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Shift Work

Warren Silverman MD Medical Director ACCESS HEALTH SYSTEMS. Shift Work. Or: What time is it anyway?. What is Shift Work?. Regularly scheduled work outside of the normal daytime working hours of 7AM-6PM Permanent night shifts Afternoon or evening shifts Shifts beginning before 6AM.

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Shift Work

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  1. Warren Silverman MD Medical Director ACCESS HEALTH SYSTEMS Shift Work Or: What time is it anyway?

  2. What is Shift Work? • Regularly scheduled work outside of the normal daytime working hours of 7AM-6PM • Permanent night shifts • Afternoon or evening shifts • Shifts beginning before 6AM

  3. Condensed work weeks with extra long weekends • Variable or rotating shifts • Day to evening or day to night • May change weekly or monthly

  4. Why do we need shift work? • Critical services on 24 hour basis • Police, fire, military, healthcare, utilities, transportation, • A production process > 8 hours or continuous • Expensive machinery that must be used continuously to be profitable • Support services for other shift workers • Convenience

  5. Who does shift work? • Men do more night and rotating shifts • Women do more evening and part time work • Younger > Older workers • African-American > Caucasian • Single > Married • Single Mothers > Married Mothers • In 2 job married couples ¼ - 1/3 have at least one shift worker

  6. 20 Million Americans do shift work ; 26% of men, 18% of women • Drop out rate: 20% at year 1; 33% at 2 years • Tolerance declines with age • Cumulative effects • Decreased physiological reserve > 40

  7. Factors describing shift • Permanent (fixed) or rotating • How long? • How many days before a rest day • How many rest days on a “weekend” • Overtime? • Length of rest between shifts • Is there rest during shift • Is Schedule regular and predictable

  8. Permanent Nights • Most permanent night workers never really get used to the schedule • Many nights they feel tired and sleepy • Fatigue because of return to day hours on days off • Family and friends active during the day • Errands and chores during the day • Sleep less during the day

  9. Rotating Shifts • Can never adapt to a set work schedule • Used to be more “fair” to all workers • Rotating shift workers have more complaints than others about physical and psychological health • Special Risks

  10. Special Features • Speed • The number of consecutive days before a shift change • Direction • Forward or clockwise (day-evening-night) • Reverse (day-night-evening)

  11. Longer rotations (3-4 weeks) may allow better adaptation to shift • Shorter (1-2 days) allows no time to get used to night shift, but can get through it quickly to get to rest day. Used more in Europe than US

  12. Work-Rest Ratios • If an 8 hour shift = 16 hours to do everything else and sleep • If a 12 hour shift, only 12 hours to do everything else. • Family duties do not decrease no matter the shift time leading to less sleep and rest • Fatigue is cumulative

  13. Unpredictable schedules • Health care workers with emergencies or covering call ins • A factory breakdown or last minute rush order • A last minute “call board” assignment to move an order • Being on call and getting called in (Doctors do know about this!)

  14. How does the body work • Internal Biological Clock • Circadian rhythm • Regulated by sunlight and darkness

  15. Circadian Rhythm

  16. Circadian Rhythm • Different body functions vary during the 24 hour day • Metabolism (energy from food) is greatest in the afternoon to evening • Most people most alert 4-6 PM and most sleepy 4-6 AM • Personal differences between people

  17. Circadian body rhythms • Hormone and gastric secretions • Bronchial reactivity • Blood Pressure • Sexual arousal • Anxiety • Work performance • Metabolic Rate • Short term memory • Family interactions

  18. The body has a natural cycle of 25 hours • Internal and external factors synchronize us to a 24 hour day • The internal clock is located in the suprachiasmatic hypothalmus

  19. External clues “Zeitgebers” • Light/Dark cycle • Timing of meals • Social interactions • Actual time clock

  20. Sleep ( Not now!) • Night workers get the least sleep (6.6 hours) • Evening workers get the most sleep (7.1 hours) • Day workers get medium amounts (6.7 hours) • Rotating workers sleep the least of all.

