Abstract:
Background Air particulate matter pollution has become one of the main factors threatening human health, playing an important role in the occurrence and development of cardiovascular diseases and respiratory diseases. Chronic bronchitis (CB) is a common respiratory disease, most of which are complicated with emphysema and cor pulmonale, and seriously affects the quality of life in patients and poses huge economic burden to families and society. There are limited studies on the long-term exposure to particulate matters and CB.
Objective This study aims to assess the association between long-time exposure to high concentrations of PM10 and the risk of CB of residents.
Methods A retrospective cohort study was conducted among 37 915 residents in four cities in northern China, including Rizhao, Tianjin, Shenyang, and Taiyuan, from 1998 to 2009. Questionnaire survey was used to obtain demography, lifestyle, disease history, and selfreported CB. PM10 concentrations were sourced from the national monitoring sites of ambient air quality in each city. With the annual average concentration of PM10 from the time of inclusion into the cohort to the time of CB onset as exposure estimate, Cox proportional risk regression model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI), and to examine the interaction of PM10 exposure with gender, age, body mass index (BMI), education, income, smoking, outdoor exercise, and other factors.
Results With a mean follow-up of 11.78 years, 354 new cases of CB were reported, and the cumulative incidence was 9.3‰. The baseline age of the study subjects was (44.09±13.87) years, and the baseline body mass index was (22.64±2.95) kg·m-2. After adjusting for age, gender, BMI, lifestyle, CB family history, and other confounding factors, the HR (95% CI) of CB was 1.616 (1.546-1.688) for every 10 μg·m-3 increase of PM10. The stratified analysis results showed significant associations between PM10 and CB incidence across different age, BMI, education, and exercise groups (Pinteraction < 0.05); and compared with the age group < 45 yearsHR (95% CI):1.324 (1.252-1.401), the BMI group < 24 kg·m-2HR (95% CI):1.553 (1.477-1.634), the low education groupHR (95% CI):1.582 (1.502-1.667), and the group with inactive outdoor exerciseHR (95% CI):1.489 (1.407-1.576), the age group ≥ 45 yearsHR (95% CI):1.888 (1.787-1.996), the BMI group ≥ 24 kg·m-2HR (95% CI):1.825 (1.673-1.992), the high education groupHR (95% CI):1.753 (1.614-1.904), and the group with active outdoor exerciseHR (95% CI):1.800 (1.687-1.920) had a stronger interaction with PM10 exposure. The results did not change significantly in the sensitivity analysis.
Conclusion Long-term exposure to high concentrations of PM10 may increase the risk of CB of residents in northern China, and it has a stronger impact on those who are 45 years of age or older, with BMI ≥ 24kg·m-2, and more active in outdoor exercise.
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