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.

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A Ray of Sunshine

One of the fascinating things about cancer is that it touches every aspect of biology. Of course, most will know that it’s caused by mutations – changes in the material that carries our genetic code. But many influences play on the genetic keyboard of DNA and those that are part of the world around us are a very mixed bunch. In Betrayed by Nature I split them into two: those we can do something about and the rest. The latter includes radiation from the ground… it’s all around us, we’ve evolved bathed in it and, apart from not living where the levels of radon are particularly high, there’s nothing we can do about it – so just forget it.

At the other end of the spectrum, so to speak, comes sunshine. We’ve evolved with that too – indeed we wouldn’t be here without it. Aside from driving photosynthesis in plants, humans use the radiant energy of the sun to make vitamin D (sometimes called the “sunshine vitamin”). Vitamin D deficiency is one cause of the childhood bone defect rickets, a condition that has reappeared in the UK in recent years because some kids are seeing less of the sun. So for humans catching the rays is desirable but we teeter along a sunny tightrope between what we need and what may ultimately be fatal. The risk comes from the ultra violet component of sunlight – radiation that has sufficient energy to damage DNA directly, making it a mutagen that can cause cancer. The cancer in question is, of course, melanoma that develops from abnormal moles on the skin. The global incidence of melanoma is increasing and, in the UK, about 90% of cases are estimated to be linked to exposure to ultra violet light. To most folk this means sunshine but those so inclined can walk the tightrope horizontally by using sunbeds (incredibly, in 1999 Cancer Research UK found that a quarter of men and a third of women questioned said they’d used a gizmo of this sort in the previous six months).

Which goes to show that human beings seem unable to resist the pursuit of the unattainable. The fair skinned think it cool to be darker whilst pharmaceutical giants are apparently making pots from selling creams to Indian ladies on the pitch that they will lighten their skin!

… and not so good

Good rays …

With a sigh for humanity let us pass from risks we take for no reason other than vanity or stupidity to those we may feel obliged to take as the lesser of two awkward options. There’s almost no chance that anyone reading this hasn’t had an X-ray of some sort. We have them to give our dentist a precise guide to the cause of our agony, rather than have him solve the problem by a series of trial and error excavations, or to tell our orthopaedic surgeon how best to go about piecing together the results of our latest stress-test on the human frame. We know X-rays are bad for us – they’re even more energetic than ultra violet radiation, so they’re a super-mutagen. Waves of cancer you might say.

So the issue here is one of choice. It’s a bit like a general anaesthetic: they do tend to make you throw up and about one in every 100,000 is fatal but, confronted with surgery, which would you vote for: a whiff of halothane or the offer of a slug of whisky and a rag to bite on? Computed tomography (CT) is an alternative application of X-rays but, instead of a single shot giving a two-dimensional image, CT acquires a large number of such images, taken as the radiation beam moves through the body, to give a 3-D picture. This can represent whole organs, and it has become an immensely powerful diagnostic tool since its introduction in the early 1970s. However, there’s no advance without anguish, and the additional information provided by a CT scan requires much more radiation than a traditional X-ray (typically 10 millisievert (mSv) compared with about 0.04 mSv for a chest X-ray). As our annual dose of “unavoidable” natural radiation is about 3 mSv it’s probably safe to say that these medical exposures are not a serious hazard – although babies in the womb are particularly sensitive to radiation. Even so, there are estimates that about 1% of USA cancers are due to CT scans, although there is no evidence that doses below 100 mSv induce tumours in animals.

A new study has enlarged the picture by finding that CT scans of children under 15 may increase the risk of leukemia and brain cancer. Three-fold increases were estimated for acute lymphoblastic leukaemia as a result of five to ten scans and for brain tumours by two or three scans. This sounds somewhat scary but it’s worth noting that these diseases are very rare in children. In the UK the incidence in under-20 year olds is just over four per 100,000 of leukemia – slightly less for brain or central nervous system cancers.

So the evidence indicates a small increase in an already low level of risk. As ever in life, therefore, it’s a matter of balance. The sensible advice for children (and everyone else for that matter) is not to have CT scans unless they are likely to provide critical clinical information that cannot be obtained by other means, for example, ultrasound or conventional X-rays.

Reference

Pearce, M.S., Salotti, J.A., Little, M.P., McHugh, K., Lee, C., Kim, K.P., Howe, N.L., Ronckers, C.M., Rajaraman, P., Craft, A.W., Parker, L. and de González, A.B. (2012). Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study. The Lancet 380, 499–505.