Age, Alzheimer's disease, and the big picture

Abstract

The recently published revised National Institute on Aging/Alzheimer's Association clinical diagnostic criteria for Alzheimer's disease (AD) (Albert et al., 2011; Jack et al., 2011; McKhann et al., 2011; Sperling et al., 2011) have been hailed for incorporating a number of timely and important advances. They reflect new understanding that has been gained since the previous criteria were published in 1984 (McKhann et al., 1984). They include recognition of the state of mild cognitive impairment that is present before the threshold is crossed into dementia; they recognize the potential role of biomarkers in enhancing the specificity of diagnosis; they also address emerging work in the preclinical stage of AD that could help in understanding the sequence and stages of the core pathology before symptoms emerge. Among the previously listed diagnostic features that have disappeared was the requirement that onset of dementia occur before the age of 90 years. Meanwhile, the Neurocognitive Disorders Work Group for DSM-5 (the 5th edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders; American Psychiatric Association, 2010) is also doing away with the previous distinction between early-onset and late-onset dementia in AD, where an arbitrary division had been placed at age 65 (American Psychiatric Association, 2000). These changes are driven by the lack of biological data to support the age-based dichotomy, while recognizing the unique genetic characteristics of the relatively rare, autosomal dominantly inherited forms of AD which typically occur early. However, the disappearance of the age-based diagnostic dichotomy by no means implies that age is irrelevant to AD.