Racial comparisons of MRI and PiB PET in acute stroke

Abstract

AbstractBackgroundStroke and Alzheimer disease share risk factors and often co‐occur, and both have been reported to have a higher prevalence in African‐Americans. However, the interaction of race, stroke, and Alzheimer disease has not been established.MethodWe compared MRI and PiB PET biomarkers of non‐demented participants with and without acute ischemic stroke (total n=243, age 65‐101), with a focus on comparing African‐Americans (n=42 with stroke, n=84 without) to Non‐Hispanic Whites (n=39 with stroke, n=78 without). Our assessment included radiologic reads of the number of large infarcts, small infarcts, microbleeds, and leukoaraiosis; a PET measure of amyloid binding; quantitative measures of hippocampal volume and white matter hyperintensities; and longitudinal Mini Mental State Exam (MMSE) scores. Statistical analysis used logistic regression models to predict each biomarker using race and stroke status, while controlling for age, family history, APOE4, education, sex, and high blood pressure.ResultPiB PET did not differ significantly by stroke status or by race, with 23.6% of participants being classified as amyloid positive (Figure 1). As expected in stroke, the acute stroke participants were more likely to have large infarcts, small infarcts, microbleeds, and non‐zero Fazekas scores. MMSE showed racial differences at baseline (mean 26.8 for African‐Americans, 27.9 for Non‐Hispanic Whites, p=0.03), but not longitudinally. Overall, African‐Americans were more likely to have microbleeds (32.8% vs 22.6%, p=0.04). Within the stroke group African‐Americans were more likely to have small infarcts (75.6% vs 56.8%, p=0.049). Combined, African‐Americans were also more likely to have more than 5 microbleeds ‐ the cutoff for many Alzheimer clinical trials (15.2% vs 9.6%, p=0.04).ConclusionPreclinical Alzheimer disease does not appear to be a risk factor for stroke and did not differ by race in our sample. Standard clinical MRI measures differed by stroke status, but showed few racial differences. The observed lower MMSE scores in African‐Americans has been reported previously and may arise for a variety of reasons. In individuals with stroke, African‐Americans may have more severe pathology as evidenced by greater numbers of small infarcts and microbleeds. African‐Americans may be more likely to be excluded from Alzheimer disease clinical trials due to having 5 or more microbleeds.