Declining rates of stroke in the U.S. is good news, though progress is not as dramatic in women and African-Americans.

Rates of stroke and subsequent death have dropped in the U.S. over the past two decades, but new research shows that not everyone has made the same gains.

In a study published today in the Journal of the American Medical Association, researchers found that rates of stroke decreased from 1987 to 2011. But when the researchers looked at different age groups, they found that the stroke rate fell only for those older than 65, while remaining stable for younger people.

Decreases were similar for men and women, as well as for blacks and whites. However, men still had higher rates of stroke than women, as did blacks when compared to whites, an effect seen in other studies.

Researchers also saw a decrease in stroke deaths during that time, although this was mostly due to an overall decline in deaths among people younger than 65. This decrease was also similar for men and women, blacks and whites.

The study was based on data collected on more than 14,000 people. At the start of the study, participants were between the ages of 45 and 65 and had not yet experienced a stroke.

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According to the Centers for Disease Control and Prevention, stroke is the fourth leading cause of death for Americans, killing almost 130,000 people in the U.S. each year.

Risk factors for stroke include high blood pressure, cigarette smoking, diabetes, poor diet, physical inactivity, and obesity. Public health efforts to target these risk factors — as well as better treatments for stroke — may be part of the reason for the long-term improvements.

“The decline in stroke in our study is at least partially explained by better control of stroke risk factors, as well as improved strategies for management of stroke over time,” lead author Silvia Koton of the Johns Hopkins University School of Public Health told Healthline.

Researchers saw evidence of these efforts in their study, including increased use of cholesterol-lowering drugs and a drop in smoking. In addition, the use of medications to control high blood pressure increased, especially among those over 65, which may help account for the decreasing stroke rate in that age group.

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Stroke risk varies. In particular, the risk of having a first stroke is almost twice as high for blacks as it is for whites. Blacks are also more likely to die from stroke than whites.

Some previous studies have shown no decrease over the past decades in the rate of stroke among blacks, while others have found a decrease only among black women. There is much more work to be done to bring stroke rates down for all demographic groups.

“Our findings provide evidence that stroke incidence and subsequent mortality are decreasing over time both in whites and African-Americans in some black communities in the South,” said Koton. “However, the geographical variance in the distribution of risk factors in the U.S. may have an effect on changes in stroke incidence over time.”

The study did not include Hispanics, but according to the CDC their stroke rate falls somewhere between that of whites and blacks. However, as the largest minority group in the U.S.— with high levels of Type 2 diabetes — Hispanics may be more affected by stroke in the future.

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Stroke is a leading cause of long-term physical and mental disability in adults, so surviving a stroke may not always mean a complete return of function. In the current study, researchers did not look at how well those who survived a stroke fared afterwards.

“In spite of the improvements in treatment of stroke over time,” Koton said, “a significant proportion of stroke patients suffer from disability and decreased quality of life, and stroke remains the main cause of disability among adults in the U.S.”

Even with the promising results of the new study, the future of strokes in the U.S. remains uncertain. Stagnant stroke rates among those under 65 may be a warning sign of future problems.

“Increases in obesity and diabetes in the U.S. population threaten future decreases in stroke rates,” Koton said. “Therefore, encouraging people to keep a healthy lifestyle through prevention of smoking, adopting a healthy diet and increasing physical activity, as well as keeping blood pressure and levels of blood glucose and cholesterol under control is crucial.”

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