Transcript 'Health effects of Shift Work

Circadian Rhythms
and
Shift Work
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Vicken Y. Totten MD:
Emergency Physician
and Career-long Shift Worker
Circadian Rhythms and Shift Work
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Circadian Rhythms and Shift Work
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SLEEP in literature
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Sleep, that knits the ravell'd sleave of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great nature's second course,
Chief nourisher in life's feast.
• - Shakespeare, Macbeth, Act II, Scene I
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Goals and Objectives:
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Describe normal sleep structure
Discuss Circadian Rhythm Disorders
Describe types of shift work patterns
Offer concrete shiftwork suggestions
Provide a resource list
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Biologic Rhythm Control
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Innate rhythms poly-genetically determined
Master clock in suprachiasmatic nucleus of
the rostro-ventral hypothalamus.
Mediated by light/dark cycles via cryptopsin
receptors in retina, skin and possibly
pituitary
Humans: Day = alert / Night = sleep.
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Biologic rhythms
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All body systems change rhythmically
90 minute alertness cycle
Monthly fertility cycle
Sleep/wake generally 23-26 hour cycle
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Rhythm disorders
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Normally, biologic cycles kept in synch by
signal substances such as melatonin,
cortisol and others
Disruption in these systems have profound
health implications.
Disrupted by both internal and external
signals
Cycles re-synchronize at different rates
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Circadian disruption
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De-synchronization of innate biologic /
circadian cycles.
Chronically in shiftwork and briefly from
jetlag.
Medicine is far behind industry in
recognizing the implications of shift work
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Causes of circadian rhythm
disorders
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Genetics
Medications
Pregnancy
Shift work
time zone changes
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Normal Sleep Architecture:
Stages of sleep
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Non-REM (NREM) sleep - Stages I-IV
brain idle, body mobile
REM - Body paralyzed, Brain active (more
metabolically active than during waking)
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Stage 1 - transition period.
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Normally 10 minutes. Eyes rove.
Most people awakened during Stage 1
claim they are not asleep.
“Micro-Sleeps”
Driving while fatigued
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Stage 2 - Deeper, fewer eye
movements.
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Shallowest restorative sleep.
About half of adult sleep in Stage 2.
20 min. before progressing to next stage.
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Stages 3/4 - Slow wave sleep
(SWS), (delta sleep)
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Most restorative & restful; vital for physical
recuperation.
Majority occurs early in the sleep period.
Difficult to arouse from SWS.
First stage to be “made up” after sleep
deprivation.
SWS deprivation causes fatigue, muscle
aches.
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REM sleep
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brain on, body off.
Vital for psychological well-being;
Isolated REM deprivation -> 1st irritability > psychosis -> death
EEG similar to wakefulness.
Dreams, irregular pulse, respiration,
increased BP, loss of muscle tone, and
absent spinal reflexes.
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REM sleep
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First episode occurs after 90-120 minutes of
NREM sleep.
Recurs in about 90 minute cycles, getting
more frequent towards awakening
REM periods become longer as night
progresses.
REM disorders include sleepwalking / talking /
night terrors
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“Core Sleep”
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Horne: first three SWS cycles with their
REM periods
"optional" sleep the rest of the night:
more REM, less SWS
Core sleep: about 5 hours for most
persons
Only core sleep made up.
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“Sleepiness”
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2 components: core versus optional
missing core sleep (physiologic) -- disrupts
physiologic systems
missing optional sleep (psychological) -mostly psychological / mood effects
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Excess Sleepiness in Shift Workers
Up to 45% of night-shift
workers experience ES.
Up to 36% of rotatingshift workers experience
ES.
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Circadian disruption
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Day /awake and night / sleep are the
normal human condition.
When switching to a day / sleep and night
/ awake, various physiologic cycles
become desynchronized
Hospitalization with loss of ‘Zeitgibers”
Re-synchronization at different rates
Generally, all systems can shift 1 hr per
day.
