To varying degrees, all diseases are the result of naturenurture interactions. Evolutionary biological theory indicates that diseases that unfold during the late stages of life are attributable to those interactions that have escaped the force of natural selection and thus, in the absence of some intelligent biomedical or environmental interventions, may be inevitable components of senescence. These patterns can be expected to vary among species and among members of a given species. For those members of our species living in the Western world, dementias of the Alzheimer type (DATs) appear to be extraordinarily prevalent. Incidence doubles about every 5 years beginning at age 65 years.1 Prevalence rates as high as 37.0% to 63.2% (95% confidence limits) have been reported for those over age 85 years.2
See also p 955.
In the course of less than a decade, there have been major advances on the genetic side of the