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A groundbreaking study published on Thursday in The Lancet reveals that ambient particulate matter air pollution has emerged as a top risk factor for subarachnoid haemorrhage (SAH), a severe type of brain stroke, placing it on par with smoking. For the first time, the study highlights the significant role of air pollution in causing this life-threatening condition.
The research, conducted by an international team of scientists from India, the US, New Zealand, Brazil, and the UAE, found that air pollution contributed to 14% of deaths and disabilities resulting from SAH, aligning with the impact of smoking. The study emphasized that air pollution, when coupled with high temperatures and metabolic disorders, has driven a sharp rise in stroke cases and fatalities over the past three decades.
Alarming Global Increase in Stroke Cases and Deaths
Between 1990 and 2021, the global stroke burden has surged, with the number of new stroke cases increasing by 70% to 11.9 million in 2021. Stroke-related deaths rose by 44% in the same period, reaching 7.3 million. These statistics highlight the growing public health crisis, despite advancements in stroke prevention and treatment.
The study identified 23 modifiable risk factors responsible for 84% of the global stroke burden in 2021. The top five risk factors were high systolic blood pressure, particulate matter air pollution, smoking, high LDL cholesterol, and household air pollution, with variations observed based on age, gender, and geographical location.
Progress in Reducing Stroke Risk, But Challenges Remain
Despite the increasing stroke burden, there has been some progress in tackling key risk factors. Between 1990 and 2021, global efforts to reduce particulate matter air pollution led to a 20% reduction in its contribution to stroke, while smoking-related stroke cases dropped by 13%.
Co-author Dr. Catherine O. Johnson, Lead Research Scientist at the University of Washington’s Institute for Health Metrics and Evaluation (IHME), stressed the importance of addressing these modifiable risk factors, particularly in the context of climate change.
“With 84% of the stroke burden linked to modifiable factors, there are tremendous opportunities to alter the trajectory of stroke risk for the next generation. Given that ambient air pollution is reciprocally linked with ambient temperature and climate change, the importance of urgent climate actions and measures to reduce air pollution cannot be overestimated,” said Dr. Johnson.
Tackling Stroke in Low- and Middle-Income Countries (LMICs)
One of the most concerning findings is that more than three-quarters of stroke cases occur in low- and middle-income countries (LMICs). This underscores the need for targeted interventions in these regions to address risk factors such as poor air quality, inadequate healthcare infrastructure, and metabolic disorders.
The study also reported a 32% increase in disability-adjusted life years (DALYs) lost to stroke between 1990 and 2021. This metric reflects the overall amount of healthy life lost due to disability, illness, and premature death. In 2021, strokes accounted for 160.5 million DALYs, up from 121.4 million in 1990.
Call for Urgent Action
The researchers called for urgent, sustainable solutions to reduce modifiable stroke risk factors, including high blood sugar and excessive consumption of sugar-sweetened beverages. They emphasized the need for public health interventions focused on obesity and metabolic disorders, especially in LMICs.
Additionally, they recommended the implementation of clean air zones and public smoking bans, which have proven successful in reducing stroke-related risk in several regions.
While stroke remains the third leading cause of death globally, after ischemic heart disease and COVID-19, the study reinforces that it is both preventable and treatable. The findings underscore the need for coordinated global efforts to tackle air pollution, promote healthier lifestyles, and improve access to medical care, especially in the world’s most vulnerable regions.