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Adverse Health effects of shiftwork
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Breast Cancer, Endometrial Cancer : increased in
women who are not exposed to enough
darkness; mechanism unclear; proposed
mechanism is melatonin deficiency.
Prostate Cancer: increased most in rotating shift
workers when compared to fixed-night shiftworkers, who have an extremely minimal risk.
Peptic Ulcer Disease /Obesity / Cardiovascular
Disease
Pregnancy Issues: night work and high work
load increase the risk of spontaneous abortion
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Inter-relationships are complex
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Obesity, pregnancy, high fat diets and
circadian rhythm
Npas2 is a key organizer of the circadian
system; if maternal diet is high fat, the
fetal liver fetal histone code is maltranscribed, and leads to appetite and
circadian disorders in the offspring.
www.bcm.edu/obgyn/index.cfm?pmid=11
856
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Common Circadian Rhythm
Disorders
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Jet Lag or Rapid Time Zone Change
Syndrome:
Delayed Sleep Phase Syndrome (DSPS)
Advanced Sleep Phase Syndrome (ASPD)
Shift Work Sleep Disorder (SWSD)
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Jet Lag / Shift work
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Personal cycles out of synchrony with local
conditions.
Sleepy when alertness is required; alert
when sleep required
Caused by travel across time zones, shift
work and sometimes by adolesnce
Can cause chronodysruption, since
different systems re-synchronize at
different rates.
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Zeitgibers (from Gr. “Time Tellers”)
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the physical and social clues which tell us
what time it is.
Most powerful is light.
Others include taste and
smell of usual breakfast
food, going to work,
sound of daytime activities
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Night Owls vs. Morning Larks
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Night people = easier adjustment to shift
work
Tend to be phase delayed
Day people = harder with shift change;
more stable once adjusted
Tend to be more synchronized and more
resistant to re-setting
Residency survey: EP s have more night
types than normal populations
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Delayed Sleep Phase Syndrome
(DSPS)
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A disorder of sleep timing.
People with DSPS tend to fall asleep very
late
Difficulty waking up in time for work,
school, or social engagements
Common, perhaps normal in adolescence
“Owls”
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Advanced sleep-phase syndrome
(ASPS)
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ASPS persistent early evening sleep onset
time (between 6:00 pm and 9:00 pm) and
spontaneous early morning wake-up time
(between 3:00 am and 5:00 am).
Variably associated with inadquate sleep.
Less common than DSPS
Associated with extreme age and
depression.
“Larks”
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Non 24-Hour Sleep Wake Disorder
(N24HS/W disorder):
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Innate 23-25 hr cycles constantly reset by
zeitgibers
Normal sleep pattern but inate cylce is
neither firm nor maintained.
Struggles with “Free cycling”
Inconsistent insomnia that occurs at
different times each night.
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Definitions for
Emergency
Medicine
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On - call
On duty
Sleep deprivation
Chronodisruption
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On Call versus On Duty
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“On call”: night work between working days =
pure sleep deprivation
Possibility of sleep while on call
Usually does not cause circadian rhythm
disruptions -- body cycles remain in phase
“On duty” implies expected time of usual type of
work
Isolated night shifts “on duty” (less than once
per week) physiologically function as ‘on call’
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Sleep deprivation
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loss of "optional sleep" (sleeping less than
one's habit) causes drowsiness, no other
serious effects
"core sleep" deprivation (less than 5 hours
of slow wave sleep)
Sleep deprivation causes both physiologic
and psychological ill effects
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Shift work prevalence
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Not a new phenomenon, but now vastly
more frequent.
25% of American workers are shift
workers at some point in their lives.
