Persistence in the use of pharmaceuticals by the elderly. Evidence from annual claims.

An analysis of four-and-a-half years of claims data from the Pennsylvania Pharmaceutical Assistance Contract for the Elderly (PACE) program shows a pronounced degree of persistence in annual prescription drug expense by individual enrollees from year to year, particularly among the heaviest users. There is evidence of eventual regression to the mean, but it takes a substantial length of time--far longer than observed for other types of health care used by the elderly. The study findings raise questions about the insurability of drug expenses in non-group Medigap policies.