Ambulatory circadian monitoring (ACM), a complementary tool in sleep medicine

Abstract

In developed societies it is common to suffer from sleep disorders due to primary alterations in the circadian system (CS). Moreover, sleep disorders lead to CS disturbances, thus diagnosis and treatment of circadian and sleep disorders should not be addressed separately. The aim of this work is to present the ambulatory circadian monitoring (ACM) and its utility for sleep medicine. To this, wrist temperature (T), motor activity (A), body position (P), light exposure (L) and environmental temperature (ET) were monitored in subjects suffering from different sleep pathologies. Eight healty volunteers and eight patients, attending to two sleep clinics3,4, with different pathologies (SHAOS, ASP, DSP, free-running rhythm, short sleeper, aging and menopause), participated in this study. Volunteers were subjected to ACM during a week using a multichannel device (KronowiseTM, Chronolab, Univ. of Murcia) integrating five sensors: three built into a wristwatch (T, L, ET) and two on a bracelet (A and P). Sleep-wake states were inferred using the integrated variable TAP and Circadianware software (Chronolab, Univ. Murcia). Rhythmic and sleep analysis were performed by non- parametric, Fourier and periodogram analysis. Circadian robustness was assessed by the circadian function index (CFI) calculated from rhythm stability, fragmentation and amplitude of TAP variable. Polygraphic representation of variables recorded by ACM allowed the differentiation of sleep pathologies. Accurate circadian phase estimation, and thus, ASP and DSP detection, was determined using the L5 timing (the five consecutive hours of minimum TAP). SHAOS was associated with impaired T rhythm, together with increased A during the five consecutive hours of minimum activity (L5). Sleep pathologies can be discriminated by biphasic representation of CFI and one index of sleep depth, (L5 for A or TAP). Patient with SHAOS, DSP and free-running sleep, suffered from chronodisruption (dissociation between T and A, P and sleep rhythms). The ACM allows a reliable assessment of CS status and the detection of sleep pathologies, particularly abnormal sleep phase and non-deep and fragmented sleep, such occurs in SAHOS, insomnia, and hot flushes. The proposed procedure contributes to an integrated diagnosis and treatment for sleep and circadian disorders in sleep clinics. Study supported by RETICEF (RD12/0043/0011), MINECO (BFU2010-21945-C02-01), TIN2009-14372-C03–01 to MC and INNPACTO (IPT-2011-0833-900000) to JAM.