Does race predict stroke readmission? An analysis using the truncated negative binomial model

Background: Although it is known that the risk of first-ever stroke is higher for blacks than for whites, it is unclear what their relative risk is for stroke recurrence. Methods: Using statewide inpatient data from California, 4,784 blacks and 33,684 whites having one or more stroke admissions during the year 2000 were identified. For blacks and whites, age- and sex-adjusted incidence rates were calculated for the index stroke admission using direct standardization (to the U.S. resident population for the year 2000). Various statistical models for count data were applied, with the best one being used in subsequent age-specific multivariate analyses for the number of stroke admissions. Results: For the index stroke admission, the age- and sex-adjusted incidence rate per 100,000 was 366 (95% Cl 355-377) for blacks and 204 (95% Cl 202-207) for whites. Those having two or more stroke admissions accounted for less than 20% of the total number of patients. The truncated negative binomial (TNB) model gave the best fit not only to the California data but also to the data reanalyzed from several prior studies done in various countries [i.e., the United Kingdom (Oxfordshire and South London), Switzerland (Lausanne), Australia (Western Australia) and the United States (Nueces County, TX)]. In this study, predictors of stroke readmission changed according to age. For those aged 65-74 years old, blacks showed a higher risk of readmission than whites by 40% after adjustment for patient and hospital factors (RR 1.40, 95% Cl 1.19-1.64). This excess risk was lower in other age groups. Conclusions: These findings suggest that blacks remain a high-risk group after an initial stroke and warrant appropriate intervention. Future studies on recurrent stroke should consider age-specific TNB models.