Abstract
The circadian clock governs virtually all processes in the human body, including sleep-wake behaviour. Circadian misalignment describes the off-set between sleep-wake cycles and clock-regulated physiology. This strain is predominantly caused by external (societal) demands including shift work, early school start times and fast travels across time zones. Sleeping at the ‘wrong’ internal time can jeopardise health and safety, and we therefore need a good quantification of this phenomenon. Here, we propose a novel method to quantify the mistiming of sleep-wake rhythms and demonstrate its versatility in day workers and shift workers. Based on a single time series, our Composite Phase Deviation method unveils distinct, subject- and schedule-specific geometries (‘islands and pancakes’) that illustrate how modern work times interfere with sleep. With increasing levels of circadian strain, the resulting shapes change systematically from small, connected forms to large and fragmented patterns. Our method shows good congruence with published measures of circadian misalignment (i.e., Inter-daily Stability and ‘Behavioural Entrainment’), but offers added value as to its requirements, e.g., being computable for sleep logs and questionnaires. Composite Phase Deviations will help to understand the mechanisms that link ‘living against the clock’ with health and disease on an individual basis.
Highlights
The circadian clock governs virtually all processes in the human body, including sleep-wake behaviour
Chronotype is calculated from mid-sleep on work-free days after evening shifts (MSFEsc), which interfere the least with circadian sleep times[24]
Composite Phase Deviations (CPD) density plots illustrate the extent of this misalignment between internal time and external time: increasing external strain progressively expands the CPD shape in all chronotypes until peripheral regions start to bud off the central shape (‘peninsulas’, panel c) and eventually form isolated islands under severe strain. These severe misalignments occur in extreme chronotypes in rotational shift work, where external strain increases to such an extent that sleep after the night shift and sleep before the morning shift becomes completely disconnected from their natural sleep-wake pattern (Fig. 4d)
Summary
The circadian clock governs virtually all processes in the human body, including sleep-wake behaviour. Circadian misalignment is especially pronounced in workers on rotational shifts and is thought to partly be responsible for their well-documented health problems (including obesity and diabetes[10,11,12,13], cardiovascular diseases[14,15,16], and different cancer types[17,18]) It is often defined as sleeping at the wrong circadian time, i.e., as desynchrony between sleep-wake behaviour and circadian physiology, such as rhythms of body temperature, melatonin and cortisol secretion. We show the potential scope and versatility of this method by using it in different populations, namely day and shift workers
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have