HEALTH-CARE COSTS FOR VOLUNTEERS AND NON-VOLUNTEERS IN AN INTERVENTION FOR PEOPLE WITH OSTEOARTHRITIS

Objective. To determine whether older people who volunteered for a hea lth intervention study used the health care system differently from a randomly selected group of eligible non-volunteers. Methods. Three hun dred sixty-three volunteers and 92 non-volunteers were compared; both groups were members of a large health maintenance organization (HMO). Results. Volunteers were more educated and had been members of the HMO longer, Volunteers used the health care system significantly more at all time periods, but their cost per contact was significantly lower t han that for non-volunteers, Non-volunteers were more likely to have a comorbid condition and had fewer arthritis-related health care contac ts. Conclusions. There will always be problems in generalizing results of studies with volunteers, but volunteers are, nevertheless, the mos t appropriate controls if the experimental participants are also volun teers, Designs should ideally include both volunteer and nonvolunteer controls.