ArticlesGlobal and regional effects of potentially modifiable risk factors associated with acute stroke in 32 countries (INTERSTROKE): a case-control study
Introduction
Stroke is a leading cause of death and disability, making the prevention of stroke a global health priority.1, 2 In the first phase of the INTERSTROKE study3 (n=6000, 22 countries), ten common, potentially modifiable risk factors were associated with 90% of the population attributable risk (PAR) of acute ischaemic stroke and intracerebral haemorrhage. Although phase 1 of the study provided new information about the composite attributable risk of key risk factors in an international population, the population size was insufficient to reliably describe regional variations in the effect of risk factors, variations within key populations (eg, age, sex), and whether these risk factors varied in their effect on stroke pathological subtypes (ischaemic and haemorrhage stroke).4
Detailed assessment of the importance of risk factors within regions of the world is necessary to find out whether approaches to stroke prevention should differ by region or population characteristic (eg, age, sex, and ethnic origin),4, 5 and whether variations in the importance of risk factors might explain the marked worldwide variations observed in incidence and subtypes of stroke.6 The Global Burden of Disease systematic analysis has reported modelled estimates of the contribution of potentially modifiable risk factors to the global and regional burden of stroke.7, 8 However, estimates are derived from studies of differing methods, with variable use of neuroimaging to establish primary stroke subtype, and under-representation of populations in low-income countries and middle-income countries, where the burden of stroke is largest.6, 9
The aim of the second phase of the INTERSTROKE study was to increase and broaden the sample size to more than 13 000 cases of acute stroke and 13 000 controls in 32 countries to test the hypothesis that variations exist in the effect of common risk factors for stroke by major regions of the world, in key populations (eg, ethnic origin, age, sex), and in subtypes of stroke.
Section snippets
Study design and participants
INTERSTROKE is a large, international case-control study.10 Participants were recruited between Jan 11, 2007, and Aug 8, 2015, from 142 centres in 32 countries in Asia (China, India, Pakistan, Philippines, Thailand, and Malaysia), Africa (Mozambique, Nigeria, South Africa, Sudan, and Uganda), Europe (Croatia, Denmark, Germany, Poland, Russia, Sweden, the UK, Ireland, and Turkey), the Middle East (Iran, Saudi Arabia, Kuwait, and United Arab Emirates), North America (Canada), Australia, and South
Results
26 919 participants were recruited from 32 countries from Jan 11, 2007, to Aug 8, 2015, comprising 13 447 cases of acute first-ever stroke and 13 472 controls (403 [3·0%] of controls had chronic bronchitis, 948 [7·0%] had malaria, 263 [2·0%] had tuberculosis, 127 [0·9%] had venous thrombosis, and 107 [0·8%] had peripheral vascular disease; appendix p 14). Neuroimaging was completed in 13 441 (99·9%) of 13 447 cases. Questionnaires were completed by patients (5573 [41·4%]), proxy respondents
Discussion
In the first phase of the INTERSTROKE study (n=6000),3 we reported preliminary estimates of the association of common risk factors with the PAR for stroke in an international population, but phase 1 was of insufficient scope to report estimates by regions or in key populations. In this full-scale study (which includes phases 1 and 2 of the INTERSTROKE study), we provide more robust and reliable estimates for the contribution of these ten potentially modifiable risk factors in a larger
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