Study protocol of the 'HEAL-HOA' dual randomized controlled trial: Testing the effects of volunteering on loneliness, social, and mental health in older adults.

Background: Interventions to reduce loneliness in older adults usually do not show sustained effects. One potential way to combat loneliness is to offer meaningful social activities. Volunteering has been suggested as one such activity - however, its effects on loneliness remain to be tested in randomized controlled trials (RCT). Methods: This planned Dual-RCT aims to recruit older adults experiencing loneliness, with subsequent randomization to either a volunteering condition (6 weeks of training before delivering one of three tele-based loneliness interventions to older intervention recipients twice a week for 6 months) or to an active control condition (psycho-education with social gatherings for six months). Power analyses require the recruitment of N = 256 older adults to detect differences between the volunteering and the active control condition (128 in each) on the primary outcome of loneliness (UCLA Loneliness Scale). Secondary outcomes comprise social network engagement, perceived social support, anxiety and depressive symptoms, self-rated health, cognitive health, perceived stress, sleep quality, and diurnal cortisol (1/3 of the sample). The main analyses will comprise condition (volunteering vs. no-volunteering) × time (baseline, 6-, 12-, 18-, 24-months follow-ups) interactions to test the effects of volunteering on loneliness and secondary outcomes. Effects are expected to be mediated via frequency, time and involvement in volunteering. Discussion: If our trial can show that volunteers delivering one of the three telephone-based interventions to lonely intervention recipients benefit from volunteer work themselves, this might encourage more older adults to volunteer, helping to solve some of the societal issues involved with rapid demographic changes.