10. Effect of potential community membership on the impact of a health promotion program

Influence on health behavior from peers is well known and it has been shown that participants in an online physical activity promotion program are generally more successful when they share their achievements through an online community. However, more detailed insights are needed into the mechanisms that explain the influence of a community on physical activity levels (PAL). This paper discusses a detailed analysis of a data set of participants in an online physical activity promotion program. The analysis focuses on the comparison two groups of participants, namely participants who will join an online community at some point in time and participants who will never join such a community. A well-balanced selection is made to eliminate to a large extent factors that dilute the effect of the willingness to partake in a community. We create statistical models that describe the PAL increase at the end of the program. A comparison of these models shows that participants that will participate in a community not only have a higher PAL at the start of the program, but also that the PAL increase is significantly greater compared to participants that will not become community members. The results further support the hypothesis that the possibility to share achievements is an important feature of successful health promotion programs. At the same time, it raises the question whether part of the success is caused by a selection bias, as people that are willing to participate in a community are already more active at the start.