Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
An Incremental Model of Chronic Disease. The model is characterized by early age of onset, progression at various rates, and passage of a symptomatic threshold at which time a clinical diagnosis may be made. Reprinted with permission from J.F. Fries and L.M. Crapo, Vitality and Aging (San Francisco: W.H. Freeman, 1981).
