Shift Work: Is it Killing You?
And Survival Manual
Timothy Daum MD
Spectrum Health
Grand Rapids
“Working at night must be
regarded as an inherently
unnatural act”
Principles and Practice of Sleep Medicine
Third Edition
• Optimal sleep and wakefulness requires proper
alignment between our schedule and our
underlying internal clock.
• Humans are the only animal that routinely go
against their internal clocks.
• Fooling Mother Nature is not easily accomplished
and has its price.
Background
• We live and work in a 24/7 world
• Up to a quarter of workers spend a
significant part of their work hours on nonday shifts
• Higher percentage of health care workers
involved in shift work
We are Diurnal Animals
• Humans are inherently active during the day
• We have an intrinsic circadian (about a day)
pacemaker that affects almost all biologic
rhythms.
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Temperature regulation
Hormone secretion
Cognitive function
Sleep-Wake rhythms
• This circadian rhythm is kept on target by
exposure to sunlight.
• Designed to improve chances of survival
Circadian Rhythm
Accidents vs. Time of Day
Shift Work and Circadian
Rhythms
• It is difficult to perform at peak capacity
when our internal clock is telling us it is
time for sleep.
• Coversely, It is difficult to sleep when our
internal clock and external factors (light) is
telling us we should be awake and active.
Shift Work and Circadian
Rhythms
• If we traveled 12 time zones we would
completely adjust our circadian rhythms
over time
– We adjust about 1 time zone per day
• With shift work we never completely shift
our circadian rhythm
– Lack of correlation between light and
sleep/wake cycle
Circadian Adjustment in Young
Adults
Circadian Factors
• Even if we adjust our internal circadian
rhythm over the course of a week, most
people revert to the normal schedule over
weekends requiring we restart our
adjustment every week.
Sleep Diary of a Night Shift Worker
Shift Work - Factors
Shift Work Factors
• Circadian Factors
– Sleep is disrupted as we try to sleep during
daylight hours
– We are trying to work during the time our body
is in a “down” phase
– Our circadian rhythms are out of phase
Shift Work Factors
• Sleep Factors
– Shift workers get 5-7 hours less sleep per week
than those on day shifts
• REM sleep mainly affected
– Most shift workers are in a state of chronic
sleep deprivation
• Performance and safety issues
Shift Work Factors
• Domestic Factors
– The majority of the world remains on a daylight
schedule
• Parenting obligations
• Phone calls
• Noise levels
– Shift work is a significant strain on
relationships
• Increased risk of divorce by 57%
Shift Work Disorder
• International Classification of Sleep
Disorders, 2nd Edition
• Insomnia or excessive sleepiness related to
a recurring work shift that overlaps the
usual sleep time.
– 32% of night workers meet diagnostic criteria.
– More prevalent with increasing age.
Shift Work Disorder: Risk
Factors
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Older age
Women
Morning larks
Reverse rotating
– Evening, Day then Night
Health Effects of Shift Work
• Cardiovascular morbidity and mortality
– Increased risk of MI
• Gastrointestinal effects
– Dyspepsia
– Higher rate of ulcers
• Endocrine
– Impaired glucose tolerance
• Accidents and work performance
• Psychiatric
– Higher rates of depression
– Higher rates of alcohol/substance abuse
Shift Work and Cardiovascular
Morbidity
• Shift work had been associated with:
– Higher lipid levels
– Increased risk of hypertension
– Higher incidence of coronary artery disease
• RR 2.0 for 6-10 years of shift work
• RR 2.8 for 16-20 years
Shift Work and Mortality
• Indian Railway
Company
• Very complete
records
• Different job types
between day and
shift workers
Increased Risk of Accidents:
Sleeping in the Cockpit
How to Survive Shift Work
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Be a night owl (Delayed sleep phase individual)
Avoid daytime light
Sleep in a totally dark room
Melatonin 1-3 mg before sleep has a weak
beneficial effect
• Short acting sleeping pills improve sleep with no
proven increase in work performance
• Provide enough time for sleep
• Napping prior to work
How to Survive Shift Work
• Caffeine has been shown to improve shift-work
performance
• Modafanil (Provigil) is FDA approved for shift
work
• Permanent shifts provide more sleep than rotating
shifts
• Clockwise rotating schedule
– Slow rotations (at least 5 days per shift) are probably
better than rapidly rotating schedules
How to Survive Shift Work
• Address other potential causes of sleepiness
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OSA
Restless Legs
Narcolepsy
Idiopathic Hypersomnia
How to Survive Shift Work
• If all else fails:
• GO INTO MANAGEMENT!