Sleep scientist Dr Chris Harvey on the effects of night shift work

Hello my name is Chris Harvey. I work at the Sleep and Circadian Neuroscience institute at the University of Oxford. Funded by the Wellcome Trust, our research focuses mostly on sleep and psychosis but we're also interested in sleep in adolescence and sleep and sleep disorders particularly insomnia. Talking about the effects of shift work on an individual we know that shift work affects people across various domains. So first there's the health domain. People work shifts and particularly night shift workers tend to report and increased rate of depression, of anxiety, of cancer, of diabetes, cardiovascular disease..... and of weight gain. We also know that they have lower happiness ratings in their work and in their home lives. There's a greater incidence of divorce in people that work shifts. They often report engaging less in social activities and we also know that the children of shift workers underperform at school. So the effects of shift work can be both physical and psychological. So we know that shift work effects the health and happiness of an individual we also know that it effects their performance at work. Shift workers tend to report a greater incidences of poor memory. They also show slower reaction times in experimental tasks and we know for example that nurses on night shift report four times as many errors during the night shift as they do compared to day shift workers and they attribute these errors to tiredness. One thing that's less obvious is how shift work effects your performance but also your perception of your performance. So to give you a way to think about this think about driving if you're driving while sleep deprived your performance suffers more than it does than if you were driving over the legal drinking limit. Another thing that happens when you are sleep-deprived is you tend to overestimate how well you perform in a given task. So shift workers, particularly towards the end of their shift who are very sleep deprived aren't the best judges of how well they are doing or what they are capable of delivering. The long-term consequences shift work can be quite severe. So what happens when you're working a night shift.... well you're working at a time when your body is physiologically prepared for sleep it wants to sleep Towards the end of your night shift you have quite a lot of sleep debt. So you're constantly fighting against sleep deprivation. How does your body fight against sleep deprivation to keep you going? Well the first thing it does is increase the activity of the stress system. This then leads to an increase in blood pressure and in heart rate. This puts extra strain on the cardiovascular system. This feeds into the heart disease that has been associated with sleep deprivation or sleep disruption. To get the energy it needs, to keep going and to keep these stress systems active to keep you awake the body also increases appetite to get more energy through food. The foods that it craves tend to be things that are unhealthy for you that are energy rich, high sugar foods. This feeds into weight gain and type 2 diabetes and over the long term these issues can be very damaging for shift workers and are more pronounced in this population. You will also have associated with shift work, greater incidences of mood disorders such as depression again probably associated with sleep disruption but also the social aspects of night shift not having as fulfilling a social life or a family life. People don't adapt to night shift or very few people adapt successfully to night shift. Now, why is that? That's because of our circadian systems or circadian processes. So, what are these? Our circadian system is basically our inner timekeeping system. So every aspect of our our behaviour and physiology follows a cycle throughout the 24 hour day. Things like; hormone release, heart-rate... they all follow a pattern throughout the 24 hours. So, how does this system work? It is controlled primarily by daylight. We have cells in our eye which sends signals to the brain, telling the brain how bright our surroundings are. They basically tell the brain what time of day it is outside and based on this the brain then sets different physiological processes happening. So as the sun rises, the signals from the light go into the eye telling the brain that it's time to wake up. As the sun moves across the sky and it begins to get darker, the body starts to prepare for sleep because it can detect the brightness of the surroundings and knows that nighttime is happening. Every single cell in our body a circadian clock, has a circadian rhythm. These systems have existed across evolution and across species so these processes have been in place for a long time and they're very difficult to change because they're part of our evolutionary heritage. So how come we can adapt when we travel across timezones? We can get over jetlag but we cannot adapt to shift work or night shift as easily. Well, the main reason for that is when you travel, you go somewhere new you live in a new light dark cycle and it's the light dark cycle that controls this system so your circadian processes will eventually shift to suit your system. You will also change in that situation every other aspect of your lifestyle when you socialise, when your work, when you eat... and these things are feeding into a change in that system. We obviously can't do this with shift workers You can't say to someone that they have to spend their entire day in darkness and expose themselves only light around the period that they are working and during their shift. That would be unethical and cruel, and would probably lead to things like depression for example. So what can be done to help shift workers and to minimise the negative effects of shift work one of the things that may help is manipulating exposure to light. So we know that light controls these systems and it controls your body clock. So before going to a night shift and during a night shift it may be useful to expose yourself to bright light, particularly to blue light which is the part of the light spectrum that the eye is most sensitive to. You can get for example goggles that shine blue light directly into the eye. This will tell the system that it's daytime and it's time to be awake. The other thing to do with light exposure is minimising light exposure close to when you want to sleep. so towards the end of a shift, on the journey home making sure that you don't get too much light into the system cause again that will tell your body that it's daytime and it's time to wake up. So you can for example get glasses which block blue light. This may prove useful in getting a better quality sleep when you do get the opportunity to finally go to bed. As well as managing light exposure the introduction of naps during a shift can be useful Research has shown that having a nap during night shift improves memory improves levels of tiredness and improves performance but naps have to be managed properly - a nap should be either 20mins or 90mins and nothing in-between and ideally a nap shouldn't happen too close to when you plan to go to bed because it will make it more difficult to fall asleep and get your full 8 hours sleep Another thing that needs to be considered from an occupational health point of view is the options that are available to night shift workers particularly when it comes to the food that they're eating so it behooves the employer to make sure that these individuals have healthier options available to them So as an employer why should you care about sleep and sleep disruption in your workforce? Well sleep disruption has a massive effect on the individual in terms of their quality of life in terms of their health and their happiness but also in terms of their productivity and performance at work so improving sleep helps not only the employee personally and professionally it also helps the organisation because the quality and the volume of work produced will be greater Secondary to this the things you can do to manage sleep such as napping or manipulating light aren't prohibitive and aren't costly but they could potentially lead to an improvement in the workforce's health and the productivity of the company