Is population mobility an obstacle to continuity of care? Attrition rates over five years in 17 Ontario practices.

The University of Western Ontario Hypertension Study provided an opportunity to study attrition rates over a five-year period in the population of 17 family practices in southwestern Ontario. The baseline population consisted of all patients between the ages of 20 and 65 years who were active in the practices in 1978. During the five years of the study, a medical assistant in each practice recorded data on morbidity, mortality, and patients leaving the practice. The follow-up of nonresponders to a demographic questionnaire provided additional data on patient moves. The overall five-year move rate was 13.2 percent for men and 16.6 percent for women. Those in the 20- to 29-year age group had the highest rates, and those in the 30- to 39-year age group had the next highest. The rates for men stabilized after the age of 40 years to between 8 and 10 percent, and for women after 40 years to between 11 and 13 percent. The move rates were higher in urban than in rural practices. Ninety percent of hypertensive patients received continuous care over the five-year period. In southwestern Ontario, population mobility does not appear to be a major barrier to continuing care.