Owl or lark: Munich university pilot project looking into people's body clocks - effects on shift work investigated at ThyssenKrupp Electrical Steel116 employees of the electrical steel manufacturer ThyssenKrupp Electrical Steel in Bochum have taken part in a five-month experiment involving changes to their work shifts - in the interests of science and their own health. As part of a basic research project Prof. Dr. Till Roenneberg and Dr. Céline Vetter from Ludwig Maximilian University in Munich are investigating the subject of chronobiology, i.e. the effects of time on physiology and human behavior. "Valuable research data came from ThyssenKrupp Electrical Steel, one of our subsidiaries," explains Dieter Kroll, chief human resources officer at ThyssenKrupp Steel Europe and initiator of the project, which was launched as part of the demography management program 'ProZukunft'. "Workers in the finishing department took part in the project and helped obtain important insights for the organization of shift work." The results of the study are expected to be available in spring 2013.
Chronotypes "lark" and "owl"
"Our lives are ruled not only by a clock on the wall but also by a biological clock that controls many of the processes inside the body," explains Roenneberg. The effects of our body clock are most apparent in our sleep-wake behavior: "Everybody has a different time window during which our body clock switches us to sleep or activity, and this determines our chronotype. Early chronotypes, i.e. the 'larks' wake up early in the morning and go to bed early. Late chronotypes, or 'owls' prefer to go to sleep later but also wake up later."
Shift work - in time with the body clock
For this reason, shift workers find it difficult to balance their work with their internal clock, says Roenneberg: For example, after a night shift 'larks' sleep for much shorter periods than 'owls' because their body clock is set for activity. The late sleeping pattern of an 'owl' results in a sleep deficit before an early shift - causing a kind of 'social jetlag': The body clock and social clock are not in synch. "Lack of sleep and sleep outside our personal sleep window can have various adverse effects on our health," says Roenneberg. For example we may become more susceptible to illness or obesity, or turn more often to nicotine or alcohol.
Modern health management
"Taking chronotypes into account in shift work is an important aspect of employee health management that has so far been neglected worldwide," says Kroll. "Based on existing laboratory findings on this subject we got workers from our electrical steel subsidiary to take part in a five-month field experiment. It involved modifying the shift system to take into account the chronotypes of shift workers as well as productivity requirements."
Questionnaire, clock and sleep diary
First the workers' chronotypes were determined with the aid of a detailed questionnaire. Following evaluation and the introduction of new shift rosters, the employees worked for a five-month period in a shift pattern matching their chronotype as far as possible. At three points - under the existing system, shortly after the switchover, and at the end of the five-month project - the workers wore special equipment to measure their activity and kept a sleep diary to record long-term effects. After the five months the workers returned to the old shift system and were subsequently questioned about their wellbeing and the 'social compatibility' of the respective shift systems.
Analysis under way
The data collected during the project are now being analyzed by Prof. Roenneberg's team at Munich University. Initial results will not be available until spring next year. "We expect the chronobiological adjustment of the shift system to bring improvements in numerous factors - for example increases in sleep duration and improvements in sleep quality. We won't know the detailed results of the shift changeover until we've analyzed the data thoroughly," says Roenneberg. Depending on the outcome of the study, there could be medium-term implications for shift work: "One consequence could be a rethink about rotating shifts and their effects on people," explains project mentor Kroll: "In the interests of health and personal wellbeing it would be helpful if we could take employees' individual chronotypes into consideration when planning shift work in the future."