Disparities in stroke mortality in middle-aged black Americans were mostly attributed to differences in the incidence of stroke as opposed to case fatality, according to a new study published in Stroke.
“Therefore, to reduce the black–white disparity in stroke mortality, interventions need to focus on prevention of stroke in blacks,” the authors wrote.
Despite advances in prevention, risk factor management, and poststroke care, a morality disparity persists for black stroke patients compared to white stroke patients. It is unclear whether the disparity is due to a higher incidence of stroke or a higher fatality rate for black patients with stroke.
Previous studies suggest that after 45 years of age, blacks have approximately 3 times the risk of stroke mortality than their white peers. Using data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort, George Howard, DrPH of the Department of Biostatistics at the University of Alabama in Birmingham, and colleagues sought to investigate the potential causes of this racial stroke disparity.
The cohort included 29 682 black and white Americans 45 years of age or older that were followed longitudinally every 6 months with telephone interviews and medical record retrieval.
The patients had follow-up information for an average of 6.8 ± 2.7 years. During that period, there were 1168 strokes, including 242 fatalities. White patients tended to be older (65 vs 64 years), had fewer stroke related risk factors, and were less likely to have low education and income.
Investigators found a significant race and age interaction for fatal stroke (P=.0042). When patients were categorized by age in decades, they found the black-to-white mortality ratio at age 45 years decreased from approximately 4.0 to 1.0 at age 85 years. However, in the youngest decade category there were a total of 5 stroke fatalities with 4 among black patients, which resulted in a wide confidence interval.
Likewise, there was a significant interaction between race and age for time to any fatal or nonfatal stroke. The youngest decade category (45 to 54 years of age) had a black-to-white ratio that decreased from approximately 3.0 to about 1.0 in the group aged 75 to 84 years of age.
Finally, multivariable analysis revealed that the odds of a fatal stroke increased by 61% with each decade (odds ratio [OR]: 1.61; 95% confidence interval [CI]: 1.35-1.91). Neither sex (OR: 1.02; 95% CI: 0.76-1.36) nor race (OR: 1.20; 95% CI: 0.89-1.62) were tied to stroke case fatality.
These results suggest that the racial disparity in stroke mortality is mostly secondary to differences in stroke incidence. Previous analysis of the REGARDS study indicated that about 40% of the disparity in the group aged 45 to 65 years is tied to prevalence of traditional stroke risk factors (defined by the Framingham Stroke Risk Function, especially diabetes and hypertension, both of which occur at higher rates in the black population.
The authors offered several potential explanations for the other 60% of the disparity. First, there is a need for more awareness, treatment, and control of stroke risk factors. Second, risk factors, particularly hypertension, appear to be more prevalent and less likely controlled in the black population.
Also, nontraditional stroke risk factors such as obesity, diet, and physical inactivity are more severe or prevalent in the black population. Furthermore, the impact of poverty, discrimination, and psychosocial factors may place black patients at an even bigger disadvantage.
“We are at the early phase of processes to better understand these alternative pathways that potentially contribute to the black-white disparity in stroke incidence, and we need to redouble our efforts to the investigations of these pathways,” the authors concluded.
Disclosures: The study was funded by the National Institutes of Health.
Howard G, Moy CS, Howard VJ, et al. Where to focus efforts to reduce the black–white disparity in stroke mortality: incidence vs case fatality? Stroke. 2016. doi:10.1161/STROKEAHA.115.012631.