An ischemic stroke is caused by a clot or blockage in an artery or blood vessel carrying oxygen and nutrients to or inside the brain. The image shows a clot forming in the carotid artery. 
Image credit: American Heart Association

A paper on the observational study, by the University of Southern California-Los Angeles, is published in the Journal of the American Heart Association.

For their study, the team analyzed data from the Nationwide Inpatient Sample - a national database that collects information on around 8 million hospitalizations a year in the United States.

Stroke is a disease that affects the arteries carrying oxygen and nutrients to and inside the brain. It occurs when one of these blood vessels is either blocked by a clot (ischemic stroke) or bursts (hemorrhagic stroke). The vast majority of strokes are ischemic.

The sooner a person having a stroke is treated, the better their chances of surviving with minimum long-term effects.

Lack of oxygen to the brain can result in long-term disability of the parts of the body controlled by the affected part of the brain.

Stroke admissions falling overall, rising for some groups

The researchers found that across the U.S., the number of adults admitted to hospital for acute ischemic strokes - the type caused by artery blockages - fell by 18.4 percent over the period 2000-2010.

Within the overall trend, however, the analysis reveals some stark contrasts among different age groups and between African-Americans and other racial groups.

For example, hospital admissions for acute ischemic strokes fell for older people, by 28 percent for those aged 65-84, and by 22.1 percent in those aged 85 and over.

However, for young adults aged 25-44, they rose by 43.8 percent, and for those aged 45-64, they rose by 4.7 percent.

Age-adjusted hospitalizations for acute ischemic stroke during the same 2000-2010 period also fell for white people (down 12.4 percent) and Hispanics (down 21.7 percent), but they went up by 13.7 percent in African-Americans.

The findings also show that, in line with previous studies, stroke hospitalizations were lower for women than men, and rates fell more steeply for women (down 22.1 percent) than men (down 17.8 percent) over the decade.

First author Dr. Lucas Ramirez, a neurology resident, notes that while their study was not designed to investigate the reasons for the reduction in older Americans, he and his colleagues suggest efforts to prevent the risks for these types of stroke - such as reducing high blood pressure and controlling blood sugar - could be a factor.

"African-Americans already had the highest rate of stroke hospitalizations and it has unfortunately increased. This reinforces that we need to make sure that our efforts for stroke prevention and education reach all groups."

Dr. Lucas Ramirez