Background: With a growing population of older adults, there is an increased need to focus on age-related research. However, recruiting this demographic can be difficult due to numerous factors. Therefore, there is a critical need to understand which recruitment methods yield the most successful and cost-effective results amongst older adults.

Methods: Multiple recruitment strategies were employed to enroll 200 older adults (ages 60-85) into a randomized controlled trial investigating the impact of a behavioral sleep intervention on cognitive function. Success and cost-effectiveness of each strategy was evaluated, including percentage of participants recruited, contact-to-enrolled conversion percentage, overall cost, and cost per participant.

Results: The total contact-to-enrolled conversion rate was 10.2 % with an overall recruitment cost of $20,220 and a per-participant cost of $101. The highest percentage of enrolled participants (49 %) was recruited through the Alzheimer's Disease Research Center (KU ADRC) registry, which had the highest overall cost ($13,175). Radio advertisements, print advertisements, and KU ADRC registry had both high conversion rates (19-33 %) and high per-participant costs ($134-227). Facebook advertisements and friend/family referrals had low per-participant costs ($17 and $0, respectively) and high conversion rates (23 % for both), but only provided 10 % of the enrolled participants.

Conclusion: Utilizing multiple recruitment sources is essential for successful recruitment into behavioral research studies. Recruitment sources with higher costs per participant tended to have the highest conversion rate, apart from Facebook and family/friend referrals. While high-cost strategies are likely necessary, including relational and social media-based strategies may offer cost-effective methods for recruiting older adults.