Short-Term Fine Particulate Matter Exposure Increases COPD Hospitalizations

Short-term exposure to fine particulate matter (PM_2.5) increases hospitalizations in patients with chronic obstructive pulmonary disease (COPD), according to a study published in BMC Public Health.

The researchers explained that the risk of COPD is known to increase with exposure to pollutants, especially PM_2.5. They noted that several past studies have reported that PM_2.5 has a greater impact on humans than coarse particles (PM₁₀) because it can be inhaled deeper into the alveoli of the lungs, resulting in alveolar inflammation and, ultimately, COPD.

Although past studies have examined the connection between PM_2.5 exposure and COPD hospitalizations, the results were inconsistent. Consequently, the researchers evaluated the short-term association between PM_2.5 exposure and COPD hospitalization risk by analyzing related studies.

To do so, 2 reviewers conducted searches in PubMed, Scopus, Web of Science, and Google Scholar for relevant studies published between January 1, 2010, and May 1, 2022, using the keywords “air pollution” and “COPD.” From their initial search, the researchers found 9518 studies. After examining each study further, 15 remained; the researchers clarified that the results of a case-crossover study from 4 regions of Australia were considered separate studies, meaning they used 19 studies for analysis.

Air pollution

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Based on data extracted from the 19 studies, the researchers determined the relationship between COPD hospitalization and PM_2.5 exposure by measuring the OR by plotting random-effects models to calculate the pooled effect size (χ² = 349.95; df = 18; I² = 94.86%; P = .007; Z = 2.68; P < .001). From these models, they found the random pooled effect size (OR) for the relationship to be 1.016 (95% CI, 1.004-1.029).

Also, the researchers found only a slight increase (1.6%; 95% CI, 0.4%-2.9%) in COPD hospitalization for every 10 μg/m³ daily increase in PM_2.5 concentration. Additionally, through funnel plots and the Egger’s test, they found no publication bias regarding the association between PM_2.5 exposure and COPD hospitalization (bias = 1.508; 95% CI, –1.475-4.49; t = 1.066; P = .301).

Through subgroup analyses, the researchers found the risk of COPD hospitalization to be higher in patients 65 and older; they attributed this to elderly people being at higher risk of air pollution’s harmful effects, but there are limited studies on the impact of PM_2.5 exposure in this age group. The analyses also revealed that the association between PM_2.5 and COPD hospitalization was stronger in Asian countries, which they attributed to these countries having the highest concentrations of PM_2.5 in comparison to those of North America and Europe.

The researchers also acknowledged their study’s limitations, one being that the number of selected studies was limited. Also, they diagnosed patients with COPD based on their symptoms and the International Classification of Diseases External (ICD-9 or ICD-10); they did not base COPD diagnoses on spirometry, which could lead to biased or distorted results. Despite these limitations, the researchers explained that their study’s results demonstrated the need to decrease PM_2.5 exposure and related COPD hospitalizations.

“The development of transportation and public health policies to control PM_2.5 at the global standards will reduce the incidence of COPD,” the authors concluded. “The present study provides evidence that the time has come to take necessary measures and continuous assessment to improve air quality.”

Reference

Delavar MA, Jahani MA, Sepidarkish M, Alidoost S, Mehdinezhad H, Farhadi Z. Relationship between fine particulate matter (PM2.5) concentration and risk of hospitalization due to chronic obstructive pulmonary disease: a systematic review and meta-analysis. BMC Public Health. 2023;23(1):2229. doi:10.1186/s12889-023-17093-6