The Global Stroke Burden

By Sarah Song, MD, MPH

Sarah Song

Stroke is a devastating and debilitating disease. It is the second leading cause of death in the world, comprising approximately 10 percent of all deaths and killing 5.5 million people each year, with 44 million disability-adjusted life-years (DALYs) lost.^1,2 In 2010 alone, there were 16.9 million strokes worldwide, of which 70 percent occurred in low- and middle-income countries; this trend is expected to increase over the next 20 years.^1,3

Presently, low- and middle-income countries account for more than 85 percent of the global stroke mortality.⁴ Stroke mortality rates are especially high in Africa and Asia, where the burden of preventing and treating communicable diseases may shift resources away from cardiovascular disease and stroke.⁵ However, the burden from chronic and non-communicable diseases is likely to exceed the burden from communicable diseases in low- and middle-income countries in the near future.

A global focus on reducing mortality and morbidity from cardiovascular disease and stroke is more urgent than ever. Major problems shared by many countries are a lack of infrastructure, inadequate systems of care, effective programs to address cardiovascular risk factors, financial difficulty and shortage of trained health care workers.^3,6 Advocacy efforts, partnerships between countries, efficient and cost-effective targeted interventions and allocated funding and resources are necessary to tackle the worldwide stroke burden.

Stroke began to be tracked globally via surveillance systems in 1968 with the World Health Assembly, after which data including incidence, mortality and case-fatality was tracked. In more recent years, a more sophisticated stepwise approach to stroke surveillance has been recommended by the World Health Organization to include not only individuals with non-fatal events in the community, but also those admitted to the hospital.

Stroke risk factors are also tracked using a stepwise surveillance approach, including demographic and self-reported data, physical examination and objective laboratory results.¹ These measures have helped to show the great disparity between low- and middle-income countries and high-income countries, with national per capita income being the highest predictor of stroke burden, exclusive of cardiovascular risk factors.⁷

Overall, between the countries with the highest stroke mortality and the lowest stroke mortality, a tenfold difference in age-adjusted mortality rates and DALYs lost was observed.⁷ Globally, the highest at-risk countries are in Eastern Europe (with Russia having the highest stroke mortality rate), Asia and Africa, along with some in the South Pacific and the Carribbean.⁷

The economic impact of stroke has also been severe. For example, in 2005 it was estimated that the losses to gross domestic product due to vascular diseases was nearly $1 billion in China and India. This economic disparity is expected to increase in the near future in low- and middle-income countries.¹

Health systems of care for stroke require financing, staffing and structure in order to produce results. For example, the administration of intravenous alteplase (IV tPA) has been seen to significantly improve outcomes after acute ischemic stroke. However, giving IV tPA appropriately to eligible patients requires infrastructure and organization. Several countries have successfully developed systems to administer IV tPA (e.g., Brazil, Argentina, China and India), but there are still many barriers in low-income countries where medical services may be scarce and not easily accessible due to geography or human resources, and IV tPA may be prohibitively expensive.

In addition, funding is not proportional to economic and patient burden. For example, in 2011, funding for three of the major infectious diseases (HIV/AIDS, tuberculosis and malaria) was 35 times greater than funding for all non-communicable conditions combined.³ Therefore, besides the need for much greater funding in the realm of stroke and cardiovascular diseases, it has been suggested that community interventions and a focus on primary care might be the most cost-effective and efficient approach to stroke on a global level.^3,6,7

Although stroke burden is significant regardless of cardiovascular risk factor burden, the overall risk factor burden is increasing in low- and middle-income countries.⁶ For instance, hypertension is held accountable for approximately 54 percent of global stroke burden; this could be especially important as a target for intervention in countries such as China, where rates of hypertension are increasing.¹ As many of the population in low- and middle-income countries with stroke are working age (41-65) adults, more smoking has been seen in working-age adults than in other age groups.

The obesity epidemic continues to rise (with an estimated 10 percent of children globally considered overweight). The three-year INTERSTROKE study, based in 84 centers in 22 countries, confirmed that 88 percent of strokes were attributable to 10 risk factors: hypertension, smoking, waist-to-hip ratio, diet risk score, physical activity, diabetes mellitus, alcohol intake, psychosocial factors (including depression and stress), cardiac causes and the ratio of apolipoprotein B to apolipoprotein A1.⁴ The study, published in 2011, noted that targeting these risk factors on a primary care level, and focusing on healthy lifestyles, could substantially improve the global stroke burden.⁶

Other targets for low-cost, high-efficacy interventions could include educational campaign programs, such as the Go Red for Women Campaign and World Heart Day, which have been effective in spreading education and increasing disease awareness.⁶ In addition, cost-effective interventions such as the polypill, which incorporates three medications into a single pill, could help reduce costs and improve compliance with medications.^{6, 7}

It also may be beneficial to incorporate new and innovative, yet still cost-effective, techniques to address the global burden of stroke. Some innovative approaches to address primary stroke prevention, namely by using smartphone technologies, have been suggested and are being tested. Researchers from New Zealand have developed the Stroke Riskometer app, which assesses responses to a short questionnaire and determines the five- and 10-year risk for stroke using a validated algorithm similar to the Framingham risk score.⁸ It also incorporates education, comparison with similar individuals and an opportunity to share risk assessment results with others. An update of this app allows for participation in an international epidemiological research study (the Reducing the International Burden of Stroke Using Mobile Technology, or RIBURST study), which involves more than 160 countries.

Besides the interventions on a patient and community level, countries with high rates of stroke mortality must set priorities that are attainable and commensurate to resources. Better definition of stroke traits and determinants in low- and middle-income countries are needed to develop culturally-specific stroke prevention strategies. International agencies must work together to develop more novel strategies to attack the stroke epidemic. The UN General Assembly already has attempted to do this by setting a goal of reducing mortality from non-communicable diseases by 25 percent by the year 2025.³ Collaboration, vision and innovation are needed to reduce the global stroke burden and the stroke disparities that exist between countries.

References

1. Mukherjee D, Patil CG, “Epidemiology and the Global Burden of Stroke,” World Neurosurg, 76 (2011): S85-90.
2. Deresse B, Shaweno D, Epidemiology and In-hospital Outcome of Stroke in South Ethiopia, J Neurol Sci, 355 (2015):138-42.
3. Berkowitz AL, Stroke and the Noncommunicable Diseases: A Global Burden in Need of Global Advocacy, Neurology, 84 (2015):2183-4.
4. O’Donnell MJ, Xavier D, Liu L, et al, Risk Factors for Ischemic and Intracerebral Hemorrhagic Stroke in 22 Countries (the INTERSTROKE Study): A Case-control Study, Lancet, 376 (2010):112-23.
5. Kim AS, Johnston SC, Global Variation in the Relative Burden of Stroke and Ischemic Heart Disease, Circulation, 124 (2011):314-23.
6. Fuster V, Voute J, Hunn M, et al., Low Priority of Cardiovascular and Chronic Diseases on the Global Health Agenda: A Cause for Concern, Circulation, 116 (2007)1966-70.
7. Johnston SC, Mendis S, Mathers CD, Global Variation in Stroke Burden and Mortality: Estimates From Monitoring, Surveillance and Modeling, Lancet Neurol, 8 (2009):345-54.
8. Feigin VL, Krishnamurthi R, Bhattacharjee R, et al., New Strategy to Reduce the Global Burden of Stroke, Stroke, 46 (2015):1740-7.