Latest / Safe As Podcast / E27: Sleepy or Drunk - which is more dangerous?

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E27: Sleepy or Drunk - which is more dangerous? · Safe As Podcast

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  Among the most dangerous lie you'll ever tell yourself is I'm
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  fine. I can manage on less sleep.
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  Because while you might feel fine, your brain is quietly
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  operating at a level that put you and everyone around you at
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  serious risk. Today we're pulling back the
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  curtain on the silent epidemic of sleep debt.
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  And while your toughness is actually your biggest
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  vulnerability, sleepiness isn't a weakness, but a biological
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  certainty. Good day everyone.
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  I'm Ben Hutchinson and This is Safe as a podcast dedicated to
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  the thrifty analysis of safety, risk and performance research.
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  Visit safetyinsights.org for more research.
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  Today's study is from Marif ET al 2005 titled Fatigue related
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  impairment in the Speed, Accuracy and Variability of
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  Psychomotor Performance Comparison with Blood Alcohol
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  Levels published in the Journal of Sleep Research.
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  They compared the effects of being awake for up to 24 hours
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  against different blood alcohol concentrations and really
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  looking for where performance impairments intersected for the
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  adults were tested. This is one of several studies
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  from different authors which did something similar where they
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  compared time awake or your extended wakefulness against the
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  similar performance impairments from blood alcohol.
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  What really set this study apart is that they argued that the
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  prior studies from other authors overestimated the effects.
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  So let's jump into some of the context.
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  First, what do we mean by fatigue?
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  Fatigue is a word that's used to describe a lot, but in this
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  context we're referring to mental fatigue which is a state
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  of tiredness, drowsiness and or mental or physical exhaustion
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  which reduces a person's ability to perform work safely and
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  effectively. Fatigue effects a lot of
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  different things like near behavioural, cognitive and
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  psycho motor aspects. Includes drowsiness and micro
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  sleeps, impairments and reaction time, alertness, decision
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  making, risk taking, a lot of stuff.
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  We're primarily interested in the effects of sleep and
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  circadian factors, which really results about because of
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  incomplete rest and recovery and some other types, which is
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  called time 1 task fatigue. Quoting a couple of authors not
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  from this study but prominent researchers Dawson and
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  McCulloch. Fatigue is about sleep, stupid.
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  That's why I keep going back to sleep now.
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  Three prior studies directly compared the effects of fatigue
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  and alcohol intoxication on performance using the same
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  cognitive tests. Now, these studies agree that as
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  little as somewhere around 18 to 24 hours of sustained
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  wakefulness, that means someone's been awake for, you
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  know, 18 to 24 hours, could induce impairments in the speed
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  and accuracy of their cognitive performance that were equal to
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  or greater than individuals with blood alcohol concentrations of
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  .1%. So in Australia, twice the legal
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  limit. So these other studies suggested
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  that even moderate levels of fatigue produce performance
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  decrements equivalent to or greater than those observed that
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  alcohol intoxication deemed unacceptable or even illegal
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  when driving, working or operating dangerous equipment.
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  However, the prior studies didn't account for variations
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  within groups or individuals which this study accounted for.
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  Just note that I've skipped over all of the precise methods that
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  they use in this study. So what did they find?
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  After 24 hours of sustained wakefulness and with a blood
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  alcohol of .08%, individuals showed their maximal cognitive
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  impairment. So things didn't get worse after
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  those two points that were measured in this study.
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  However, the magnitude of impairment found for fatigue was
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  equivalent only to that observed for .05%.
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  Now I say only, but remember this impairment of, you know,
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  being awake for 24 hours been equivalent to .05%.
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  It's still an illegal blood alcohol concentration in many
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  countries, including mine. However, when accounting for
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  individual variance, the magnitude of performance
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  impairment after 24 hours been awake was equivalent to .05 and
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  not the higher point 1% that was spent in some of the earlier
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  studies. However, per prior work, both
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  sustained wakefulness and alcohol intoxication impair the
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  speed of cognitive performance. This suggests that previous
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  studies that have not accounted for variability in the
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  performance have actually overestimated the effects of
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  fatigue on cognitive performance.
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  Now despite the study finding marginally smaller impairments
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  in fatigue related impairment, the magnitude of impairment that
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  was observed is still serious and warrants attention.
