Exceptional brain aging in a rural population-based cohort

Context: The 2000 US Census identified 50,454 Americans over the age of 100. Increased longevity is only of benefit if accompanied by maintenance of independence and quality of life. Little is known about the prevalence of dementia and other disabling conditions among rural centenarians although this information is important to clinicians caring for them. Purpose: To determine the prevalence of disabling conditions, including cognitive impairment, among the very elderly in a rural setting to guide clinicians in their care. Methods: We performed a population-based cohort study of all residents 97 years and older in the Klamath Basin, a rural region in southern Oregon. The prevalence of disabling conditions was determined by in-person examination. Findings: About 100% of the target sample was identified. Of the eligible 67 individuals ≥97 years old, 31 were evaluated in-person. The prevalence of dementia (probable or possible Alzheimer's disease or vascular dementia) was 61.3% (95% CI: 43.8, 76.2), mild cognitive impairment was 29.0% (95% CI: 16.1, 46.6), and no dementia was 9.7% (95% CI: 3.4, 25.0). Parkinsonism and the APOEe4 allele were rare. Systemic vascular disease was almost universally present. Conclusions: While cognitive impairment was nearly universal in this rural population of very elderly persons, almost 40% had not progressed to full dementia. Determining risk factors for dementia in this population can identify strategies to prevent progression to dementia among younger elderly populations.