Why lack of sleep is bad for your health

Claim made by: NHS Choices
Location: http://www.nhs.uk/livewell/tiredness-and-fatigue/pages/lack-of-sleep-health-risks.aspx

People who sleep less than seven hours a day are 30% more likely to be obese than those who get nine hours or more of sleep.

Update 2015-12-14

First email:

"Dear Ben,

Thank you for your email to NHS Choices website requesting evidence to support the claim that sleep deprivation can lead to weight gain. I refer you to these two articles in the first instance.
http://www.ncbi.nlm.nih.gov/pubmed/18239586

http://www.hsph.harvard.edu/obesity-prevention-source/obesity-causes/sleep-and-obesity/
Kind Regards,
The NHS Choices Service Desk"
----

I could find no data in these articles that supported the claim on the website, so I asked precisely where the data were and received a second email:

"Dear Ben

Thank you for your email

The Nurses’ Health Study where short sleepers had 30 percent higher risk of gaining 30 pounds over the course of the 16-year study can be found at (http://www.ncbi.nlm.nih.gov/pubmed/16914506?dopt=Citation)2006; 164:947-54.

If you have any further questions feel free to contact us.

Kind Regards,
The NHS Choices Service Desk"
----

I read the study and found multiple problems with the way the data were presented on the NHS website, which I detailed in my reply:

"Hi,

Thank you again for your response. There are several problems that I would like to highlight with the way these data are presented on the NHS website.

1) The study you refer to uses 7 hours of sleep as a baseline, not 9 hours.

2) The data from Table 3 do not support the claim. Using data from model 3 (adjusted for the most confounding factors):

- Women sleeping 5 hours or less were 28% more likely to gain 15kg over the study period and 15% more likely to become obese than women who slept 7 hours.
- Women sleeping 6 hours were 10% more likely to gain 15kg over the study period and 6% more likely to become obese than women who slept 7 hours.

There are two problems here. First, the NHS website only uses the figure (~30%) from the most extreme case for a 15kg weight gain (5 hours or less sleep), but the weight gain for sleeping 6 hours is much lower. Hence, the 30% figure is not representative of those who get 6 hours sleep. Second, a 15kg weight gain does not necessarily lead to obesity (e.g. some of those individuals were already obese). The study specifically states different figures for women who became obese, which are 6-15%.

3) The way in which this is worded doesn't paint a very clear picture of causality. 'People who sleep less are more likely to be obese' doesn't mean that sleeping less causes obesity. Perhaps obesity causes people to sleep less, or there is a confounding factor. The longitudinal data from the paper support the argument that sleep deprivation leads to weight gain, but this isn't presented clearly.

4) This is only one study and is limited to middle aged women, so attaching blanket statistics without context can be misleading. The literature does support the theory that sleep deprivation increases the risk of subsequent weight gain and obesity, but there is no magic number to attach to this.

Might I suggest the following wording to clear up any ambiguities:

"Sleeping less may lead to weight gain and obesity! Several studies have found that people who sleep less than 7 hours a day tend to gain more weight and have a higher risk of becoming obese than those who get 7 hours of sleep."

Please let me know your thoughts on this.

Best wishes,
Ben"
----

To which I received the following reply:

"Dear Ben

We have made the editorial amendments suggested, though it may take a day or two to show up on the site while the page refreshes.

If you have any further questions feel free to contact us.

Kind Regards,
The NHS Choices Service Desk"
----

The website has now been updated to the following:

"Sleeping less may mean you put on weight! Studies have shown that people who sleep less than seven hours a day tend to gain more weight and have a higher risk of becoming obese than those who get seven hours of slumber."

Not perfect, but an improvement!

Rating

It's nonsense

Comments: 2

Medium
Ben Ashby

Professor Jim Horne from Loughborough University, who is an expert on sleep research, had this to add:

"Claims that sleeping fewer than 7 hours leads to obesity, diabetes and heart disease are quite misleading and can unnecessarily increase the worries of those with insomnia.

1. There are natural, healthy differences between people in their sleep need. The healthy average is about 7.5 h with a standard deviation of about 1.5h - normal range 6-9h

2. The acid test of insufficient sleep is sleepiness throughout much of the day - No sleepiness apart from a natural dip early afternoon indicates adequate sleep

3. There is no evidence that habitually sleeping 6-7 hours will have any adverse health benefits (given that 2 above applies)

4. Even 5h sleepers who probably do have insufficient sleep are unlikely to put on more than about 2kg per year as a direct consequence of this 'lack of sleep'. To lose this, then rather than increase sleep by 2 h per day, then 15 min daily brisk waking and a better diet are far more effective and healthier

5. Simply judging sleep on its duration is rather crude and neglects the importance of its quality

6. Daytime naps can be very beneficial and these are usually overlooked

7. only about a third of any lost sleep needs to be regained (its the increased sleep intensity that is the key)

8. There is no substantive evidence that our so called sleep debt is any worse today than it was eg 50 years ago

9. The claim that' those who sleep less than seven hours a day are 30% more likely to be obese than those who get nine hours or more of sleep' is misleading especially as those sleeping more than 9h are also at a similar risk from other health problems

In sum the this information site need to be corrected."

-1
Medium
Ben Ashby

The way the data were presented was incorrect, but it seems that there is good evidence to suggest that sleep deprivation can lead to weight gain and obesity. I therefore rated the evidence for this specific claim as nonsense, but that does not go for the general link between sleep deprivation and weight gain.

-9

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