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Why Data Show Stroke Incidence and Mortality Declines

Valeo, Tom

doi: 10.1097/
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Investigators reported that the number of deaths that occurred within 10 years of a stroke declined by about 8 per 100 each decade of the study, but those younger than 65 survived longer. However, in contrast to other studies that found stroke incidence and mortality among African-Americans was not improving as rapidly, the declines in this case were similar for both whites and blacks.

Stroke incidence and mortality declined among men and women as well as among whites and African-Americans from 1987 to 2011, according to results from an ongoing prospective study reported in the July 16 edition of the Journal of the American Medical Association (JAMA). However, the decline in incidence was concentrated mainly among those older than 65, while the decrease in mortality after stroke was concentrated among those younger than 65.

The results suggest that growing rates of obesity among young people may slow further declines in stroke, said the first author Silvia Koton, PhD, a member of the Sackler Faculty of Medicine in the Stanley Steyer School of Health Professions at Tel Aviv University.

“Our findings are encouraging,” said Dr. Koton, who is also a visiting faculty member at the Johns Hopkins Bloomberg School of Public Health. “However, the absence of a decline in stroke incidence among people younger than 65 is a warning sign. In the United States as well as in other countries, rates of obesity are increasing, and obesity is associated with increased risks of high blood pressure, diabetes, and high levels of cholesterol. Our findings suggest that both physicians and policy makers need to pay closer attention to specific subgroups. We need better preventive measures, especially for young people, to keep our gains and increase this trend toward a decrease in stroke incidence and mortality.”

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The researchers followed 14,357 participants of the Atherosclerosis Risk in Communities (ARIC) study, begun in 1987. The participants were between the ages of 45 and 64 at baseline, and had never experienced a stroke.

By 2011, 1,051 of participants (7 percent) had had a stroke, with 929 having ischemic strokes, 140 hemorrhagic strokes, and 18 both stroke types. The number of deaths that occurred within 10 years of a stroke declined by about 8 per 100 each decade of the study, but those younger than 65 survived longer. However, in contrast to other studies that found stroke incidence and mortality among African-Americans was not improving as rapidly, the declines in this case were similar for both whites and blacks.

During that time the use of cholesterol lowering drugs among study participants increased from 2.8 percent of participants to 14.3 percent, and smoking decreased from almost 26 percent to 14.7 percent. However, rates of hypertension and diabetes increased by 40 percent overall.

“If you look at the entire 24-year follow-up, the incidence of stroke declined by about 50 percent, and there was also a substantial decrease in mortality after stroke,” said Dr. Koton.

These results are supported by another study that was published in July in The American Journal of Medicine; the paper reported the incidence of strokes in the Medicare population has decreased by approximately 40 percent over the last two decades — a decline greater than expected based on the group's risk factors. Mortality also declined by 15-20 percent.

Among the reasons for the decline in mortality, Dr. Koton cited treatment of acute stroke patients by specialized stroke teams and the use of tissue plasminogen activator, as well as other forms of reperfusion therapy for ischemic stroke. “We now offer our acute stroke patients much better treatments than in the past, but it is very important for people to know they should get to a hospital as soon as possible, because some of these treatments can be given only in a short window of time after onset of stroke symptoms.”

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The declines in stroke incidence and mortality found among African-Americans may not generalize to the population at large, according to Dawn Kleindorfer, MD, a professor of neurology at the University of Cincinnati (UC) College of Medicine, and lead author of a 2010 paper in Stroke that found a higher stroke incidence among African-Americans compared with whites.

“Since the blacks in the ARIC study come almost exclusively from Jackson, MS, and most of the whites are from other parts of the country, the results may reflect a geographic bias,” said Dr. Kleindorfer, who is also vascular neurology division chief and co-director of the UC Stroke Team. “This may be an effect [associated with living in] Jackson, not being black.”

In addition, the racial comparison may be skewed somewhat by age. “Participants had to be 45 to be in study, and we know the youngest ages are where you find the largest racial disparity in stroke,” she said. “We're finding that the incidence of strokes in young people is increasing in blacks and staying the same in whites.”

Another difference that Dr. Kleindorfer and her colleagues have found in their research involves awareness of risk. “What we're finding in the Cincinnati region is that blacks tend to be less aware of risk factors for stroke, and less likely to perceive risk,” she said. “Blacks tended to feel they weren't at as high a risk as whites, when it's exactly the opposite.”

