Daytime napping just got dangerous

Longer naps during the day linked to sharp increase in health risks


In an effort to further define the condition known as ‘metabolic syndrome’, sometimes dubbed ‘Syndrome X’, a team from the University of Tokyo has been researching the possible correlation of daytime sleeping with subsequent health problems.

Metabolic syndrome is the perfect storm of symptoms related to cardiovascular problems. They include obesity – particularly body fat around the waist, high cholesterol, high blood pressure and elevated blood sugars.

Up to 15 million people in the UK are thought to experience this combination of symptoms which makes them likely to develop type 2 diabetes or even suffer a stroke or heart failure later in life.

Doctors are keen to find a way to diagnose and treat the condition before it turns into a full blown illness or heart condition. One simple solution, of course, is to encourage weight loss through a change of diet and increased exercise.

There have already been many studies which link obesity and metabolic syndrome to issues like sleep apnoea and insomnia but this is one of the few to widen the terms of reference to sleeping patterns throughout the day.

The Japanese researchers collated and examined data from 21 studies involving over 300,000 participants of both Asian and Western origin.

Subjects were asked how often and for how long they ‘napped’ during the day and their answers were compared to the medical data on obesity and type 2 diabetes.

Their headline grabbing findings make shocking reading.

Those who took naps lasting less than 40 minutes showed no increase in the risk of developing metabolic syndrome.

Once the duration of naps tipped over 40 minutes however the risk was dramatically increased by 50%.

Sleeping for periods of longer than an hour was linked to a 46% increase in the risk of diabetes and an 82% increase in the risk of heart disease.

They also indicated that consistent tiredness during the day increased the risk of diabetes by 56%.

Before we start thinking of sleep as a cause of health problems, however, it is worth considering whether fatigue and the need to nap are more likely to be symptomatic of the syndrome rather than a contributory factor to it.

People who are so tired that they need to sleep for more than an hour during the day are probably not getting enough rest through the night. This may suggest a metabolic disorder that is yet to manifest in other ways.

The results also fly in the face of earlier European research in which a Greek study found that sleeping during the day significantly reduced blood pressure. The researchers in Athens found that daytime sleepers had, on average, a 5% lower systolic blood pressure throughout the day compared with those who stayed awake.

In the Greek study the longer the subjects slept during the day, the more beneficial the effect on their blood pressure.

The current recommendation from the National Sleep Foundation is that naps of 20-30 minutes during the day improve alertness and reduce stress.

Perhaps we all need to set our alarms for 39 minutes before we curl up on the sofa…just to be on the safe side.



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