Invention of the light bulb: 1883
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Shift work definition
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Work a defined period of time, then off for
a period
Working time can be at any time of the
24-hr day
Fixed shifts -- working the same time
every day
Rotating shifts -- working time of day
changes from time to time
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Shift length
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length of shift: most common is 8 hours
others are 10, 12 and 6 hours
more mistakes made in the last 4 hours of
a 12 hour shift than in the first 8 hours
Shift changes become more difficult after
age 40
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Serious adverse health
consequences of shift work
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20% decrease in life span
62% sleep disturbance
higher rate of accidents on the job
high risks of fatal commuting accidents
800% risk of ulcers
1500% incidence of depression and mood
swings
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Shift work is also linked to:
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drug and alcohol abuse
altered immune response
infertility in women
high divorce rate.
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Cardiovascular effects of shift
work is ...
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linked to chronic hypertension
increased cardiovascular mortality
(risk worse than smoking a pack of
cigarettes per day)
risk for dysrhythmias (PVC, MAT, SVT)
risk of sinus arrest (up to 12 sec in one
study)
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Tolerance to shift work
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Better in younger persons (under 40, or
pre-menopausal)
Better in childless persons
Better in natural owls than natural larks
20% of people have no trouble changing
shifts,
60% have moderate hardship, and
20% have extreme difficulty.
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Shift work patterns
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most work has been done on 8 hour shifts
12 hour shifts no longer permitted in most
industries
rotating shifts
isolated shifts
random shifts
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Shift schedules
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Optimum: days only; in synchronous with
your own best working time
Next best: same shift every day, even if
not most suited to your optimal time; or
isolated nights
Worst: randomly rotating shifts
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Rotation patterns: Swing shifts
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Phase advance: one week days, one week
evenings, one week nights
Phase retreat: (Southern Swing): one
week days, one week nights, one week
evenings
Of the two, phase advance is more
physiologic and more easily tolerated
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Randomly changing
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almost universally condemned
forbidden by most unions
highest physiologic risk and stress
practiced mostly by physicians
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Isolated nights
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defined as less than one night per week
equivalent to a bad night on call
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Important!
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One can adjust by 1-2 hrs. / 24, or one
week to move forward by one (8 hr) shift
Therefore, maintain the same schedule
when not working
most permanent night workers switch to
day-life when not at work and reap the
same ill effects as random-shift changers
Optimal: one month or more between
changes
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What about physicians?
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MD = Maximum Denial
Socialized to ignore their own needs
Trained to be ‘tough’
poor role models
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Cardiovascular effects in
physicians:
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palpitations and dysrhythmias
Brodsky M, Wu D, Denes P, Kanakis C,
Rosen KM: Arrhythmias documented by 24
hour continuous electrocardiographic
monitoring in 50 male medical students
without apparent heart disease. Am J
Cardiology 1977;39:390-395
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Cardiovascular effects
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sinus arrest with syncope in residents
Guilleminault C, Pool P, Motta J, Gillis AM:
Sinus arrest during REM sleep in young
adults. NEJM: 1984;311:1006-10
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More studies
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Physicians aren’t immune to poor health
effects of shift work
Åkerstedt T, Knutsson A, Alfredsson L, Theorell T: Shift work
and cardiovascular disease. J Work Environ Health: 1984;
10:409-414
Åkerstedt T. Psychological and psychophysiological effects of
shift work. Scand J Work Environ Health. 1990;16(suppl
1):67-73
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Performance of physicians
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Poor performance with micro-sleeps (nonrestorative) during rote tasks
Documented micro and mini-sleeps during
drive home even in those who did not think
they had slept
Åkerstedt et al: Physicians during and following
night call duty--41 hour ambulatory recording of
sleep. Electroencephalography & Clinical
Neurophysiology: 1990; (76) 193-196
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Physician learning
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Decreased performance, learning of
deleterious habits and physiologic harm.
