Shift workers experience chronic circadian misalignment, which can manifest itself in reduced melatonin production, and has been associated with metabolic disorders. In addition, chronotype modulates the effect of night shift work, with early types presenting greater circadian misalignment when working night shift as compared to late types. Melatonin supplementation has shown positive results reducing weight gain in animal models, but the effect of exogenous melatonin in humans on body weight in the context of shift work remains inconsistent. The aim of this study was thus to evaluate the effects of exogenous melatonin on circadian misalignment and body weight among overweight night shift workers, according to chronotype, under real-life conditions. We conducted a double-blind, randomized, placebo-controlled, crossover trial where melatonin (3 mg) or placebo was administered on non-night shift nights for 12 weeks in 27 female nurses (37.1 yo, ±5.9 yo; BMI 29.9 kg/m², ±3.3 kg/m²). Melatonin (or placebo) was only taken on nights when the participants did not work night shifts, that is, on nights when they slept (between night shifts and on days off). Composite Phase Deviations (CPD) of actigraphy-based mid-sleep timing were calculated to measure circadian misalignment. The analyses were performed for the whole group and by chronotype. We found approximately 20% reduction in circadian misalignment after exogenous melatonin administration considering all chronotypes. Moreover, melatonin supplementation in those who presented high circadian misalignment, as observed in early chronotypes, reduced body weight, BMI, waist circumference, and hip circumference, without any change in the participants’ calorie intake or physical activity levels.

中文翻译：

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外源性褪黑激素可减少早期类型的昼夜节律失调和体重

轮班工人会经历慢性昼夜节律失调，表现为褪黑激素分泌减少，并与代谢紊乱有关。此外，睡眠类型会调节夜班工作的影响，与晚班类型相比，早班类型在夜班工作时表现出更大的昼夜节律失调。在动物模型中，补充褪黑激素已显示出减少体重增加的积极效果，但在轮班工作的情况下，外源性褪黑激素对人类体重的影响仍然不一致。因此，本研究的目的是根据现实生活条件下的时间类型，评估外源性褪黑激素对超重夜班工人昼夜节律失调和体重的影响。我们进行了一项双盲、随机、安慰剂对照、交叉试验，其中 27 名女护士（37.1 岁，±5.9 岁；BMI 29.9 kg/ m ²，±3.3 kg/m ²）。褪黑激素（或安慰剂）仅在参与者不上夜班的晚上服用，即在他们睡觉的晚上（夜班和休息日之间）服用。计算基于体动记录仪的睡眠中期时间的复合相位偏差（CPD），以测量昼夜节律失调。分析是针对整个群体并按时间类型进行的。我们发现，考虑到所有生物钟类型，给予外源性褪黑激素后，昼夜节律失调减少了约 20%。此外，对于那些昼夜节律高度失调的人（如早期生物钟类型中观察到的那样），补充褪黑激素可以降低体重、BMI、腰围和臀围，而参与者的卡路里摄入量或体力活动水平没有任何变化。