Day and night shift schedules are associated with lower sleep quality in Evening-types

Abstract

Eveningness has been suggested as a facilitating factor in adaptation to shift work, with several studies reporting evening chronotypes (E-types) as better sleepers when on night shifts. Conversely, eveningness has been associated with more sleep complaints during day shifts. However, sleep during day shifts has received limited attention in previous studies assessing chronotypes in shift workers. Environmental light exposure has also been reported to differ between chronotypes in day workers. Activity is also known to provide temporal input to the circadian clock. Therefore, the aim of this study was to compare objective sleep, light exposure and activity levels between chronotypes, both during the night and day shifts. Thirty-nine patrol police patrol officers working on a fast rotating shift schedule (mean age ± SD: 28.9 ± 3.2 yrs; 28 males) participated in this study. All subjects completed the Morningness-Eveningness Questionnaire (MEQ). Sleep and activity were monitored with actigraphy (Actiwatch-L; Mini-Mitter/Respironics, Bend, OR) for four consecutive night shifts and four consecutive day shifts (night work schedule: 00:00 h-07:00 h; day work schedule: 07:00 h-15:00 h). Sleep and activity parameters were calculated with Actiware software. MEQ scores ranged from 26 to 56; no subject was categorized as Morning-type. E-types (n = 13) showed significantly lower sleep efficiency, longer snooze time and spent more time awake after sleep onset than Intermediate-types (I-types, n = 26) for both the night and day shifts. E-types also exhibited shorter and more numerous sleep bouts. Furthermore, when napping was taken into account, E-types had shorter total sleep duration than I-types during the day shifts. E-types were more active during the first hours of their night shift when compared to I-types. Also, all participants spent more time active and had higher amount of activity per minute during day shifts when compared to night shifts. No difference was found regarding light exposure between chronotypes. In conclusion, sleep parameters revealed poorer sleep quality in E-types for both the night and day shifts. These differences could not be explained by sleep opportunity, light exposure or activity levels. This study challenges the notion that E-types adapt better to night shifts. Further studies must verify whether E-types exhibit lower sleep quality than Morning-types.

Night Shift Work, Chronotype, Sleep Duration, and Prostate Cancer Risk: CAPLIFE Study

“…As previously mentioned, it has been proposed that a better alignment of chronotype with rotating or night shift work may lead to less circadian disruption, and hence influence the association between PCa and night shift work [ 42 ]. Furthermore, evening types have been thought to adapt better to night shifts; however, evening types have also been shown to have poorer sleep quality for both day and night shifts [ 56 ]. This may explain our findings of an increased risk in those with an evening chronotype.…”

Efeito da rotação dos turnos de trabalho sobre o desempenho psicomotor: um estudo prospectivo e observacional sob condições de vida real

“…Thus, even when exposed to a wide range of schedules imposed by the rotating shift work, this group presented few oscillations in relation to the measured variables, which is probably explained by the better adaptability of the intermediate chronotype in in most of the working hours of this schedule, especially to work during the day and in evening shifts. Schmidt et al, (2012) and Martin et al, (2015) studies highlighted that workers with intermediate chronotype showed a better adaptationas less misalignment and loss displacement of sleep -both for morning shifts and night shifts compared to evening chronotypes (Martin et al,2015), as we found in this study. Previous studies have also suggested that workers with evening chronotypes tend to tolerate better night shifts and morning individuals present a higher level of circadian misalignment when submitted to night work schedules (Juda, Vetter and Roenneberg, 2013).…”

“…O efeito isolado do trabalho em turnos sobre a vigilância psicomotora e sua interação com variáveis que conhecidamente deterioram o estado de alertacomo a obesidade e o cronotipo do indivíduo (MARTIN et al, 2015) tem sido pouco explorado na literatura. Sabe-se que indivíduos obesos tendem a apresentar valores de tempo de reação mais vagarosos e um maior número de lapsos de atenção ao longo do rodízio.…”

“…Acreditase que os intermediários tendem a apresentar uma melhor performance psicomotora em programas com rodízio de turnos. Porém, diante da diversidade dos programas, os quais impactam diretamente na performance psicomotora, é necessário cautela e mais estudos para tais afirmações (MARTIN et al, 2015) (SCHIMIDT et al, 2012) (REINK et al, 2015.…”

Significance of early morning insomnia for keeping the work continuity of shift workers

“…The reason of this phenomenon is unclear. However, considering that early morning awakening is one of cardinal symptoms of shift work disorder [5], workers with eveningness chronotype are possibly prone to have shift work disorder based on their low stability of sleep schedule [6,7]. In other words, although short-term adaptation of shift work increases along with the greater tendency toward eveningness, eveningness chronotype does not necessarily lead to long-term continuity of shift work.…”