Association between Socioeconomic Status and Chronic Obstructive Pulmonary Disease in Jiangsu Province, China: A Population-Based Study
Chronic obstructive pulmonary disease (COPD) is a significant public health issue globally, ranking among the top three causes of death worldwide. In China, the burden of COPD is particularly severe, with an estimated spirometry-based prevalence of 13.7% among individuals aged 40 years and above. COPD is a preventable and treatable condition, but its extrapulmonary effects contribute to pulmonary function impairment and increased prevalence. Understanding the risk factors associated with COPD is crucial for designing effective prevention strategies. Recent studies have highlighted the role of socioeconomic status (SES) in the incidence of COPD, prompting this investigation into the relationship between SES and COPD in Jiangsu province, China.
This study aimed to explore the association between SES and COPD among adults aged 40 years and above in Jiangsu province, China, and to examine the potential direct and indirect effects of SES on COPD morbidity. The research was conducted as a cross-sectional study between May and December 2015, using a multistage sampling approach to select participants. COPD was diagnosed based on spirometry, respiratory symptoms, and risk factors. SES was measured using three indicators: education, occupation, and monthly family average income (FAI). Mixed-effects logistic regression models were employed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the SES-COPD relationship. Pathway analysis was conducted to further investigate the pulmonary function impairment of patients with different SES levels.
The study included 2421 participants with a mean age of 56.63 years. The overall prevalence of COPD was 11.8%, with higher prevalence observed in men (17.8%) compared to women (6.0%). The prevalence of COPD increased with age, with the highest prevalence (27.9%) in individuals aged 70 years and above. No significant difference in COPD prevalence was found between urban (12.6%) and rural (11.0%) residents. Smokers had a significantly higher prevalence of COPD (20.0%) than non-smokers (6.0%). Additionally, residents exposed to outdoor air pollution with PM2.5 concentrations ≥75 mg/m3 had a higher COPD prevalence (13.8%) than those with lower PM2.5 exposure (10.7%).
Educational attainment was negatively associated with COPD prevalence in men. Participants with higher education levels (≥13 years of schooling) had a lower risk of COPD (OR: 0.41, 95% CI: 0.16–1.07) compared to those with only compulsory education (≤9 years). White-collar workers were at a lower risk of COPD (OR: 0.60, 95% CI: 0.43–0.83) than blue-collar workers. Similarly, participants in the upper FAI tertile had a reduced risk of COPD (OR: 0.68, 95% CI: 0.49–0.97) compared to those in the lower tertile. These negative associations between SES indicators and COPD prevalence were significant only among men.
Pathway analysis revealed that SES indicators had both direct and indirect effects on pulmonary function. Education, FAI, and occupation directly influenced post-bronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC), FEV1, FVC, and FEV1 percentage of predicted (FEV1% pred). Education had an indirect effect on FVC and FEV1% pred through outdoor air pollution, with indirect effect coefficients of 0.011 and -0.018, respectively. Occupation affected FEV1/FVC through body mass index (BMI), cigarette smoking, and indoor air pollution, with a total indirect effect coefficient of -0.009. FAI indirectly influenced FEV1/FVC (b = 0.025) through cigarette smoking and indoor air pollution, and FVC (b = -0.037) through cigarette smoking and outdoor air pollution.
The findings suggest that SES disparities in COPD prevalence are influenced by multiple factors, including smoking, air pollution, and BMI. Individuals with lower SES are more likely to engage in unhealthy behaviors, have poor nutrition, and face challenges in accessing healthcare services, all of which contribute to higher COPD risk. Additionally, low SES individuals may have less protection against environmental risk factors such as outdoor and indoor air pollution. The gender disparity in the SES-COPD relationship may be attributed to differences in smoking behavior and exposure to air pollution, with men more likely to smoke and work in jobs with higher outdoor air pollution exposure.
This study underscores the importance of addressing SES disparities in COPD prevention strategies. Tailored interventions for different SES groups are essential to reduce COPD prevalence and improve lung function outcomes. Future research should continue to monitor the SES-COPD relationship, particularly in the context of ongoing social and economic development in China.
The study has several strengths, including the use of spirometry for COPD diagnosis, the inclusion of multiple SES indicators, and the control of major COPD risk factors such as smoking and air pollution. However, there are limitations to consider. The cross-sectional design precludes causal inferences, and the sample size was not sufficient for gender-stratified analysis, resulting in few COPD cases among women. Additionally, SES data were self-reported, which may introduce recall bias. Despite these limitations, the study provides valuable insights into the SES-COPD relationship and highlights the need for targeted public health interventions.
In conclusion, education, occupation, and FAI are inversely related to COPD prevalence in Jiangsu province, China, particularly among men. SES has both direct and indirect effects on pulmonary function impairment, mediated by factors such as smoking, air pollution, and BMI. Addressing SES disparities is crucial for effective COPD prevention and management, and future studies should continue to explore the dynamic relationship between SES and COPD in the context of changing socioeconomic conditions.
doi.org/10.1097/CM9.0000000000001609
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