[Recruitment strategies for reaching adults aged fifty years and older with low socioeconomic status for participation in online physical activity interventions].

Generally, the health condition of those with higher socioeconomic status (SES) is better compared to those with lower SES. Electronic health (eHealth) interventions provide an unique opportunity to improve health and lifestyle of populations that are difficult to reach with more traditional interventions. The application of appropriate strategies to reach low SES populations with eHealth interventions is thus of major importance to reduce health inequalities. Therefore, the aim of this study was to provide insight into the reach, sample characteristics and costs of three pre-planned strategies for recruiting adults aged fifty years and older with low SES for participation in an online physical activity intervention. The intervention consisted of computer-tailored physical activity advice at three occasions and an integrated activity tracker. Recruitment took place via gyms, invitation letters via a municipality and social media advertisements. Additional procedures were followed to reach specifically the low SES group. Response rates, sociodemographic characteristics and costs per strategy were assessed. The highest response was shown for the municipality approach (n = 281), followed by social media (n = 71) and gyms (n = 45). The most low-educated participants were reached via the municipality (n = 128), followed by social media (n = 9) and gyms (n = 8). Recruitment costs were € 2142,37 for the municipality approach, € 96,81 for social media and € 0 for gyms. In conclusion, recruitment via the municipality approach has the highest potential for reaching low SES participants of the three applied strategies, although the higher recruitment costs need to be taken into account.