THURSDAY, May 17 (HealthDay News) -- The prevalence of stroke varies widely across the United States, with some states reporting rates more than twice as high as other states, a new study found.
Stroke prevalence also differs by race and ethnicity, age group and educational level, the researchers said.
Compounding the problem, less than half of stroke victims arrive at a hospital within two hours of the start of symptoms, when therapy is most effective, a second report found.
Both reports are published in the May 18 issue of the Morbidity and Mortality Weekly Report, a publication of the U.S. Centers for Disease Control and Prevention. May is also National Stroke Awareness Month.
Stroke is the third-leading cause of death in the United States. This year, an estimated 700,000 people in the United States will have a stroke, and 160,000 will die from it. Of those who live, 15 percent to 30 percent become permanently disabled, and 20 percent require institutionalization during the first three months after the stroke.
"Stroke is a huge public health problem both in the U.S. and in many developing countries," said Dr. Ralph Sacco, a stroke expert and professor and chairman of neurology at the University of Miami Miller School of Medicine. "The numbers are going up, principally because our population is aging, and people are surviving after heart disease and therefore at risk for stroke. Some projections say it won't be too long before we see about a million strokes per year in the U.S."
Previous stroke data had found stark regional differences, with a higher prevalence in the southeastern states, the so-called "Stroke Belt." There has also been state-specific and even county-level mortality data, but this is the first time state-specific prevalence estimates have been available.
"The novel finding in this report is that we have prevalence estimates which are a good gauge of disability and are important to begin to understand health-care costs, because strokes can be expensive to treat," said Jonathan Neyer, the first study's lead author and an epidemiologist with the CDC's Division for Heart Disease and Stroke Prevention.
The authors looked at state-by-state statistics for adults aged 18 and older.
Stroke prevalence ranged from a low of 1.5 percent in Connecticut to a high of 4.3 percent in Mississippi.
Almost one quarter of states, as well as the District of Columbia, had a stroke prevalence rate of 3 percent or above. Those states were Alabama, Arkansas, Illinois, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Nevada, Oklahoma, Tennessee, Texas and West Virginia.
The lowest levels of stroke prevalence -- less than 2.6 percent -- were in Arizona, Colorado, Connecticut, Maryland, Massachusetts, Minnesota, Montana, New Jersey, North Dakota, Puerto Rico, Rhode Island, Vermont, Wisconsin, and Wyoming.
The national prevalence was 2.6 percent, which mirrors previous findings, the study authors said.
"Our findings correspond with a lot that is already known in the literature, but the amount of variation and magnitude of variation between states and ethnic/racial groups is always noteworthy," Neyer said.
While the prevalence of stroke was similar among men (2.7 percent) and women (2.5 percent), there were great differences among racial and ethnic groups. American Indian/Alaska Natives had the highest rate (6 percent). Blacks had almost double the rate of whites, 4 percent vs. 2.3 percent, respectively. Asians had the lowest rate at 1.6 percent.
Stroke prevalence was almost twice as high in people with less than 12 years of education (4.4 percent) compared to college graduates (1.8 percent).
No one knows for sure why these disparities exist. But a likely explanation is that the higher rates are seen among groups of people with more risk factors.
The second study found delays in getting proper treatment to stroke victims. Only 48 percent of stroke patients arrived at an emergency department within two hours of the onset of symptoms. People who were transported by ambulance tended to get to a hospital within the two-hour window compared with those who didn't go by ambulance -- 56.8 percent vs. 36.2 percent, respectively.
Victims of ischemic stroke -- caused by a clot in a vessel supplying blood to the brain -- are most likely to benefit from clot-busting tissue plasminogen activator (tPA) therapy within two hours of initial symptoms.
The difference between arrival at an emergency department and brain imaging was also shorter for those arriving by ambulance.
Fewer blacks or African-Americans (42.4 percent) arrived within the critical two-hour window than did whites (49.5 percent).
Prevention remains key when it comes to stroke.
"We have acute therapies that work to treat stroke, but most of those therapies only work if given within the first few hours after a stroke," Sacco said. "Therefore, the importance of prevention becomes even greater."
"The major risk factors for stroke are high blood pressure, preexisting heart disease, atrial fibrillation, which is a very common heart rhythm abnormality, high blood cholesterol levels, diabetes, tobacco use, alcohol use, physical inactivity and obesity," Neyer said.
"If people take measures to stay physically active, eat a healthy diet, control their blood pressure and cholesterol levels either through lifestyle modifications or through taking medications, all of those things will lower their risk of having a stroke," he said.
Another expert agreed.
"The bottom line conclusion of this study is that prevention of stroke is the most important thing," said Dr. Ann Miller, director of the Stroke Center at Montefiore Medical Center in New York City. "Prevention is really the best kind of treatment for stroke. Once the process has become established it's just intervening, trying to limit damage, so it's critical to control hypertension, stop smoking and limit alcohol intake."
The CDC has more on stroke prevention.
SOURCES: Jonathan Neyer, epidemiologist, Division for Heart Disease and Stroke Prevention, U.S. Centers for Disease Control and Prevention, Atlanta; Ralph Sacco, M.D., professor and chairman, neurology department, University of Miami Miller School of Medicine; Ann Miller, M.D., director, Stroke Center, Montefiore Medical Center, New York City; May 18, 2007, Morbidity and Mortality Weekly Report