Abstract
STUDY OBJECTIVES: Dim light melatonin onset (DLMO) is the best-established marker of central circadian phase and may contribute to unraveling the role of the circadian system in obesity. This study evaluated DLMO among individuals with obesity using a home-based assessment and explored its clinical correlates and procedural variations. METHOD: Fifty-eight women (mean [SD] age 40.9 [7.8] years) and body mass index (41.4 [6.6] kg/m(2)) completed a home-based DLMO assessment, measures of sleep quality, diurnal preference, and cardiometabolic parameters. Procedural variations we explored included individualized versus standardized DLMO thresholds, 7 versus 3 days assessment of sleep onset timing (SOT), as well as diary-based, actigraphy-based, or a "combined" method to calculate SOT, and hourly versus half-hourly saliva sample data points. Correlation coefficients and univariate ANOVA models were used for statistical analysis. Bland-Altman plots were used to inform agreement between methods. RESULTS: DLMO was detected in 98.2% and 89.6% of participants using an individualized or a standardized threshold, respectively. DLMO correlated with SOT but not with body mass index, cardiometabolic parameters, sleep quality, or diurnal preference. A later SOT and a larger phase angle of entrainment (DLMO-SOT) correlated with younger age and with eveningness. Most procedural alternatives showed good agreement with the original methods. CONCLUSIONS: Home-based assessment yielded a high rate of detectable DLMO in women with obesity. Diurnal preference was not correlated with central circadian phase, suggesting that other factors (e.g. behavioral, sociodemographic) may be relevant in chronotype assessment in this population. We offer implications for future research including procedural variations to consider.