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Green RC, Cupples LA, Go R, et al. Risk of Dementia Among White and African American Relatives of Patients With Alzheimer Disease. JAMA. 2002;287(3):329–336. doi:10.1001/jama.287.3.329
Author Affiliations: Genetics Program and Department of Neurology, Department of Medicine, School of Medicine (Drs Green and Farrer and Ms Benke) and Department of Epidemiology and Biostatistics, School of Public Health (Drs Cupples and Farrer), Boston University, Boston, Mass; Department of Epidemiology, University of Alabama School of Public Health, Birmingham (Dr Go); Departments of Medicine and Pharmacology, Morehouse School of Medicine, Atlanta, Ga (Drs Edeki, Griffith, Williams, and Hipps); Department of Neurology, Mayo Clinic, Jacksonville, Fla (Dr Graff-Radford); and Department of Psychiatry, Medical University of South Carolina, Charleston (Dr Bachman).
Context Evidence exists that the incidence of Alzheimer disease (AD), as well
as risk attributable to specific genetic factors such as apolipoprotein E
(APOE) genotype, may vary considerably among ethnic
groups. Family studies of probands with AD offer an opportunity to evaluate
lifetime risk of dementia among relatives of these probands.
Objective To compare lifetime dementia risk estimates among relatives of white
and African American probands with probable or definite AD.
Design and Setting Risk analysis using data collected by questionnaire and supplemental
records between May 1991 and March 2001 at 17 medical centers contributing
to the Multi-Institutional Research in Alzheimer's Genetic Epidemiology Study.
Participants A total of 17 639 first-degree biological relatives and 2474 spouses
of 2339 white AD probands, and 2281 first-degree biological relatives and
257 spouses of 255 African American AD probands.
Main Outcome Measures Cumulative risk of dementia by age 85 years, stratified by ethnicity
and sex of relatives and by APOE genotype of probands.
Results Cumulative risk of dementia in first-degree biological relatives of
African American AD probands by age 85 years was 43.7% (SE, 3.1%), and the
corresponding risk in first-degree biological relatives of white AD probands
was 26.9% (SE, 0.8%), yielding a relative risk (RR) of 1.6 (95% confidence
interval [CI], 1.4-1.9; P<.001). The risk in spouses
of African American AD probands of 18.5% (SE, 8.4%) was also higher than the
risk in white spouses of 10.4% (SE, 1.7%) but did not reach statistical significance
(RR, 1.8; 95% CI, 0.5-6.0; P = .34), likely due to
the smaller sample size of African Americans. The proportional increase in
risk of dementia among white first-degree biological relatives compared with
white spouses of 2.6 (95% CI, 2.1-3.2) was similar to that of 2.4 (95% CI,
1.3-4.4) in African American first-degree biological relatives compared with
African American spouses. Female first-degree biological relatives of probands
had a higher risk of developing dementia than did their male counterparts,
among whites (31.2% vs 20.4%; RR, 1.5; 95% CI, 1.3-1.7; P<.001) as well as among African Americans, although this was not
significant among African Americans (46.7% vs 40.1%; RR, 1.2; 95% CI, 0.9-1.7, P = .30). The patterns of risk among first-degree biological
relatives stratified by APOE genotype of the probands
were similar in white families and African American families.
Conclusion First-degree relatives of African Americans with AD have a higher cumulative
risk of dementia than do those of whites with AD. However, in this study,
the additional risk of dementia conferred by being a first-degree relative,
by being female, or by the probability of having an APOE ∊4 allele appeared similar in African American and white families.
These data provide estimates of dementia risk that can be used to offer counseling
to family members of patients with AD.
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