Sleep Deprivation: What a nightmare
Sleep Deprivation: What a nightmare
I first wrote this article in June 2016 for Australian Sailing. I've been talking about Sleep in my Masterclass course. Several participants enquired about getting a copy of the article so I decided this was a good place to post the article. Hope you find it interesting.
Sleep deprivation and fatigue have been implicated in some of the world’s biggest human and environmental disasters, including the nuclear reactor meltdowns at Three Mile Island, and Chernobyl. At Three Mile Island shift workers, on between 0400 and 0600, failed to notice the plant loosing coolant. In the marine environment, when the Exxon Valdez supertanker ran aground in Alaska in 1989, the crew had had very minimal rest in the 24 hours leading up to the disaster. The third mate was allegedly sleeping at the helm just prior to the grounding.
Closer to home, fatigue played a role in the grounding of Price Waterhouse Coopers (Shockwave) on Flinders Islet and the tragic loss of two lives[i]. When the yacht ran aground at approximately 0235 am the helmsman, who was also the skipper and the navigator in this race, had, except for a few minutes break, been steering for seven hours.
Research in the workplace has shown that sleep deprived workers are 70 percent more likely to be involved in work-related accidents, while a study of marine incidents in the UK found that a third of all groundings involved a fatigued officer alone on the bridge at night[ii].
The effects of sleep deprivation include:
· Increased reaction time
· Decreased alertness
· Degraded attention and vigilance
· Decreased motivation
These effects will be familiar to offshore sailors, especially when watch systems are not adhered to. The effects will also be familiar to skippers and navigators outside the watch system, especially those who don’t manage their own sleep effectively.
What does the law say?
While most sailing is done outside the rules of commercial vessels, it is still worth considering industry standards as a starting point for avoiding fatigue in offshore sailing. IMO and AMSA rules state that the minimum hours of rest for a seafarer must be 10 hours in any 24 hours and that this rest may be divided into two periods, of which one period must be at least six hours[iii]. They also state that the interval between consecutive periods of rest must not exceed 14 hours.
What does the research say?
With fatigue such an important factor in workplace health and safety, sleep has been a key area of research. Following examination of research papers on sleep deprivation, I compiled the following key findings:
1. Sleep history in the 24 hours before work is a strong predictor of accidents in industry. In trucking, the prior sleep threshold for a decrease in accidents was 6-7 hours[iv]. For air pilots, restricted sleep in both the 24- and 48-h period prior to a commercial flight sector was found to be associated with degraded operational performance from the perspective of threat and error management[v]. Effects on performance were seen at a threshold of 6 h sleep in the prior 24 h, and 13 h sleep in the prior 48 h, with the 24-hour period found to be more important.
2. The minimum amount of sleep in a 24-hour period to maintain baseline waking performance has been quantified as 5 hours. Less than this results in impairments after 2-3 consecutive nights.
3. Preparatory naps counteract the effects of sleep deprivation better than a nap after the missed sleep. 16 hours between rest is way too long and performance impairment rises greatly at this point. Six hours between naps has been shown to be effective for marine pilots on the Great Barrier Reef[vi].
4. Frequent naps slow the accumulation of sleep debt.
5. Even an ultra-short period of sleep (6-10min) is sufficient to enhance memory processing[vii].
6. Sleeping partially upright makes it easier to wake up after a nap.
7. The ideal length of time for a nap appears to be 10-20 minutes and a full sleep cycle is around 90 minutes. If you sleep for longer than 20-30 minutes and wake before completing a full sleep cycle, then you will often wake feeling groggy and lethargic.
8. If possible, naps or sleep time in early afternoon and early morning are most effective. This is because you are most likely to sleep at these times due to your circadian rhythm.
9. Research conducted on people working a standard 5-day week suggests that the weekend does provide a level of recuperation for those who have gone into sleep debt during those days of work[viii].
How can we use this knowledge in offshore sailing?
Based on my own experience and the studies outlined above, here are my tips for best managing your sleep during a long offshore race. They are most applicable to those outside a watch system.
1. It is important to begin an offshore passage with a low sleep debt. Make sure you get good sleep in the two nights before going offshore, and especially the night before.
2. Nap when the opportunity arises rather than waiting for fatigue to set in. Plan to nap at least every six hours. When possible, I like to grab a nap on the first afternoon of an offshore race after we are clear of the start and dangers. It sets me up well for the first night.
3. For navigators, map out a timeline for a full 24-hour period. Include items like radio skeds, weather downloads, key weather transitions, and tricky navigation areas coming up. Schedule in naps, prioritising the early afternoon and early morning for nap times.
4. Length of sleep time is important. Nap for 20 minutes or less, or sleep for at least 90 minutes where possible. Interestingly, my own experience matches the research. I find that I have a 90-minute sleep cycle and wake naturally after then. If I sleep longer than 20 minutes but am woken up before the 90-minute cycle, then I feel groggy and disorientated and it takes me a few minutes before I can make a reasoned decision.
5. Use an alarm. This allows you to take a short nap without worrying about waking up. Also ask the crew to wake you at a particular time as a backup.
6. Take a caffeine nap. Have a coffee then go to sleep for 20 minutes. After 20 minutes the coffee kicks in and you can wake up feeling refreshed.
7. Consider taking the short naps out of the bunk. It might make it easier to wake up.
8. If you are in a race that goes for longer than 3-5 days, try to get an extra rest every 4 or 5 days to help recover some of your sleep debt. This will help you maintain performance over the full period of the race.
9. For those in a watch system, get sleep while you can. Don’t wait until you are tired. Once you are in sleep debt it is very hard to come back from it.
10. For those developing a watch system, recognise that early morning and afternoon are key sleep times so try to make sure all crew members get an opportunity to rest in these periods.
FIGURE ONE Alertness against time of day showing the two significant dips in a 24 hour period. Figure taken from www.robsonforensic.com/articles/shift-work-sleep-deprivation-and-industrial-accidents-expert-article Sleep Res. (2008) 17, 3–10J. Sleep Res. (2008) 17, 3–1
References [i] CYCA Flinders Islet Internal Inquiry Report.pdf https://cdn.revolutionise.com.au/site/vqhmeqp8zgzkrjp0.pdf Accessed 12 Nov 2020.