Race and risk of schizophrenia in a US birth cohort: another example of health disparity?

Bresnahan, Michaeline
Begg, Melissa D
Brown, Alan
Schaefer, Catherine
Sohler, Nancy
Insel, Beverly
Vella, Leah
Susser, Ezra

¹Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
²New York State Psychiatric Institute, New York, NY, USA
³Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA
⁴College of Physicians and Surgeons, Columbia University, New York, NY, USA
⁵Kaiser Permanente Division of Research, Oakland, CA, USA
⁶City College Medical School, CUNY, New York, NY, USA
⁷Veterans Affairs Medical Center, San Francisco, CA, USA

Accepted 14 February 2007

^*Corresponding author. Department of Epidemiology, Mailman School of Public Health, 722 W. 168th St., NY, NY 10032, USA. E-mail: [email protected]

International Journal of Epidemiology 36(4):p 751-758, August 2007.

Background

Immigrant groups in Western Europe have markedly increased rates of schizophrenia. The highest rates are found in ethnic groups that are predominantly black. Separating minority race/ethnicity from immigration in Western Europe is difficult; in the US, these issues can be examined separately. Here we compared rates of schizophrenia between whites and African Americans and evaluated whether the association was mediated by socioeconomic status (SES) of family of origin in a US birth cohort.

Methods

Study subjects were offspring of women enrolled during pregnancy at Alameda County Kaiser Permanente Medical Care Plan clinics (1959–66) in the Child Health and Development Study. For schizophrenia spectrum disorders, 12 094 of the 19 044 live births were followed over 1981–97. The analysis is restricted to cohort members whose mothers identified as African American or white at intake. Stratified proportional hazards regression was the method of analysis; the robustness of findings to missing data bias was assessed using multiple imputation.

Results

African Americans were about 3-fold more likely than whites to be diagnosed with schizophrenia [Rate Ratio (RR)=3.27; 95% confidence interval (CI): 1.71–6.27]. After adjusting for indicators of family SES at birth, the RR was about 2-fold (RR=1.92; 95% CI: 0.86–4.28). Using multiple imputation in the model including family SES indicators, the RR for race and schizophrenia was strengthened in comparison with the estimate obtained without imputation.

Conclusion

The data indicate substantially elevated rates of schizophrenia among African Americans in comparison with whites in this birth cohort. The association may have been partly but not wholly mediated by an effect of race on family SES.