Concordance rates for cognitive impairment among older African American twins

Abstract

Background There is significant attention to the growing elderly African American population and estimating who and how many within this population will be affected by cognitive impairment. Objective The etiology of cognitive impairment has not been well studied in African Americans and the contribution of genetic and environmental influences to cognitive impairment is not clear. Methods We calculated concordance rates and heritability for cognitive impairment in 95 same-sexed pairs of African American twins from the Carolina African American Twin Study on Aging (CAATSA). The sample had an average age of 59.6 years ( SD = 8.6 years, range 50-88 years) and 60% were female. The Telephone Interview for Cognitive Status (TICS) was used to assess cognitive impairment with a lower cutoff based on our previous research with African Americans. Results Thirteen of the monozygotic (MZ) twins (30.2%) and 9 of the dizygotic (DZ) twins (17.3%) were cognitively impaired. The concordance rate was 72% for MZ and 45% for DZ. We found the heritability for cognitive impairment to be 54%. Conclusions The study findings indicate that cognitive impairment is highly heritable, suggesting that genetics may play a relatively large role in the development of cognitive impairment in African American twins.