Stroke Mortality Down, but Global Burden Remains High

Damian McNamara

March 18, 2019

A new, comprehensive look at the global burden of stroke has revealed some positive trends as well as some areas that need more attention.

Data from the annual Global Burden of Diseases, Injuries, and Risk Factors (GBD) report show that the rate of death from stroke decreased worldwide during a quarter of a century.

The global stroke mortality rate dropped 36% from 1990 to 2016. At the same time, stroke incidence and disability rates declined. However, the absolute numbers paint a grimmer picture.

The global burden of stroke is high — there were more than 80 million stroke survivors in 2016.

"Although age-standardized deaths due to stroke have been decreasing, the overall burden of stroke remains high, continues to increase, and is unlikely to decrease without interventions to address stroke risk factors," write the nearly 100 authors of the 2016 GBD report.

"Our main take-home message would be the importance of primary prevention to reduce the incidence of stroke," lead author Catherine Owens Johnson, neurology researcher at the Institute for Health Metrics and Evaluation, University of Washington in Seattle, told Medscape Medical News.

The findings were published online March 11 in Lancet Neurology.

Second Largest Cause of Death

The new mortality and stroke burden findings for 2016 align with those in the 2015 GBD results, which were previously reported by Medscape Medical News.

The researchers note, however, that several factors make the current figures more precise, including the following: improvements in inpatient data collection; an expansion of the oldest age group from 80 years and older to new cohorts of 80 – 84 years, 85 – 89 years, 90 – 94 years, and 95 years and older; and an update of a prior systematic review of the literature.

They also adjusted their findings, including expected stroke mortality and disability rates, in accordance with a sociodemographic index (SDI). The SDI incorporates education, income, and total fertility rates in different regions around the world.

In general, as SDI increased over time, the burden of stroke decreased in most regions. There were almost 14 million new stroke cases worldwide in 2016.

Stroke was the second largest cause of death globally that year and was associated with an estimated 5.5 million deaths.

Only ischemic heart disease caused more deaths worldwide the same year.

Better Outlook for Women

Fewer women died from stroke in 2016 than men (approximately 2.6 million vs 2.9 million).

The numbers of deaths globally from ischemic stroke and hemorrhagic stroke were approximately the same. About 2.7 million people died from ischemic stroke, and another 2.8 million from hemorrhagic stroke.

With respect to disability-adjusted life years (DALYs), a calculation that includes both years of life lost and years lived with disability, stroke again ranked as the second most common cause globally. The number of global DALYs rose from 95 million in 1990 to 116 million in 2016.

The outlook was more positive for women then for men, with fewer overall stroke DALYs (51 million vs 66 million).

Although stroke incidence was similar between women and men younger than 55, men aged 55 to 75 experienced a significantly higher incidence than women in the same age range.

In addition, ischemic stroke contributed to fewer DALYs than did hemorrhagic stroke (52 million vs 65 million).

The investigators also quantified stroke incidence, disability, and deaths for countries around the world.

They found that the highest incidences of stroke, as adjusted for age, were in East Asia, particularly China, with 354 cases per 100,000 person-years. The lowest incidences were in central Latin America, especially El Salvador, with 97 cases per 100,000 person-years.

A potential limitation is that the GBD stroke data do not include the effect of atrial fibrillation on the global stroke estimates.

Crucial Information

"The findings presented in this manuscript provide crucial information that could serve as the basis for resource allocation for stroke prevention, evidence-based planning for acute stroke care, and stroke rehabilitation facilities," the investigators write.

Population growth combined with improved survival add to the burden, increasing the prevalence of chronic stroke, they note.

"Additionally, we provide evidence that most of the burden of stroke can be attributed to modifiable risk factors and identified risk clusters that can be targeted to reduce the incidence of stroke," the researchers write.

Metabolic risk factors accounted for 72% of the stroke DALYs in the study. These factors included high systolic blood pressure, high body-mass index, high fasting plasma glucose level, high total cholesterol level, and low glomerular filtration rate.

Behavioral factors such as smoking, poor diet, and low physical activity accounted for 66% of attributable DALYs. Environmental risks, including air pollution and lead exposure, accounted for 28%.

The investigators note that the totals exceed 100% because many of these risk factors are mediated partly or wholly through another risk factor.

"In addition to targeting behavioral risk factors, effective screening for conditions that increase stroke risk, such as hypertension, atrial fibrillation, and diabetes mellitus, is essential," they write.

In the future, the GBD researchers plan to assess the burden due to subarachnoid hemorrhage and intracerebral hemorrhage separately.

In addition, "We are investigating the possibility of including estimates of transient ischemic attack to the GBD. These estimates indicate that an individual is at high risk for a stroke," Owens Johnson said.

Modifiable Risk Factors

Philip B. Gorelick, MD, who is affiliated with the Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, writes in an accompanying editorial that although most of the new report's information "is not novel, many of the risks are modifiable and have been shown to reduce stroke, and thus, are important to track and emphasize" for continuing efforts to prevent stroke.

"It has become apparent that population growth and aging have the potential to result in a greater absolute pool of people at risk of stroke and people who will have a stroke, despite the current declining stroke incidence," adds Gorelick, who is also affiliated with the Population Health Research Institute at McMaster University of Health Sciences and Hamilton University, Ontario, Canada.

Forecast estimates in the United States suggest that individuals older than 75 and some minority ethnic groups will be affected disproportionately by 2050, he notes.

"We will need to continue to support efforts to prevent stroke by risk factor modification, make stroke prevention available in low-income areas of the world where stroke incidence might be high, and discover novel stroke prevention and rehabilitation strategies," Gorelick writes.

The study was funded by the Bill and Melinda Gates Foundation. Owens Johnson has disclosed no relevant financial relationships.

Lancet Neurol. Published online March 11, 2019. Full text, Editorial

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