Study protocol for a theory-informed randomized controlled trial of a lifestyle and sleep intervention to improve quality of life and physical activity in inactive adults: the SleeP exercIse nutRition heALth+ SPIRAL+ study.

BACKGROUND: Sleep, physical activity, and diet are key determinants of health, each independently associated with chronic disease risk and mortality. These behaviors also interact: insufficient sleep can impair physical activity and dietary choices, while regular exercise and healthy diet promote better sleep. Although lifestyle interventions commonly target physical activity and diet, few simultaneously address sleep. Emerging evidence suggests that even small improvements across all three behaviors can reduce all-cause mortality, highlighting the potential of multi-behavior approaches. However, the effects of a lifestyle intervention simultaneously targeting sleep, physical activity, and diet on quality of life and physical activity levels in inactive adults remain largely unexplored. METHODS: The SPIRAL+ study is a single-center, randomized controlled trial conducted in France, among non-exercising adults aged 18–80 years. Participants (n = 201) will be randomized to one of three groups: (1) lifestyle intervention (physical activity and diet) (2), lifestyle plus sleep intervention, or (3) control. Assessments will be conducted at baseline, 6 months (post-intervention), and 12 months. The primary outcomes are health-related quality of life (EQ-5D-5 L) and daily step count (measured by accelerometer) assessed immediately after the 6-month intervention. Secondary outcomes include whether intervention effects are sustained at 12 months, along with markers of physical fitness (cardiorespiratory fitness, body composition, handgrip strength), physical activity and sedentary behavior (accelerometry), and sleep (home-based sleep test, actigraphy, and validated questionnaires). Additional self-reported outcomes will cover diet, mental wellbeing, motivation, quality of life, and psychological constructs related to health behavior change. A qualitative component will explore barriers and facilitators to adherence through semi-structured interviews. DISCUSSION: This trial will evaluate whether adding a sleep component to a lifestyle intervention improves quality of life and physical activity levels in inactive adults. If effective, the findings will support the integration of sleep into multi-behavior interventions to enhance health outcomes and inform future public health strategies. TRIAL REGISTRATION: Clinical Trials NCT06424847.