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密切相关，但上述两类变量同时亦与体脂水平存在关联，这可能会干扰二者原有关联的研究分析。本研究以年轻女性为研究队列，旨在探讨体脂与昼夜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名年龄介于18至30岁的女性受试者。为评估昼夜节律性，受试者连续6天佩戴体温传感器，并计算与节律振幅及稳定性相关的各项指标。本研究同时评估了体脂相关指标（体重指数（body mass index, BMI）、体脂量、腰围及臀围）、睡眠与昼夜节律变量（睡眠节律与睡眠质量、社交时差（social jet lag）及时型（chronotype））、能量摄入及体力活动水平。采用偏相关分析检验昼夜节律与睡眠相关变量同体脂指标之间的关联。研究结果显示，体温昼夜节律模式显著依赖于体重指数，且在较小程度上受睡眠变量影响。具体而言，本研究发现更高的体脂水平与更低的节律振幅、节律解释方差占比、体温24小时节律的日内变异度（intradaily variability）及L10值显著相关。此外，睡眠质量是唯一同时与体脂及腕部体温昼夜节律模式显著相关的变量，而社交时差与时型仅与体温昼夜节律模式存在关联。因此，本研究认为，通过昼夜节律分析研究睡眠健康或睡眠紊乱时，应将体重指数纳入考量因素。