From 2000 to 2010, age-adjusted hospitalization rates for acute ischemic stroke decreased by 18.4 percent. The rates declined by 3.89 percent per year from 2000 to 2005 and increased by 0.03 percent per year from 2006 to 2010.

However, the rates increased for African Americans and for people from 25 to 44 years old and from 45 to 64 years old.

Lead researcher Lucas Ramirez, MD, of the Keck School of Medicine at the University of Southern California in Los Angeles, and colleagues published their results online in the Journal of the American Heart Association on May 11.

The researchers analyzed data from the Nationwide Inpatient Sample, which includes information on approximately 8 million stays per year at nonfederal U.S. hospitals. They obtained discharge data from Jan. 1, 2000 through Dec. 31, 2010 and used software to estimate the number of acute ischemic stroke admissions during that time period.

The age-adjusted stroke hospitalization rates were 250 per 100,000 in 2000 and 204 per 100,000 in 2010. During that time period, the rates increased from 16 to 23 per 100,000 for adults from 25 to 44 years old and from 149 to 156 per 100,000 for adults from 45 to 64 years old. Meanwhile, the rates decreased from 845 to 605 per 100,000 for adults from 65 to 84 years old and from 2,077 to 1,618 per 100,000 for adults who were at least 85 years old.

In addition, the rates decreased from 272 to 212 per 100,000 women and from 298 to 245 per 100,000 men.

Further, the rates decreased by 21.7 percent for Hispanics, decreased by 12.4 percent for whites and increased 13.7 percent for African Americans. In 2010, the rates were 358 per 100,000 for African Americans, 170 per 100,000 for Hispanics and 155 per 100,000 for whites.

“Our findings should be interpreted with caution, since changes in stroke hospitalization rates are affected not only by true changes in incidence, but also stroke literacy and health beliefs (influencing likelihood of seeking medical attention), pre-hospital recognition and triage of patients with stroke symptoms, and hospital protocols/healthcare provider literacy (affecting the likelihood of hospitalizing individuals with stroke symptoms),” the researchers wrote. “In addition, the new imaging- based definition of transient ischemic attack and more widespread use of magnetic resonance imaging may also affect the proportion of individuals coded as transient ischemic attack vs. [acute ischemic stroke].”

The researchers cited a few limitations of the study, including its observational design, which meant they could not assume causal relationships. They also said there could have been coding errors in the dataset.

Further, they said the rates of acute ischemic stroke were underestimated in Hispanics because of differences in race/ethnic categories in the Nationwide Inpatient Sample vs. U.S. census data. In addition, they could not verify diagnoses and determine ischemic stroke subtypes or stroke severity.

“Despite these limitations, the study has several strengths including a large sample size, nationwide representation, and clinician based diagnosis of [acute ischemic stroke],” they wrote. “Further research is required to determine the causes of the disparate hospitalization rates, to better ascertain nationwide race/ethnic-, sex-, and age-specific trends in incidence, and identify strategies to target subgroup populations who are most vulnerable.”