LIFE EXPECTANCY for a person born in the year 1900 was about 50 years. Public health measures implemented during the 20th century have markedly reduced mortality in early and middle life. The result is a life expectancy of nearly 80 years for a person born in the year 2000.1 The increase in longevity has resulted in a large and increasing number and proportion of the US population being over the age of 65 years, a demographic trend that will continue well into the 21st century.2 Persons in this age group are at high risk for several chronic conditions that are relatively rare among younger persons. Progressive loss of memory and other cognitive abilities is one of the most common problems affecting older persons.3-5 Furthermore, since cognitive impairment is associated with significant morbidity and mortality,6-8 the identification of modifiable risk factors for cognitive decline is a major public health priority. Unfortunately, much less is known about factors that predict cognitive decline than is known about factors that predict many other common chronic problems of older persons.