Michael Cleary Gaffney: Blame It On My Chronotype

Each of us have preferences to what we like, be that  in types of music we listen to, the people we date and the types of food we eat.  Similarly each of us have a preference for the timing we go to sleep and wake up.  Some of us are regarded as owls, that is, we have a strong tendency to go to bed late at night and get up late during the day while larks are at the other end of the spectrum and express a preference to get up early in the morning and go to bed early at night. This preference is referred to as chronotype – the timing of the day in which one is most optimally mentally and physically active. Our chronotype is defined in part genetically but also environmental factors play a function. Typically, it is observed that males are more oriented towards evening types compared to females. Secondly, later chronotypes have a different version of the circadian clock Per3 gene compared to morning types. Age plays a significant role in determining our chorontype with toddlers and younger children expressing a morning type preference and teenagers expressing an owl type phenotype. This preference is oriented back towards a lark preference as we grow older.

Unfortunately, our work and school schedules do not take into account our chronotype. Most of us who work 9-5 days typically rely on the alarm clock to wake us up during the weekdays and at the weekends we adjust and wake at our time preferences. Some researchers have investigated whether working against our chronotype has deleterious consequences for our cognitive performance. Results have found that  morning types perform a range of cognitive tasks and IQ tests more efficiently in the morning than in the afternoon whereas, evening types demonstrate the reverse. This is even observed in cognitively challenged individuals who display superior performance in neuropsychological testing when tested at their optimal time of day than when not.

In order for optimal performance output it is fundamental for society to start taking ones chronotype into account. This is especially pertinent to teenagers whom are routinely working against their chronotype as a result of being required to be in school from the early hours of the morning. Not only are they going to bed late as a result of their late night preference they are expected to get out of bed early which is going against their natural circadian clock. Therefore, teenagers, when at school are typically sleep deprived. This deprivation has deleterious consequences for alertness and scholastic performance. This is a grave cause of concern given that academic achievement during second level is an indicator of the type of profession/course studied at university.

A pioneering experimental study at the University of Oxford has investigated whether starting school times later in the morning has any major advantages compared to the tradition school time start. Although still ongoing, preliminary results have found that starting the school day later for teenagers is resulting in better academic and social performance compared to students who start school early in the morning. This is primarily down to students having less sleep deprivation which in turn leads to better alertness and students being more alert at this time as a result of their chronotype (see video below for more details).

So next time you think your teenage son or daughter is being lazy for not getting out of bed early in the morning remember, they have a scientific excuse.


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