Academic journal article Care Management Journals

A Population Study of Alzheimer's Disease: Findings from the Cache County Study on Memory, Health, and Aging

Academic journal article Care Management Journals

A Population Study of Alzheimer's Disease: Findings from the Cache County Study on Memory, Health, and Aging

Article excerpt

There are several population-based studies of aging, memory, and dementia being conducted worldwide. Of these, the Cache County Study on Memory, Health and Aging is noteworthy for its large number of "oldest-old" members. This study, which has been following an initial cohort of 5,092 seniors since 1995, has reported among its major findings the role of the Apolipoprotein E gene on modifying the risk for Alzheimer's disease (AD) in males and females and identifying pharmacologic compounds that may act to reduce AD risk. This article summarizes the major findings of the Cache County study to date, describes ongoing investigations, and reports preliminary analyses on the outcome of the oldest-old in this population, the subgroup of participants who were over age 84 at the study's inception.

Keywords: Alzheimer's disease; dementia; epidemiology; Alzheimer's prevention

There are a number of population studies of memory in aging in the world. Of the investigations that have followed a defined population of elderly individuals over time, the five largest include the Rotterdam Study (the Netherlands; Breteler, van den Ouweland, Grobbee, & Hofman, 1992), the Canadian Study of Health and Aging (Canadian Study of Health and Aging, 1994), the Indianapolis-Ibadan Dementia Project (USA-Nigeria; Hendrie et al., 1995), the Cache County Study on Memory, Health and Aging (USA; Breitner et al., 1999), and the Chicago Health and Aging Project (USA; Bienias, Beckett, Bennett, Wilson, & Evans, 2003). Among these investigations, the Cache County study includes one of the largest cohorts of individuals aged 85 or older, often referred to as "the oldest-old." The primary aims of this study are the examination of risk and protective factors for Alzheimer's disease (AD). This article summarizes the major findings from the Cache County study, with an emphasis on results pertaining to the oldest-old. It also describes ongoing investigations and presents information pertaining to the outcome of the oldest segment of the population after 7 years of follow-up.

BACKGROUND AND RESULTS TO DATE

Located in northeastern Utah, Cache County consists of a number of rural communities and towns, the total approximating 90,000 (70,000 in 1990). In 1990, the average life expectancy in the county was 77.54 years for males and 82.01 years for females (Murray, Michaud, McKenna, & Marks, 1998). For males aged 65 years or older, the life expectancy ranked among the highlit in the nation, exceeding national norms by approximately 10 years (Manton, Stallard, & Tolley, 1991). Together with low rates of outmigration, lifestyle factors that promote health, and a positive view of research, these characteristics of the Cache County population have made it ideal for longitudinal studies of aging. To date, participating members of the population have undergone three waves of cognitive screening and dementia assessment to determine the prevalence of dementia, the 3-year incidence rates, and the role of various factors that influence the risk of subsequent dementia.

Dementia Prevalence Rates

At baseline (1995-1996), 5,092 or 90% of the permanent residents of the county aged 65 years and older underwent a multistage dementia screening and assessment procedure (Breitner et al., 1999). They also donated buccal samples for genotyping at the polymorphic locus of Apolipoprotein E (APOE). APOE genotype was determined using PCR amplification (Richards et al., 1993) and restriction isotyping (Saundcrs et al., 1993). The majority of the participants were White (99%), with a mean (SD) age of 75.9 (7.3) and mean (SD) educational level of 13.1 (2.9). Prevalence rates (standard errors) of dementia were 9.6% (0.5) for the entire population and 7.8% (0.6) for males and 10.8% (0.6) for females. As expected, the prevalence of dementia increased with age, ranging from 1.4% in the youngest age group (65-69 years) to a high of 38.0% in the oldest age group (90+). …

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