Influence of shift-work schedule on circadian disruption in nursing staff

Introduction Many shift work schedules (SWS) have been proposed to promote performance and to reduce circadian impairment, however, few studies have been devoted to demonstrate the benefits of such shifts under real work conditions. The aim of this study was to characterize the impact of different SWS, on circadian disruption assessed by ambulatory circadian monitoring (ACM), in nursing staff. To this, wrist temperature (T), motor activity (A), body position (P), light exposure (L) and environmental temperature (ET) were recorded. Materials and methods Two hundred eighty-six healthy nursing staff (45 males and 241 females) enrolled in eight different SWS (Permanent 8 h-day, PD; Permanent night, PN; morning with nights, MN; evening with nights, EN; permanent 12 h-day, 12D; anti-stress, AS and rotating three-shifts, R3), from 22 to 62 years old, participated in this study. Volunteers were monitored by ACM during 7–10 days using a multichannel device (KronowiseTM, Chronolab, Univ. of Murcia). Circadian robustness was assessed by the circadian function index (CFI) of composite TAP variable. The regularity of life style was measured by calculating Interdaily stability (IS). Restfulness (RS), a measure of sleep quality, was calculated from L5 of TAP and expressed as a score from 0 to 10 (10 = very restfully sleep). As phase marker was selected the midpoint of TL5 from TAP (the midpoint of five consecutive hours of minimum values). Results The circadian status evaluation on nurses staff by ACM showed that those subject engaged in both PD and 12D shifts presents higher stability (IS) and RS scores than those subjects on PN, MN, EN and R3 schedules. However, the more disruptive shift seems to be PN, since nurses under this schedule show the lowest stability, CFI and RS values, besides presenting the most delayed TL5. The remaining shifts present an intermediate situation between PD and PN. Conclusion As expected, the two permanent day shifts (PD and 12D) are the less chonodisruptive, since nurses under this schedule present more robust and regular rhythms with deeper sleep during the night. On the contrary a PN shift produces higher rhythm instability and more superficial sleep. So according to our results when working during the night is a must rotating shifts (AS, R3) seems to be more recommendable than MN or EN. Acknowledgements To RETICEF (RD12/0043/0011), MINECO (BFU2010–21945-C02–01), and INNPACTO (IPT-2011–0833-900000) with FEDER cofounding to JAM.