Participation rates in a case control study: The impact of age, race, and race of interviewer

PURPOSE: Despite concerns about declining participation rates in epidemiolo gic studies in recent years, relatively few papers have discussed obstacles to recruiting study participants or strategies for optimizing response rat es. This report describes factors associated with nonparticipation in a pop ulation-based, case-control study of breast cancer and discusses ways to ov ercome barriers to participation. METHODS: Contact and cooperation rates were calculated for participants in the Carolina Breast Cancer Study (CBCS), stratified by case status, age, ra ce, and race of interviewer. Demographic and breast cancer risk factor char acteristics of partial and full responders also were compared. RESULTS: Contact rates and cooperation rates varied by case/control status and demographic characteristics. Contact rates were lower among controls, y ounger women, and black women. Cooperation rates were lower among controls, older women, and black cases. Cooperation rates were higher among both bla ck and nonblack women when participants and interviewers were concordant on race. CONCLUSIONS: Obstacles to recruitment seem to differ among race and age sub groups, suggesting chat recruitment strategies may need to be tailored to p otential participants based upon demographic characteristics. Strategies ha ve been implemented to improve response rates in this and other epidemiolog ic studies; however, additional research and innovation in this area are ne eded. Ann Epidemiol 1999;9:188-195. (C) 1999 Elsevier Science Inc. All righ ts reserved.