Does shift work affect your brain power?

11 November 2014

Interview with

Hannah Critchlow, The Naked Scientists

If you were listening to us at the end of a nightshift or on your way into work afterSleeping Student getting up before dawn, our first item may not come as a surprise. Researchers say that doing anti-social shifts over many years can actually dent your brain power.

But why is this?  And if you stop working irregular hours or nightshifts, can your cognition recover.  Hannah Critchlow has been taking a look at the study for us and joined Naked Scientist Ginny Smith to discuss the results...

Hannah -  Well, it's long been known that if you have altered sleep patterns, or you don't have enough sleep, then it will affect, most probably, your metabolic or your cardiovascular.  So, it could give health problems for example with your heart or with ulcers for example.  It can also affect your mood and it can have short term effects on your memory or your cognitive functions.

But what hasn't been known before is whether changes in sleep patterns and doing rotational shift work would have a long term effect - so, 10 years down the line.  

So, this study has been our first in its kind.  It's looked at over 3,000 people and it's followed them over a 10-year period and then found out that firstly, yes, shift work can actually affect cognition and it had a detrimental effect on memory and speed of processing in these different tasks.  But then they also found out that if you stop to doing shift work, then within 5 years, you would actually reverse that cognitive decline and go back to normal, as it were.

Ginny -  How much shift work do you have to do before you see these effects?  Is it just a case of a night of not getting enough sleep and you have memory problems or is it something more complicated?

Hannah -  If you don't sleep well for one night then yes, your memory might be slightly skewed the next day.  But they were showing that it's kind of over a 2-year period that you start seeing a really significant or slightly significant effect on cognition.  If you work on shift work for 10 years, then you'll show a really significant decline in your cognitive function, to a point where your behaviour, your cognitive age is similar to someone who's 6 years older than you.

Ginny -  Wow!  That sounds like a huge effect.  If it's not just the case that you haven't got enough sleep, if it's something that carries on for longer than that, do they know anything about what the mechanism is that causes these problems?

Hannah -  Well, they hypothesise that it might be because your sleep patterns are altered, your cortisol levels are also altered.  So, cortisol is kind of the stress chemical of the brain if you like, and it helps in some ways.  It helps us to wake up in the morning.  If you've got altered sleep patterns - you're sleeping at different times and waking up at different times - then obviously, your cortisol levels would be changed.  Cortisol we know, affects kind of the key region in the brain that's involved in learning and memory.  It's an area the hippocampus.  This area of the brain is also very important because it's one of the few areas of the brain where you get new nerve cells being born throughout life.  This might be important for learning and memory.  

So, it may be that this kind of chronic shift work is affecting the new nerve cells being born via the cortisol levels.  The authors of the study are propositioning that possibly, if you are unable to stop shift work then it might be a good idea to do other things that might help boost the birth of new brain cells in the hippocampus.  So for example, exercise and socially interacting with other people, that can help boost new nerve cells and also, exercise decreases cortisol level, so that could be good.

Ginny -  And they looked at people after they quit shift work as well and found that this problem went away.  So, how long did it take and what happened with those people?

Hannah -  So, if people had stopped doing shift work and they're now working in a more standard 9:00 to 5:00, then within 5 years, their cognitive profile would be similar to age and socio-economic matched controls.

Ginny -  So, if you are a shift worker, it's not the end of the world.  Your brain will get better as you give it up and even if you can't give it up, there are things you can do to improve your learning memory and your general cognition.

Hannah -  Exactly.

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