What is circadian rhythm?

Circadian rhythm is a mechanism that regulates wakefulness in a 24 hour cycle. It causes daily fluctuations in a variety of physical and mental processes linked to the predictable changes in natural light levels. Regular sleeping habits (i.e. sleeping and waking at similar times) that match natural light changes (i.e. sleeping during darkness and waking during daylight) are important for an optimal circadian rhythm. Therefore, occasional activities like staying up later at the weekend or flying across time zones which desynchronise the relationship between light levels and sleep/wake timings can impact this system. Shift working, which requires people to be awake during darkness and asleep during daylight for consecutive days, can have more long-lasting effects on this mechanism.  

What are the effects of circadian disruption?

Persistent sleep deprivation can alter cognition. For example, attention deteriorates, with reaction time slowing and lapses in attention increasing following a 12 hour shift. Other processes like visuomotor control (e.g. hand-eye coordination) working memory (e.g. remembering a phone number you just read) are also impacted by sleep loss.

New approach to testing?

Using computerised assessments (similar to those found in ‘brain training’ programs) we intend to evaluate specific areas of cognition in shift workers. This will provide a direct measure of performance and enable us to construct a detailed profile of the effects of shift working on cognition.  

Why is this important?

This area is of considerable importance given that night shift workers, despite potential cognitive compromise, are often expected to work as effectively and productively as those on shifts more compatible with the circadian rhythm. They may also be more likely to be injured in high risk environments. Therefore optimisation of shift patterns and working practice to moderate any cognitive changes could have significant benefits to both workers and their employers. 

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