%0 Journal Article
%T Increasing incidence of dementia in the oldest old: evidence and implications
%A Bryan D James
%A Julie A Schneider
%J Alzheimer's Research & Therapy
%D 2010
%I BioMed Central
%R 10.1186/alzrt32
%X The oldest old, persons living into the 10th and 11th decades of life, are the fastest growing segment of the population, with numbers expected to quadruple to over 8 million by 2050 [1]. Because advancing age is a major risk factor for dementia, this demographic shift may significantly increase the burden of dementia borne by our society. Indeed, the dementia incidence in persons aged 65 to 90 has been reported to double every 5 years [2]. However, few studies have had sufficient numbers of participants older than 90 years of age to provide accurate estimates in the oldest old and some studies have suggested a slowing of the incidence in the oldest old [3,4]. Further work is thus needed to determine the incidence of dementia in the oldest old. The present work not only has important implications for public health planning, but is also relevant for studies of etiopathogenesis and strategies for prevention and treatment.In a pivotal study addressing this question, Corrada and colleagues present data showing that the incidence of dementia continues to exponentially rise in the oldest old [5]. The authors studied 330 persons from The 90+ Study, a longitudinal cohort study of dementia in the oldest old. Participants were originally members of an epidemiological study of a retirement community in the 1980s [6]; 950 of the 1,150 persons at least 90 years old in 2003 were enrolled. Analyses for this study included only non-demented persons at baseline, as ascertained by in-person evaluation, who had at least one follow-up over 4 years. The authors found that the incident rate of dementia increased exponentially, from 12.7% per year for 90 to 94 year olds, to 21.2% per year for 95 to 99 year olds, to 40.7% per year for persons aged 100 years and older. The estimated doubling time for incidence rates was 5.5 years and is comparable with that observed for persons aged 65 to 90.The results of this study contrast with other studies that showed a slowing of dementia incidence af
%U http://alzres.com/content/2/3/9