Strengths and limitations
RECRUITMENT
Strengths of this study are the utilisation of a wide range of recruitment strategies and the monitoring of used strategies and recruitment yields to explore their effects. Nevertheless, determination of the most decisive strategy for participants to register was not possible since participants were not asked for the most decisive method and had the option to register multiple strategies instead of just one. Also, the relatively small sample size when exploring sociodemographic differences in recruitment strategy effectiveness and cardiometabolic measurements likely led to wide confidence intervals. For the interpretation of the results, we therefore focused on interpretation of effect sizes rather than statistical significance. Moreover, this study did not investigate the influence of the order in which recruitment strategies were used and time intervals between recruitment strategies on their (cost)-effectiveness. Furthermore, since this study was performed during the COVID-19 pandemic, this may have affected recruitment yield, but we were unable to quantify this impact. Last, we lack sufficient insight into reasons why 181 eligible participants did not proceed with study enrolment, since most of them did not respond after having received the information letter. Some replied that participation appeared more comprehensive (e.g. with at-home blood measurements) than anticipated which may have been a barrier for others as well.