Shift Work By M H Davari M D

Shift Work By M. H. Davari M. D

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

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

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

How many workers work shift work in North America? • 5 -6 % work evening shifts • 4 -5% work permanent night shift • 4 -5 % work rotating shifts 13 – 16% of total work force work some shift work Total of shift workers estimated to be 24 -25 million 7

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

How does the body work v. Internal Biological Clock (Circadian rhythm) v. 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.

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 2 Insufficient daytime sleep leads to increased fatigue & sleepiness 3. Increase in health problems 4. Increase in social and domestic problems

Alertness and Accidents • Fatigue affects alertness in many shiftworkers • 80 -90 % of shiftworkers feel sleepy during night shift (? % nap!) • Studies show increase in accident rate • Tendency for more severe / serious accidents to occur

Numbers Fatigue Related Accidents Midnight Noon Midnight

Numbers Meter Reading Errors Midnight Noon Midnight

Biological Rhythms Relative Alertness Drowsy Fully Alert Midnight Noon Midnight

Fu Al ll er tn es s Time of Day & Major Accidents Exxon Valdez 00: 15 15 Chernobyl 01: 23 Bhopal 01: 00 5 Dr ow sy 10 Three Mile Island 04: 00 12 Noon 15 18 21 00 Midnight 03 06 09 12 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 antineoplastic 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

Psychological • 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

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

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

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-eveningmorning) • Rapid • slow

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

Quickly rotating shift system: Clockwise rotation: • Minimize sleep deprivation (Fischer et al. , 1997) • Better tolerated by the shift workers, Improve production & well-being • Minimize circadian rhythm disruption (Knauth 1993, 1995) • Improve social contacts (Knauth 1993, 1995) • Improve alertness and wellbeing (Williamson & Sanderson 1986, Phillips et al. , 1991) (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 ( < 8 hr) : heavy manual work • Longer shift (12 hr) : light job