Predictors of response and mode of response in the Environmental Polymorphisms Registry (EPR) Health and Exposure Survey

Background

The EPR was established by the National Institute of Environmental Health Sciences to facilitate genotype-driven translational research of complex diseases. More than 18,000 participants have enrolled over 12 years and provided a blood sample for genetic analyses. Contact information is updated annually. We recently administered a follow-up survey to participants to gather phenotypic data for future studies and seek to optimize response rates while minimizing costs for future surveys.

Methods

We targeted 15,257 active EPR participants for survey participation. To maximize response while minimizing cost, participants were invited to complete the survey first by web, then by mailed survey, and finally by telephone interview.  We calculated response rates by mode of administration and used bivariate analyses to examine variations in response by demographic factors.

Results

Overall, 8,843 (58%) of those contacted completed the questionnaire. Among respondents, 97% chose the mailed (53%) or web-based survey (44%). Few participants (3%) completed the telephone survey after having the opportunity to respond via the web or mail. Response to the mailed survey was highest among minorities ages 55 and older (80%).

Conclusions

Despite up to 12 years between enrollment and follow-up, almost 60% of participants completed a questionnaire. Multi-modal data collection was beneficial, with two modes accounting for more than 97% of responses. Mailed surveys were particularly instrumental in reaching older minority populations. Telephone interviews contributed little to overall response, so we may consider prolonging web and mail-based approaches in the future and eliminating costly telephone interviews. Researchers working with similar populations should consider using enrollment data on response rate and modes of response by demographic and other factors to tailor approaches to mode of contact at follow-up to enhance response rates.