Marked Increase in Alzheimer's Disease Identified in Medicare Claims Records Between 1991 and 1999

BACKGROUND: Epidemiologic evidence suggests that African Americans have higher rates of Alzheimer's disease (AD) than do whites. Examining longitudinal trends in the number of persons who are identified as having AD in administrative databases may provide insights into this phenomenon. METHODS: We analyzed 9-year longitudinal data (1991-1999) for 29,679 Medicare beneficiaries who were screened for the National Long-Term Care Survey. Cases of AD were identified using ICD-9-CM diagnosis codes from Medicare claims files. RESULTS: Age-adjusted rates of Medicare beneficiaries identified as having AD rose from 1991-1999 for all groups studied, but particularly among African Americans. In 1991, African Americans made up 6.5% of the identified AD cases but comprised 11.0% of cases in 1999 (X(2) = 6.79, p =.005). The rate of increase in identification of AD was particularly large for women who were aged 85 years and older. CONCLUSIONS: Reasons for increased identification of AD in Medicare claims is likely multifactorial; sharp increases among African Americans may reflect improved access.