A systematic review of population based studies of
A systematic review of 56 population-based studies of the incidence and early case fatality of stroke, published from 1970 to 2008, showed that, in ten low-income and middle-income countries, the age-adjusted incidence of stroke more than doubled, from 52 per 100 000 person-years in 1970–79 to 117 per 100 000 person years in 2000–08—an increase of 5·6% per year. However, the incidence of stroke in 18 high-income countries almost halved, from 163 to 94 per 100 000 person-years—a decrease of 1% per year. These data suggest divergent patterns of stroke epidemiology in different socioeconomic regions of the world, but might be subject to selection or sampling bias because of sampling of only ten of the world\'s low-income and middle-income countries over four decades, and diagnostic or stroke classification bias because of a failure to distinguish major pathological subtypes of stroke (ie, ischaemic haemorrhagic), which have different diagnostic criteria, causes, and outcomes.
In , Rita Krishnamurthi and colleagues from the Global Burden of Diseases, Injuries, and Risk Factors Study 2010 (GBD 2010) and Stroke Expert Group estimate the incidence, mortality, and DALYs of first-ever ischaemic and haemorrhagic stroke (intracerebral and subarachnoid haemorrhage) in all 21 regions of the world in 1990, 2005, and 2010. The investigators derived the estimates from a systematic review of all relevant studies published between 1990 and 2010. 119 studies were identified in which pathological subtypes of stroke were confirmed by buy PX-478 2HCl imaging or autopsy in at least 70% of cases. Specific analytical techniques were used to calculate regional and country-specific estimates of incidence and mortality rates and DALYs lost, by age group and country income status.
Surprisingly, the major finding is that, in 2010, most of the global burden of stroke was due to haemorrhagic, not ischaemic, stroke. Haemorrhagic stroke constituted a third (31·5%) of the 16·9 million incident stroke events (20% in the high-income countries and 37% in the low-income and middle- income countries), which is higher than hitherto appreciated. However, despite being only half as common as ischaemic stroke, haemorrhagic stroke caused more than half (51·7%) of the 5·9 million stroke-related deaths, and three fifths (61·5%) of the 102·2 million DALYs lost throughout the world. The number of years of life lost were greater with haemorrhagic stroke because it affected people at a younger age (mean 65·1 years [SD 0·11]) than did ischaemic stroke (73·1 years [0·10]) and had a higher case fatality (57% 25%).
Stroke is a leading cause of death and disability worldwide, mandating the need for a global strategy for stroke prevention. Central to the development of a strategy for stroke prevention is the need to establish the importance of modifiable risk factors for stroke, both globally and within regions and countries. Whereas the age-adjusted incidence of stroke is decreasing in high-income countries, it is increasing in low-income and middle-income countries. Until recently, our knowledge of risk factors for stroke was derived almost exclusively from western Europe and North America. Phase 1 of the INTERSTROKE study, which assessed the importance of risk factors in 22 high-income, middle-income, and low-income countries, reported that 90% of the population-attributable risk for stroke was associated with ten risk factors: hypertension, smoking, physical inactivity, poor diet, obesity, dyslipidaemia, diabetes mellitus, psychosocial stress, depression, and cardiac causes (eg, atrial fibrillation). Despite inclusion of 3000 cases and 3000 controls, this study was not large enough to reliably assess whether there were important regional variations in the effect of risk factors. Such information is essential to implement region-specific population-based interventions to reduce the burden of stroke. The full-scale INTERSTROKE study, which now includes more than 26 000 participants from 31 countries, and which is expected to be reported in 2014, will provide reliable estimates of the importance of risk factors for stroke (both overall and by subtype) in different regions of the world. Regional variations in the importance of risk factors for stroke might relate to variations in the prevalence or strength of association of common risk factors, or to the presence of unique risk factors in some regions or populations (eg, specific infections or rheumatic heart disease).