The incidence of stroke and its serious consequences, such as death or life-long disability, has increased significantly between 1990 and 2021 worldwide. Since 1990, premature death from stroke has increased by 72%, according to the results of a new study just published in The Lancet Neurology.
Among the risk factors that have contributed to this global increase in strokes are the negative impact of high temperatures on health and particulate air pollution, which is involved in subarachnoid haemorrhage (fatal brain haemorrhage), which the study identifies for the first time, equating exposure to such pollution with smoking.
Estimating the burden of stroke and associated risk factors at global, regional and national levels is crucial for designing evidence-based health policies, as well as for planning prevention and resource allocation. This study focused on providing these estimates for the period from 1990 to 2021.
Climate change and pollution increase the risk of stroke
Data on incidence, prevalence, mortality and disability-adjusted life years (DALYs) related to different types of stroke, including ischemic stroke, intracerebral hemorrhage and subarachnoid hemorrhage, were analyzed in 204 countries and territories from 1990 to 2021. These indicators were age-adjusted and expressed per 100,000 person-years.
In addition, the burden of stroke attributable to 23 risk factors was assessed, grouped into six categories: air pollution, smoking, lifestyle, diet, environmental factors and metabolic risks. All this was done using the standard methodology of the Global Burden of Disease Study (GBD), which also included an analysis by region and socioeconomic level (quintiles of the Socio-demographic Index, SDI).
In 2021, stroke was the third most common cause of death globally (7.3 million deaths, uncertainty range 6.6–7.8 million), accounting for 10.7% of all deaths, second only to ischemic heart disease and COVID-19. It was also the fourth leading cause of years of life lost due to disability (160.5 million DALYs), accounting for 5.6% of total DALYs. In the same year, there were an estimated 93.8 million people with prevalent stroke and 11.9 million new cases.
The study revealed inequalities in the burden of stroke and its risk factors by region, country or territory, and socioeconomic status. Since 2015, there has been a slowdown in the reduction of cases, and even an increase in incidence, mortality, prevalence and DALYs rates in some regions such as Southeast Asia, East Asia and Oceania, especially in countries with lower levels of development and in people under 70 years of age. Globally, 65.3% of strokes were ischemic, 28.8% were intracerebral hemorrhages and 5.8% were subarachnoid hemorrhages.
“The increase in the impact of stroke on global health observed in recent years demonstrates the need for global policies aimed at combating air pollution and climate change”
The most worrying stroke risk factors, which showed a considerable increase in their impact, included: high body mass index (BMI) (88.2%), high ambient temperatures (72.4%), high fasting blood glucose levels (32.1%), consumption of sugary drinks (23.4%), lack of physical activity (11.3%) and hypertension (6.7%).
The authors conclude that the burden of stroke has increased between 1990 and 2021, as has the influence of several risk factors, and there is an urgent need to implement effective, accessible and affordable measures to improve surveillance, prevention (focusing on blood pressure, lifestyle and environmental factors), acute care and rehabilitation, in order to reduce the burden of stroke worldwide.
“A relevant finding of this work is the relationship (detected for the first time) between air pollution by suspended particles and a higher risk of subarachnoid hemorrhage,” said Andrés García Pastor, a neurologist at the Stroke Center of the Gregorio Marañón General University Hospital, who did not participate in the study, in statements to SMC Spain. “The synergistic effect between air pollution, climate change and rising temperatures has been shown to influence the risk of vascular diseases and, in particular, stroke,” he added.
“The increase in the impact of stroke on global health observed in recent years shows that the prevention strategies used to date are insufficient or inadequate and that they probably need to go beyond individual lifestyle changes. Global policies aimed at combating air pollution and climate change are needed,” concludes the expert.
