Differences in Daily Rhythms of Wrist Temperature Between Obese and Normal-Weight Women: Associations With Metabolic Syndrome Features

Abstract

The circadian rhythm of core body temperature is associated with widespread physiological effects. However, studies with other more practical temperature measures, such as wrist (WT) and proximal temperatures, are still scarce. The aim of this study was to investigate whether obesity is associated with differences in mean WT values or in its daily rhythmicity patterns. Daily patterns of cortisol, melatonin, and different metabolic syndrome (MetS) features were also analyzed in an attempt to clarify the potential association between chronodisruption and MetS. The study was conducted on 20 normal-weight women (age: 38 ± 11 yrs and BMI: 22 ± 2.6 kg/m²) and 50 obese women (age: 42 ± 10 yrs and BMI: 33.5 ± 3.2 kg/m²) (mean ± SEM). Skin temperature was measured over a 3-day period every 10 min with the “Thermochron iButton.” Rhythmic parameters were obtained using an integrated package for time-series analysis, “Circadianware.” Obese women displayed significantly lower mean WT (34.1°C ± 0.3°C) with a more flattened 24-h pattern, a lower-quality rhythm, and a higher intraday variability (IV). Particularly interesting were the marked differences between obese and normal-weight women in the secondary WT peak in the postprandial period (second-harmonic power [P2]), considered as a marker of chronodisruption and of metabolic alterations. WT rhythmicity characteristics were related to MetS features, obesity-related proteins, and circadian markers, such as melatonin. In summary, obese women displayed a lower-quality WT daily rhythm with a more flattened pattern (particularly in the postprandial period) and increased IV, which suggests a greater fragmentation of the rest/activity rhythm compared to normal-weight women. These 24-h changes were associated with higher MetS risk. (Author correspondence: [email protected])

Keywords:

• Abdominal obesity
• Circadian
• Core temperature circadian rhythm
• Cortisol
• Melatonin
• Metabolic Syndrome
• Obesity
• Skin temperature

ACKNOWLEDGMENTS

This work was supported by the Government of Education, Science and Research of Murcia (Project BIO/FFA 07/01-0004) and the Spanish Department of Science and Innovation (project AGL2008-01655/ALI) National Heart, Lung, and Blood Institute grant HL-54776, National Institute of Diabetes and Digestive and Kidney Diseases grant DK075030, and contracts 53-K06-5-10 and 58-1950-9-001 from the US Department of Agriculture. Teresa Hernandez and Ana Espallardo are acknowledged for their previous work in the initial part of this study.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.