An often-deadly type of stroke -- subarachnoid hemorrhage -- is on the upswing in the United States, particularly among Black people, new research shows.
Unlike the more common ischemic stroke, subarachnoid hemorrhage happens when there is bleeding in the space between the brain and the membrane that covers it. It is often caused by an aneurysm, a bulge in a blood vessel, that bursts or leaks.
This type of stroke, which comprises about 5% to 10% of strokes, is rising in certain groups, especially older men and women, middle-aged men and disproportionately in Black people, researchers say.
"It's on the rise, but the rise is not universal," said study co-author Dr. Fadar Otite, assistant professor of neurology at SUNY Upstate Medical University in Syracuse, N.Y.
Some of this can be explained by risk factors like high blood pressure. Black people have been more likely to develop high blood pressure at earlier ages and to have uncontrolled blood pressure, Otite said.
"But I truly believe that the underlying factors responsible, especially for the racial differences in subarachnoid hemorrhage, actually go beyond risk-factor control, but into other factors like access to health care, access to poverty and even structural racism," Otite said.
A characteristic of subarachnoid hemorrhage is having the worst headache of your life, Otite said. "A particularly severe headache that just comes out of the blue and gets to maximum severity within a very short term," he noted.
This would be less likely to occur with other forms of stroke, such as ischemic stroke, which is due to a blood clot rather than a bleed.
"Although other signs of strokes, such as weakness and facial droop and speech disturbances, can also occur in subarachnoid hemorrhage, headache would be much more consistent with subarachnoid hemorrhage compared to the others," Otite said.
Additional signs could be severe vomiting, confusion, sleepiness or even becoming comatose within a short period of time.
For the study, researchers reviewed state hospitalization databases in New York and Florida between 2007 and 2017. They found more than 39,000 people were hospitalized for non-traumatic subarachnoid hemorrhage -- caused by a ruptured aneurysm or high blood pressure rather than trauma.
The team then used U.S. Census data to calculate the annual rates for this type of stroke in those two states, breaking down the information by age, gender, race and ethnicity.
While numbers of this type of stroke were 11 per 100,000 in all participants, women had 13 cases per 100,000 and men had fewer -- 10 per 100,000.
For middle-aged men, 45 to 64, rates were 4 per 100,000. But incidence rose with age, with men 65 and up having 22 cases per 100,000.
In Black people, the rate was 15 per 100,000 compared to white people's average of 10 per 100,000.
Incidence increased by almost 2% a year for Black adults while it didn't change for other racial groups, the study found.
Overall, incidence increased by 0.7% on average per year, rising 1.1% in middle-aged men, 2.3% in in older men and 0.7% in older women, the study showed.
Otite said the increase in older groups of patients may be related to increased usage of blood thinners for treating conditions like abnormal heart rhythm (atrial fibrillation). "And it can also be in part due to increased utilization of imaging over time to screen for patients presenting with neurological complaints like headache in the emergency room," he said.
Better preventive health care could help reduce the racial gap, Otite noted.
Some of these aneurysms could be found before the rupture, and that's more likely to happen with good access to health care, Otite said.
Knowing trends in different types of strokes can also help experts identify gender and equity gaps that can be addressed to improve patient outcomes, said Dr. Alexis Simpkins, a stroke specialist at Cedars-Sinai in Los Angeles.
"I thought that it was an important study," said Simpkins, who wasn't involved in the research.
Stroke is the leading cause of long-term disability and adults worldwide, Simpkins noted.
People need to be monitored and treated for high blood pressure, and they must manage their risk factors for it, she said.
"So safe places to exercise outdoors, access to medications, access to physicians -- all of those things can lead to the accumulation of life years lived with stroke risk factors," Simpkins said.
Researchers were not able to differentiate between patients whose strokes were caused by aneurysms and those who had strokes that weren't, which is a study limitation.
The findings were published Oct. 26 in the journal Neurology.
For more on strokes, see the American Stroke Association.
SOURCES: Fadar Oliver Otite, MD, assistant professor, neurology SUNY Upstate Medical University, Syracuse, N.Y.; Alexis Simpkins, MD, PhD, director, vascular neurology research, and Stroke RNA, Imaging, and Protein Predictors for Patient Tailored Treatments (SkRIPT) Program, Cedars-Sinai, Los Angeles; Neurology, Oct. 26, 2022