'Winter thickens the blood' is just one of the many sayings about the weather that most of us would dismiss as old wives' tales. In fact, scientists and medics are coming round to the idea that the weather really can have an effect on our physical and mental health, as Angela Epstein reports...
FORECAST: RAIN
WEIGHT GAIN: A team from Aberdeen University found miserable weather made it harder for dieters to shed weight. They found those who were overweight had lower levels of vitamin D - which is created when the body is exposed to sunlight.
The amount of vitamin D in the blood influences the functioning of a hormone called leptin, which tells the brain when the stomach is full. The obese produced a tenth less vitamin D than those of average weight.
E.COLI: Heavy rain, particularly in rural areas, raises the risk of catching this potentially fatal bug. Only a few weeks ago NHS experts in Ayrshire and Arran in Scotland were asking people who live in or visit the countryside to take steps to cut their risk of infection, by frequent handwashing for instance, following heavy rainfall.
Dreary forecast: Scientists say dieters find it harder to shed weight during heavy rain and people are more likely to catch the potentially fatal bug E. coli
The concern is that farmers' slurry contains E.coli O157 bacteria from cattle muck; heavy rain can wash the slurry into streams and form puddles; the bacteria can then be found in mud stuck to boots, or spread by pets.
ACHING SCARS: Many people with old injuries maintain that their scars ache when the weather is threatening.
Monica Seles, the tennis star who was stabbed in the back during a tennis tournament in Germany, told one interviewer that her scar would tingle when rain was coming.
'One possible reason for this could be rapidly falling atmospheric pressure which signals the onset of stormy weather,' explains Dr Adam Carey, consultant to the British Olympic Association.
'When outside pressure drops, it may cause normal tissue to expand and contract. However, since scar tissue is not elastic, but rather dense and rigid, it is unable to adapt to the change in pressure, resulting in a pulling sensation that may lead to pain.'
PREMATURE LABOUR: Low pressure can trigger complications for pregnant women.
'When the weather is bad we see more women coming in with pre-natal complications such as high blood pressure,' says Dr Bowen Simpkin. 'These complications can trigger labour.'
JOINT PAIN: As the old wives claim, damp weather does seem to make joint pain and osteoarthritis worse. While there is no conclusive evidence to explain this, it may be due to pressure receptors ( baroreceptors) in the joint sensing the drop in atmospheric pressure when the weather changes from dry to rainy, says Robert Moots, professor of rheumatology at University Hospital Aintree in Liverpool.
'The level of fluid in the joint then fluctuates in response to these changes, which might trigger pain in the nerves.'
FORECAST: VERY HOT
SUICIDE: Hot weather increases the risk of suicide, according to the Institute of Psychiatry.
Researchers looked at 50,000 suicide cases in England and Wales, between 1993 and 2003, and found that once the average daily temperature went above 18c there was a rise in the number of people who kill themselves.
'Most suicides take place when people are intoxicated and they are more likely to be so when the weather is hot,' says Dr Jan Wise, a consultant psychiatrist based in London's Harley Street.
'The other issue is inability to cope with exceptionally hot weather when we are not used to it.'
FORECAST: COLD SNAP
BELL'S PALSY: The number of cases of Bell's palsy, which causes sudden facial paralysis, rises in colder weather, according to research.
Dr Paul Griffiths, a Manchester-based GP, says: 'Bell's palsy is an auto-immune condition that can be triggered by an undiagnosed virus. And as we see more viruses in the winter, this could be the connection.'
HEART ATTACK AND STROKE: Around 20,000 people die each year in the UK as a result of strokes and heart attacks linked to a dramatic drop in temperature.
Though no single theory can explain this, it is believed cold temperatures cause the arteries to narrow, restricting blood flow and reducing oxygen supply to the heart.
Cold weather also makes the heart work harder because more oxygen is needed to maintain body heat. This could lead to a heart attack in vulnerable people such as the elderly.
