Sleep is managed in part by your circadian rhythm which will start to prepare your body for sleep at roughly the same time each day, meaning that doing this each day is a good thing. While it is common for many people to sleep, and wake later at weekends, this can lead to circadian misalignment and a phenomena referred to in one research paper as ‘social jet lag’.
As well as keeping sleep times relatively consistent, it pays to have a set sleep schedule which prepares you for sleep and allows you to wind down. Daily stress and busy minds which won’t shut off are two of the most common subjective causes for sleep disturbance and this makes a lot of sense in the context of what you have learned.
Stimulants such as alcohol and nicotine can cause a very alert state not conducive to sleeping. Caffeine is especially effective here as it has a half life ranging from 1.5-9.5 hours depending on your size, genes and other factors (smoking increases this). Half life in pharmacology means the time that ½ of an active compound takes to clear your system, so if your caffeine half-life time is 6 hours then taking 200mg at 10am would leave 100mg at 4pm, 50mg at 10pm and 25mg at 4am.
Of course, that is not to say that caffeine being in your system at any level will impact on sleep, but it has been documented that 400mg taken 6 hours before sleep causes sleep disturbance, and that 300mg taken 15 minutes before bed did not impact REM sleep, but significantly reduced stage 3 sleep and increased stage 2 sleep (indicating an inability for the adenosine-clearing shutting down of brain areas to occur). Ultimately the recommendation to reduce habitual caffeine intake in the afternoon and eliminate within 6 hours of sleep (or more if possible) seems an important one.
Alcohol when consumed in moderate amounts seems to induce relaxation and therefore leads to greater onset of sleep, but doses over 0.32g/kg of bodyweight (so around 19g or 2 units for a 60kg individual) seem to impair sleep quality. A dose of 0.49g/kg in the hour before bedtime seems to impair REM sleep onset and alter wave amplitude in non-REM sleep indicating increased sleep intensity. Overall, it would seem that a small amount of pre-bed alcohol may be beneficial but larger amounts are to be avoided.
It should be relatively obvious that a comfortable room is one which is more conducive to good sleep. Sleepfoundation.org recommend that the room should be cool to allow for the natural drop in your core temperature to occur, with 16-19C being their recommended ambient range. Your mattress, pillows and duvet should be clean, comfortable and breathable, and you would ideally have blackout curtains, minimal electronics (switched off at the mains to reduce noise and standby lights), a fan or white noise machine if you prefer these and ear plugs if needed near busy roads. Many of these are optional so ensure that whatever your room is like suits you, but consider these suggestions as a good place to start.
During the night, you transition your sleep between different stages, and during REM sleep you can often experience short awakenings, typically lasting a few seconds, which you don’t remember. If, however, you are stimulated (either by caffeine, by mental stress or by light in the room) you can become fully awake and it can take a long time to get back to sleep.
Perhaps one of the biggest culprits here is needing the toilet. During the progressively deeper stages of sleep and REM sleep your urine production is switched off so as to prevent night time accidents, but upon waking this is not the case and excessive liquid consumption before bed can lead you to becoming fully awake in the middle of the night and being forced to get up, turn on a bathroom light and interrupt melatonin secretion, relieve yourself and then return to bed where you may struggle to return to proper sleep.
The amount of liquid that could be classed as excessive is always going to vary individual to individual and day-to-day, but it’s worth keeping an eye on your intake and noticing at what point you’re forced to get up during the night.
Exercise alters endocrine, nervous system and somatic functions so it makes sense that it would impact sleep. The exact form which this impact takes is largely dependent on the type of exercise undertaken and the amount of time between the exercise bout and sleep, but the effects are relatively consistent.
Exercise undertaken during the day has a small positive impact on sleep, evident because a greater amount of stage 3 sleep is seen. Late evening training, on the other hand, seems to have the opposite effect. This is likely to be due to the impact exercise can have on cortisol, dopamine, adrenaline and noradrenaline. Interestingly, chronic exercisers also experience shorter sleep onset latency (they fall asleep faster), reduced time awake during the night and significantly longer total sleep time. It has yet to be elucidated at the time of writing, whether this is because of the impact of acute exercise sessions, or the somatic responses to chronic exercise including improved body composition, cardiac function, glucose control and immune function.
Note: Aerobic exercise is the modality typically used in research that seeks to explore the association between sleep and exercise, but it is likely that resistance training would have the same effects.
Large meals or foods which cause indigestion for individuals would ideally be avoided. Sleepfoundation.org recommend avoiding spicy, very rich or very ‘heavy’ meals, and it’s worth noting that many chocolate bars contain some natural caffeine.
With that said, consumption of a higher carbohydrate food prior to bed can reduce sleep onset time due to a phenomenon called postprandial somnolence (which many experience after larger meals).
Finally, it is possible to improve performance during periods of sleep restriction by engaging in short (sub 30 minute) naps. While this may result in some amount of immediate sleep inertia, after this has dissipated, workers show an increase in performance when compared with workers who have not napped, as well as reduced subjective tiredness. Napping should not be considered a replacement for sleep because, as you have seen, a full sleep cycle can take up to 120 minutes. With that said it is worth noting that there is evidence a nap during sleep debt situations may not impact night time sleep but may improve waking function. Being that the human circadian rhythm naturally dips at both 2-3am and 2-3pm, and therefore it could be argued that we evolved to take an afternoon nap, for those who struggle to complete a full night’s sleep due to their schedule (shift workers, for example) this could be a viable option.