Dementia is a clinical syndrome that can be caused by a range of diseases or injuries to the brain. Although it can affect young people, it is most commonly seen in older individuals because dementia prevalence increases with age. Given the aging of the population worldwide, dementia is already epidemic and one of the top 10 causes of disability in developed countries (Murray and Lopez 1997). As shown in Figure 13–1, by 2040 an estimated 81 million new cases of dementia will occur worldwide, mostly in the developing world (Ferri et al. 2005). In the United States, as many as 15 million new cases of dementia are expected in the next several decades (Hebert et al. 2003). Given that dementia is a chronic disease, with estimates of its duration ranging from 3–4 years in community settings (Graham et al. 1997) to 10–12 years in clinical settings (Rabins et al. 2006), it poses a unique public health problem with serious effects on its victims, their families, and society at large. In the United States alone, it is estimated that by 2050, the annual cost of dementia will be close to $400 billion in direct and indirect expenses (Murman 2001; Murman et al. 2007).