However, earlier this year a study of adults with a history of heart attack, by the German Research Centre for Environmental Health, found another potential cause.
Researchers discovered that just five consecutive days of colder than average weather led to increased blood levels of two chemicals - Creactive protein and interleukin 6 - that can cause inflammation in the vascular system.
Stroke is also more likely to happen, according to a report by John Moores University in Liverpool, because blood thickens in cold weather, which increases the risk of coronary and cerebral thrombosis.
COLDS AND FLU: We all know we are more vulnerable to colds in the winter - that's because the cooling of the nose causes a slowdown of the infection-fighting cells in the nose, explains Professor Ron Eccles, director of the common cold centre at Cardiff University.
It also slows down the tiny hairs which normally sweep away viruses in mucus.
Scientists at the U.S. National Institute of Health believe that flu viruses tend to strike in cold weather, because during low temperatures a hard rubbery coating forms around the virus, giving it the protection it needs to pass from person to person.
This coating melts in the higher temperatures of the respiratory tract, allowing the virus to infect cells.
FORECAST: THUNDERSTORMS
HEADACHES: 'The change in atmospheric pressure just before a thunderstorm often triggers headaches,' explains Dr Andrew Dowson, clinical leader of the East Kent Headache Service.
When the pressure drops, brain and nerve cells start interacting differently, causing head pain.
ASTHMA: Many sufferers find their condition worsens if there's a thunderstorm when pollen counts are high - the timing depends on to which pollen they are allergic.
'The gusty weather that precedes a storm whisks up the pollen, which then bursts into a size that is more breathable into the lungs,' explains Professor Jean Emberlin, director of the National Pollen and Aerobiology Research Unit.
'Meanwhile, the electrical charge generated by the storm affects how long the pollen is then retained in the lungs, bringing on an attack.'
In June 2005, a sixfold rise in the number of emergency admissions for asthma in the UK was reported over one weekend as the result of thunderstorms.
FORECAST: HUMID
EAR INFECTIONS: 'Outer ear infection or otitis becomes more common when humidity is high, as the ear canal is more likely to get damp,' explains GP Dr Cath White.
'This creates the perfect warm and moist environment for bacteria to flourish.'
Otitis is an inflammation of the skin lining the ear canal and can cause itching and discharge.
Research at Nahdha Hospital in Oman found that people living in areas with high humidity were twice as likely to have problems with ear wax because of this bacteria.
GOUT: Attacks of gout are more frequent on days of high humidity, possibly because of the effects of dehydration, a Boston University study found.
FORECAST: WINDY
STRESS: When the weather is very windy, the body can react as if it is under attack and produce so-called 'fight or flight' reflexes such as raised heart rate and heightened emotions.
MIGRAINE: 'Windy conditions can trigger a migraine,' explains Dr Dowson. 'One reason for this is the effect on the hypothalamus, the area of the brain that monitors the body's functions; it can lead to constriction or swelling of the blood vessels in the head and cause the pain associated with migraine.'
Scientists at the University of Calgary in Canada looked at the links between migraine sufferers having an attack and the occurrence of Canadian Chinook winds - warm westerly winds specific to Alberta, Canada, which have a definite onset time and are an indicator of profound weather change.
Of the 75 patients studied, 32 were more likely to have migraines during Chinook weather conditions than on days without them.
AND THE GOOD NEWS...
CANCER: We all know sunny weather causes skin cancer, but it could also help protect against other cancers.
A study by the Institute for Cancer Research in Oslo, Norway, examined what happened to people diagnosed with cancer in Norway between 1964 and 2000, and found that the risk of dying within three years of diagnosis with prostate, breast, colon or lung cancer, or with Hodgkin's lymphoma, was up to 50 per cent lower for those diagnosed during summer and autumn compared with winter.
One explanation could be that vitamin D - which is produced by sunlight exposure on the body - helps stop the growth of tumours.
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