  21. Sleep during the day is usually 2-3 hours shorter • It is lighter sleep and more easily disturbed by noise • There are more activities and noise during the day

  22. Sleep • Sleep after night work • Shorter, less satisfying or refreshing • Delta Sleep • Repair and Maintenance functions

  23. Sleep loss makes it easier to fall asleep at inappropriate times • Will decrease concentration • Increase accidents ( driving, dangerous machinery) • Sleep can occur in short episodes lasting a few seconds without even realizing it. Very dangerous time.

  24. Night workers have a drop in alertness at 2-4 AM • Accidents at 3 Mile Island, Bhopal, Chernobyl, and the Exxon Valdez oil spill each occurred between midnight and 4 AM

  25. Sleep deprivation • Mild sleep disruption may not have significant impact • Cumulative increasing each night • Disordered sleep is compounded by circadian dysrhytmia

  26. Sleep Deprivation • Six days of restricted sleep (4 hours per 24-hour period) caused changes to the sleep architecture similar to the changes seen in people suffering from depression. • changes in several natural body rhythms of hormone secretion • Melatonin • cortisol • thyroid-stimulating hormone • leptin • Prolactin • growth hormone.

  27. What happens if we remove cues and disturb the internal clock? • Desynchronosis: • Core body temperature and digestive secretions may remain near daily mean levels • Entrainment • When we try to regain our rhythms with light dark cycles • Different physiologies may entrain at different rates and we may lose the normal phase relationship of one to another

  28. Signs of desynchronosis • Sleep disturbance • Short term fatigue • Irritability • Loss of Appetite • Judgment alteration

  29. What does The Dark do? • Triggers changes leading to sleep • Dropping blood pressure • Dropping heart rate • Dropping breathing rate • Dropping temperature • Slowed digestion

  30. Two physiologies most critical to work and safety are core body temperature and sleep/wakefulness

  31. Rotation • While forward rotation works better with circadian rhythms of the body, reverse rotation is more common in the US (workers pick up an extra “day off” going from night to evening)

  32. Clockwise shift rotation • Phase delaying: places less strain on the human internal clock • Higher worker satisfaction • Fewer health complaints and work schedule complaints • 20% increased productivity c/w phase advanced shifts

  33. Counter clockwise • Phase advancing: • For every hour of advancement a full day is needed for entrainment (ie: phase advancement to an earlier shift every 7 days necessitates a week or longer to adapt after each rotation) • 25% of workers may not adapt

  34. Other observations • Air travel: • Entrainment is much easier westbound than eastbound • “Night owl” type personalities adapt better to night and rotating shifts than “morning larks” • Rotation every 21 days results in 70% fewer complaints than every 7 days

  35. Sleep stages

  36. Stage 1 • Initial part of sleep • 10-15 minutes • Slow rolling eye movements • EEG = Alpha waves • If awakened during this phase, will deny sleeping

  37. Stage 2 • Largest part of sleep @ 50% • Infrequent or absent eye movement • EEG = occasional sleep spindle bursts • Deprivation of this stage may lead to total sleep loss • Not usually “made up” after sleep deprivation

  38. Stages 3 & 4 • Slow wave sleep (SWS): deep • Muscle tone; variable • Arousal; difficult • EEG: High voltage; Delta waves • Important to body repair • Not as susceptible to circadian factors

  39. REM • After 1-2 hours • Paralysis of muscles with occasional twitches • Body loses some thermoregulatory ability • Heart rate and blood pressure very variable • Restorative and dream sleep • Important for psychosocial adjustment and development • Greatly influenced by circadian factors

  40. Cycling between stage 4 and REM • Increased with caffeine • REM suppressed with alcohol • Sedatives increase stage 2 non restorative sleep • Older less SWS, more frequent awakenings and less sleep time • Younger greater frequency and longer REM intervals

  41. Health Effects Immediate Long term

  42. Health Hazards • Gastrointestinal Problems • Cardiovascular problems • Sleep and stress related disorders • Drug and Alcohol use • Risks from prolonged exposure to chemical and biological substances and other hazards • Effects on pregnancy

  43. Digestive • Increased incidence of ulcers. • Often eat at night when digestion and other body functions are slowed down • May eat less nutritious foods at night (snack foods) • Drink more caffeine products at night

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