Asken MJ, Raham DC: Resident
Performance and Sleep Deprivation: A
Review. J. Med Educ 1983;58:382-388
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Overall performance
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Found that shift work affected rote tasks
and the highest intellectual tasks equally
as much; moderately challenging but well
known tasks suffered least. Implication for
physicians: we make more mistakes on
the more serious cases
Tilley et al The sleep and performance of shift
workers. Human Factors, 1982; 24: 624-41
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Exercise tolerance
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Sleep deprivation had little effect on acute
exercise tolerance in normal persons
Chen H: Effects of 30-h sleep loss on
cardiorespiratory functions at rest and in
exercise. Med Sci Sports and Exerc: 1991;
23(2):193-198
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Shift length
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Used temperature as a marker for slowing of
physiologic activities
Concluded that 12 hour shifts lead to
increased mistakes poorer per-hour
productivity
Daniel J, Potasova A; Oral temperature and
performance in 8 h and 12 h shifts .
Ergonomics 32(7):689-96 , 1989 Jul.
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Strategies to improve health for
shift workers
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sleep hygiene
napping at work
shift rotation patterns
food & exercise
social life
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If you must be a shift worker:
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Learn how to sleep well
Learn how to change your circadian
rhythms smoothly
Use circadian principles to make your work
and home life better
Educate your schedule-maker
Educate and enlist your family
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Living the Strategic Life
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Avoid vigorous exercise at least 4 hours
prior to bedtime (Regular exercise is
recommended.)
Avoid cigarettes, alcohol, and caffeine 4-6
hours prior to bedtime
Avoiding large meals and excessive fluids
just before bedtime
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Light therapy:
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Timing of light
Minimum of 30-60 minutes not long after
wakening to promote adaptation and
wakefullness
Re-synchronising ASPS light in the early evening
and nighttime hours delays the cycle
DSPS light therapy in the early morning hours
stimulates morning alertness and an earlier
bedtime.
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Environmental control
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Light – adequate at work (6,000-7,000
Lux)
Dark – during sleep time (less than full
moon) (consider eye shades)
Noise – shut out during sleep. Isolate
sleep room, use earplugs
Room temperature – warm sleepers vs
cool sleepers
Exercise, Diet
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Sleep Hygiene
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Temperature: between 22 - 24 C
Bedroom: Condition yourself that Bed =
Sleep time
Ritual: helps to create a ‘stimulusresponse’ conditioning
Keep sleep time sacred, and minimize
care-giving responsibilities during that
time.
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Diet
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troubled by early awakening? => try
bedtime snack.
Milk products seem to improve sleep.
Alcohol: a single drink can help tense
people relax, but alcohol actually alters
sleep structure by postponing REM
Great care to eat appropriately during the
working / waking time
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Exercise
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Athletes: get more delta
(SWS, restorative) sleep.
Time of day important:
pm exercise has more
effect.
Exercise should be
completed more than
one hour before sleep
time
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Light – most important for
humans
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intensity is important: 7,000 Lux
about the same as a heavily overcast day
most indoor lighting is inadequate
new ‘energy saving’ fixtures are even more
inadequate
implication to hospital administration: high intensity
lights over physicians / nurses working areas
improves productivity and minimizes mistakes.
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Timing of light pulses is
important
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2-3 hours of high intensity light within one
hour of awakening
implication for shift workers: either go
outside while the sun is still up before
going to work the night shift, or buy and
use a high intensity light at home
Fluorescents in windows.
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Drugs and Pharmacology
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Drugs to sleep or to wake or resynchronize
MDs: temptation and access to non-legal
drug use
health care shift workers are at high risk
for drug addiction
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Melatonin
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Melatonin is a re-synchronizer
used in the treatment of circadian rhythm
sleep disorder especially in blind persons
OTC “diet supplement” dosing guidelines
not established. My use: 6-6-3-3
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Melatonin
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3-6 mg, taken one hour prior to desired
(new) sleep time
Diminished (genetically?) in aging.
Full effects of chronic exposure not yet
known.
Not FDA regulated, but seems to be
extremely safe for brief use as in phase
adjustment.
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Melatonin stimulant Ramelteon
(Rozerem)
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Rx only.
stimulates melatonin release
Ramelteon promotes the onset of sleep
and helps normalize circadian rhythm
disorders.
