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Tobacco use and risk of acute stroke in 32 countries in the INTERSTROKE study: a case–control study

202423 citationsOpen accessUniversity College Hospital, Ibadan

In plain language

A large-scale international case-control study across 32 countries examines how current tobacco use and environmental tobacco smoke exposure affect the risk of acute first stroke and its subtypes. Evaluating 13,462 stroke cases and 13,488 controls, the research demonstrates that current smoking significantly increases overall stroke risk, showing a stronger link to ischaemic stroke than intracerebral haemorrhage. Among ischaemic stroke subtypes, large vessel stroke displays the strongest connection to smoking. The risk extends to both filtered and non-filtered cigarettes, with non-filtered types carrying higher odds. Passive environmental tobacco smoke exposure also heightens the risk of both ischaemic stroke and intracerebral haemorrhage in a dose-dependent manner, particularly with over ten hours of weekly exposure. The magnitude of risk and population attributable risk differs across regions and income levels, reaching highest levels in high-income countries.

Key takeaways

  • Current smoking increases the risk of acute stroke, showing a stronger association with ischaemic stroke than with intracerebral haemorrhage.
  • Large vessel stroke has the strongest association with current smoking among ischaemic stroke subtypes.
  • Both filtered and non-filtered cigarettes elevate stroke risk, with non-filtered varieties presenting higher odds.
  • Exposure to environmental tobacco smoke raises the risk of both ischaemic and haemorrhagic stroke in a dose-dependent manner.
  • The risk and population attributable risk of stroke linked to smoking vary significantly across regions, peaking in high-income nations.

Why it matters

Stroke remains a principal cause of death and disability globally. Demonstrating that both active smoking and passive secondhand exposure substantially increase stroke risk across different subtypes underlines the universal danger of tobacco. Because the risks differ by country income level and cigarette type, public health organisations can use these insights to tailor regional tobacco control strategies and enforce smoke-free environments.

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Abstract

Background: Smoking is a major risk factor for the global burden of stroke. We have previously reported a global population attributable risk (PAR) of stroke of 12.4% associated with current smoking. In this study we aimed to explore the association of current tobacco use with different types of tobacco exposure and environmental tobacco smoke (ETS) exposure on the risk of stroke and stroke subtypes, and by regions and country income levels. Methods: The INTERSTROKE study is a case-control study of acute first stroke and was undertaken with 13,462 stroke cases and 13,488 controls recruited between January 11, 2007 and August 8, 2015 in 32 countries worldwide. Association of risk of tobacco use and ETS exposure were analysed with overall stroke, ischemic and intracerebral hemorrhage (ICH), and with TOAST etiological stroke subtypes (large vessel, small vessel, cardioembolism, and undetermined). Findings: Current smoking was associated with an increased risk of all stroke (odds ratio [OR] 1.64, 95% CI 1.46-1.84), and had a stronger association with ischemic stroke (OR 1.85, 95% CI 1.61-2.11) than ICH (OR 1.19 95% CI 1.00-1.41). The OR and PAR of stroke among current smokers varied significantly between regions and income levels with high income countries (HIC) having the highest odds (OR 3.02 95% CI 2.24-4.10) and PAR (18.6%, 15.1-22.8%). Among etiological subtypes of ischemic stroke, the strongest association of current smoking was seen for large vessel stroke (OR 2.16, 95% CI 1.63-2.87) and undetermined cause (OR 1.97, 95% CI 1.55-2.50). Both filtered (OR 1.73, 95% CI 1.50-1.99) and non-filtered (OR 2.59, 95% CI 1.79-3.77) cigarettes were associated with stroke risk. ETS exposure increased the risk of stroke in a dose-dependent manner, exposure for more than 10 h per week increased risk for all stroke (OR 1.95, 95% CI 1.69-2.27), ischemic stroke (OR 1.89, 95% CI 1.59-2.24) and ICH (OR 2.00, 95% CI 1.60-2.50). Interpretation: There are significant variations in the magnitude of risk and PAR of stroke according to the types of tobacco used, active and ETS exposure, and countries with different income levels. Specific strategies to discourage tobacco use by any form and to build a smoke free environment should be implemented to ease the global burden of stroke. Funding: The Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, Canadian Stroke Network, Swedish Research Council, Swedish Heart and Lung Foundation, The Health & Medical Care Committee of the Regional Executive Board, Region Västra Götaland, and through unrestricted grants from several pharmaceutical companies with major contributions from Astra Zeneca, Boehringer Ingelheim (Canada), Pfizer (Canada), MERCK, Sharp and Dohme, Swedish Heart and Lung Foundation, UK Chest, and UK Heart and Stroke.

Research topics

  • Acute Ischemic Stroke Management
  • Smoking Behavior and Cessation
  • Global Public Health Policies and Epidemiology

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DOI: 10.1016/j.eclinm.2024.102515

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