WEEK 10- SHIFT WORK & SLEEP Flashcards
What is fatigue?
(Distinguish between acute and chronic fatigue)
Fatigue: A state of feeling tired or drowsy that results in reduced
mental and/physical human performance
Acute: can be caused by one very long work day, traveler jet leg, unpredictable events, etc.
Chronic: caused by rotating hours of work, permanent night shift, consistent irregular work hours, extended overtime, etc.
What are some effects of fatigue ?(individual, organizational and societal levels)
Individual: decreased alertness and RT, poor decision making, decreased motivation, reduced memory and recall etc.
Organizational: increased absenteeism and turnover, increased accidents, abusive behaviour in the workplace, decrease productivity, decrease organizational commitment (OC), decreased positive social interactions etc.
Societal: increase MVAs, increased stress related illnesses, poorer health outcomes, negative impact on familial relations and community engagement
What are some methods used to measure fatigue ?
- employee interviews
- questionnaires (ex. Epworth Sleepiness Scale, Karolinska Sleepiness Scale)
- Fatigue Risk Index
- EEG
- Flicker Fusion Tests
- Psychomotor/Cognitive Tests
What causes fatigue?
3 MAIN CAUSES:
1. Long work hours
2. Sleep Debt
3. Time of day/ circadian rhythms
What is considered long work hours?
- Work hours are considered “long” if they are > 41 hours/week or >8 hours/day
Health effects of long Work Hours - ## “Karoshi” (occupation induced sudden death)
What are the health effects/outcomes associated with long work hours?
- “Karoshi” (occupation- related sudden death)
- increased risk of CVD
- increased risk of depression and anxiety
- secondary health behaviours (alcohol, smoking, substance abuse)
-Increased risk of occupational injury - weight/BMI changes
What are the performance effects/outcomes associated with long work hours?
- slower reflexes and RT
- automatic behaviour–> less attention to detail–> more mistakes
- slurring/staggering
- difficulty concentrating
- decreased memory
- poor logic, decision making, and problem solving skills
- decreased motivation
- less alertness and watchfulness/ attention to detail
- increased errors (over-arousal and under-arousal)
What are the two types of sleep debt?
- Cumulative Sleep Debt- more than 8 hours accumulation (ex 1-2 less sleep/night for one week)
- Acute Sleep Debt- less than 8 hours of sleep in 24 hours
Briefly outline the stages of the sleep cycle
– Stage 1: 10-15min, transition between awake and light sleep
– Stage 2: “Clinical sleep” BP & HR drop. Roughly 50% of sleep cycle
– Stages 3&4: Restorative stage of sleep when body and mind growth/repair occur
REM SLEEP: occurs ~70 -90 min after onset of sleep, with 5 cycles occurring per night. REM is when Mental activity/ dreaming occurs. Changes in BP and HR also occur. After the first REM stage, we cycle through stages 2,3,4 & REM for the rest of the night
What are the health effects/outcomes associated with sleep debt?
- fatigue (obvs)
- reduced immune function
- metabolic syndrome
- CVD / CHD
- Mental Health disorders (anxiety, depression, etc)
What are the performance effects/outcomes associated with long work hours?
– Cognitive processing decrements
– Poorer learning and storing new material
– Reduced decision making
– Reduced innovation and creativity
– Reduced planning (self-initiated cognitive activity)
– Increased errors–>increased accidents
What are circadian rhythms?
Circadian rhythms are internal( endogenous) clocks which regulate various bodily processes such body temperature, metabolism, heart rate, blood pressure, etc.
- best measured by body temperature
What are Zeitgebers ?
Zeitgebers refer to the external or environmental synchronizers which act as cues for circadian rhythms. The light/dark cycle is the most important, but eating, social behaviours, physical activity etc, are also relevant.
Briefly explain how light & darkness influence melatonin production & circadian rhythms
Light enters the eye through the pupil and hits the optic nerve in the back of the eye near the retina. The optic nerve then sends signals up into the suprachiasmatic nucleus (SCN), a structure located in the hypothalamus responsible for the regulkation pg melatonin. In the presence of light (during the daytime), the SCN INHIBITS release of melatonin from the pineal gland. In the absence of light however (nigh time), the SCN stimulates the release of melatonin from the pineal gland. Once released form the pineal gland, melatonin enters the blood stream. As a neurohormone, melatonin has various downstream effects on the body, such as lowering blood pressure. Ultimately, the release of melatonin stimulates biological processes which prepare the body for sleep.
