Implementation of Research Protocols Assessing Sleep and Circadian Rhythms in Challenging Real-Life Settings: A Critical Appraisal of a Study Protocol, Including Researchers’ Reflections and Participants’ Perspectives

Sleep and circadian research in real-life environments is challenging but essential. This study presents the design and implementation of a data-collection protocol in a highly challenging real-life setting over 56 days, examining both researchers' and participants' perspectives on its strengths, limitations, and key challenges, and highlighting the lessons learned relevant to future studies in similar contexts. Thirty military submariners completed a questionnaire after the 56-day pre-mission, mission, and post-mission data collection to assess their views on the study and each task. Compliance with measurements (questionnaires, diaries, actigraphy, and blood collections) was quantified and correlated with participants' answers. Mean global satisfaction was 3.57 ± 0.77 (0-5 scale) and declined across study phases, with a significant change only in the post-mission phase (<i>p</i> < 0.001). Higher work satisfaction correlated with better global study satisfaction (ρ = 0.396; <i>p</i> = 0.030). Diaries were rated the most burdensome task, while blood collections generated the most polarized responses. Compliance with continuous measurements was high, but these also decreased in the third phase of the study, significantly for actigraphy (<i>p</i> < 0.001), although without clear predictors, including satisfaction. In this extreme setting, satisfaction and compliance declined significantly in the final phase of the study, without clear predictive factors. Having different engagement strategies for different work shifts is also an important consideration for future studies.