Features, Epidemiology, and Neuropathology

AD is the leading cause of senile dementia and effective therapy remains in want (Sisodia, 1999). The symptoms of typical AD begin with a loss of short-term memory that slowly progresses to profound memory functions (Corey-Bloom et al., 1994). Initially, impaired short-term memory often manifests itself as 

AD affects more than four million people in the United States and prevalence studies demonstrate an exponential rise of dementia linked to advancing age (Katzman, 2001). The number of cases of dementia in the developed world is projected to rise from 13.5 million in 2000 to 21.2 million in 2025, and to 36.7 million in 2050 (Katzman and Fox, 1999). Currently the number of deaths caused by AD is similar to the number of deaths caused by stroke. AD and stroke together rank as the third most common causes of death (Ewbank, 1999). 

In addition to age, other factors are associated with an inaeased risk of AD. In developed countries, AD appears to be more common in women. Lack of education is a risk factor for senile dementia in China and Europe (Zhang et al., 1990 Schmand et al., 1997). Head trauma is also a risk factor for both sporadic (Mortimer et al., 1991) and familial AD (Guo et al., 2(XX)). Silent myocardial infarcts and coronary stenosis triple the risk for AD (Aronson et al., 1990 Sparks et al., 1990), suggesting the importance of vascular risk factors. Other potential risk factors being studied include diabetes and hypertension (Ott et al., 1999 Peila et al., 2(X)2 Qiu et al., 2(X)5). As discussed below, a large number of genetic mutations are now associated with either early-onset AD or with increased risk of late-onset AD. 

---