Major study of 59 million Americans finds fine particulate matter from air pollution increases heart disease risks

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

Study: Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. Image Credit: Kzenon/Shutterstock.comStudy: Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. Image Credit: Kzenon/Shutterstock.com

Background

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

Chronic exposure raises the risk of CVD-related hospitalization and death. Studies frequently focus on one or two CVD subtypes, neglecting to detect susceptible ones.

Comparing effect sizes across subtypes might help us understand processes and advise targeted strategies to lessen the impact of PM2.5.

About the study

In the present population-based cohort study, researchers evaluated exposure-response correlations between chronic PM2.5 exposure and the probability of initial hospitalization for seven main CVD subtypes and their composite.

The study covered Medicare beneficiaries aged 65 years and above in the continental United States (US) from 2000 to 2016. The team linked calibrated fine particulate matter estimations to each participant’s residence postal code as a proxy for exposure assessment.

The primary outcome measures were the initial hospitalization risks for cerebrovascular diseases, ischemic heart diseases, cardiomyopathy, heart failure, valvular heart diseases, abdominal and thoracic aortic aneurysms, arrhythmia, or a combination of these cardiovascular disease subtypes.

The researchers created a causal-type framework resistant to confounding effects and bias caused by inaccuracies in exposure-response estimations.
The study included Medicare beneficiaries aged 65 years and above residing in the United States (US) and registered with the fee-for-service program from 2000 to 2016.

The researchers created a distinct cohort for each CVD subtype by tracking each beneficiary annually till the initial hospitalization for that CVD subtype, death, or study termination, whichever came first.

They created another study cohort by monitoring each beneficiary year till the initial hospitalization for the examined CVDs, mortality, or study termination, whichever occurred first, to investigate the risk of the initial hospitalization for the composite CVD outcome.

The researchers utilized spatially weighted logistic regressions to estimate ambient PM2.5 values daily at 1.0 km2 grids across the United States from 2000 to 2016.

They blended 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 calibrations to improve grid-level particulate matter estimations and eliminate biases in health-effect estimations caused by exposure errors.

Results

The research included 59,761,494 individuals with 476,953,892 follow-up years; the majority were white (84%), with a higher number of female beneficiaries (55%). Most participants (75%) were between the ages of 65 and 74 when they began the research.

During the trial, 18% of participants registered with Medicaid. 22% required hospitalization due to a combination of cardiovascular diseases. The most frequent CVD subtype was ischemic heart illness, which affected 8.8% of recipients.

Other common illnesses were cerebrovascular disease (7.7%), heart failure (6.6%), and arrhythmia (6.5%). Three-year mean exposure to PM2.5 was related to an increase in the relative risk of initial hospitalization for cerebrovascular illnesses, ischemic heart diseases, cardiomyopathy, heart failure, abdominal and thoracic aortic aneurysms, and arrhythmia.

Exposure-response curves for composite cardiovascular disease showed a monotonically elevated risk related to fine particulate matter exposure.  

Compared to exposures ≤5.0 µg m-3 [air quality standard issued by the World Health Organization], the relative risks at exposures ranging from 9.0 to 10 µg m-3, encompassing the United States mean of 9.70 µg m-3 during the analysis, was 1.3.

Composite CVD-related hospitalization risk rose from 2.6% with exposures of less than or equal to 5.0 µg m-3 to 3.4% with exposures ranging from 9.0 to 10 µg m-3.

The effects lasted for ≥3.0 years following PM2.5 exposure. Education, age, healthcare access, and neighborhood socioeconomic deprivation influenced PM2.5 sensitivity.

The highest risk for composite cardiovascular disease and the most common cardiovascular disease CVD subtypes (cerebrovascular disease, ischemic heart disease, and cardiac failure) was related to immediate PM2.5 exposure at lag 0, and a significantly reduced impact at lag 1.0 followed by a decrease at lag 2.0.

Female beneficiaries were more likely to develop composite cardiovascular disease, heart failure, and ischemic heart disease, although cardiomyopathy risk was lower.

Younger beneficiaries and individuals aged between 65 and 74 years are more likely to be admitted to the hospital for CVD and subtypes. Those living in areas with lower high school graduation rates, higher deprivation levels, or longer hospital distances likely experienced the most outcomes.

Conclusion

The study findings showed that chronic exposure to fine-sized particulate matter increases the risk of cerebrovascular illnesses, ischemic heart diseases, cardiomyopathy, heart failure, arrhythmia, and abdominal and thoracic aortic aneurysms.

Exposure-response curves for several CVD subtypes shifted, indicating a lack of a safe threshold for cardiovascular health.

Adhering to the WHO’s air quality standards of ≤5 µg/m3 can provide considerable advantages. Susceptibility varied by participant age, healthcare access, educational achievement, and neighborhood deprivation.

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

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