Recruitment of nursing homes and residents in a cluster-randomised controlled trial to improve oral health (MundZaRR): a structured analysis of trials and tribulations.

backgroundThe cluster-randomised controlled MundZaRR trial aimed to improve the oral health of nursing home (NH) residents through a complex intervention programme. Recruitment in NH settings is notably challenging. Since there is only a limited number of reports from comparable studies on recruitment, we aimed to analyse the challenges and barriers related to the recruitment process of MundZaRR.

methodsNHs in Southwestern Germany were recruited by the study team, and residents via NH contact persons, e.g. NH managers. We aimed for 618 recruited residents from 18 NHs. Due to two COVID-19 pandemic-related interruptions, recruitment occurred in three phases from September 2019 until June 2022. The recruitment strategies had to be adapted during the course of the pandemic (e.g. from face-to-face to email/telephone contact). The recruitment process was continuously documented and analysed descriptively.

resultsA total of 111 NHs were deemed eligible, and finally 18 NHs agreed to participate (participation rate: 16%). Overall, 358 individual consents were obtained, n = 89 (25%) from residents and n = 269 (75%) from their representatives, resulting in an average participation rate (corresponding to the NHs' total number of beds) of 27% (min = 10%, max = 85%). Major challenges were the withdrawal of eight clusters (with n = 87 residents) from the first recruitment phase and the high number of residents who deceased during the recruitment process (n = 75). The COVID-19 pandemic, associated with time constraints and staff shortages at the NHs, was another significant barrier. At the individual level, obtaining informed consent from residents' representatives was particularly challenging.

conclusionDespite using various strategies and intensive efforts, we achieved the planned number of clusters, but failed to reach the targeted sample size of residents. The pandemic-related measures and negative effects as well as the process of obtaining consent from residents' representatives were major challenges. Personal contact with NHs and flexible approaches for reaching residents' representatives seem to be important strategies. However, future cluster-randomised studies with comparable vulnerable populations should assume a higher number of clusters and carefully pilot recruitment strategies in preceding feasibility studies.

trial registrationClinicalTrials.gov NCT04140929. Registered on 24 October 2019. https://clinicaltrials.gov/study/NCT04140929 .