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Astronauts on the International Space Station get only around 6 hours of sleep a night compared with the 8.5 scheduled by NASA.[1] I think 6 hours is sadly not uncommon for many people! In fact, 2013 research published by Travelodge showed Britons get just short of 6 and a half hours a night.[2] Can we get by on a that? Or do we need more? A 2015 Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society said healthy adults needs at least 7 hours of sleep a night.[3] Less than that and we’re looking at increased likelihoods of weight gain, obesity, diabetes, hypertension, heart disease, stroke, depression, and even death. That didn’t look too attractive to me, so I started researching how our sleep, and that of astronauts, is affected by diet, environment, mental state, and more; and began developing a sleep toolkit to draw from in any situation. Here are a couple of tools I use to improve my sleep – no matter which planet I’m on!

  1. Work with the rhythm of the 90’s

Our circadian rhythm is our internal clock, running in the background of our brain and body 24/7 – including while sleep, and signalling different phases of activity during sleep.[4] Throughout sleep we have cycles of sequences that move from lighter sleep to deeper sleep, and back to lighter sleep again. These cycles are approximately 90 minutes long, but vary throughout the night.[5] That means roughly every 90 minutes we move into a lighter sleep phase from which we can be woken more easily. Bad news if it is a noisy environment (hello barking dogs!), but good news if waking refreshed is an attractive idea. Ever been woken by the alarm and felt super groggy with what was supposed to be a good 8 hours’ sleep? I’ve definitely had the alarm go off in a deeper part of my sleep cycle and woken more tired that I ‘should’. Here’s a trick I’ve used to help me be ready to roll first thing: if I need an alarm, I set it to go off at a time that’s a 90-minute increment from when I expect to be asleep (not go to bed, but be asleep). So, if I’m planning to be asleep at 9pm, my alarm will be set for 4:30am or 6am. Both see me more fresh than a 5 or 5:30am alarm.

  1. Coffee no-ffee

Sometimes a bad night’s sleep is hard to avoid and reaching for a strong coffee in the morning is very attractive! The challenge is that caffeine is a stimulant that stays. A kick first thing is helpful sometimes, but the half-life of caffeine is around 4-6 hours.[6] And with the average latte in Australia containing nearly 200mg caffeine (love me a double shot!), that means I still have 100mg left in my tank nearly 6 hours later, 50 mg in the tank a further 6 hours later, etc. And that is from one cup. Drink another cup mid-morning or mid-afternoon? Then add that to the tank-that-never-empties. Why does this matter? A caffeine molecule looks remarkably similar to a molecule of adenosine. Adenosine is a compound our body makes during the day which attaches to adenosine receptors, building up and making us sleepier at the pointy end when we would normally go to bed. But if caffeine is around, it blocks adenosine receptors, and prevents all that sleepy goodness from building up.[7] No wonder a good cuppa wakes us up! But that ‘never-empty-tank’ effect… wonder some nights I wasn’t so sleepy  after an extra cup during the day. My coffee trick: I use coffee strategically, aware of the endlessly-filling petrol tank effect. I have a few coffee-free days each week so that the tank empties. On those days, I am markedly more tired at night, and fall asleep faster; and as a bonus, when I next have a cup of coffee – it has extra zing! An alternative I use when I do go for the bean is a coffee-curfew – no coffee after breakfast. Research shows 200mg caffeine ingested at 7:10am is still detectable in the saliva at 11pm.[8] There are a multitude of factors which affect sleep. These two areas (reducing the impact of caffeine on adenosine and working with 90-minute sleep cycles) are just a couple that could be useful for spaceflight, as well as improving my journey to sleep better on Earth.


1. LK Barger et al., ‘Prevalence of sleep deficiency and use of hypnotic drugs in astronauts before, during, and after spaceflight: an observational study’, The Lancet Neurology, vol. 13, issue 9, 2014, pp. 904-12.
2. MarketWired, ‘The Weekend Lie-in has Been Laid to Rest as We Become a Nation of Snoozesters’,, August 22, 2013, available: <;sourceType=3>.

3. NF Watson et al., ‘Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society’, Sleep, vol. 38, issue 6, 1 June 2015, pp. 843-4.

4. PM Fuller, JJ Gooley & CB Saper, ‘Neurobiology of the sleep-wake cycle: sleep architecture, circadian regulation, and regulatory feedback’, Journal of Biological Rhythms, vol. 21, issue 6, December 2006, pp.482-93.

5. MA Carskadon & WC Dement, ‘Normal Human Sleep: An Overview’, in: MH Kryger, T Roth & WC Dement (Eds.), Principles and practice of sleep medicine, 5th edition, pp 16-26. St. Louis: Elsevier Saunders.

6. NL Benowitz, ‘Clinical pharmacology of caffeine’, Annual Review of Medicine, vol. 41, 1990, pp. 277-88.

7. ibid.

8. HP Landolt et al., ‘Caffeine intake (200 mg) in the morning affects human sleep and EEG power spectra at night’, Brain Research, vol. 675, issue 1-2, 27 March 1995, pp. 67-74.

published: 3 April 2018