and the severity of TD was assessed using the Fagerstrom Test for Nicotine Dependence. COPD was diagnosed when the ratio of forced expiratory volume in 1 second to forced vital capacity was <0.7 in a postbronchodilator pulmonary function test according to the 2017 Global Initiative for Chronic Obstructive Lung Disease criteria. Logistic regression was used to examine the correlation between MSDP and COPD, adjusting for age, sex, BMI, educational attainment, place of residence, ethnic background, occupation, childhood passive smoking, residential fine particulate matter, history of childhood pneumonia or bronchitis, average annual household income, and medical history (coronary heart disease, hypertension, and diabetes). Mediation analysis examined TD as a potential mediator in the link between MSDP and COPD risk. The significance of the indirect effect was assessed through 1000 iterations of the “bootstrap” method.

Results
The study included 5943 participants (2991 with COPD and 2952 controls). Mothers of the COPD group had higher pregnancy smoking rates (COPD: n=305, 10.20%; controls: n=211, 7.10%; P<.001). TD was more prevalent in the COPD group (COPD: n=582, 40.40%; controls: n=478, 33.90%; P<.001). After adjusting for covariates, MSDP had a significant effect on COPD (β=.097; P<.001). There was an association between MSDP and TD (β=.074; P<.001) as well as between TD and COPD (β=.048; P=.007). Mediation analysis of TD in the MSDP-COPD association showed significant direct and indirect effects (direct: β=.094; P<.001 and indirect: β=.004; P=.03). The indirect effect remains present in the smoking population (direct: β=.120; P<.001 and indirect: β=.002; P=.03).

Conclusions
This study highlighted the potential association between MSDP and the risk of COPD in offspring, revealing the mediating role of TD in this association. These findings contribute to a deeper understanding of the impact of prenatal tobacco exposure on lung health, laying the groundwork for the development of relevant prevention and treatment strategies.