Sleep characterization — a marker of metabolic health: actigraphy data

Visceral obesity is a key component of metabolic syndrome and has a significant influence on the reduction of life expectancy. We considered key sleep characteristics recorded by actigraphy as the main risk factors of obesity development. Objective. To study the sleep characteristics and its correlation with metabolic risk progression in subjects with obesity. Materials and methods. A comparative one-time single-center study including women with I degree of obesity (WHO) (n=80) comparable by age — 43.61±2.57 years was carried out. An assessment of anthropometric parameters and lipid metabolism indicators was performed on the basis of multidisciplinary clinic of Tyumen State Medical University. Patients were divided into 2 groups depending on the value of waist circumference/height (WC/height): the 1st group — WC/height<0.6 cm which corresponds to «absence of high metabolic risk», the 2nd group — WC/height ≥0.6 cm that is «high metabolic risk». PSQI (Pittsburgh sleep quality index for the last month) questionnaire of all participants was carried out and actigraphy was performed to assess sleep characteristics. Additionally, the parameters of circadian rhythms of body and wrist skin temperature were evaluated. Melatonin concentration in saliva was examined in all patients using Sunrise Bio-Rad («Bio-Rad Laboratories, Inc.», USA) apparatus. Statistical data processing was conducted using IBM SPSS Statistics, 26.0.0.1 version («IBM Corporation», USA). Results. WC/height index was 0.56±0.02 cm in the 1st group (n=32), while the 2nd group subjects (n=48) had a higher risk — 0.60±0.03 cm, p=0.001. The results of the questionnaire corresponded to the main parameters defined by actigraphy in both groups, however longer wake time after sleep onset (WASO) was in the 2nd group subjects. At the same time, negative correlations between sleep duration and WC increase (r=–0.663, p=0.001), increase of triglyceride (r=–0.378, p=0.001) and low-density lipoproteins (r=–0.245, p=0.001) levels in blood plasma were found. Additional factors confirming circadian desynchronization in the 2nd group subjects were decrease of wrist skin temperature (36.28±0.04 °C) and lower concentration of melatonin level at secretion peak (at 3:00 a.m.) compared to the 1st group subjects (6.27 [2.79; 10.67] pg/ml and 8.70 [5.46; 14.11] pg/ml, respectively). Conclusion. The sleep characteristics studied by us according to the actigraphy data (duration less than 7 hours, reduction of sleep efficiency less than 80%, long episodes of wake time after sleep onset) are the key parameters of «sleep-wake» cycle disorder and along with circadian disorders of body and wrist skin temperature may be early predictors of metabolic abnormalities in women with I degree of obesity.