A Royal Society of Medicine Meeting Review by April Cashin-Garbutt, MA (Cantab)
Sleep deprivation often hits the headlines and we are frequently told we need 8 hours a night. But how much sleep do we really need? Are we sleeping less than we used to and is today's society really sleep deprived? A recent meeting at the Royal Society of Medicine aimed to answer these questions.
Historian Professor Roger Ekirch, Virginia Polytechnic Institute and State University, USA, reminded us that never before in human history should we be sleeping more soundly. Ekirch recounted the multiple ways in which sleep prior to modernity was highly vulnerable to disruption including bedding rife with house mites; frigid temperatures in poorly insulated buildings; and fear of demons and also of the peril of fire.
And so while we have every reason to think our sleep has never been better, we seem to have increasing complaints of fatigue and insomnia, in particular, middle-of-the-night insomnia. But is this really a new phenomenon?
The compressed, consolidated pattern of sleep is actually less than two centuries old. Previously most families experienced a broken pattern of sleep, with 'first sleep' from ~9pm until midnight, an hour or so awake followed by a 'second sleep'. This biphasic pattern was rarely viewed in a negative way.
The evolution into our modern consolidated sleep pattern was something that occurred over the 19th century, a time of dramatic change with reform movements and the increasing prevalence of artificial illumination.
Ekirch argued that perhaps people that suffer from the middle of the night insomnia may actually be undergoing this older pattern of sleep and patients should be relieved of anxiety and their insomnia should be better termed "wakefulness".
A similar theme was explored by Dr Catherine Coveney, University of Sussex, who discussed the pharmaceuticalisation of today's sleep: the redefining of sleep behaviors as problems requiring pharmaceutical solutions. Dr Coveney quoted a number of different studies showing self-reported regular sleep durations including the Understanding Society initiative by the Economic and Social Research Council (ESRC), which showed:
- 12% sleep <6 hours
- 23% sleep for 6-7 hours
- 55% sleep for 7-9 hours
- 10% sleep 9+ hours
Coveney also shared people's expectations and experiences of sleep. The overwhelming consensus was that sleep was highly valued by participants but it was often considered a disposable luxury in our busy lifestyles. Surprisingly, 10% of those surveyed take sleep medications 3 or more nights per week.
But are we really sleeping less than we used to? There is no strong evidence for this according to Professor Jim Horne, University of Loughborough. Horne explained how society has changed its attitudes towards insomnia and it is now more socially acceptable to talk about being sleepy. Although it is important to distinguish between ‘tiredness’, which can have many meanings, including fatigue boredom etc., and ‘sleepiness’, the likeliness of falling asleep.
In addition, there is a difference between need and desire for sleep. In the same way we can eat when we're not hungry, we can also sleep for pleasure.
So how do we know where the line is between need and desire? Well firstly it's important to understand why we need sleep. Professor John Groeger, University of Hull, outlined the two main functions: for protection and preparation; and recovery and restoration.
Professor Franco Cappuccio, University of Warwick, outlined the potential negative consequences of insufficient sleep, defined as fewer than 5-6 hours a night. He discussed the 50% increased risk of developing obesity in short sleepers, however there are difficulties with determining whether this association is causal in nature.
Despite these challenges, one thing that is increasingly being realized is that poor sleep, both in terms of quality and quantity, has negative consequences for physical, mental and performance risk. Professor Derk-Jan Dijk, University of Surrey, explained how social jetlag, the difference in wake time on weekdays to weekends, is arising due to social constraints and also increasing exposure to artificial light in the evenings.
Through mathematical modeling Dijk and team have shown that delaying social cues such as pushing back work and school start times, while an initial help for a week, would not work as a remedy long term as our body clocks would then readjust to the later start times. Other potential solutions include limiting your exposure to artificial light in the evenings and also offsetting this by getting more nature light exposure in the day, for the effects of evening light become stronger if you see less daylight.
There are also genetic differences in our clock speed: 75% of people have clock speeds of 24 hours or more and 25% have clocks under 24 hours. This could explain the difference between night owls and early birds, as the former are always fighting against a body clock that’s pushing later and the latter are doing the opposite.
In conclusion, whether or not we’re more sleep deprived than we used to be can be debated, but it is clear that, despite an average of 7-8 hours per night, we are more out of sync with our natural light-dark cycle than we’ve ever been.