Higher long-term traffic-related air pollution (TRAP) exposure was associated with higher direct annual health care costs in individuals aged 65 or older, according to a report published in Atmospheric Environment.
Associations between air pollution exposure and high emergency department (ED) and total health care costs were particularly significant among patients with cardiovascular disease (CVD).
Although TRAP is linked with a variety of negative health effects, researchers sought to clarify any impact on higher health care costs. They conducted a longitudinal study of a multi-ethnic population-based cohort served by Kaiser Permanente Northern California (KPNC) between 2013 and 2017. Participants resided in neighborhoods where highly resolved air pollution exposures were assessed.
To assess air pollution, the researchers measured hyperlocal long-term pollutant concentrations for nitrogen dioxide (NO2), nitric oxide, and black carbon at a resolution of 30 m using repeated street-level mobile measurements and linked them to residential addresses. Health care utilization costs were derived from KPNC databases. These costs were used to calculate individual annual total health care, inpatient, outpatient, ED, and pharmacy costs.
The researchers evaluated associations between TRAP exposures and health care costs using generalized estimating equation models. They adjusted for age, sex, race, body mass index (BMI), smoking, socioeconomic status, and comorbidities and assessed differences among specific susceptible population subgroups.
The study cohort consisted of 25,684 subjects aged 65 and older; consisted primarily of female, patients (56.1%); and included a majority (59.1%) of individuals who were Asian, Black, Hispanic, and other races.
Results show an IQR difference (10.1 vs 4.2 ppb) in NO2 concentration was associated with 3% (95% CI, –1% to 6%), 22% (95% CI, 11%-35%), and 5% (95% CI, 1%-8%) increases in annual total health care, ED, and outpatient costs in the baseline model. Associations between NO2 with ED and outpatient health care costs remained the most robust, even after controlling for baseline comorbidities. Associations with black carbon showed similar patterns, although smaller in magnitude.
The relationship between NO2 exposures and total or ED health care costs was higher among older participants with existing CVD. Among participants with CVD, an IQR increase in NO2 was associated with a 7% (95% CI, 1%-13%) increase in total annual health care cost and a 23% (95% CI, 17% -29%) increase in ED costs.
These findings align with previous research showing that populations with existing CVD are more susceptible to air pollution.
The results of the study indicate that long-term spatial differences in TRAP concentrations within neighborhoods were associated with higher annual ED and outpatient health care costs for older individuals. The findings were most significant for NO2 exposures and impacts on ED and outpatient costs.
The researchers found that these associations remained robust even when all 3 TRAP pollutants were included in the same model. They believe their study is the first to empirically assess the impact of urban air pollution on individual direct health care costs. However, they recommend additional studies to confirm their findings.
The authors acknowledge that the exposure assessment method used may not accurately capture the full exposure variance, although their method did reduce spatial component of measurement error. The study also did not assess out-of-pocket costs. However, the authors assert that assessing direct costs is a strength of the study, because these more closely reflect health care utilization. Differences between direct and OOP costs would reflect variability in insurance plan type, which is not causally related to air pollution, they note.
While it is possible that some residual confounding may have occurred related to covariate interactions, the analysis was designed to account for several potential confounders such as age, race, neighborhood, BMI, and comorbidities.
Alexeeff SE, Roy A, Shan J, et al. Association between traffic related air pollution exposure and direct health care costs in Northern California. Atmos Environ. Published online July 3, 2022. doi:10.1016/j.atmosenv.2022.119271
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