And now for something really useful

Not a health food

The only health story you’re likely to have read this week is about chocolate. Is it good for your heart? Maybe, but we don’t really know. We need more, and better, studies. Not that they’ll make any difference, now that the chocolate=healthfood meme is so firmly established.

I’ve nothing against chocolate, and quite a lot for it, especially the Lindt extra-fine 70% stuff. I don’t need permission from my doctor to eat it, and neither do you. It’s stuffed with fat and sugar, of course, so how much of it you eat is between you and the bathroom scales. It might do something useful to your endovascular system, but isn’t that just a bonus? Mackerel and cabbage are good for you, but you don’t see that all over the front pages.

Anyway. The useful stuff that you won’t have read about elsewhere. How much do you know about your risk of getting a deep vein thrombosis (DVT)? It’s a particularly nasty condition that happens when a blood clot lodges in the deep veins of your legs, usually your calf. It causes not very pretty swelling and pain. If you’re really unlucky, it can travel up your blood vessels to your lung, causing a lethal pulmonary embolism.

DVT can be brought on by lengthy inactivity, such as sitting down for eight hours on a cramped flight, and certain medicines increase the chances of getting it. These include common medicines such as the contraceptive pill and HRT, as well as anti-psychotic drugs.

Some people are more vulnerable to it than others – older people, people who are overweight or smoke, or have certain chronic diseases – but it doesn’t just happen to old, unfit people. I know several people in their 30s who’ve had it, meaning they spend the next six months or so taking warfarin (a blood-thinning medicine that plays havoc with how much alcohol you can drink, among other inconveniences).

The difficulty is knowing how the risk affects you as an individual. I’m used to hearing from my GP that the pill increases the chances of a DVT, and being asked to confirm that I accept that. But what is my risk to start with? How much should I worry about this increased risk? Then there are long haul flights. Should I invest in flight stockings, or just wiggle my toes every so often? For older people or those with other medical conditions, the calculations get more complicated.

Luckily, some clever people* have put together this handy tool, the QThrombosis risk calculator. You can use it to work out your baseline risk of having a DVT over the next 5 years. You can play with it too, so I can see that the contraceptive pill makes no discernible difference to my personal, very low DVT risk. A useful bit of knowledge for my next GP appointment. If the risk was higher than I’d like, I could see what effect it would have if I lost a few pounds, or gave up smoking. Or changed sex, although that wouldn’t be especially practical.

The tool is based on sound science, which I analysed for the BMJ’s Best Health website. It shows that the drugs to really worry about are anti-psychotics, and the biggest risk of DVT is having been admitted to hospital recently, not hopping on a plane. I can imagine the tool being fantastically helpful for doctors, but it also helps anyone interested in taking responsibility for their own health.

I’d say it was idiot-proof, but on my first go I somehow muddled up inches and centimeters, professing myself to be about 60cms high, with a truly outrageous BMI. Even then my 5-year risk was less than 1%, which is quite reassuring in itself.

*Professors Julia Hippisley-Cox and Carol Coupland, of Nottingham University

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