Feeling under the weather?

From hay fever, to winter colds, to sunburn, we all know that the weather affects our health. But to what extent?

According to a new book by PAT THOMAS, the weather can contribute to respiratory problems, strokes and even heart attacks, and as many as one in three of us is 'weather sensitive'. Here is our complete guide to what exactly is happening to your body when you feel 'under the weather'.

COLD

Overall, the number of deaths on an average winter day is 15 per cent higher than on an average summer day.

The average body temperature is around 37c/98.6f, and it is potentially life-threatening for the body's core temperature to vary from this by more than two degrees centigrade.

The body core is made up of the vital organs - the brain, heart, lungs, kidneys and digestive tract. Enzymes within these organs assist in the important biochemical reactions.

These enzymes operate best in a temperature range of 35-40c/95-104f. Outside this range, they may undergo loss of function or death, and bodily functions may become impaired. The result can be death from hypothermia.

Angina

The incidence of angina and heart attack peaks during autumn and winter. In fact, within 24 hours of a temperature drop, the incidence of coronary problems will increase. In the cold, blood pressure increases and cholesterol rises, as does the stickiness of the blood. These changes put extra pressure on already weakened hearts.

Stroke

Ischaemic stroke (the most common form of stroke, caused by a blood clot) and intracerebral haemorrhage (bleeding from the blood vessels in the brain itself) are two types of stroke that are most often triggered by winter weather.

This is because blood thickens as the temperature drops. More pressure is put on the heart, and blood is pushed around at a faster rate to keep the body's temperature up.

The change in blood pressure can also cause atrial fibrillation, or chaotic heartbeats, which is one of the most frequent causes of stroke and heart failure.

In cold weather, there are also more chronic infections, which may also increase the risk of stroke.

Seaonsal Affective Disorder (SAD)

SAD is a condition that affects around half a million people in the UK, leaving them feeling lethargic and low in the dark winter months.

SAD sufferers often have unusually high levels of melatonin - a hormone that regulates our sleep-wake cycle - possibly because of the shorter daylight hours. This gives them an increased urge to sleep and a reduced desire to interact with other people.

It may even be that the symptoms of SAD are a form of primitive protection. Having a natural low, especially in winter, may be important for recharging our batteries and enabling the natural 'high' that follows in spring and summer.

Exercise-induced asthma

Exercise-induced asthma is common in winter when you breathe in very cold, dry air. Such air cools the mucous membranes of the upper respiratory tract, eventually causing irritation.

When cold air is suddenly breathed in during exercise, the body may react, contracting the smooth muscle around the bronchioles. This leads to tightness in the chest, with coughing, wheezing and shortness of breath.

WIND

Respiratory problems
Strong wind on your skin creates friction and can dry your nasal passage and eyes, as well as increasing the concentration of dust, allergens and particulate matter in the air. Windy air also contains positive ion molecules that are thought to cause a dry throat, husky voice, headache, an itching or obstructed nose, and reduced breathing capacity.

Stress

In extreme wind, the body can react as if it is under attack, bringing on a stress reaction of producing adrenal hormones. This is known as the fight-or-flight response.

Above a certain wind speed, the skin begins to transmit warning signals to the brain, making us feel anxious and irritable. A wind above 20mph is said to trigger a deep primitive instinct to take shelter.

Exhaustion

The body can't sustain the 'stress' mode for long, and with the adrenal glands pumping out stress hormones such as dopamine, exhaustion descends at the end of a windy day.

CLOUD

Cancer

If you live in perpetually cloudy and winter-like conditions, you may have low vitamin D levels from limited exposure to the sun.

Experiments have shown that vitamin D blocks the proliferation of breast, colon and prostate cancer cells. In America, there are two to three times more cases of prostate, breast and colon cancer in cloudy climates than in sunnier areas.

Schizophrenia
Some experts believe that lack of sunshine during pregnancy can cause schizophrenia. It has been found that babies born between February and March are 10 per cent more likely to develop schizophrenia than those born at other times of the year.

