Study protocol of a sequential, multiple assignment, randomised trial using an adaptive intervention to reduce loneliness among Chinese older adults in Hong Kong

Background Loneliness is a prevalent and alarming issue among older adults that requires effective interventions. While randomised controlled trials have been commonly undertaken to explore reduction in loneliness, there is a growing recognition that a comprehensive treatment strategy involving multiple interventions may yield better outcomes. Therefore, this study aims to develop and identify a two-stage adaptive intervention that combines telephone-delivered behavioural activation (Tele-BA) and mindfulness techniques (Tele-MF) to reduce loneliness in older adults in Hong Kong.Methods A Sequential, Multiple Assignment, Randomised Trial (SMART) design will be adopted. 244 lonely older adults will be recruited from the community and randomly assigned to either one of the 4-week two-stage, embedded adaptive interventions involving different sequences and dosages of Tele-BA and Tele-MF (eg, 4 weeks of Tele-BA followed by booster sessions for responders or 4 weeks of Tele-BA followed by 4 weeks of Tele-BA with motivational component or 4 weeks of Tele-MF for non-responders) based on a set of decision rules. The primary outcome will be loneliness measured by the Revised University of California Los Angeles (UCLA) Loneliness Scale. Secondary outcomes, such as De Jong Gierveld Loneliness Scale, perceived stress, sleep quality and depressive and anxiety symptoms, will be assessed. Adhering to the intention-to-treat principles, the data will be analysed using linear mixed models. The findings may have implications for the development of psychosocial adaptive interventions involving BA and MF to reduce loneliness and improve well-being among older adults in Hong Kong using the SMART design.Ethics and dissemination Ethical approval was obtained by the Human Research Ethics Committee at The Education University of Hong Kong (reference: 2022-2023-0117). The findings from this study will be presented in academic conferences and submitted for publication.Trial registration number ChiCTR2300077472.