Does the damp cause arthritis? Can air pressure shifts bring a headache? Will the temperature influence a baby's sex? David Robson finds some surprising evidence for the folklore.

In 2013, neuroscientists reported one of the strangest case reports in the history of medicine: a man who claimed to be able to smell the weather. An approaching storm, he said, produced an almost unbearable odour of skunk excrement, mixed with onions.  The scientists were at a loss to explain what could be causing these strange symptoms.

Everything from your risk of a heart attack to the sex of your unborn child may depend on the forecaster’s predictions

Most of us are thankfully lacking this rather unwelcome talent, but even subtle shifts in the atmosphere seem to correlate with changes in our bodies. While scientists have yet to confirm many of these proposed links, the evidence so far is intriguing. If true, it would mean everything from your risk of a heart attack to the sex of your unborn child may, to a greater or lesser extent, depend on the forecaster’s predictions.

Read on to discover the myths and the genuine mysteries.

1) Rain gives you rheumatism… maybe
Despite anecdotal reports that wet and windy conditions inflame the joints, the evidence is about as clear as a British summer. A review in 2011, looking at nine studies to date, concluded that there was no consistent effect of the weather on the symptoms of rheumatoid arthritis. In fact, the apparent link may just be a case of “confirmation bias”. If you already believe that rain brings pain, you are more likely to notice the rainy days where you feel discomfort, and ignore those when you feel fine.

Even so, it’s by no means a closed case and other studies disagree. Perhaps the confusion arises from the fact that it’s very difficult to take into account other factors – such as the clothes the patients were wearing, and whether the patients stayed in or out of doors.

2) Falling air pressure is a pain in the head
Feeling weighed down? That’s because there’s about a tonne of air pressing down on our heads at any one time. It sounds like a recipe for a headache – and for some people, it just might be. Kazuhito Kimoto at the Dokkyo Medical University in Japan and colleagues asked 28 migraine patients to keep a diary of their headaches for a whole year. Comparing their reports with data from a nearby weather station, he found that their pain often coincided with falling air pressure.

Sales of headache pills rise as the barometer drops

Although Kimoto’s team only studied a small group of participants, a second paper seemed to confirm the effect, finding that the sales of painkillers rise as the barometer drops. One reason could be that the falling air pressure disrupts the vestibular system – the cavity in our heads that helps us to keep balance – bringing about the dizzy spells, and eventually, migraine.

3) The biting cold can freeze your heart
Besides being the season of colds and flu, the winter also brings a regular rise in heart attacks. According to one Chinese study, deaths from heart disease rise up to 40%, compared to spring and summer. Despite decades of research, no one knows exactly why, though the Chinese study found that the colder temperatures seem to increase blood pressure – which is known to increase the risk of a heart attack.

4) More Sun, more sons…
You might think that our population is divided exactly 50:50 between men and women, but this too swings depending on the weather. In the Northern Hemisphere, for instance, more sons are likely to be conceived during warmer years than those with particularly cold spells. (Puzzlingly, women in London also gave birth to more daughters and fewer sons nine months after  a bad outbreak of smog in December 1952.)

Exactly why that happens is a complete enigma. It could be that the temperature alters hormonal balances, or the production of sperm. Some have argued that it’s an evolved mechanism, to boost a mother’s chances of passing on her genes: sons are less likely than a daughter to reproduce, if they are in poor condition, so our bodies decide the sex based on our current environment. In any case, the effect is tiny, and seems to vary from region to region. Although these trends are biologically interesting, they certainly shouldn’t guide your family planning.

5) Death by cosmic ray
The Sun is constantly showering the earth with geomagnetic storms and cosmic rays. The Earth’s atmosphere should protect us from the worst of this space weather – but we may not be completely safe. A team from Lithuania recently examined the records of more than one million deaths over a 25-year period – and they found that mortality from heart disease and stroke seemed to peak during periods of extreme space weather events.

Those born during periods of extreme space weather have a shorter average life-span, by about five years

Even more strangely, another study found that those born during periods of heightened activity have a shorter average life span, by about five years – compared to those born in calmer periods; it also seemed to reduce their fertility.

Clearly, more investigations will be needed to confirm the results and try to find an explanation. It is hard enough to swallow the fact that our health depends on something as unpredictable as the weather here on Earth – let alone a random storm of charged particles 92 million miles away. It seems that our fates really might be decided in the heavens after all.

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