Ramelteon is approved by the Food and
Drug Administration (FDA) for insomnia
characterized by difficulty falling asleep.
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Hypnotics: Benzodiazipines
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Benzodiazepines: short acting for sleep
onset or napping. Triazolam (Halcion)
Medium or long-acting: for sleep
maintenance. estazolam [ProSom]
quazepam [Doral]
Possibility of rebound insomnia
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Benzodiazepines side effects
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can disrupt sleep architecture
may have residual sedative effects lasting
into the next working period
many are fat soluble and will leach out
over many days
illegal in some working environments
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Non-benzodiazepine hypnotics
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Less effect on sleep architecture than
benzos, less rebound insomnia
Zolpidem (Ambien) moderate to long
acting
Eszopicline (Lunesta) moderate duragion
Zaleplon (Sonata) short acting
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OTC hypnotics
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Benadryl – 25-50mg. Tachyphylaxis
Alcohol – disrupts sleep architecture
Herbs: hops, valerian, passion flower
Marijuana – legal issues, prolonged effects
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Diphenhydramine / sedative
antihistamines
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sedative antihistamines help induce sleep,
and in some, help maintain sleep
effect on sleep architecture is minimal
tachyphylaxis: effects wane within days
may produce prolonged sedation,
interfering with performance and
maintenance of new schedule when not at
work
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Alcohol
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disrupts sleep architecture
delays REM sleep
variable effect on sleep latency
recommendation for shift workers: finish
your alcohol more than one hour before
scheduled sleep time
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Cheat Sleep: stimulants
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OTC: primarily caffeine
Illegal: Cocaine, “Speed” and various
“uppers”
Legal:
• amphetamines and amphetamine –like drugs
• Ampakines and their sucessors
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Amphetamines
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methylphenidate (Ritalin, Metadate,
Concerta)
dextroamphetamine Plus amphetamine
(Adderall)
Dextroamphetamine (Dexedrine)
lisdexamfetamine dimesylate –
metabolized to methamphetamine
(Vyvanse)
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Ampakines and their successors
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Modafinil (Provigil, Alertec, Modavigil, Modalert,
Modiodal, Modafinilo, Carim, Vigia)
analeptic drug manufactured by Cephalon, and
is approved by the FDA for shift workers
Armodafinil (Nuvigil) is the active (−)-(R)enantiomer of the racemic drug modafinil
Side effects include potentially cognitive
enhancement, and loss of effect of BCPs
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Caffeine
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harmless in small doses
taking caffeine to get through the night
shift may interfere with day sleep
careful with timing of caffeine intake
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Optimal phase adjustment
strategies
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bright light early in waking time
significant exercise later in waking period
optimize sleeping conditions: aluminumfoil on the windows, ear plugs, eye
shades, fan
stay on the same schedule without varying
by more than an hour as long as you can
Consider Melatonin.
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Summary
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American society is more 24 / 7
EM always 24 / 7
Use circadian principles to improve your
well being and prolong your professional
life and your personal life
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Resources
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American Academy of Sleep Medicine
One Westbrook Corporate Center, Suite
920
Westchester, IL 60154
(708) 492-0930
National Sleep Foundation
1522 K Street, NW, Suite 500
Washington, DC 20005
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Enhancing adaption
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Rotating shiftwork schedules: can we
enhance physician adaptation to night
shifts?
Smith-Coggins R , Rosekind MR , Buccino
KR , Dinges DF , Moser RP
Acad Emerg Med 1997 Oct;4(10):951-61
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Best single reference
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"Why we Sleep" by James Horne.
Published by Oxford University Press
Walton St Oxford OX2 6DP 1988
a classic overall reference
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Web Links
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Northwestern University, Center for Sleep &
Circadian Biology,
About Circadian Rhythms
National Sleep Foundation,
Strategies for Shift Workers
National Sleep Foundation,
Sleep and the Traveler
National Institute of Mental Health, How
Biological Clocks Work
Sleepnet.com
Circadian Rhythms and Shift Work
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