Health impacts of shift work: review of the evidence Prof Derk-Jan Dijk, PhD, FRSB, FMedSci Tuesday 16 October 2018, 1.00-5.00pm Attlee Suite, Portcullis House

What do we mean by shift work? According to the Health and Safety Executive Standard work schedule/standard daytime hours A work schedule involving an activity during the day, commonly for a period of eight hours between 7.00 am and 7.00 pm. There is no specific definition of shift work in law Shift work means A work activity scheduled outside standard daytime hours, where there may be a handover of duty from one individual or work group to another A pattern of work where one employee replaces another on the same job within a 24-hour period Alternative definition: Start of work between 2pm and 6.30am Tuesday, 30 April 2019

Examples of shift work Work during the afternoon, night or weekend, typically with periods of the work schedule outside standard daytime hours Extended work periods of 12 hours or more, often associated with compressing the working week Rotating hours of work Split shifts, where work periods are divided into two distinct parts with several hours break in between Overtime Standby/on-call duties Tuesday, 30 April 2019

Typical Shift Work Schedules Characteristics/things to consider Shift pattern Permanent shifts Rotating shifts Forward rotation Backward rotation Shift rotation Fast rotation Slow rotation Shift timing Night shifts Early morning starts Afternoon starts Daytime shifts Shift duration 8-hour shifts 12-hour shifts Shifts longer than 12 hours Variable shift lengths Split shifts Rest breaks within shifts Tuesday, 30 April 2019

Prevalence of shift work? Depends on precise definition/varies by sector/ country https://www.eurofound.europa.eu/data/european-working-conditions-survey UK employees working shifts 22% UK employees working at least one night shift per month UK night workers (2017) 3.2 million; 11.7%; [TUC report] USA work time arrangements outside 6.00am - 6.00pm 29% 2009 RCN survey of the nursing workforce: 57% worked shifts and of those 58% internal rotation 32% day shifts 10% permanent night shifts U.S.: data from the 2010 National Health Interview Survey. Tuesday, 30 April 2019

https://www. eurofound. europa https://www.eurofound.europa.eu/data/european-working-conditions-survey NL=14% UK=22% HR Croatia: 40% Tuesday, 30 April 2019

Health impact of shift work The Evidence Base 2016 Based on 38 meta-analyses 24 systematic reviews Narrative reviews Articles outlining possible mechanisms Tuesday, 30 April 2019

Circadian Photoreception Conceptual Framework Circadian Homeostat Sleep-Wake Cycle Light-Dark Cycle Biological time Sleep-wake history Shift Work Circadian Photoreception Modified from: Dijk and Lockley 2002 Waking functioning/ Health Individual Genetic variation

Health impact: Accidents & Sleepiness During shift (but may include commute) Shift and night work and long working hours--a systematic review of safety implications Wagstaff and Sigstad Scand J Work Environ Health. 201;37:173-85 Shift work Long Working Hours  increase in accident rate ranged from 50%-100% Sleepiness during shifts Shift Work Sleep Disorder (International Classification of Sleep Disorders, 3rd Edition) Insomnia/excessive sleepiness Reduction of total sleep time Present for at least three months Prevalence: 10-23% Tuesday, 30 April 2019

Croydon tram crash 'caused by driver falling asleep and speeding' The final report into the accident said the driver could have fallen into a “microsleep” during a 49-second period when the tram was passing through three consecutive tunnels in the hours of darkness. Inspectors said it was possible a “sleep debt” accumulated by the driver, who was regularly sleeping less than six hours before waking up at 3.20am to go to work, could have made him fatigued. Tuesday, 30 April 2019

Sleepiness Akerstedt and Wright. Sleep loss and fatigue in shift work and shift work disorders Sleep Med Clin 2009 4:257-271

Night shift Day shift Commute home Tuesday, 30 April 2019 Modified from Dijk, Duffy, Czeisler J Sleep Res 1992

Health impact: Sleep Subjective sleep quality (during ‘shift’) Non-refreshing Awakening difficult  Early morning shift Sleep duration (during ‘shift’) Short after night shift: [subjective 5h:51min; objective 5.0-5.5h] Short before morning shift [subjective 6h:37min; objective 5.5-6.0h] Long after evening shift [subjective 8h:12min] Exacerbating factors: Short recovery times between shifts Fast rotation When sleep during shift days and recovery days is considered No strong evidence for chronic sleep loss Chronic sleep disturbances (e.g. insomnia symptoms) Risk Ratio: 1.16 [95% Confidence Interval 0.97-1.38] Tuesday, 30 April 2019

Health impact: Cardiovascular disease Based on systematic review and meta-analysis of 34 observational studies More than 2 million people Findings Shift work associated with increased risk for Myocardial infarction (Pooled RR: 1.23; 95%CI 1.15-1.31) Ischaemic stroke (pooled RR: 1.05; 95%CI 1.01-1.09) Highest risk associated with night shift (RR: 1.41) Evening shift: not significantly related Tuesday, 30 April 2019

Health impact: Metabolic disorders The Relationship Between Shift Work and Metabolic Risk Factors: A Systematic Review of Longitudinal Studies. Proper et al. Am J Prev Med. 2016 50:e147-e157 Shift work is associated with Obesity/weight gain One estimate of RR: 1.14; 9%CI 1.01-1.28 Impaired glucose tolerance Type 2 diabetes 12 cohort studies, 226 652 participants OR 1.12 (95% CI: 1.06-1.19) 10 cohort studies OR 1.15 (95% CI 1.08-1.22)

Health impact: Cancer Breast cancer 2007 International Agency for Research on Cancer  shift work probably increases the risk for breast cancer Since 2007 Three reviews conclude Insufficient or limited evidence Four reviews report that Long exposure (> 20 years) associated with elevated risk for breast cancer RRs and 95% CIs 1.19 (1.05 to 1.35) 1.20 (1.08 to 1.33) 1.19 (1.08 to 1.32) 1.06 (1.01 to 1.10) Tuesday, 30 April 2019

Health impact: Cancer OR 1.32; 95% CI 1.12-1.55 Prostate Cancer Meta-analysis based on eight studies Shift work is associated with increased risk for prostate cancer RR 1.24; 95%CI: 1.05-1.46 2.8% increase in risk for each five year’s duration of night shift work Colorectal cancer Meta-analysis based on six studies Night shift work is associated with increased risk for colorectal cancer OR 1.32; 95% CI 1.12-1.55 11 % increase in risk for each five year’s duration of night shift work Tuesday, 30 April 2019

Health impact: VARIA Areas of interest Mortality Cognitive decline Depression Multiple sclerosis Quality of Life Individual differences Sex Age Chronotype Tuesday, 30 April 2019

Health impacts of shift work: review of the evidence Conclusions Shift work is associated with a variety of adverse health outcomes Negative effects of shift work may be mediated by Sleep disturbance Circadian disturbance Life style factors Diet Physical Activity Etc., Tuesday, 30 April 2019

Peripheral circadian rhythm disruption when sleep is mistimed In phase Out of phase In phase: 1,396 rhythmic ‘genes’; 6.4% Out of phase: 228 rhythmic ‘genes’; 1.0% These changes were observed despite melatonin and cortisol not being affected Night Archer et al. PNAS 2014;111(6):E682-91

Archer and Oster J Sleep Res 2016

Health impacts of shift work: review of the evidence Prof Derk-Jan Dijk, PhD, FRSB, FMedSci Tuesday 16 October 2018, 1.00-5.00pm Attlee Suite, Portcullis House