Stroke Rounds: Incidence Down, Survival Up — For Some
Stroke incidence declined significantly in the U.S. among men and women and for both blacks and whites over the last 2 and a half decades, but the decline was largely confined to older adults, research showed.
On the other hand, while deaths from stroke also fell for both sexes and races during the same period, the decrease was mainly seen in adults under age 65, researchers reported in the July 16 issue ofJAMA.
Between 1987 and 2011, the study showed an overall 24% decrease per decade in stroke incidence and an overall 20% decrease per decade in mortality, according to Silvia Koton, PhD, of Israel’s Tel Aviv University and Johns Hopkins University, and colleagues.
Better Treatments, Fewer Smokers
These stroke incidence data appear to reflect both positive and negative trends in stroke prevention and treatment over the last few decades, Koton said.
On the plus side, increased use of statins and hypertension medications and a dramatic decline in smoking may largely explain the lower stroke rate among people over the age of 65, while the rise in obesity and diabetes in younger adults could explain the lack of progress in reducing stroke incidence in younger adults, Koton told MedPage Today.
“More younger adults are obese, and when obesity increases so does hypertension and diabetes,” she said. “Hypertension is the main risk factor for stroke. I think this is a warning sign for us to take these risk factors as seriously in younger people as we do in older people.”
Stroke Leading Cause of Disability
Stroke is the leading cause of physical and cognitive long-term disability in the U.S., with more than 600,000 first strokes and 800,000 total strokes occurring annually, the researchers wrote.
Several studies have shown overall declines in stroke incidence among whites but not African Americans in recent years. Some found no change in stroke incidence in blacks, while others found stroke declines among black women but not black men.
A 9-year follow up of the Atherosclerosis Risk in Communities (ARIC) study cohort found the highest age-adjusted case-fatality rates among black men, followed by black women, white men, and white women, while age-adjusted case-fatality rates tended to be higher among black participants and men.
The newly published prospective cohort study followed 14,357 black and white ARIC participants for 24 years (282,097 person-years).
None of the participants had a history of stroke at study entry between 1987 and 1989. The mean baseline age of the participants was 54 (SD 5.8); 55.4% of the participants were women and 26.5% were black. Baseline information on cardiovascular risk factors was collected through physical examinations and interviews.
Study participants were followed up (via examinations, annual phone interviews, active surveillance of discharges from local hospitals, and linkage with the National Death Index) through December 31, 2011. Physician reviewers adjudicated all possible strokes and classified them as definite or probable ischemic or hemorrhagic events.
The researchers estimated trends in rates of first-ever stroke per decade of calendar time using Poisson regression incidence rate ratios (IRRs), and mortality was analyzed using Cox proportional hazards regression models and hazard ratios (HR).
Stroke Incidence Steady in Those Under 65
A total of 1,051 (7%) participants had strokes during the follow-up period (929 ischemic strokes and 140 hemorrhagic strokes; 18 participants had both during the study period).
Crude incidence rates were 3.73 (95% CI 3.51-3.96) per 1,000 person-years for total stroke, 3.29 (95% CI 3.08-3.50) per 1,000 person-years for ischemic stroke, and 0.49 (95% CI 0.41-0.57) per 1,000 person-years for hemorrhagic stroke.
At the 9-year follow-up (visit four), reported use of cholesterol lowering drugs was more than five times higher than at baseline (14.3% vs 2.8%). There was a 40% increase in the proportion of hypertension and diabetes in the cohort and an 80% increase in CHD prevalence. The smoking rate decreased substantially during this time from almost 26% to 14.7%.
The latest data on participants followed for more than two decades revealed that:
- Stroke incidence decreased over time for both white and black participants (age-adjusted IRR per 10-year period, 0.76 [95% CI 0.66-0.87] representing an absolute decrease of 0.93 per 1,000 person-years overall).
- The decrease in age-adjusted incidence was evident in participants who were age 65 years and older (age-adjusted IRR per 10-year period, 0.69 [95% CI 0.59-0.81]; absolute decrease of 1.35 per 1,000 person-years), but it was not evident in participants younger than 65 years (age-adjusted IRR per 10-year period, 0.97 [95% CI 0.76-1.25]; absolute decrease of 0.09 per 1,000 person-years; P=0.02 for interaction).
- Overall, mortality after stroke decreased over time (HR 0.80 [95% CI 0.66-0.98]; absolute decrease of 8.09 per 100 strokes after 10 years [per 10-year period]).
- The mortality reduction could be attributed mostly to the decrease at younger than age 65 years (HR 0.65 [95%CI, 0.46-0.93]; absolute decrease of 14.19 per 100 strokes after 10 years [per 10-year period]), but was similar across race and sex.
Older Stroke Patients May Get Less Treatment
Koton said the observation that post-stroke mortality gains were limited to younger adults could be due to less aggressive treatment of older stroke patients.
“We didn’t study this, but there are reports suggesting that, after a large stroke, older patients often do get less treatment,” she said. “This may be at the request of the patient or the patient’s family.”
Neurologist Ralph Sacco, MD, professor and chair of neurology at Florida’s University of Miami Miller School of Medicine, said the reduction in stroke incidence in older African-American men is a particularly “positive and noteworthy” finding.
In an editorial published with the study, Sacco — a past president of the American Heart Association — noted that African Americans enrolled in ARIC lived in the southern U.S., with a small sample coming from Forsyth County, North Carolina, and a larger one from Jackson, Mississippi.
He wrote that the results for African Americans may not be generalizable to other regions of the country.
Another study limitation was the failure to include Hispanics in the study, he wrote.
“The higher incidence of diabetes, obesity, physical inactivity and stroke in Hispanics in the United States raises significant concerns for increased stroke burden, but community-based studies on Hispanic-white disparities in stroke incidence trends remain scarce,” he wrote.
Sacco told MedPage Today the latest analysis of the ARIC cohort contains both good news and cause for concern.
“The best-case scenario would have been to see declines in stroke incidence and mortality across all ages,” he said. “We now know that if we control blood pressure, cholesterol, and smoking we can have an important impact on stroke incidence in older populations. But we can’t rest on our laurels. We have to be vigilant about addressing these risk factors as well as obesity, physical inactivity, and diet in younger populations.”
The study was funded by the National Heart, Lung and Blood Institute.
The researchers declared no relevant relationships with industry.
From the American Heart Association: