Sleeping Soundly. Part 1.
Sleep is a vital component of many aspects of our health, yet for many people a good nights sleep is a rare luxury with studies suggesting that around 30% of the UK adult population are chronically sleep deprived.
Lack of quality sleep significantly affects our memory, our mood and our immune system. It restricts our bodies ability to heal and develop, all whilst playing havoc with our hormones.
Simply put, addressing our sleep quality is one of the most powerful ways we can transform our daily experience. Often it can feel like our sleep shortage is simply unavoidable, but there are several key factors affecting our sleep that we absolutely can address.
Let’s start with one of the biggest; the natural cycle of light and dark.
Our earth, and our body exist as a series of interdependent cycles and rhythms, some last hours, some months, some years! Rhythms that last approximately a day are called circadian (from the Latin circa, about and diem, day)
Our body contains its own highly sophisticated internal clock located in the suprachiasmatic nucleus (just above the cross of the optic nerves). Our SCN carefully integrates information from almost every system in our body with cues or “zeitgebers” taken from the environment in order to entrain our internal environment with our surroundings. This includes signalling when to start producing digestive enzymes, and when to start winding the body down for sleep.
When one rhythm is knocked out of sync, the various feedback loops soon lead to others following suit. We end up raring to go late and night, and groggy in the morning or worse! Remember the last time you took a long haul flight? Or perhaps worked a night shift? The “lag” experienced is simply the result of your clock trying to recalibrate the internal with the external environment.
Melatonin is a hormone secreted by the pineal gland in response to increasing darkness measured at the SCN, and is commonly known as the “sleep hormone”, however it’s strong antioxidant properties also means it plays a key part in reducing inflammation levels in the body.
As a circadian cycle, melatonin runs reciprocally with cortisol. Therefore when melatonin is high and cortisol low you’ll feel relaxed and drowsy, ready for sleep, and vice versa.
Another key player in our sleep/wake cycle is adenosine. This neurotransmitter begins to build up throughout the course of our daily activity, with the result that it begins to inhibit areas of the brain that keep us awake and we begin to relax and become sleepy. Overnight the adenosine is metabolised and it’s inhibiting effect on wake-promoting centres is removed. This process is known as the homeostatic sleep drive, and essentially runs as a measure of how long we’ve been awake, how much energy we’ve expended and therefore how sensible it is to continue
These two processes usually peak around 9pm and signal (all being well) the transition to sleep.
So. How can we minimise interference in these two separate but synergised systems?
As a coffee lover myself it pains me to say… but coffee really does significantly affect sleep.
Caffeine works by blocking the adenosine binding with the wake-promoting centres with the desired effect that we continue to remain alert and energised, albeit by warping our bodies measure of how long we’ve been awake and how hard we’ve worked in that time.
The half life of caffeine varies from person to person in a range of 4 to 6 hours. This essentially means that if you drink a double espresso, then half of that espresso is still active in your system up to 6 hours later, and a quarter of the original dose still active 12 hours after drinking the coffee.
Aswell as affecting adenosine accumulation, caffeine directly affects the circadian clock with a standard 200mg dose shifting the clock back by 45minutes if drunk within 4 hours of usual bedtime.
However, there is another factor we are exposed to daily which has a much more powerful recalibration effect then coffee. Light.
In a similar study, participants were exposed to bright light 4 hours prior to their usual bed time only to have their circadian phase delayed by an hour and a half. Twice as long as the coffee group!
The effect of light varies between the different wavelengths of light, which each colour and/or frequency of the spectrum prompting different biological effects. Blue and UV lights have the most impact on our circadian rhythms, with light in the red spectrum actually helping to promote sleep.
This of course makes sense from an evolutionary perspective. Levels of blue light in sunlight are naturally highest around midday, with the red spectrum making its appearance most prominently as the sun sets.
Modern LED bulbs also contain more blue spectrum light than the good old incandescent light bulb.
The presence of blue light has been shown to significantly suppress the release of melatonin, research at Harvard demonstrated that 6 hours exposure to blue light, resulted in a 3 hour shift in the participants circadian rhythms. Not only was sleep delayed but the amount and quality of REM sleep was particularly diminished (more on this in another post soon!)
Interestingly, if you have pale eyes you are more sensitive to light than your darker eyed companions.
In order then to optimise the effect of light on our circadian rhythms we should expose ourselves to light first thing when we wake up (ideally within 30minutes and with some skin out to soak up that sunshine!), and limit our exposure to bright and especially blue lights as the evening wears in. Within an hour of sunset attempt to turn off all overhead lighting, and if sleep really is a problem then consider eliminating all artificial light sources two hours before your bed time and switch out your bedside lamp for a Himalayan salt lamp. As best as possible sleep in a pitch black room.