Trends in the public health significance, definitions of disease, and implications for prevention of Alzheimer's disease.

Purpose: Although Alzheimer's disease (AD) was described over a century ago, there remains no cure, and with the global demographic shift to older ages, the impact is increasing rapidly. This article summarizes how the conceptualization of AD has evolved in response to research advances. Current challenges, including the impact of multimorbidity are outlined and potential targets for prevention are discussed. Recent Findings: The ability to study AD neuropathology in vivo and results from longitudinal epidemiologic studies have led to a consensus that AD has a long preclinical course spanning decades. This view is driving efforts to identify early markers that will identify individuals at risk for AD dementia. Summary: Critical questions remain regarding the pathological mechanisms underlying AD and their relation to clinical symptoms. Nevertheless, evidence suggests that interventions targeting modifiable risk factors may slow or prevent the onset of disease while the search for a cure continues.