Discussion
physical disability
PHYSICAL DISABILITY
In this randomized trial, we examined whether the use of animation videos can increase participation in health surveys. At day 22 in the survey period, a slightly positive effect was observed for the animation video targeted men aged 16–24 years. When comparing the animation videos, the targeted animation videos tended to produce higher response proportions compared to the non-targeted animation video. However, only a significant difference was observed for men aged 16–24 at day 22. However, in general, a similar or slightly lower response proportion was observed in the intervention group who received an invitation letter including an animation video compared to the control group who received the generic invitation letter without an animation video. This was seen both at day 22 and by the end of the survey. When looking at the effect of the animation videos in different demographic subgroups, a slightly lower response proportion was observed in the intervention group among divorced and among sample members living in cities compared to the control group. Overall, both negative and positive effects of targeted animation videos was observed, and future surveys researcher should carefully select the target group and content in the video to gain a positive effect on response proportion and sample composition.Previous studies have documented that the use of videos has advantages for public health promotion compared to paper materials or spoken instructions [The major strength of the present study was the incorporation of a randomized trial in a large nationally population sample. This made is it possible to study the effect of animation videos in a real-life setting based on a highly scientific method. The study thereby adds to the scientific knowledge about the use of animation videos as a mean to reduce nonresponse in health surveys. Further, the large sample size made it possible to study the effect of both targeted and non-targeted animation videos. Yet, in cannot be rejected that lack of statistical power is the reason for the non-significant findings in subgroups. The study also had some methodological limitations. First, 7.5% of the study sample were excluded as they were not registered to receive digital post, with the majority being in the age group 75 years or older. The criteria for unsubscribing Digital Post include low technical skills and mental or physical disability [