It’s 6am again. The unrelenting tone from your bedside table reminds you it’s time to roll out of your duvet cocoon and get ready to face the working world. You swat your shrieking phone as it gets louder and more persistent. A quick swipe of the screen and you notice the day. It’s Friday.
A relieved smile spreads across your face.
Well, at least tomorrow means a lie-in.
The typical working week for most will involve dragging ourselves out of our warm, cosy beds and forcing our legs to make the long cold trek to the bathroom. Yet, we know that come the weekend we will be able to catch up, even briefly, on the sleep denied to us during the week. Although we will moan to friends and colleagues, our society seems perfectly content with depriving ourselves of sleep during the working week only to catch it up during the weekend. We would likely prefer a few minutes (or hours) more in the morning, but many of us don’t consider this practice as detrimental to our health. The shift from short to long sleep is considered a part of life.
This is far from sensible as the effects of sleep deprivation are well known, even if you don’t spend your days buried in journals with helpful names such as ‘Sleep’.
There is a name (there always is) for the shifting of sleep patterns throughout the working week – social jet lag. This refers to the changes in our sleep timing and duration depending on when we’re working (e.g. sleeping less on workdays and more on free days), and how this can confuse our internal clocks which try to keep our sleep patterns regular and predictable. These are the same internal clocks which influence whether you are an owl or a lark – an evening or morning person. This misalignment affects people differently, and it is not hard to see why night owls, who want to sleep later and wake up later, may suffer more.
Social jet lag is a problem for society. It is associated with depression, an increased risk for heart disease, more frequent smoking, and increased stimulant use in general. Understandably, the effects seen from sleep deprivation, including difficulties in concentration, memory, social functioning and mood, are also associated with social jet lag.
Despite the mental and physical health issues reported, the available data had been largely correlational. This makes it hard to draw definite conclusions on whether society’s current schedule of sleep is bad for us in the long-term.
However, a recent study published earlier this year has attempted to address this. A team of researchers at the University of Harvard sought to understand whether repetitive patterns of sleep restriction and catch-up sleep have a negative impact on our health and wellbeing, or whether we may simply get used to it.
More specifically, they wanted to try to work out whether there is a difference in our own subjective view of this sleep pattern and how our body, behind the scenes, might respond in terms of stress and immune functioning. Do we adapt to the sleep loss in both domains? Previous evidence suggested we might not but this hadn’t been convincingly tested over a long period until now.
To assess these questions, they recruited 14 participants who were studied in a controlled hospital setting over three weeks. During each week, the participants spent 5 days sleeping for 4 hours and 2 days sleeping for 8 hours. After a few months, the same participants were invited back to conduct the same experiment sleeping for 8 hours each day over the 25-day experiment. The results of each were compared to try to understand the impact of the working week’s sleep patterns.
The group asked participants about how sleepy they felt, their perceived effort to do anything, and how stressed they felt each day at 4 hour intervals throughout the study. Alongside this, objective measures of stress and immune functioning were also assessed via blood samples collected on 7 of the 25 study days. Specifically, they looked at the levels of a chemical messenger of the immune system known to promote inflammation, interleukin-6, and the levels (total and stability) of cortisol, a hormone released in response to stress (amongst other factors).
The participants’ diet and exercise were controlled to reduce the impact of these variables, and they could have visitors to reduce the impact of isolation, and deviation from normal routines, where possible.
So, what did they find?
Over the three weeks, when participants were restricted to only 4 hours’ sleep they (unsurprisingly) felt sleepier and reported a greater effort to do anything compared to when than when they could sleep for 8 hours (e.g. during the weekend in the restricted condition and every day for the control condition). Interestingly, the ‘effort to do anything’ ratings became increasingly similar for the restricted and control condition over the three weeks, and participants reported no extra stress when asked to halve their sleep to 4 hours for the restriction condition. Overall, this suggests that participants, although sleepy, were subjectively fine with the simulated typical work sleep pattern. There was even evidence that participants started to adapt as their reported effort to carry out tasks diminished by the third week of only 4 hours sleep.
By contrast, the objective results showed a less optimistic picture. The researchers found an increased dysregulation of cortisol as the weeks of sleep restriction went on, and an increase in morning cortisol compared to the control condition. However, both returned to normal following recovery sleep at the weekends. In terms of immune system functioning, unstimulated IL-6 levels were significantly higher for the first week of sleep restriction and then remained elevated but non-significantly so compared to the control condition. For the stimulated IL-6 levels, these were significantly elevated during the week for the second and third week of the restriction condition compared to the control.
These results highlight that although participants seemed to be no more stressed subjectively in depriving themselves of sleep during the week, it seems that this pattern of sleep was not something the body simply ‘gets used to’. Instead it seems that the body still shows an increase in the inflammatory marker IL-6, increased cortisol upon awakening, increased dysregulation of cortisol, and inhibition of IL-6 in the presence of cortisol-like molecule. This hints at a heightened stress and immune response which, importantly, does not appear to adapt to the effects of chronic sleep loss during the week. Although recovery sleep during the weekend mitigated this effect somewhat, there was some evidence to suggest that two days was not enough to return immune functioning (stimulated IL-6) back to normal.
You may be thinking that increases in IL-6 and increased inhibition of IL-6 seem counter-intuitive, but the authors had a potential explanation. They highlighted that this may be the product of a particularly active immune response following chronic sleep to deal with its physiological effects (i.e. the increased sensitivity to cortisol’s effect is lessened due to a need to remove toxins built up in the brain).
In addition, you may also want to argue that 4 hours sleep during the week is hardly typical of most people’s work schedule, and that this experiment is far from representative of real life. However, this is a weak argument as the effects of sleep deprivation have already shown to be cumulative. It is more likely that losing an hour or two during the workday has negative effects but over longer periods than are suggested by this study.
So, it seems that even though we may consider depriving ourselves of sleep during the week manageable, and even get used to it, the same cannot be said for our body. This study suggests that we don’t get used to sleep loss during the working week. Moreover, recovery sleep during the weekends may not be enough to compensate for a week of fighting our internal clocks.
Although this study only examined a small number of people and a small number of specific measures, it still highlights the persistent effects of restricted sleep on our immune and stress systems. It also provides some hints as to how we may be able to successfully convince ourselves that this pattern of sleep is not detrimental to our health. If we feel subjectively okay, if not slightly lethargic, about this lifestyle then there would be no immediate drive to change it – at an individual or society level.
Granted, necessity and an inability to pay the bills may also be powering this too…
Rutters, F., Lemmens, S. G., Adam, T. C., Bremmer, M. A., Elders, P. J., Nijpels, G., & Dekker, J. M. (2014). Is social jetlag associated with an adverse endocrine, behavioral, and cardiovascular risk profile?. Journal of biological rhythms, 0748730414550199.
Simpson, N. S., Diolombi, M., Scott-Sutherland, J., Yang, H., Bhatt, V., Gautam, S., … & Haack, M. (2016). Repeating patterns of sleep restriction and recovery: Do we get used to it?. Brain, Behavior, and Immunity.
Van Dongen, H. P., Maislin, G., Mullington, J. M., & Dinges, D. F. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. SLEEP-NEW YORK THEN WESTCHESTER-, 26(2), 117-129.
van Leeuwen, W. M., Lehto, M., Karisola, P., Lindholm, H., Luukkonen, R., Sallinen, M., … & Alenius, H. (2009). Sleep restriction increases the risk of developing cardiovascular diseases by augmenting proinflammatory responses through IL-17 and CRP. PloS one, 4(2).