Therefore, while she considers the results of the JAMA paper encouraging, Dr. Kleindorfer does not consider them evidence that there is no longer a racial disparity regarding stroke incidence and mortality. “Clearly there is,” she said, “and our data suggest that it's not getting better over time.”

Neurologists can help promote the downward trend in stroke, however, by making patients more aware of stroke risk factors. “As neurologists we tend to think that we see patients only after they have a stroke, so there's nothing we can do to affect incidence, but I don't think that's true,” she said. “If neurologists would take just a couple of minutes to review stroke risk factors with their patients, and make sure that patients with atrial fibrillation are on an anticoagulant, or check to see if their blood pressure is well controlled, I think they could help prevent that first event.”

Sudha Seshadri, MD, FAAN, a professor of neurology at Boston University School of Medicine, who has been an investigator with the longitudinal Framingham Heart Study, agrees that simple interventions make the largest contribution to the decline in stroke incidence and mortality. “It is likely that better control of blood pressure was the most significant factor followed by better management of atrial fibrillation and lower prevalence of smoking,” she said. “The appearance of stroke at younger ages is worrying, especially in light of improvements in controlling risk factors. Perhaps this is due to increased incidence of obesity and diabetes. I don't think we know completely the reason.”

In addition to raising awareness of stroke risk factors, neurologists can also help reduce incidence and mortality by improving the evaluation and treatment of patients who experience a transient ischemic attack, according to Joshua Z. Willey, MD, an assistant professor in the Division of Stroke at Columbia University Medical Center.

“These are patients who are going to be at a higher risk for ischemic stroke, and with rapid evaluation and treatment it may allow for catching the patient before the event occurs,” he said. “That's where I see role of neurologists – catching TIAs and getting the management plan in place as soon as possible.”

Neurologists could also reduce stroke mortality by getting involved with the development of stroke units at their hospitals, Dr. Willey added. “That seems to be one of the interventions that reduces short- and long-term mortality related to all strokes,” he said. “This involves the use of multidisciplinary plans of care, early mobilization, adherence to nursing, therapy and physician protocols.”

Ralph L. Sacco, MD, FAAN, who co-authored an editorial about the study in the same issue of JAMA, found the reductions in stroke incidence among older African-Americans an encouraging development, but he also expressed concern that increased longevity will pose challenges to maintaining the downward trend.

“I think as we try to project into the future, the aging of our population and the improved survival after cardiovascular diseases will mean we'll still see a greater burden as measured in terms of prevalence of stroke in the United States,” said Dr. Sacco, chairman of neurology and Miller professor of neurology, epidemiology, and human genetics at the University of Miami Miller School of Medicine, the Olemberg family chair in neurological disorders, and chief of neurology at Jackson Memorial Hospital in Miami.

In their editorial, Dr. Sacco and his co-author, Chuanhui Dong, PhD, a research assistant professor in the Basic Science Division at the Miller School, credited the downward trends in stroke incidence and mortality to greater use of medications that lower cholesterol and blood pressure, and to a decrease in smoking. However, obesity, diabetes, and lack of physical activity “could be a potential explanation for the lack of a decline in stroke incidence in middle-age and younger populations,” they said.

“As neurologists we don't often think about prevention, but we need to be advocates for lifestyle changes among our patients,” Dr. Sacco told Neurology Today. “Statistics seem to indicate that obesity, diabetes, lack of physical activity, and poor diets are going to have a larger impact on the health of the population. As neurologists we need to be thinking about primary prevention every single day.”

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•. Koton S, Schneider AL, Rosamond WD, Shahar E, Sang Y, Gottesman RF, Coresh J. Stroke incidence and mortality trends in US communities, 1987 to 2011. JAMA 2014;312(3):259–268.
    •. Fang MC, Coca Perraillon M, Ghosh K, Cutler DM, Rosen AB. Trends in stroke rates, risk, and outcomes in the United States, 1988 to 2008. Am J Med 2014;127(7):608–615.
      •. Sacco RL, Dong C. Declining stroke incidence and improving survival in US communities: evidence for success and future challenges. JAMA 2014;312(3):237–238.
        •. More about the ARIC study.
          © 2014 American Academy of Neurology