# Actimetry-Derived 24 h Rest-Activity Rhythm Indices Applied to Predict MCTQ and PSQI
###### Abstract  
The aim of this study was to identify wrist actimetry-based indices associated with the sleep-wake rhythm characteristics of healthy individuals. The study involved 79 healthy subjects of both sexes (age range 15-62 years (mean: 21.5 \(\pm\) 9.6 years, women: 77.8%)). Each participant provided personal data, filled out two questionnaires, the Munich ChronoType Questionnaire (MCTQ) and the Pittsburgh Sleep Quality Index (PSQI), and wore a wrist actimeter for a week. A significant positive association of the chronotype with the mid-phase of the most active 10 h period (M10t: \(B=0.252\), \(p=0.015\)), the mid-phase of the least active 5 h period (L5t: \(B=0.338\), \(p=0.005\)), and the interdaily stability (IS: \(B=-0.021\), \(p=0.017\)) was noted, as well as the sleep duration with the M10t (\(B=-0.257\), \(p=0.003\)), L5t (\(B=-0.340\), \(p=0.001\)), and IS (\(B=0.042\), \(p=0.003\)). There was a significant association of social jetlag (\(B=0.320\), \(p=0.032\)) and sleep quality (\(B=0.990\), \(p=0.013\)) with motor activity in bed, as well as sleep efficiency with the acrophase (\(B=-0.043\), \(p=0.007\)). Nonparametric indices of the 24 h rest-activity rhythm are useful tools for assessing the sleep-wake rhythm of healthy individuals. wrist actimetry; the Munich ChronoType Questionnaire; the Pittsburgh Sleep Quality Index; 24 h rest-activity rhythm indices; sleep-wake rhythm characteristics +
Footnote †: journal:of this form of circadian misalignment. To solve this problem, additional research at a qualitatively higher level is required. The need for the further development of this area of chronobiology was assessed by one of the authors of the concept: _\"In fact, most studies investigating the associations between SJL and health are cross-sectional. Further longitudinal studies are needed not only to confirm causal associations but also to clarify under how much and for how long one needs to be exposed to SJL for its consequences to show\"_[9]. Based on the foregoing, there is a need to search for and put into practice objective indicators that make it possible to quantify the degree of circadian system misalignment. These methods should be fairly simple and inexpensive. It is important that these methods can be used in conditions as close to natural as possible. It is also important that they allow continuous recording of indicators for a significant amount of time to obtain a time series. Some progress has been made in this direction. A chronotype or phase of entrainment (MSFc) [2; 9] and SJL have been shown to correlate with the dim-light melatonin onset (DLMO) [17; 18; 19] and the cortisol awakening response (CAR) [20; 21; 22], indicators that have long been widely used to assess the state of the circadian system. However, the use of these indicators is difficult due to the high cost of consumables and the complexity of the analyses. There was also a correlation between SJL and the amplitude of the 24 h rhythm of the wrist temperature [23]. This method satisfies the above requirements as much as possible. One of its disadvantages is the fact that it only indirectly reflects the state of the circadian system; thus, it must be used in combination with other methods, such as wrist actimetry  
Currently, wrist actimetry is widely used to assess the state of the circadian system [24; 25; 26; 27; 28] and sleep function [29; 28]. An important advantage of the method is that it has been used to develop and test a wide range of indicators that have long been actively used in clinical practice [30; 31; 32]. Wrist actimetry is used to calculate parametric (Midline Estimating Statistic of Rhythm (MESOR), amplitude (_A_), and acrophase (\(\varphi\)) [33; 34]) and nonparametric (interdaily stability (IS), intradaily variability (IV), the least active 5 h period (L5) that is nocturnal activity, and the most active 10 h period (MI0) that is daily activity [30; 35; 31]) indices.