FOG OR FROST

Allergies

When the temperature is cool and the air relatively still, there is an increase in the amount of solid particles in the air - man-made pollutants such as soot and industrial emissions, as well as fungal and mould spores. This has been mooted as a cause of winter allergies.

HEATWAVE

Heat Oedema Excessive heat can cause heat oedema, with the swelling of fingers or ankles. It can also cause heat cramps, which are painful spasms in the arms, legs or abdomen, as well as dizziness or fainting and heat exhaustion.

Heat stroke occurs when the body's temperature rises to 104f/40c - a point at which damage to tissues in several organ systems can occur.

Low sperm count

A study in Houston, Texas, found that sperm counts were lower in summer than winter. This is backed up by figures suggesting that conception rates are also lower in hot weather, although there is some variation from country to country.

STORMY
Pain
People with rheumatoid arthritis, osteoarthritis, fibromyalgia, gout and neuralgia, and those with missing limbs or scars, can experience more pain in stormy weather.

Because tendons, muscles and bones are of differing densities, cold or humid air may cause them to expand or contract in different ways. If there is already swelling, stiffness, inflammation or abnormal mechanics in the joint, as the atmospheric pressure changes so the unequal expansion and contraction of tissues may cause increased pain.

The density of scar tissue is also different from that of normal skin.
It could also be that during colder weather, arthritis sufferers, for example, are less inclined to get outdoors and perform normal activities to keep their joints supple. Depression brought on by dreary weather may also make pain feel worse.

Sleeplessness Storms bring about a change in the electromagnetic activity of the environment. The earth is surrounded by electricity and emanates its own electromagnetic fields (EMFs).

Thunder and lightning produce weak electromagnetic fields, and within these fields are audible impulses known as infrasound. These are sonic waves which are undetectable to the human ear but affect the biorhythms of the brain and may be associated with sleeplessness.

Some people believe that infrasound is at the root of most weather-sensitivity symptoms, in particular irritation and slow reaction times.

LIGHTNING

Heart attacks Positive ion molecules in the air, as a result of a thunderstorm, can affect the circulatory system. They can raise blood pressure and may affect the electrical circuits in the heart muscle. It is estimated that around 10 per cent of lightningrelated fatalities are cardiovascular in nature.

SUNSHINE
Skin damage Sunshine generates ultraviolet radiation, which damages the skin, eyes and immune system.

Prolonged exposure to UV radiation can cause sunburn and wrinkles. Some people will suffer from extreme reactions to the sun, with conditions called protoporphyria and polymorphous light eruption, which can cause a rash, blotchy blisters and scaly patches. More commonly, sun can cause red skin pustules known as prickly heat.

Excessive sun exposure can also cause two types of skin cancer - melanoma and non-melanoma.

Non-melanoma cancer, or basal cell carcinoma, appears as small fleshy bumps, usually found on the neck and the head. It rarely spreads, but left untreated can penetrate and damage the bone.

Melanoma usually begins as a mole but is known to spread and can be fatal. Melanoma is thought to have its roots in childhood incidents of sunburns.

Immune system damage

As UV rays are absorbed by the body, there is a decreased immune response. It is this response that some scientists think contributes to the formation of malignant melanomas.

Eye damage Photokeratitis is the ocular equivalent of sunburn. It happens when the cornea of the eye is sunburned, making the eye red, inflamed and twitchy, sometimes causing blurred vision.

Research has directly linked cataracts - a gradual loss in the transparency of the lens of the eye - to exposure to UV radiation.

SEASONAL CHANGES

Seasonal changes affect your health, but the changes cannot always be explained. The structure of our blood changes according to the seasons. Blood volume increases in summer, which means your heart has to work harder.

In one UK study, blood pressure was found to be highest in April and May, and lowest in September.

In some studies, the metabolic rate has been found to be higher in winter than in summer.

Certain cancers also follow a seasonal pattern. There is a higher incidence of newly diagnosed uterine cervical cancers in February.

What season you are born in can even affect how long you live. One Russian study suggested that people born at the beginning or the end of the year can live up to two-and-a-half years longer than people born in April to July.

Extracted from Under The Weather - How Weather & Climate Affect Our Health, by Pat Thomas (Fusion Press, £10.99).