1. The biological effects of shift work

2. Shift Work Overview of key effects Shift work causes many health- related effects Shift work causes many health- related effects Disruption of circadian rhythms affects physiological function Disruption of circadian rhythms affects physiological function Shift work = health problems: poorer health habits increase vulnerability to illness Shift work = health problems: poorer health habits increase vulnerability to illness Biggest effect: Sleep disruption Biggest effect: Sleep disruption Three principal shifts: Three principal shifts: night, morning & afternoon night, morning & afternoon

3. Shift Work & risk of Coronary Heart Disease in Women The study - Kawachi et al. 1988 The study - Kawachi et al. 1988 79 109 women 79 109 women 42 to 67 years - free of diagnosed CHD and stroke 42 to 67 years - free of diagnosed CHD and stroke rotating night shifts - at least three nights p/m in addition to day and evening shifts rotating night shifts - at least three nights p/m in addition to day and evening shifts 6 or more years of shift work may increase the risk of CHD in women 6 or more years of shift work may increase the risk of CHD in women

4. De-synchronisation of circadian rhythms Fast rotating shift work changes secretary patterns of melatonin, prolactin, cortisol and testosterone (Touitou et al, 1989)

5. Shift work affects patterns of sleep and wakefulness Disrupts circadian rhythms & mechanism of sleep The most troublesome symptoms are: difficulty getting to sleep, shortened sleep drowsiness during working hours No clear indication that long-term shift work causes chronic sleep problems (Åkerstedt, 2003)

6. Risk of cancer in female Nurses Night-shift work is linked with an increased risk of breast cancer Night-shift work is linked with an increased risk of breast cancerALSO Exposure to light at night suppresses the production of melatonin, a hormone that inhibits intestinal cancers Exposure to light at night suppresses the production of melatonin, a hormone that inhibits intestinal cancers Night shift at least 3 nights p/m for 15yrs or more may increase the risk of colorectal cancer (Schernhammer et al. 1988) Night shift at least 3 nights p/m for 15yrs or more may increase the risk of colorectal cancer (Schernhammer et al. 1988)

7. Shift work: Impact on metabolic syndrome Increased risk of cardiovascular disease Increased risk of cardiovascular disease Obesity and high triglycerides levels in men & women Obesity and high triglycerides levels in men & women Obesity more prevalent Obesity more prevalent among women in all among women in all groups, but only in groups, but only in two out of four age two out of four age groups in men groups in men (Karlsson et al. 2003) (Karlsson et al. 2003)

8. Other health disorders Peptic ulcers Peptic ulcers Coronary heart disease Coronary heart disease Compromised pregnancy Compromised pregnancy outcome (Knutsson, 2001) outcome (Knutsson, 2001)

9. Influence of night shift work on psychological state Night shift - associated with psychological complaints Night shift - associated with psychological complaints Study: 18 healthy nurses (age 29; +/-2 yrs) Study: 18 healthy nurses (age 29; +/-2 yrs) Rapid shift rotation system (day work, 8:15-17:15; evening work, 16:00-22:00; night work, 21:30-8:30) Rapid shift rotation system (day work, 8:15-17:15; evening work, 16:00-22:00; night work, 21:30-8:30) Assess psychologic states using a validated questionnaire. Assess psychologic states using a validated questionnaire. High scores for confusion, depression, anger-hostility, fatigue and tension-anxiety High scores for confusion, depression, anger-hostility, fatigue and tension-anxiety Lowest scores for energy after a night shift Lowest scores for energy after a night shift

10. Does shift work lead to poorer health habits? Sent out questionnaire - 2299 respondents –S–Selected 506 who has always done shift work –1–183 workers who had never done shift work Shift workers smoke more & tend to be more overweight than day workers (KivimÄki et al., 2001)

11. The effects of short-term night-shift working Short period (5 days) of night-shift Ten nurses (8 female, 2 male; age 28.1 +/- 1.7 Finding: –pituitary-adrenal responses to CRH are markedly disrupted –mimic abnormalities seen in patients with chronic fatigue syndrome