Contacting controls: are we working harder for similar response rates, and does it make a difference?

Area of Science:

• Epidemiology
• Public Health Research

Background:

• High response rates are crucial for the validity of epidemiologic studies.
• The effort involved in achieving these rates is often not systematically documented.

Purpose of the Study:

• To quantify the effort required for initial contact and final status determination in population-based case-control studies.
• To evaluate lifestyle differences between easily and difficult-to-interview participants.

Main Methods:

• Analysis of three population-based case-control studies conducted in Utah (1991-2003).
• Recording of letter, phone, and in-person contacts to measure effort.
• Comparison of contact frequency and methods across study periods and demographic groups.

Main Results:

• The number of contacts needed to achieve a final outcome increased from 8 to 14 over the 12-year study period.
• Participants in later studies required more phone calls and in-person visits.
• Hispanic participants were more likely to receive in-person visits and noncontact letters.
• Easily contacted individuals were more likely to be overweight and less likely to have a family cancer history.

Conclusions:

• Significant increases in contact effort are necessary to maintain response rates in epidemiologic research.
• Demographic characteristics of the study population may influence the required effort.
• Understanding these trends is vital for future study design and resource allocation.