Modeling the dementia epidemic

The incidence of dementia increases steeply with age in older people, although from the tenth decade the slope may be smoother, perhaps reflecting different pathological processes in the oldest old. The prevalence depends upon interaction of age with other factors (e.g., comorbidities, genetic or environmental factors) that in turn are subject to change. If onset of dementia could be postponed by modulating its risk factors, this could significantly affect its incidence. Analysis of risk and protection factors should take into account the critical period during which these factors play a role. For example, the impact of education and diabetes mellitus occurs in early- and midlife, respectively, while maintaining optimal physical and mental activity and controlling vascular factors later in life may slow the rate of cognitive decline. Modifying factors need to be evaluated for different clinical groups, taking into account genetic background, age, and duration at exposure. The aim of the present article is to try to take stock of epidemiological data concerning factors affecting the prevalence of dementia and predict future developments, as well as to look for possible interventions that could affect outcome.