Comparing the responsiveness of older adults to online and traditional recruitment strategies to engage in health research

Recruiting older adults into cohort studies is an ongoing challenge. Although social media is increasingly used, older adults vary in their access to and comfort with digital technologies, necessitating traditional methods to complement online approaches. We use observational data embedded within the recruitment of the Beyond 50 cohort to compare targeted social media advertising with postal mailouts. Recruitment outcomes included gender distribution, response rate and cost per participant. A total of 1059 participants were recruited, of which 46.8% were female. Social media campaigns had an estimated reach of 63% of the local target population and resulted in a 0.4% response rate, of which 78% were female, at an average cost of A$4.84 per participant. Postal mailouts had an estimated reach of 11.9% of the local target population and resulted in a 4.4% response rate (4.2% female; 4.5% male), at an average cost of A$29.18 per participant. Despite higher costs, mailouts produced more efficient and gender-balanced recruitment when compared to social media. These findings highlight the importance of selecting the appropriate recruitment strategy to maximise recruitment reach, efficiency and gender equity when establishing cohorts of older adults. In addition, mailouts using a sampling frame may reduce selection and recruitment bias.