2. Fatigue is a Serious Concern
Expert consensus is that fatigue is
“the largest identifiable and preventable
cause of accidents in transport
operations…”
Cited in a 2003 report, one safety study
indicates fatigue may contribute to 20-40% of
commercial transport accidents.
Other reports suggest that 21% of aviation
incidents, 16% of marine vessel casualties,
and 31% of fatal truck accidents are fatigue
related.
3. Fatigue Factors
Operator fatigue is a function of the
sleep quality/quantity and the body
clock.
Sleep Circadian
Restriction FATIGUE
Factors
4. Blood-Alcohol/Fatigue Comparison
The effects of fatigue may be compared to the effects
of blood alcohol levels
Continuous Hours Blood Alcohol Concentration
Awake (no sleep debt) (BAC)
18.5 0.05 (significantly impaired)
21 0.08 (illegal to drive in Canada)
2 - 3 Drinks in 1 Hour
IMPAIRED
4 - 5 DRINKS = BAC 0.08 or
21 Hours Continuously
Awake
5. People Often Restrict Their Sleep = Sleep Debt
Day-after-day of sleep restriction often is a bigger
problem than long periods of continuous wakefulness
Vigilance Task Performance
25
3 Hours Sleep
5 Hours Sleep
7 Hours Sleep
Mean # of Lapses
20
9 Hours Sleep
15
10
5
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Baseline Experimental Recovery
Day
Johnson et a. (2004). Modulating the homeostatic process to predict performance during chronic sleep
restriction. Aviation, Space and Environmental Medicine, 75(3 Suppl):A141-6.
6. Sleep Restriction, Effectiveness, & BAC
After five nights of partial sleep deprivation, three drinks
will have the same effect on your body as six would when
you've slept enough. National Sleep Foundation , 4/17/2009
7. Self-judgments of Fatigue Aren't Accurate
Actual Sleepiness/Fatigue Self-Rated Sleepiness/Fatigue
4.0
Stanford Sleepiness Scale
20 4 hr sleep
6 hr sleep
Stanford Sleepiness Scale score
3.0 8 hr sleep
Vigilance Lapses
15
PVT lapses
10 2.0
5 1.0
0 0.0
-5 -1.0
BL 2 4 6 8 10 12 14 BL 2 4 6 8 10 12 14
DaysDaysSleep restriction
of of sleep Restriction DaysDaysSleep restriction
of of sleep Restriction
Objective measures show Self ratings of fatigue fail to
fatigue progressively degrades BUT recognize all but the initial
cognitive performance fatigue effects!
Van Dongen, Maislin, Mullington, and Dinges (2003)
8. The Objective Fatigue Science Approach
Scientific Research shows that it is not
possible for people to accurately
assess their own level of fatigue.
We can predict fatigue based on sleep
quality and quantity by using our Sleep
Bands and validated software.
Accident Risk can be predicted based
on the levels of fatigue.
9. How Data Is Collected and Processed
Wear the SleepBand
for 7 days
• Lightweight
• Waterproof
• Unobtrusive
Data is processed and
fatigue /accident risk is
determined by the US
Dept. of Transportation
validated SAFTE
model.
10. Accident Risk Level Management Reports
Once the data has been analyzed the
employer receives a summary Fatigue
Accident Risk Report
Reports show where in the
organization the fatigue risk is and the
levels of fatigue/accident risk
For example, the reports can tell which
shifts, locations, job type, etc. are
responsible for any increased Accident
Risk.
12. Reducing Accident Risk
Once the causes of the Accident Risk
have been identified mitigation
strategies are designed to reduce the
risk.
Once the strategies have been
implemented (usually 30-60 days) we
have the workers wear the Sleep Bands
a second time to make sure the
Accident Risk has been reduced.
14. Summary of the Process
1st Obtain the baseline for
organizational fatigue accident risk
2nd Once the sources and causes of
accident risk have been indentified a
mitigation strategy is designed to reduce risk
that includes: worker training, schedule
analysis, education.
3rd Re-access the fatigue accident risk
in 30 to 60 days to determine the
effectiveness of the mitigation steps and set
new priorities
16. For Additional Information Contact:
John.caldwell@fatiguescience.com
Fatigue Science
700 Bishop St, Suite 2000
Honolulu, HI 96813
Editor's Notes
This graph is from a study conducted at the Walter Reed Army Institute for Research. The data being graphed is the number of lapses (or failures to respond) on a vigilance task that measures sustained attention. This task is relevant to many modern jobs that require personnel to monitor systems while computers do the work. Essentially, the human is there as a backup. If vigilance/attention is impaired by something, it is more likely that warning lights, developing system problems, or other difficulties will be accidentally overlooked. On the first 3 days, people were allowed to sleep 9 hours per day. During the next 7 days, 3 groups were sleep restricted to either 7, 5, or 3 hours per night. On the last 3 days, people were allowed to secure 9 hours of recovery sleep each day.Five points to note:The group that got only 3 h per day is significantly impaired very early.However, even the 7 h group is showing a gradual deterioration throughout.Despite 3 recovery days, none of the groups returns to baseline performance.The consistent lapse increases in the restricted groups show that people are not getting used to the sleep restriction despite 7 days of trying.The insufficient recovery shows that people take much longer than was once thought to recover from chronic sleep loss (i.e., a weekend off won’t do the trick).