Comparison of response patterns in national surveys among Finnish adult population in 2020 and 2022

BACKGROUND: Self-administered survey questionnaires are an important data collection tool in public health research and epidemiology. These questionnaires can be completed electronically, which allows larger sample size and faster speed of data collection while reduced cost. Yet, a web survey might be a less feasible for older individuals. We evaluated the response patterns in the two recent surveys in 2020 and 2022. METHODS: We analysed the data from FinSote 2020 (n = 31,817) and Healthy Finland 2022 (n = 30,307) surveys in Finland. In both, invitees (aged 20+) were contacted four times via postal letter. A concurrent mixed-mode approach allowed for the invited individuals to complete either a web questionnaire or an identical paper questionnaire. In both surveys, the oldest age group (75+) received a paper questionnaire three times and those aged 20-54 years received it only once. In 2022, the survey design was changed so that a paper questionnaire was sent twice (instead of three times) for those aged 55-74 years compared to 2020. RESULTS: The overall response rate was 47 % both in 2022 and 2020. Persons aged 75 + rarely responded to web questionnaire, less than 10 % answered in web. Instead, among persons aged 20-54 years, around 80 % completed the web survey. The response mode for the web survey increased significantly from 32% to 46% for two years period. The largest increase in the proportion which completed the web survey was found in respondents aged 55-74 years (from 19 % to 49 %). In them, however, the response rate declined from 60 % to 58 %. CONCLUSIONS: In mixed-mode surveys, push-to-web approach can shift respondents to a web survey without greatly impacting response rate. However, without offering a paper questionnaire, older people are likely to be missing resulting potentially biased estimates. KEY MESSAGES: • Completing survey in web has increased recent years. This may be partly due to COVID-19 pandemic that led to a shift towards use of digital apps and online services. • The move to the web-based surveys save the costs without impacting response rates.