Long-Term Pollution Exposure Linked to Elderly ARDS Hospitalizations

Jongeun Rhee, ScD

A new study has found that long-term exposure to particulate matter (PM_2.5) and ozone concentrations has a significant association with elderly’s hospitalization for acute respiratory distress syndrome (ARDS).

The TH Chan School of Public Health-based study, presented at the 2018 American Thoracic Society (ATS) International Study in San Diego, CA, has strong implications for lung disease which has a mortality rate of 68-80% in the elderly.

Researchers from the Boston, MA institution analyzed data from more than 1.16 million hospital admissions of Medicare enrollees aged 65 years or older from 2000-2012. Each admission was for occurrences of ARDS, as defined by ICD-9-CM discharge diagnosis codes. In their analysis, 37,167 zip codes of interest were included in results, meaning there were approximately 3 elderly patient hospital admissions for ARDS in a zip code per year.

Annual average PM_2.5 and ozone concentrations during the warm season (April 1-September 30) were computed at each zip code. A 2-pollutant generalized linear mixed model with a random intercept for zip-code assuming a Poisson distribution was fitted by the researches, with over-dispersion allowed by quasi-likelihood methods. They adjusted models for sex, age, race, median household income, smoking, and weather.

The prepared long-term, comprehensive analysis of the pollutant and disease associations was both on par with current clinical research and a first-of-its-kind study.

“While there is growing evidence of the impact on lung health of numerous health pollutants, there have been few studies that have looked at acute respiratory diseases and air pollution across large populations,” lead author Jongeun Rhee, ScD, said.

In the analyzed zip codes of frequent ARDS hospital admissions, PM_2.5 and ozone concentrations were 11.0 mcg/m³ and 39.2 ppb, respectively. Researchers reported annual average increases of 1 mcg/m³ and 1 ppb of PM_2.5 and ozone associated with increases in in annual hospital admission rates for ARDS of 1% (0.97%; 95% CI; 0.88-1.07) and 0.13% (95% CI; 0.06-0.20), respectively.

In areas of low pollution — as defined by regions with annual average PM_2.5 levels less than 12 mcg/m³ — the same annual increases in the PM_2.5 and ozone were associated with annual ARDS hospital admission increases of 1.71% (95% CI; 1.52-1.91) and 0.30% (95% CI; 0.20-0.39), respectively.

Researchers were concerned to find not only a significant association between long-term pollutant exposure and ARDS hospitalization in elderly patients, but consistent results in areas of low pollution. The analysis into the role PM_2.5 exposure was a novel discovery in relation to ARDS-pollution trend studies.

“We highlighted the importance of air pollution as a environmental risk factor for ARDS, which has not been studied widely but contributed to a previous finding that was limited to ozone,” Rhee said.

ARDS, a rapidly progressive disease that is frequently diagnosed in critically ill patients, is often preceded by conditions such as sepsis, pneumonia, traumatic injury, and aspiration. Its complications such as fluid leaking into patients’ lungs lend to its significantly mortality among the elderly. The new study simply adds it to a list of pollution side effects.

“These results add to the growing body of literature on various adverse health effects at current standards that demonstrate a need to lower our exposure limits,” senior study authoer David Christiani, MD, MPH, said.

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