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Introduction Since there is less movement during sleep than during wake, actigraphy permits to indirectly evaluate the sleep-wake cycle. In general, actigraphs are placed on the wrist and based on acceleration. In this validation study, we propose an alternative way of actigraphy at the level of the arm and expressed as change of degrees per minute. Its accuracy for phase prediction and for evaluating the sleep-wake cycle is assessed by comparing with the DLMO and sleep logs, respectively. Materials and methods In this study, subjects (N = 13) went about their daily routine for 7 days, kept daily sleep logs and wore ambulatory monitoring devices. These devices measured skin temperature at wrist level (WT), motor activity (Arm Activity, AA) and body position (P) on the arm and acceleration at wrist level (Wrist Acceleration, WA). Cosinor, non parametric and Fourier analysis were performed using AA and WA methods, and the results were compared by ANOVA test. Linear correlations were also performed between both methods and WT. DLMO was used to compare and correlate with estimated phase markers. Results Only mesor, RA (relative amplitude), VL5 and VM10 (value for the five and ten consecutive hours of lower and maximum activity, respectively) showed significant differences when estimated by both methods. The remaining parameters were not significantly different between both methods and all correlations between AA and WA were high. However, when phase markers were correlated with DLMO, acrophase, M10 and L5 (timing for the ten and five consecutive hours of highest and lowest activity, respectively) for AA showed a high correlation, while for WA, only acrophase did. Regarding sleep detection, WA showed higher specificity than AA, while the agreement rate and sensitivity were higher for AA. Conclusion An alternative actigraphy method (AA) can be used to evaluate more accurately sleep-wake and motor activity-rest rhythm than conventional actigraphy, since this alternative is more sensitive and presents higher agreement rate for detecting sleep. Besides, it estimates better the phase according to its correlation with the “gold standard” for phase detection: DLMO. Acknowledgements Study supported by Instituto de Salud Carlos III, RETICEF (RD12/0043/0011), MINECO (BFU 2010-21945-C02-01 and IPT-2011-0833-900000) with FEDER cofunding to JAM, and a research fellowship to MABC (FPU2009-1051). We thank Stockgrand Ltd. for melatonin assay reagents. DJ Skene is a Royal Society Wolfson Research Merit Award holder.

Introduction It is important to develop a system able to detect the endogenous circadian phase easily, since current techniques imply either expensive hormonal quantification or uncomfortable monitorization of central temperature by rectal probes. Materials and methods In this work, a new ambulatory circadian monitoring system (ACM) was validated. To this, activity and position, wrist temperature rhythm as well as light exposure pattern were recorded for 10 days in 13 healthy subjects, thanks to an actimeter on the arm, a temperature sensor on the ventral side of the wrist and a pendant luxometer. DLMO was determined in saliva, and it was used as “the gold standard” to evaluate the accuracy of ACM to assess the circadian phase. Besides, subjects completed a sleep log and Horne-Ostberg morningness–eveningness, Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale questionnaires to evaluate diurnal preference and its influence in sleep quality. Results The peripheral wrist temperature increase in the evening (and its new indexes WTOnset or WTOn and WT increase onset or WTiO) anticipated that of melatonin; while the decrease in motor activity, position and the composite variable TAP (including wrist temperature, activity and position), and the increase in sleep probability occurred after the increase in melatonin levels. The score of morningness–eveningness and sleep quality questionnaires showed high correlations with DLMO, confirming that the later the DLMO occurs higher eveningness and worse sleep quality are reported. Conclusion This ambulatory method allows accurately detecting the circadian phase while subjects maintain their normal life style. The proposed new phase markers based on wrist temperature rhythm (named WTOn and WTiO) would be appropriate in Clinics when it is important to know the subject circadian phase, like in cancer chronotherapy or light therapy. Acknowledgements Study supported by Instituto de Salud Carlos III, RETICEF (RD12/0043/0011), MINECO (BFU 2010-21945-C02-01and IPT-2011-0833-900000) with FEDER cofounding to JAM, and a research fellowship to MA Bonmati-Carrion (FPU2009-1051). We also thank Stockgrand Ltd. (UK) for the melatonin assay reagents. DJ Skene is a Royal Society Wolfson Research Merit Award holder.