Blacks who survive cardiac arrest during hospitalization have lower odds of long-term survival compared with similar white survivors, according to new research in the American Heart Association’s journal Circulation.

Half the difference in 1-year survival rates, however, remained unexplained. Nearly one-third of the racial difference in 1-year survival was dependent on measured patient factors. Only a small proportion was explained by racial differences in hospital care and approximately one-half was due to differences in care after discharge.

Researchers studied patients 65 and older who suffered in-hospital cardiac arrest and survived until discharge between 2000-2011. Survivors from the Get With The Guidelines–Resuscitation registry whose data could be linked to Medicare claims were either black or white. Their survival was studied at 1-year, 3-year, and 5-year intervals.

“Compared with white patients, blacks had substantially lower 1-year, 3-year, and 5-year survival rates with 28% lower relative likelihood of surviving 1 year and a 33% lower relative likelihood of surviving to 5 years,” said the study’s lead author Lena Chen, MD, MS, assistant professor of internal medicine at the University of Michigan in Ann Arbor.

The black patients in this study were younger, more often female, and were sicker, with higher rates of kidney and respiratory insufficiency, pneumonia, and more often required dialysis prior to cardiac arrest, compared to white patients studied.

“Notably, black patients were less likely to have had a heart attack during hospital admission or a prior history of heart attack. As a result, they were more likely to have a non-shockable initial heart rhythm of pulseless electrical activity and to have experienced their heart stoppage in an unmonitored hospital unit,” Chen said.

The study did not look into how caregivers may have been different for black patients vs white ones, nor did it look at socioeconomic factors like household income or social support.

“Our study’s findings suggest a need to examine to what degree differences in postdischarge care explain racial differences in long-term survival after heart stoppages,” Chen said.