ABSTRACT
A further time interval went by when volunteered information was recorded but not systematically pulled together, and then in 1972, another point prevalence study began and all intervening data were systematically gathered and evaluated. The subjects were followed for 25 years starting from a natural standing age distribution in 1947. Each 1947 age group came from a different birth cohort so that the circumstances under which each age group was born differed from those of the other age groups. The denominator diminishes as age increases because it started off with a standing population, so that the last points are less reliable. The survivorship experience of the demented cases that was present in these same two populations. The differential mortality rate has become smaller, because, whereas persons in the general population are living a little longer than they used to, individuals with dementia are living a lot longer than before.