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  Even accounting for these intra and inter subject variability,
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  which statistically they accounted for, the cognitive
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  impairment founded somewhere around 24 to 26 hours of
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  sustained wakefulness was greater than that associated
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  with blood alcohol concentrations, which is illegal
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  in many jurisdictions. So these studies support that
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  individuals should not engage in cognitively demanding and high
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  risk activities like driving when they've been awake for more
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  than 20 hours. What do we make of the findings?
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  Fatigue, again primarily related to mental fatigue is a
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  significant performance shaping factor.
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  It directly impacts vigilance, reaction time, drowsiness, micro
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  sleeps, decision making. It's not a sign of weakness,
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  it's a biological certainty. So we need to design for
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  healthier working arrangements, providing for more sleep
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  opportunity and recovery time, monitoring actual working hours,
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  having cheques and balances around fatigue symptoms and
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  importantly understanding how those performance shaping
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  factors influence the safety of our work in practise and daily
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  work. What evidence based rostering
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  principles have been used? What safety critical work is
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  being done during the early morning hours, the circadian
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  Nadia or after several night shifts or during a particularly
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  early morning rise? What sleep and fitness for work,
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  health testing or screening is in place at the organisation?
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  But relying on workers self reporting their fatigue isn't
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  nearly enough. For one, they often have a
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  vested interest in working. You know, they want that sweet
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  moolah. 2 Well, people typically are decent estimators of their
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  degraded cognitive performance from acute sleep loss.
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  You know, being awake for 20 to 25 hours.
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  They typically become blinded to their impaired cognitive
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  performance from chronic sleep loss.
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  That's one or two hours sleep loss a night that creeps up over
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  days, weeks or months. So some of this other
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  researchers actually found that relating to chronic sleep loss,
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  people subjectively rate themselves as being back to
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  normal, you know, back to their usual cognitive performance,
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  even though their objective reaction time or cognitive
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  performance is still impaired. It's blinded to the impairment.
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  They're so used to it now. There's lots of systems oriented
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  tools and approaches to help manage fatigue, occupational
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  fatigue like fatigue risk management systems.
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  Dawson and McCulloch have a defences in depth approach that
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  really nicely focuses on sleep, you know, actual sleep and sleep
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  opportunity and other things. But I think really we need to be
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  clear about how fatigue interacts with our safety
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  critical work. And as some researchers have
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  said, your fatigue clock doesn't start when you start your shift,
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  it starts when you wake up. So rostered shifts and work
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  hours are only ever a very incomplete assessment of the
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  potential for fatigue impairment.
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  Now, these other studies in this one provide direct support for
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  the proposal that individuals shouldn't be engaging in
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  cognitively demanding and high risk activities, you know, when
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  they've been awake for extended periods or that wasn't directly
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  explored when they're influenced by the effects of chronic sleep
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  loss. These findings also align with
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  real world observations of fatigue related crashes that
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  tend to peak during very specific times, you know, like
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  midnight to six, because people tend to be awake for longer and
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  also due to their circadian rhythms, they tend to be more
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  drowsy during those early morning hours.
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  So limitations mostly, virtually all these have been lab studies
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  and of course lab studies don't always directly translate to
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  real world conditions, but we have more than enough evidence
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  at a group and population level to know the negative impacts of
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  fatigue and sleep loss. But also a lot of these studies
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  were conducted with healthy young adults.
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  So there are going to be other factors at play, particularly in
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  more high risk groups. So for instance, and this wasn't
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  covered in this study, long distance truck drivers are often
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  found to have the highest risk factors for like obstructive
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  sleep apnea. So the inherent risk factors
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  also interact with sleep disruption and create elevated
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  risks. And another one, many of these
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  studies use acute sleep loss. Now, while acute sleep
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  disruption like been awake for 24 hours is linked to negative
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  cognitive performance and potentially incidents, probably
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  more pernicious is the effects of chronic sleep loss where we
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  might only obtain 4 to 6 hours per night over days or weeks.
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  And this can lead to cumulative and significant drops in
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  cognitive performance and alertness, similar to acute
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  sleep loss. But as I mentioned earlier, we
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  may not really recognise it. That's it on safe as I'm Ben
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  Hutchinson, please help share, rate and review and check out
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  Safety insights.org for more research.
• 9:46
  Finally, feel free to support Safe As by shouting a coffee
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  link in the show notes.