People over the age of 90 years are a very fast growing segment of the population. A substantial proportion of these individuals are affected by dementia, with major implications for the individual as well as society. The absence of dementia in very old age may serve as a model of successful ageing. This review summarizes population-based epidemiological studies of dementia and its underlying neuropathology in nonagenarians and centenarians. The data show an age-specific and sex-specific profile of dementia in very late life, resulting from a variety of often co-occurring neuropathologies. Extensive overlap in neuropathology between cognitively normal and cognitively impaired individuals is seen. Multiple pathogenetic mechanisms appear to underlie dementia, with interaction between genetics and lifestyle in normal and exceptional cognitive ageing.
Yang Z, Slavin MJ, Sachdev PS: Dementia in the oldest old. Nature Reviews Neurology [Epub ahead of print, June 4, 2013; doi:10.1038/nrneurol.2013.105]