Lancet Study Identifies Air Pollution as Leading Risk Factor for Brain Stroke, Comparable to Smoking

New Delhi: A study released on Thursday, for the first time, revealed that ambient particulate matter air pollution is a leading risk factor for subarachnoid haemorrhage, a type of brain stroke, equal to smoking.

Conducted by an international team of researchers from India, the US, New Zealand, Brazil, and the UAE, the study found that air pollution contributed to 14% of death and disability from this severe stroke subtype, matching smoking.

The research demonstrated that air pollution, alongside high temperatures and metabolic disorders, significantly contributed to the global surge in stroke cases and deaths over the past 30 years.

Global stroke cases increased to 11.9 million in 2021, a 70% rise since 1990, while stroke-related deaths reached 7.3 million, marking a 44% increase since 1990.

Researchers pinpointed 23 modifiable risk factors accounting for 84% of the global stroke burden in 2021.

In 2021, the top five global stroke risk factors included high systolic blood pressure, particulate air pollution, smoking, high LDL cholesterol, and household pollution, varying significantly by age, sex, and region.

The study also highlighted notable progress in reducing the global stroke burden, with particulate air pollution cut by 20% and smoking by 13%.

“With 84 per cent of the stroke burden linked to 23 modifiable risk 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 co-author Dr Catherine O. Johnson, Lead Research Scientist at the University of Washington’s Institute for Health Metrics and Evaluation (IHME).

While stroke is now the third leading cause of death worldwide (after ischaemic heart disease and Covid-19), the condition is highly preventable and treatable.

The researchers called for identifying sustainable ways to work with communities to take action to prevent and control modifiable risk factors such as high blood sugar and a diet high in sugar-sweetened drinks. There is a critical need for interventions focused on obesity and metabolic syndromes, Johnson said.

They also called for measures such as clean air zones and public smoking bans, which have been successful.

The findings based on the Global Burden of Disease, Injuries, and Risk Factors Study (GBD) showed that more than three-quarters of those affected by strokes live in low- and middle-income countries (LMICs).

The study also found that worldwide, the overall amount of disability, illness, and early death -- a measurement known as disability-adjusted life years (DALYs) -- lost to stroke increased by 32 per cent between 1990 and 2021, rising from around 121.4 million years of healthy life lost in 1990 to 160.5 million years in 2021.