Adiposity and body mass index of young women are associated with altered 24-hour profile of wrist temperature and sleep quality

Sleep alterations are linked to circadian disturbances; however, these variables are also related with adiposity, which could impair the study of the previous relationship. Here, we investigated whether the association between adiposity and impaired circadian health is independent of sleep and circadian related variables in a sample of young women. One hundred ninety-two women (18–30 years of age) participated in this cross-sectional study. To evaluate circadian rhythmicity, subjects wore a temperature sensor for six consecutive days, and variables related with the amplitude and stability of the rhythm were calculated. We also assessed adiposity markers (body mass index [BMI], fat mass, waist, and hip circumference), sleep and circadian variables (sleep schedules and quality, social jet lag, and chronotype), energy intake, and physical activity. Partial correlations were conducted to test the associations between circadian and sleep-related variables with adiposity markers. Results showed the circadian pattern of temperature clearly depended on BMI and, to a lesser extent, on sleep variables. Specifically, we showed that higher adiposity was significantly associated with lower amplitude, percentage of variance explained by the rhythm, and intradaily variability and L10 values of the temperature 24 h rhythm. Furthermore, sleep quality was the only variable significantly related with both adiposity and circadian pattern of wrist temperature, while social jet lag and chronotype were only associated with the circadian pattern of temperature. Therefore, we consider BMI should be taken into account when sleep health or disturbances are studied by means of circadian rhythm analyses.

睡眠异常与昼夜节律紊乱（circadian disturbances）密切相关；然而，上述变量同时也与体脂蓄积（adiposity）存在关联，这可能会干扰前述两者关联的研究。本研究以年轻女性群体为样本，探讨体脂蓄积与昼夜节律健康受损之间的关联是否独立于睡眠及昼夜节律相关变量。本横断面研究共纳入192名年龄在18~30岁之间的女性受试者。为评估受试者的昼夜节律性（circadian rhythmicity），研究人员让其连续6天佩戴腕部温度传感器，并计算与节律振幅及稳定性相关的各项指标。本研究同时评估了多项体脂指标，包括体质量指数（body mass index, BMI）、体脂量、腰围及臀围，以及睡眠与昼夜节律相关变量（睡眠节律与睡眠质量、社交时差（social jet lag）及睡眠时型（chronotype））、能量摄入情况与身体活动水平。采用偏相关分析（partial correlations）检验昼夜节律及睡眠相关变量与体脂指标之间的关联。研究结果显示，体温的昼夜节律模式明显受体质量指数的影响，且在较小程度上受睡眠变量的影响。具体而言，本研究发现，较高的体脂蓄积水平与更低的节律振幅、节律所解释的方差百分比、体温24小时节律的日内变异性（intradaily variability）以及L10值显著相关。此外，睡眠质量是唯一同时与体脂蓄积及腕部体温昼夜节律模式显著相关的变量，而社交时差与睡眠时型仅与体温昼夜节律模式存在关联。因此，本研究认为，当通过昼夜节律分析开展睡眠健康或睡眠异常相关研究时，应将体质量指数纳入考量因素。