Ward-Caviness CK, Danesh Yazdi M, Moyer J, et al. Long-term exposure to particulate air pollution is associated with 30-day readmissions and hospital visits among patients with heart failure. J Am Heart Assoc. 2021;10(10):e019430.
Investigators employed an observational study using quasi‐Poisson regression models to associate annual average fine particulate matter at the date of heart failure (HF) diagnosis with the number of hospital visits and 30‐day readmissions.
The population data analyzed in this study are from the Environmental Protection Agency (EPA) Clinical and Archived Records Research for Environmental Studies (EPA CARES) research resource. This resource consists of electronic health records merged with environmental exposure data to facilitate environmental health studies. Investigators analyzed data from a total of 20,920 heart failure patients (10,998 women, 9,922 men). Average age was 68.8 years. There were 13,875 White participants, 5,564 Black participants, and 1,481 participants listed as “other.”
Investigators geocoded primary patient addresses at the street level and estimated daily exposure to PM2.5 (fine particulate matter with diameters of 2.5 micrometers or smaller) using a validated model.1 Each patient was linked to a 1×1–km grid cell based on their address, and investigators used this grid cell to calculate average annual air pollution exposure. They determined initial heart failure diagnosis and hospital admissions through electronic health records.
The researchers used quasi‐Poisson models that adjusted for age, race, sex, year of HF diagnosis, smoking status, neighborhood socioeconomic status, percent urbanicity, preexisting chronic disease, and short‐term air pollution exposure models to associate annual average fine particulate matter at the date of HF diagnosis with the number of hospital visits and 30‐day readmissions.
A total of 442,244 hospital visits were recorded for this cohort of patients over an average follow‐up of 2.79 years.
A 1‐µg/m3 increase in fine particulate matter was associated with a 9.31% increase (95% CI, 7.85%–10.8%) in total hospital visits; a 4.35% increase (95% CI, 1.12%–7.68%) in inpatient admissions; and a 14.2% increase (95% CI, 8.41%–20.2%) in 30‐day readmissions. These associations were robust to different modeling approaches.
The authors concluded, “Elevated air pollution exposure among patients with heart failure increases 30‐day readmissions, outpatient visits, and inpatient admissions, pointing to an overall increase in morbidity with increasing exposure.”
In the United States, the prevalence of HF is increasing. By 2030, an estimated 8 million individuals will have HF, a 46% increase from 2012. In 2012, the total cost of HF in the United States was estimated at $30.7 billion, with approximately 68% of those costs coming from direct healthcare costs such as hospital visits and inpatient stays. By 2030, the cost of HF is estimated to grow to $69.8 billion, a 127% increase.2
These filters are inexpensive and are designed to be replaced at regular intervals, yet few people are aware of this, nor are they aware that these filters are available as HEPA filters specifically designed to remove fine particulates.
In clinical practice, although our attention is focused on each individual patient, these larger trends are worth noting as they suggest whom and what we will see in the exam room.
Hospital readmission rates are now a key measurement in hospital performance evaluations, thanks to the Affordable Care Act, which imposes financial fines on hospitals for poor performance. Under the Hospital Readmissions Reduction Program, elevated 30-day readmission rates led to withholding 3% of Medicare and Medicaid fees for service payments for heart failure and 5 other conditions. While 3% may not sound like much, it amounted to hundreds of millions of dollars in 2020. While the financial concerns of corporate entities may not be uppermost on our list of worries, this research provides a valuable calculus for assessing difficult pollution exposure risks.
It is well-established that long-term exposure to air pollution raises the risk of being admitted to the hospital. A 2019 study by Danesh Yazdi reported that long‐term exposure to PM2.5 was associated with an increased likelihood of an inpatient admission among the Medicare population, even in areas where PM2.5 concentrations were below the current annual National Ambient Air Quality Standard of 12 µg/m3.3
The biological mechanisms to explain these associations have been well explained and include systemic inflammation, increased activation of the autonomic nervous system, and oxidative stress induced by penetration of PM2.5 particles into the respiratory tract.4-6
The current Ward-Caviness study looked at just the subgroup of patients with existing heart failure. To recap its results, a 1‐µg/m3 increase in fine particulate matter was associated with a 9.31% increase in total hospital visits, a 4.35% increase in inpatient admissions, and a 14.2% increase in 30‐day readmissions (see Key Findings section for confidence intervals). In these data, Black patients with HF had the highest associations between total hospital visits and long‐term air pollution exposure; the associated risk was 40% higher in Black patients than White patients. This racial disparity was even larger for 30‐day readmissions. As minority populations are often exposed to higher-than-average levels of air pollution, it is possible that some of the health disparities seen in HF patients may be driven by exposure to air pollution.7
A similar explanation may contribute to the racial disparity in breast cancer rates among Black women, who are more likely to have aggressive subtypes of breast cancer. High PM2.5 exposure has been associated with greater risk for more aggressive forms of breast cancer.8
Data such as those presented in this and other recent studies suggest that specific subgroups of patients—in this case, those with congestive heart failure—may benefit from reducing their exposure to PM2.5. While we may feel that this is a problem that should be addressed on a community, state, or national level, our patients who are suffering from disease should not be asked to wait until political leadership or even grassroots organizations effect changes. Rather they should be encouraged to take proactive measures to reduce their own exposure.
Exposure can be reduced using modern ventilation and filtration systems in homes and commercial buildings. Modern cars come equipped with in-cabin air filters. These filters are inexpensive and are designed to be replaced at regular intervals, yet few people are aware of this, nor are they aware that these filters are available as HEPA filters specifically designed to remove fine particulates.
Health practitioners should use these new data regarding congestive heart failure and PM2.5 to specifically encourage patients with cardiovascular disease to actively reduce their exposures. A 2018 clinical trial by Maestas et al (N=40), conducted in Detroit, Michigan, reported that in-home portable air filters reduced PM2.5 exposure by more than 50%.9
According to the World Bank’s database, average exposure to PM2.5 has fallen in the United States from 9.741 µg/m3 in 2011 down to 7.41 µg/m3 in 2017.10 The EPA provides up-to-date information on pollution levels by zip code at www.airnow.gov.11 If Maestas’ findings are correct and home filters drop this exposure level by half—say, a further 3.5 µg/m3 (3.5 x 9.3=32.55%)—such an intervention might reduce hospital visits for those suffering from heart failure by a third. For us, and our patients, it’s not about reducing healthcare costs but about reducing suffering, and these numbers suggest that effort spent at reducing exposure to air pollutants might do this to a significant degree and be worth it.