What is shift work? Shift work is defined as work outside of the normal daylight hours from about 7am until 6 pm Shift work is defined as work outside of the normal daylight hours from about 7am until 6 pm Midnight Noon

What is Shift Work?  One speaks of shift work if two or more persons, or teams of persons, work in sequence at the same work place.  Often, each worker s shift repeats, in same pattern, over a number of days.

 Production process > 8 hours or continuous  Expensive machinery that must be used continuously to be profitable

7 How many workers work shift work in North America? 13 – 16% of total work force work some shift work Total of shift workers estimated to be million 5-6 % work evening shifts 4-5% work permanent night shift 4-5 % work rotating shifts

Why can shift work be difficult? That is, they are biologically programmed to sleep during the day and be awake at night. e.g. owls, bats, raccoons Some animals are what scientists call NOCTURNAL 8 DIURNAL Humans are what scientists call That is, we are biologically programmed to sleep at night and be awake during the day.

How does the body work  Internal Biological Clock (Circadian rhythm)  External stimulants

Circadian Rhythm Different body functions vary during the 24 hour day Metabolism is greatest in the afternoon to evening Most people most alert 10 PM-8 AM and most sleepy 2-4 AM The body has a natural cycle of 25 hours External factors synchronize us to a 24 hour day The internal clock is located in the suprachiasmatic hypothalmus

The Suprachiasmatic Nucleus

Circadian body rhythms Hormone and gastric secretions Body tempreture Bronchial reactivity Blood Pressure Sexual arousal Anxiety Metabolic Rate Short term memory Work performance

Biochemistry and Circadian Rhythms

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

In 1879 Thomas Edison invented the light bulb. In 1879 Thomas Edison invented the light bulb.

This forever changed our ability to work at night, but not our biological programming to sleep at night. This forever changed our ability to work at night, but not our biological programming to sleep at night.

The 4 Hazards of Shiftwork 1. Increased risk of errors & accidents in the work and out of the work 2Insufficient daytime sleep leads to increased fatigue & sleepiness 3. Increase in health problems 4. Increase in social and domestic problems

Fatigue affects alertness in many shiftworkers % of shiftworkers feel sleepy during night shift (?% nap!) Studies show increase in accident rate Tendency for more severe / serious accidents to occur Alertness and Accidents

Fatigue Related Accidents Midnight Noon Numbers

Meter Reading Errors Midnight Noon Numbers

Fully Alert Midnight Noon Relative Alertness Biological Rhythms Drowsy

Exxon Valdez 00:15 Full Alertness Time of Day & Major Accidents Bhopal 01:00 Chernobyl 01:23 Three Mile Island 04:00 Midnight Noon

Exxon Valdez Disaster Cleanup cost: $2 Billion Exxon Fined: $5 Billion Environmental damage: ?$

Health Hazards Short effects: sleep disturbance Poor concentration Decrease alertness Decrease safety Prolonged exposure to chemical and biological substances and other hazards

Long effects: GI problem Reproductive effects Cancer Exacerbation of Sleep disorders Asthma Diabetes mellitus Coronary Artery Disease

GI Dis. 75% of night workers vs. 20% of day workers Complaints –Loss of appetite –Constipation –Dyspepsia –Heart burn –Abdominal pain –Flatulence Many problems may not show up until years later Reasons –Poor food quality –More caffeine –More alcohol –More tobacco –Drugs used to keep awake

Cardiovascular problems Increased incidence of ischemic disease May be related to: disturbance of circadian blood pressure and pulse rate Substance abuse more likely in shift workers Elevated triglyceride levels in phase advance workers

Hypertension Shift workers were found to have approximately 25% greater chance of developing hypertension than non shift workers

Cancer At least three nights per month for 15 or more years may increase the risk of Colorectal cancer in women 35% Shorter durations also have increased risk Due to the suppression of melatonin production with nocturnal light exposure. Melatonin has anti- neoplastic properties Breast Cancer, Attributed to inhibition of melatonin production by light exposure during the night

Cognitive Ability Recent studies have found deterioration in cognitive ability in shift workers vs. non shift workers. This increases with duration of exposure The effect seems to diminish 4 years after discontinuation

Medical evaluation: History: CAD GI dx Sleep dx Epilepsy diabetes Asthma Difficulty in night vision

Shift workers demonstrate: More depression and despondency More likely to use psychotropic drugs or require hospitalization Will have magnification of underlying depression or bipolar disorders Circadian rhythm disturbance may be a cause for depression

Social Impact Increases Divorce Family violence Social Isolation Sexual dysfunction May affect women more than men

Impaired logical reasoning and decision-making Impaired vigilance and attention Slowed mental operations Loss of situational awareness Slowed reaction time Short cuts Fatigue Effects on Performance

Major Fatigue Factors Time of Day: between midnight and 6 AM Cumulative Sleep Debt: Acute Sleep Debt: More than 17 hours since the last sleep period Continuous Hours Awake: Less than eight hours in last 24 hrs. More than eight hours accumulation.

Shift work type: 1.Fixed pattern Night Evening 2.Rotating pattern Clockwise (morning- evening- night) Rapid (less than 4 days) slow (more than 4 days) Counter clockwise (night-evening- morning) Rapid slow

3.Oscillating shift work 4.Split shift work 5.Relief Shift work

Quickly rotating shift system : Minimize sleep deprivation (Fischer et al., 1997) Minimize circadian rhythm disruption (Knauth 1993, 1995) Improve social contacts (Knauth 1993, 1995) Improve alertness and well- being (Williamson & Sanderson 1986, Phillips et al., 1991) Clockwise rotation: Better tolerated by the shift workers,Improve production & well-being (Czeisler et al., 1982) Improve sleep quality (Folkard 1993) Reduce physical, social and psychological problems (Landén 1981)

Shift work Maladaptation 15-20% of workers Signs & symptoms: Sleep dis. Fatigue Behavioral dis. GI dis. Sedative drugs usage

Shift work Maladaptation: Age > 50 Morning type Second job or heavy house work Long sleep time Fixed & regular sleep pattern Hx sleep dis. Hx GI dis. Hx cardiovascular dis. Asthma,DM,Epilepsy

How to keep worker alert? High illumination level Breaks Naps Occasional stirring music Stretching or light exercise Social interaction Snacks & caffeinated beverages FDA recommended use Modafinil (Provigil) for shift work sleep disorder

Suitable Shift systems: Daily work: not be more than 8 hr. Number of night or evening shifts: as small as possible. A full day of free time follow every night shift Contain consecutive work-free days, preferably including the weekend Clockwise rotation Rapid Shorter shift ( < 8hr) : heavy manual work Longer shift (12hr) : light job