A study in more than 3 000 US counties, involving more than 315m residents, has suggested that air pollution is linked with stress and depression, putting people under 65 at increased risk of dying from cardiovascular disease, said scientists.
The research was presented last week at ESC Preventive Cardiology 2024, a scientific congress of the European Society of Cardiology (ESC).
“Our study indicates that the air we breathe affects our mental well-being, which in turn has an impact on heart health,” said the study’s lead author Dr Shady Abohashem of Harvard Medical School.
The WHO estimated that air pollution caused 4.2m premature deaths worldwide in 2019.
Mental illness has also been linked with premature death, and this latest study examined whether air pollution and poor mental health are interrelated and have a joint impact on death from cardiovascular disease.
The study focused on particles less than 2.5 micrometres in diameter, also referred to as fine particles or PM2.5, which come from vehicle exhaust fumes, power plant combustion and burning wood, and present the highest health risk.
For the study, county-level data on annual PM2.5 levels were obtained from the US Centres for Disease Control and Prevention (CDC). PM2.5 exposure was categorised as high or low, according to WHO standards.
The researchers gathered data from the CDC on the average number of days (age-standardised) on which county residents experienced mental health issues, including stress, depression and emotional problems.
Each county was then categorised into three groups based on these numbers. Counties in the top third reported the most days of poor mental health (PMH). Age-adjusted premature cardiovascular mortality rates (under 65) per county, were obtained from the CDC.
County characteristics were sourced from the County Health Rankings project.
The study included 3 047 US counties, representing 315 720 938 residents (with more than 207m aged 20 to 64, and 50% females) in 2013. Between 2013 and 2019, some 1 079 656 (0.34%) participants died from cardiovascular disease before the age of 65.
The researchers analysed the associations between pollution, mental health and premature cardiovascular mortality after adjusting for factors that could influence the relationships.
Counties with dirty air (high PM2.5 concentrations) were 10% more likely to report high levels of PMH days compared to counties with clean air (low PM2.5 concentrations). That risk was markedly greater in counties with a high prevalence of minority groups or poverty.
The link between PMH and premature cardiovascular mortality was strongest in counties with higher levels (above WHO recommended levels: ≥10 µm2) of air pollution. In these counties, higher levels of PMH were associated with a three-fold increase in premature cardiovascular mortality compared with lower PMH levels.
Further, one-third of the pollution-related risk of premature cardiovascular deaths was explained by increased burden of PMH.
Abohashem said: “Our results reveal a dual threat from air pollution: it not only worsens mental health but also significantly amplifies the risk of heart-related deaths associated with poor mental health. Public health strategies are urgently needed to address both air quality and mental well-being to preserve cardiovascular health.”
Study details
Air pollution associates with poor mental health and amplifies the premature cardiovascular death in the United States: longitudinal nationwide analysis
S Abohashem, W Aldosoky, G Civieri, G Goudot, T Dar.
Presented at ESC Preventive Cardiology 2024 on 26 April 2024
Background
While air pollution (i.e., particulate matter with aerodynamic diameter ≤2.5mm-PM2.5) and poor mental health (PMH) are linked to premature all-cause mortality, their interrelationship and joint impact on premature cardiovascular mortality (PCVM) in the United States, is unknown.
Purpose
We sought to test the hypothesis that high exposure to PM2.5 associates with heightened PMH and an amplified PCVM risk related to PMH.
Methods
We analysed annual PM2.5 levels and average PMH (days) data from the Center for Disease Control and Prevention (CDC) PLACES databases across 3047 U.S. counties. PM2.5 exposure was dichotomised (high/low) per World Health Organisation standards; PMH was categorised into tertiles. Age adjusted PCVM rates (<65 years of age) were obtained from the CDC WONDER databases. County characteristics were sourced from County Health Rankings project. Using generalised linear mixed models with gamma distribution, we calculated rate ratios (RR).
Results
Among 315,720,938 residents lived in 3047 counties in 2013, 1,079,656 (0.34%) PCVM deaths recorded during study period (2013-2019). In the fully adjusted analyses*, high PM2.5 associated with elevated PMH (RR [95%CI]: 1.10 [1.08, 1.11], p<0.001]. In counties with high PM2.5 (≥10 µm2), PMH (T3 vs. T1) associated with a 3-fold increase in PCVM (RR: 1.15 [1.12, 1.18]) compared to low PM2.5 (1.05 [1.01, 1.08]), with p interaction <0.001. This trend persisted across PCVM subtypes (Figure1).
Conclusion
High PM2.5 worsens PMH, significantly amplifying the PCVM burden across the United States, beyond other social determinants of health. Targeted public health strategies must urgently address the interconnected pollution-mental health crisis to mitigate rising PCVM.
ESC Congress 2024 article – Air pollution associates with poor mental health (Restricted access)
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