Scientists at the University of Tokyo say napping for longer than 40 minutes increases the risk of high blood pressure and cholesterol, excess fat around the waist and high blood sugar – all risk factors for heart disease
Although indulging in a day time nap is the stuff of workday dreams, a team of scientists have warned allowing yourself the luxury could increase the risk of premature death.
Taking long naps, or being excessively tired during the day, is linked to a higher risk of developing metabolic syndrome, a new study today revealed.
The umbrella term covers a range of conditions, such as high blood pressure and cholesterol, having excess fat around the waist, and high blood sugar – all of which raise a person’s risk of heart disease.
The findings, which were presented at the American College of Cardiology’s 65th annual scientific session today, show napping for 40 minutes of longer was tied to a steep increase in the risk of being diagnosed with metabolic syndrome.
Dr Tomohide Tamada, PhD diabetologist at the University of Tokyo, and lead author of the study, said: ‘Taking naps is widely prevalent around the world.
‘So, clarifying the relationship between naps and metabolic disease might offer a new strategy of treatment, especially as metabolic disease has been increasing steadily all over the world.’
Dr Tamada and his colleagues determined when it comes to taking a nap, the magic number is 40.
Anything longer than 40 minutes snooze time during the day, and the risk of metabolic syndrome dramatically increases.
The researchers arrived at their conclusions after evaluating data from 21 observational studies, involving 307,237 people.
Participants were asked questions relating to how tired they felt during the day, for example ‘do you have a problem with sleepiness during the day’.
And researchers also asked about naps, asking ‘do you take a daytime nap’, and ‘do you sleep during the day’.
They then compared a person’s answers with their medical history, of metabolic syndrome, type 2 diabetes and obesity.
Their results showed a J-shaped relationship between the time spent napping and the risk of developing metabolic syndrome.
Those people who napped for less than 40 minutes did not show any increased risk for the conditions.
But, beyond 40 minutes the risk rose sharply.
Napping for 90 minutes increased metabolic syndrome risk by as much as 50 per cent, as did being excessively tired during the day, the researchers noted.
But, they were interested to see a slight dip or decrease in that risk among those people napping for less than 30 minutes.
Past research found napping for longer than an hour or being excessively tired during the day each corresponded to a 50 per cent increase in type-2 diabetes.
The study did not show a relationship between time spent napping and obesity, despite the close links between obesity, diabetes and metabolic syndrome.
An earlier study by Dr Yamada and colleagues, published in the June 2015 issue of Sleep, tied naps longer than an hour to an 82 per cent increase in cardiovascular disease and a 27 per cent increase in all cause death.
They also presented data at the Annual Meeting of the European Association for the Study of Diabetes in September 2015 that showed diabetes risk increased by 56 per cent if subjects were fatigued and by 46 per cent if they took naps longer than an hour.
Interestingly, all three studies showed a slight decrease in risk for their respective conditions when subjects napped for under half an hour, though Dr Yamada said more studies are needed to confirm this finding.
The National Sleep Foundation advocates naps of 20 and 30 minutes to improve alertness without leaving sleepers groggy afterward.
‘Sleep is an important component of our healthy lifestyle, as well as diet and exercise,’ Dr Yamada said.
‘Short naps might have a beneficial effect on our health, but we don’t yet know the strength of that effect or the mechanism by which it works.’
Still, the results demonstrate a need for more research on how people’s sleep habits influence metabolic syndrome and cardiovascular disease.
All told, one in three American adults do not get enough sleep, according to the US Centers for Diseases Control and Prevention.
Dr Yamada said future research should aim to identify the potential cardiovascular benefits of short naps, as well as the mechanism by which long naps, daytime sleepiness and metabolic syndrome influence each other, and whether clinicians might eventually be able to use a patients’ nap habits as a predictor for other health problems.
Although this study included data from more than 300,000 participants, it may not be representative of the world population.
Data was also dependent on self-reporting nap times, as opposed to objectively measuring sleep time in a lab or with a sleep tracker.
Source Mail UK