Twenty winks

Not now obviously but after you’ve read the first episode of this absorbing tale you may feel a nap is in order, despite the fact that in Wake up at the back we noted that snoring can give you cancer.

Setting aside that hazard, the general finding is that most people require seven or eight hours of sleep to function optimally. Fall short of that, to less than six hours even for one night, and we all know that the consequences may include a degree of grumpiness helped along by a tendency to clumsiness and generally heightened incompetence. If you happen to suffer from hypertension you could measure another result because your blood pressure will be even higher than usual for the rest of the day. However, these are all reversible states, so that real problems only come with more extended sleep deprivation and there is much evidence that this can profoundly affect memory, creativity and emotional stability, as well as leading to heart disease, diabetes and obesity. The molecular drive for the latter is that folk who are short of sleep have lower levels of the hormone leptin (which tells the brain you’ve had enough to eat) but higher levels of ghrelin (appetite stimulant). One week of only four hours nightly kip converts healthy young men to pre-diabetics in terms of their insulin and blood sugar levels.

The cancer link

To all of which must be added the dribble of reports over many years that disrupted sleep patterns, such as result from shift-work, may increase the risk of a variety of cancers (these include breast, prostate, bowel and endometrial cancers and also non-Hodgkin’s lymphoma). The effects are moderate (that is, the risk rise is small – typically up to 20%), making these findings suggestive rather than conclusive, although they are bolstered by a considerable number of studies on animals. So sleep, or rather lack of it, is yet another of these things that seems to affect cancer but for which really hard evidence is lacking. It’s not a9f5f190difficult to see why. You can’t put a number on ‘a good night’s sleep’ (though you can now get phone apps that record your every snort and contortion) nor do we understand the biological consequences of sleep disruption, and then there are the perpetual problems that everyone’s different and cancers take years to show themselves. However, you can put a figure on how you feel about sleep: our friends at the wonderful Karolinska Institute in Stockholm have come up with a Sleepiness Scale (1 = very alert, 9 = very sleepy, great effort to keep awake) – which could replace the traditional grunt when asked ‘How are you?’ ‘Oh, much as usual, about eight on the Karolinska Scale.’

Sleeping Off Breast Cancer

Trawling the literature it seems that the majority of cancer/sleep studies focus on the breast and a word about two of the most recent will suffice to paint the picture. In a large group of Japanese ladies over the age of 40 those who said they slept for less than six hours were markedly more likely to develop breast cancer than those who slept longer. Over nine hours a night (sleep that is) even appeared to give a degree of protection.

The main culprit for the breast cancer/sleep link is shift work, illustrated by the Danish military where women working night-shifts are more prone to breast cancer than those with normal sleep patterns and there is an upward trend in risk with years of night-shift work.

An association with ovarian cancer has also been reported although, somewhat perplexingly, that study didn’t show that the risk got bigger the longer night-shifts were worked. This rather confusing picture may reflect individual variation. As we all know, some folk are ‘larks’ – up at the crack of dawn – my lady wife is one – whereas others are ‘owls’ who perform better the later it is (no prize for guessing what kind of bird I am – bit of domestic incompatibility there!). It may be that ‘owls’ suffer less from night-shift perturbation and they may therefore be more likely to opt for that mode of work – and indeed the Danish study found that ‘larks’ on night-shifts were more likely to get breast cancer. As if that’s not enough, irregular shift patterns make it more difficult for women to conceive and working only nights increases the chances of miscarrying.

Similar results have been found for other cancers, notably of the bowel – 50% more likely to occur in those who sleep an average of less than six hours a night than those who zzzz for over seven. Put another way, the less than six hours risk is about the same as having a first degree relative with the disease or eating lots of red meat – and similar to that for breast cancer.

Mu Treadmill

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Mice Sleep Too

It’s not a bad idea to keep in mind that we are very similar to mice – we’ve got more or less the same number of genes and exercising (on a treadmill for example) helps to keep at least some cancers at bay. Another similarity is that sleep deprivation upsets the works so that, for example, in models of colon cancer it reverses the beneficial effects of moderate exercise.

So insomnia is no laughing matter, however it comes about, and next time we’ll put two and two together by looking at the molecular story – after which you really may need forty winks.

 References

Kakizaki, M. et al. (2008).  Sleep duration and the risk of breast cancer: the Ohsaki Cohort Study. Br J Cancer  99, 1502–1505.

Hansen, J. and Lassen, C.F. (2012). Nested case-control study of night shift work and breast cancer risk among women in the Danish military. Occup Environ Med., 69, 551–556.