Define shift work, double day shifts, continuous 3 shift systems, discontinuous 3 shift systems, split shifts, permanent shifts, irregular shifts,
Shift work : covers a broad spectrum of systems of dividing 24 hours into time spans. Involves dividing work in temporary shifts. Common in the healthcare field, for blue-collar workers, and public safety personnel.
Double day Shift: 2, 8 hour shifts
Continuous 3 shift systems: 24/7 operation (mon-sun). Normally four groups of workers operating the system and rotation occurs weekly or more frequently
Discontinuous 3 shift systems: three groups of workers operate for 24 hours over 5 days and nights (ex. mon-fri)
Split shifts – splitting the daily hours of work into two or more shifts – common in food/transport
Permanent/Fixed Shifts – workers stay on one shift indefinitely (ex. 7am-3pm)
Irregular shifts – shift duration and length not defined in advance. Workers work variable hours/shifts throughout the week. (ex. on call shifts)
Forward shift rotation – mornings to evenings to nights
Backward shift rotation – mornings to nights to evenings
Compressed hours – any shift longer than 8 hours which results in a work week less than 5 days. (ex. the “4 on 4 off” schedule requires workers to work 4, 10 hour shifts, as opposed to 5, 8 hour shifts)
What are the health effects/outcomes associated with shift work?
- increase risk for cancer (breast and ovarian cancer in women, colon cancer in both sexes, prostate cancer in men)
- increase risk for CVD (due to changes in HR and BP by messed up circadian rhythms )
- increase risk of GI disorders, weight problems, etc
- asthma, diabetes, and epilepsy are all exacerbated by shift work
- harmful secondary health effects (increased rates of smoking, alcohol and drug abuse, etc)
- increased psychological stress
- stress caused by high demand-low control , and role overload are possible
- less satisfaction with work-life balance
- research shows more time is spent in REM sleep during an overnight sleep compared to a morning or daytime sleep
- social isolation
What are the performance effects/outcomes associated with shift work?
- increased accidents amongst night shift workers
-medical errors are higher at night and early morning (i.e, night shifts) - higher absenteeism ( especially morning shift after night work)
How do shift workers become agents of risk ?
1) performance decrements and human error : decreased concentration, motivation, reaction time with circadian rhythm disturbance
2) sleep loss creates “night shift paralysis” (temporary paralysis due to sleep loss)
3) Reckless attitude caused by circadian dysfucntion
Briefly explain the physiological mechanism relating night shift work to cancer
Melatonin has anti-cancerous effects.
- In women, melatonin may work as an anti-estrogen agent. This is important because estrogen is a mitogen meaning it stimulates cell growth and proliferation but cannot distinguish between healthy and unhealthy cells. Therefore, chronic high levels of estrogen may lead to development of cancer cells.
- Melatonin not only decreases estrogen levels, but also inhibits angiogenesis (capillary proliferation), reduces cancer cell invasion decreases telomere activity (role in during cancer cell replication) helps with apopsis of unhealthy cells (programmed cell death)
- Increased exposure to light–> less melatonin production–> damage to circadian genes–> formation of abnormal cells
-Also, individuals who work night shift are exposed to less sunlight as they sleep during the day time. This results in decrease vitamin D which is an antioxidant and lays a role in immune function
Compare rotating shift work to fixed shift work
fixed shift: workers are permanently assigned to a particular shift,
Rotating shifts: Workers move from shift to shift
- Generally speaking, rotating shifts are more likely to be associated with problems than fixed shifts
- particularly true if the direction of the rotation is from day to night to evening (as opposed to day to evening to night).
- Rotating shifts lead to sleep disturbances, which in turn are associated with medical (e.g., gastrointestinal) and psychological (e.g., anxiety and depression) difficulties.
- Fast rotation rate (rotation every 2-3 days)
–>better bc workers do not have time to synch their circadian rhythms
- slow rotation rate (rotation every 2-3 weeks) –> worse because it takes ~2-3 weeks for circadian rhythms to adjust, meaning these workers will have just begun to adjust to their new sleep schedules when they start a new rotation
- WORST ROTATION IS 2 WEEK (SLOW) BACKWARDS ( DAY–>NIGHT–>EVENING) ROTATION !!
