In a recent study published in BMJ, researchers evaluated the exposure-response relationship between chronic fine particulate matter (PM2.5) exposure and the probability of first hospitalization in cardiovascular disease (CVD) subgroups.

study: Exposure-response association between chronic exposure to fine particulate matter and risk of hospitalization for major cardiovascular diseases: a population-based cohort study. Image credit: Kzenon/Shutterstock.com

background

PM2.5, a trace component of air pollution, significantly contributes to CVD by inducing inflammation, vasoconstriction, cardiac electrical abnormalities, and blood clot formation.

Chronic exposure increases the risk of CVD-related hospitalization and death. Research often focuses on one or two CVD subtypes, neglecting the detection of susceptible subtypes.

Comparing the impact sizes between subtypes could help understand the process and advise targeted strategies to reduce the impact of PM2.5.

About research

In the current population-based cohort study, researchers evaluated exposure-response relationships among chronic PM._2.5 Probability of exposure and first hospitalization for seven major CVD subtypes and their composites.

The study looked at Medicare beneficiaries aged 65 and older in the continental United States from 2000 to 2016. The researchers linked calibrated fine particulate matter estimates to each participant’s postal code of residence as a proxy for exposure assessment.

The primary endpoint was the risk of initial hospitalization for cerebrovascular disease, ischemic heart disease, cardiomyopathy, heart failure, valvular heart disease, abdominal and thoracic aortic aneurysm, arrhythmia, or a combination of these cardiovascular disease subtypes.

The researchers created a causal framework that is resistant to confounding effects and bias caused by inaccuracies in exposure-response estimates.
The study included Medicare beneficiaries age 65 and older who resided in the United States and were enrolled in fee-for-service programs from 2000 to 2016.

The researchers created separate cohorts for each CVD subtype by following each beneficiary annually until the first hospitalization for the CVD subtype, death, or end of the study, whichever came first.

They investigated the risk of first hospitalization for a composite CVD outcome by monitoring each beneficiary until the first hospitalization for the CVD under study, mortality, or end of study, whichever comes first. A study cohort was created.

Researchers used spatially weighted logistic regression to estimate daily environmental PM2.5 values ​​in a 1.0 km2 grid across the United States from 2000 to 2016.

They fused predictions from machine learning-based algorithms and incorporated information sources such as weather, satellite imagery, land use factors, monitoring information, and chemical model simulations.

They used regression calibration to improve grid-level particulate matter estimates and eliminate bias in health effect estimates caused by exposure errors.

result

The study included 59,761,494 people with a follow-up period of 476,953,892 years. The majority were white (84%), and the number of female beneficiaries was higher (55%). Most participants (75%) were between 65 and 74 years old at the start of the study.

During the study period, 18% of participants enrolled in Medicaid. 22% required hospitalization due to a combination of cardiovascular conditions. The most common CVD subtype was ischemic heart disease, which affected 8.8% of recipients.

Other common illnesses were cerebrovascular disease (7.7%), heart failure (6.6%), and arrhythmia (6.5%). Average 3-year exposure to PM2.5 was associated with increased relative risks of first hospitalization for cerebrovascular disease, ischemic heart disease, cardiomyopathy, heart failure, abdominal and thoracic aortic aneurysms, and arrhythmia.

Exposure-response curves for composite cardiovascular disease showed a monotonically increasing risk associated with fine particulate matter exposure.

Comparison with exposures of ≤5.0 µg m-3 [air quality standard issued by the World Health Organization]the relative risk was 1.3 for exposures ranging from 9.0 to 10 μg m-3, including the US mean value of 9.70 μg m-3 during the analysis.

The overall CVD-related hospitalization risk increased from 2.6% for exposures below 5.0 μg m-3 to 3.4% for exposures in the 9.0-10 μg m-3 range.

The effects persisted for more than 3.0 years after PM2.5 exposure. Education, age, healthcare access, and neighborhood socio-economic poverty influenced her PM2.5 susceptibility.

The highest risk for complex cardiovascular disease and the most common CVD subtypes of cardiovascular disease (cerebrovascular disease, ischemic heart disease, heart failure) was associated with immediate PM2.5 exposure at lag 0; The effect decreases significantly at lag 1.0, followed by a decrease at lag 2.0.

Female beneficiaries were more likely to develop complex cardiovascular disease, heart failure, and ischemic heart disease, but had a lower risk of cardiomyopathy.

Younger beneficiaries and individuals aged 65 to 74 years are more likely to be hospitalized for CVD and subtypes. People living in areas with lower high school graduation rates, higher poverty levels, and longer distances to hospitals were likely to experience the most outcomes.

conclusion

Study results showed that chronic exposure to fine particulate matter increases the risk of cerebrovascular disease, ischemic heart disease, cardiomyopathy, heart failure, arrhythmia, and abdominal and thoracic aortic aneurysms.

The exposure-response curves of several CVD subtypes have shifted, indicating a lack of safe thresholds for cardiovascular health.

Adhering to the WHO air quality standard of 5 μg/m3 or less has significant benefits. Susceptibility varied by participant age, access to health care, education, and neighborhood poverty.

Arrhythmia and heart failure are among the most vulnerable CVD subtypes in patients exposed to PM2.5.