Bhatti, P. et al. (2012). Nightshift work and risk of ovarian cancer. Occup Environ Med., 0:1–7. doi:10.1136/oemed-2012-101146.

Thompson, C.L. et al. (2011). Short Duration of Sleep Increases Risk of Colorectal Adenoma. Cancer 117, 841–847.

Zielinski, M.R. et al. (2012). Influence of chronic moderate sleep restriction and exercise on inflammation and carcinogenesis in mice. Brain, Behavior, and Immunity 26, 672–679.

Wake up at the back

Living with someone of the opposite sex, or getting married as it used to be known, is an interesting experience. One of the things you rapidly discover that your Mum never warned you about is that women are a distinct species.  You missed that revelation in your biology classes? Serves you right for snoozing on the back row but, as a recap of the evidence, consider the following. Species often show major differences in sensory perception – thus our cat is much better than I am at seeing in the dark, though he misses out a bit in daylight as cats don’t have colour vision. When it comes to hearing it’s a bit the other way round: most of the time you can shout at him til you’re hoarse with absolutely no effect – but one faint clink of a food bowl at the back door and, yet again, he’ll set a new Feline Fifty metres Steeplechase record from the front garden. And dogs, as is well known, hear frequencies way beyond what we can pick up.

Not in my lectures!!

The gentle sex has similarly evolved beyond what mere man can manage. Take colour, for example, at which men are, as we’ve noted, quite good – compared to cats. But, as you discover the first time you are taken ‘clothes shopping’ by your wife, other half, inamorata, partner, mistress or whatever, women have evolved far beyond merely spotting that blue is different from red and being able to recite Richard Of York (to remind themselves of the rainbow sequence). They see ‘combinations’ – so you are curtly informed that what has taken your fancy ‘just doesn’t go together’ in the sort of voice that adds ‘any nitwit can see that’ without the need to expend breath on the last seven syllables.

They’re at a similarly lofty level of evolution when it comes to sound. My lady wife avers that I snore – all the time (when asleep, that is) and very loudly. So much so that she tends to use a bed at the opposite end of the house for sleeping and only ventures within sonar range for other purposes. I’d always explained this behaviour as a manifestation of the amazing imagination possessed of the female that us boys are, of course, completely lacking. However, I’ve now come to appreciate that, like Fido (who sleeps in the kitchen), she simply has exquisitely sensitive aural apparatus. So maybe I do snore – but only very quietly or at ultra high frequency, so that I would be undetectable at rest to my own species and only my beloved and the dog would know what was going on (oh, and the cat because he can see the heaving chest).

Which is very reassuring since some fellows at the Universities of Wisconsin and Barcelona have got together to discover that snoring makes you nearly five times more likely to develop cancer. Strictly the problem is sleep disordered breathing (SDB) – which happens when there’s some kind of blockage of the upper airway and, apart from disrupting sleep, it can make you snore. Of course, there’s evidence that sleep disruption can contribute to all sorts of problems from heart disease to car crashes but this is the first study making a link to cancer.

No problem for me (discounting the wife’s super sonar) but should real, habitual snorers panic? Please don’t for most of the usual reservations to this type of study apply – relatively small numbers (1522) for example. The volunteers came from an alluringly named body of men and women called the Wisconsin Sleep Cohort, set up in 1988 for prospective studies of sleep disorders. In fact the interesting ones here are what we might call the Winsomniacs – the 365 of the Cohort who can’t do it rather than the majority of Badger State dreamers. Split in this case into sub-groups of SDB severity – the strongest association being with the most severe SDB. Although the authors did their best to allow for other factors (obesity – a common cause of SDB – diabetes, smoking, etc.) it’s almost impossible in this type of study to eliminate everything bar the one factor you’re focussing on.

The most frequent linked cancer was of the lung, followed by bowel, ovary, endometrial, brain, breast, bladder, and liver. And the cancer risk was up to four-fold greater for the worst afflicted.

Do the boffins have any helpful suggestions? Not really. Those unlucky enough to be severely affected can try a gadget called a continuous positive airway pressure device but, for the rest, console yourselves that the risk is small and the data so far are very preliminary. Put another way, you have more important things to think about – like finding a partner (preferably with sub-standard sonar detection capability) who loves you so much they’re willing to poke you in the ribs whenever you become aurally intrusive.

References

http://www.telegraph.co.uk/health/healthnews/9278214/Snoring-can-raise-cancer-risk-five-fold.html

Javier Nieto, F.J. et al. (2012). Sleep-disordered Breathing and Cancer Mortality: Results from the Wisconsin Sleep Cohort Study. American Journal of Respiratory and Critical Care Medicine 186, Iss. 2, pp 190–194.