County characteristics impact premature stroke mortality

County-level stroke mortality occurring outside a stroke unit correlated primarily with demographics and health care and environmental factors, according to results from a retrospective, cross-sectional study published in JAMA Network Open.

The study analyzed disparities in premature stroke mortality between U.S. counties. The researchers also found that a significant portion of deaths that occurred in the hospital was linked more with county population health and demographics.

“The findings of this study provide insight into which features may predispose certain counties to stroke mortality disadvantage,” Suhang Song, PhD, of the Taub Institute for Research in Alzheimer’s Disease and the Aging Brain at Columbia University, and colleagues wrote. “Our findings also show that counties with higher percentages of rural, female, Black, Asian and uninsured populations were more likely to have higher mortality of stroke causes not specified as hemorrhage or infarction.”

The retrospective, cross-sectional study included patients ages 25 to 64 years who died from stroke in 2,637 U.S. counties between 1999 and 2018. The researchers collected data from the U.S. National Center for Health Statistics of the CDC (the CDC WONDER database). Song and colleagues compiled information on age, sex, race, underlying cause of death, place of death, county and year from the database and death certificates. Patients had to have an underlying cause of death related to stroke, including subarachnoid hemorrhage, intracerebral hemorrhage, cerebral infarction, stroke not specified as hemorrhage or infarction, other cerebrovascular disease or sequelae of cerebrovascular disease.

The researchers used generalized linear Poisson regressions to examine factors associated with county-level mortality, including demographic composition, socioeconomic status, health care and environmental features and population health. The researchers calculated counties’ Theil index scores to evaluate mortality disparities.

Between 1999 and 2018, 385,831 stroke-related deaths occurred among those aged 25 to 64 years. Death occurred at a higher rate among men (13.59 per 100,000) compared with women (10.53 per 100,000) and among those ages 55 to less than 64 years (31.84 per 100,000) compared with younger patients. Patients identifying as Black accounted for the most deaths out of any other racial group (24.86 per 100,000).

Overall, the age-adjusted rate of death was 12.04 per 100,000 people, with 27.96% occurring out of a stroke unit and 69.26% occurring in the hospital.

Mortality rates did not change significantly during the study period. However, the proportion of deaths due to stroke that occurred outside of the stroke unit increased from 23.56% to 34.57%. Overall, the leading cause of death was intracerebral hemorrhage, at a rate of 4.29 people per 100,000 people, but other causes and sequelae of cerebrovascular disease accounted for the largest proportion of deaths out of the stroke unit (55.2%). The county with the highest mortality was 20.78 times as high as the county with the lowest mortality (65.04 vs 3.13 deaths per 100,000 population). The southeastern stroke belt band, from the Ohio River Valley to the Mississippi River Valley, had counties with the highest rates of mortality, according to the study results.

The researchers found that demographic composition was 29.4% associated with premature stroke mortality; socioeconomic status, 19.6%; health care and environmental features, 22.7%; and population health, 28.2%. For deaths that occurred outside of the stroke unit, county-level premature stroke mortality had an association of 31.6% for demographic composition and 25.8% for health care and environmental features. Deaths that occurred in the hospital had a county-level mortality association of 29.8% for population health and 28.7% for demographic composition.

Environment, age, race (specifically Black and Asian patients), insurance status and physical activity were positively linked with mortality in the stroke unit and in the hospital. Meanwhile, foreign citizenship, income and health care quality index were negatively associated with mortality rates for both out of stroke unit and in-hospital mortality. In addition, factors associated with county-level mortality varied by stroke subtypes, and for each subtype, premature stroke mortality correlated with demographic composition.

“This study serves to suggest that strategies should address specific factors that underlie the mortality disparities, especially for the out-of-stroke-unit deaths and stroke of uncertain cause and be tailored to local context before implementing interventions for the neediest counties,” Song and colleagues wrote. “Our results also suggest there is a need to improve the quality of stroke subtype mortality data for documentation of out-of-stroke-unit death on the death certificate.”