Increasing questionnaire response: evidence from a nested RCT within a longitudinal birth cohort study

Area of Science:

• Epidemiology
• Public Health Research

Background:

• High questionnaire response rates are crucial for study validity and generalizability in research.
• This study assessed response rates in a large longitudinal epidemiological study.
• The research aimed to improve response rates and address deprivation-related imbalances.

Purpose of the Study:

• To measure questionnaire response rates in a large longitudinal epidemiological study.
• To evaluate the impact of changes in data collection on response rates.
• To determine if interventions addressed response imbalances across different deprivation levels.

Main Methods:

• Analysis of response rates from a prospective, comparative study on water fluoridation's impact on children's oral health.
• Implementation of changes to questionnaire layout and cover letters during data collection.
• A nested randomized controlled trial comparing three reminder methods for questionnaire completion.

Main Results:

• Data were analyzed for 1824 individuals.
• Resending the complete questionnaire to non-responders yielded the highest response rate increase (25%).
• Telephone calls were the only method that showed potential in addressing deprivation-related response imbalances.

Conclusions:

• Low initial response rates raised concerns about non-response bias in the longitudinal study.
• Resending questionnaires proved most effective for increasing participation.
• Targeted efforts and data weighting can help mitigate biases and improve population-level conclusions.