Abstract Introduction Circadian timing and sleep alignment have been linked to metabolic dysfunction, yet few studies have examined whether within-person annual changes in dim light melatonin onset (DLMO) and alignment influence metabolic outcomes. This study examined whether annual change in DLMO timing and alignment predicted changes in metabolic markers Methods In this secondary analysis participants aged 18-65 with BMI 25 (N = 89) completed two annual assessments including DLMO, 7-day actigraphy, and metabolic measurements (body fat %, BMI, waist–hip ratio, A1C). Circadian alignment was calculated as the duration between DLMO to sleep onset. Annual change variables were computed as Visit 5 (12-month follow-up) minus baseline. Baseline associations between DLMO and alignment were examined via linear regression. Additional linear regression models tested whether annual changes in DLMO and alignment predicted one-year changes in adiposity and A1C, adjusting for age and sex. Results Participants (age 35.31 ± 9.76 years; 48.2% female) demonstrated an average DLMO shift of –0.35 minutes (SD = 50.5 minutes), indicating essentially no overall delay or advance in circadian phase across 12 months. In contrast, circadian alignment shifted earlier by an average of –1.04 hours (SD = 1.29 hours), reflecting earlier sleep timing relative to circadian phase. Annual change in alignment was initially associated with one-year BMI change; however, the association was not robust and became non-significant after removal of a high-influence observation. Annual change in DLMO did not significantly predict changes in BMI, waist–hip ratio, A1C, or body fat %. In the body fat model, sex (B = –1.71, p = .029) and age (B = –0.09, p = .029) were significant predictors. Conclusion Circadian timing and sleep–circadian alignment were closely related at baseline, and annual alignment shifts were associated with one-year BMI change. However, annual changes in circadian phase and alignment did not consistently predict other metabolic markers. These findings suggest that sleep–circadian alignment may play a role in weight trajectories, although further research is required to clarify these associations. Support (if any) Study was supported by the National Institute on Minority Health and Health Disparities (R01ND018517).
Medina-Poeliniz et al. (Fri,) studied this question.