Is the weather making you ill?

If you feel weak in the winter and sick in the summer, you are not imagining it. The weather really does affect our health – and can be lethal

For a weather-conscious nation we are comically bad at coping with snow and ice. Traffic jams, grit shortages and school closures are part of the British winter landscape.

But it is not only our routine that suffers. So does our health. Cold temperatures lower immunity and thicken the blood, increasing the risk of infection and heart attacks. Grey skies depress mood, icy conditions increase injuries.

Weather can affect health in any season – and in ways that are unexpected. The storm that blows in from the Atlantic, the anticyclone that builds above the North Sea or the pall of cloud that lingers for days may all have an impact. An icy snap in winter or a heatwave in summer can cost hundreds of lives.

The Met Office established a department of health forecasting eight years ago to help identify the threats posed by changes in the weather and protect the vulnerable. The service is being expanded each year and now provides early warning of adverse conditions to tens of thousands of vulnerable people, by phone, email and text message.

Winter Cold

The threat is greatest to those most vulnerable to the cold – people with chronic health conditions such as heart disease. There are more heart attacks in cold weather – blood vessels in the skin contract in the cold to preserve heat, making it harder for the heart to pump the blood round the body. But it is not the cold alone that is the killer – it is the cold combined with high levels of circulating viruses that poses the greatest threat. Cold depresses the immune system and makes us more vulnerable to infection. The Met Office sends alerts to 30,000 people at risk when snow and ice are on their way and virus levels, as measured by the Health Protection Agency, are high. Paid for by Primary Care Trusts, the individuals receive an automated telephone call asking if they are well and whether they have enough medication to last at least two weeks. Their answers are relayed to their GPs, who can respond as necessary.

Wayne Elliott, the head of health forecasting at the Met Office, says: "It is a bespoke service for people suffering from chronic bronchitis and other respiratory conditions. We have rolled it out from the Moray Firth in Scotland to the Scilly Isles in the south. We use a formula that calculates the risk. It is normal most of the year but when the cold weather and high virus levels combine and it becomes 'elevated', that triggers the calls. It is much more sophisticated than the general cold weather warnings we issue through the media and our website."

Around 25,000 extra people die in the winter months compared to other times of the year in England and Wales. Last year there were 40,000 excess deaths, as a result of the unusually low temperatures. Extra deaths also occur during heatwaves in summer, but they are different – the result of what is called "death displacement". Evidence shows that summer heatwave deaths tend to involve people who would have died soon anyway – and are followed by a dip in deaths during the months after a heatwave.

Winter deaths, by contrast, are genuinely "excess" – they are not followed by a dip in the subsequent months. And they are worse in Britain than in countries with colder winters, such as Scandinavia.

Gloomy skies

Dull days are depressing for anyone, and make it hard to remember the warmth and brightness of last summer's sunshine. But for some, gloomy weather can make them mentally ill.

A second service offered by the Met Office provides alerts when two or more gloomy days are forecast for individuals who suffer depression or other mental problems in winter – Seasonal Affective Disorder (SAD) is the technical term. Those signed up to the scheme are provided with a light box, a manual for cognitive behaviour therapy [self-administered] and an information leaflet on the importance of eating well and exercise, paid for by their primary care trusts.

Mr Elliott admits he was a late convert to the cause, but is now convinced of the value of the service and is looking for new primary care trusts to adopt it, especially in Scotland – arguably the gloomiest place in the British Isles. "Two years ago we were approached by Cornwall PCT who had reviewed their mental health services and found this issue – the weather – came very high up in the list of factors that people said affected their mood. It was across the spectrum from those with severe psychosis to people complaining of poor performance and irritability at work. We ran a pilot scheme in Cornwall with 90 people last year and this year we are extending it to over 200 in Trafford, Bracknell and Manchester as well as Cornwall again. When an extended period of gloomy weather is forecast lasting two or more days we alert them by text message or email – they tend to be younger than the respiratory disease patients – to get their light boxes out."

The light boxes emit a much stronger light than ordinary electric bulbs, which is thought necessary to banish the winter blues. However, the evidence is equivocal and many doctors think any benefit is due to the placebo effect.

Mr Elliott is unabashed. "A lot of it is psychological – but I am an absolute defender of that being important. If patients are reporting that they feel better with the treatment then it is worth doing."

He adds: "We don't see much innovation in mental health compared with areas such as cancer so it is encouraging to get results. We would very much like a Scottish PCT to start a scheme but with the present uncertainty in the NHS they are reluctant to experiment with a new service."

Heatwaves

It may be hard to imagine in the depths of winter, but each summer brings the threat of stifling temperatures. They cause mere discomfort to most, but for some they can be lethal. The heatwave of August 2003 showed that hot weather can kill. There were more than 2,000 deaths in England, and 27,000 across continental Europe. Most of the victims were elderly people, who can be vulnerable to heat exhaustion. The experience of 2003 led the Government to issue a heat wave plan with four levels of alert. Measures include staying out of the sun, avoiding the outdoors from 11am to 3pm, wearing loose clothes and a hat, taking cool showers, and consuming cold food and water.

Each year from 1 June to 15 September, the Met Office runs a Heat-Health Watch system with the Department of Health. It forecasts day and night-time maximum temperatures which are monitored regionally. When they pass certain thresholds – lower in the north and higher in the south because they are tied to average temperatures – an alert is sent to health professionals and people working in social care so they can take action to minimise the impact on those they are looking after.

Sunshine, pollution, pollen

Every year about 50,000 people in Britain develop skin cancer – disfiguring lesions on the skin – though most can be successfully treated. About 6,000 develop melanoma, the most serious form of skin cancer and more than 2,000 of these die. Deaths from melanoma have quadrupled since the 1970s, reflecting Britons' increased love of the sun.

Severe sunburn is the main cause, repeated year after year – especially before the age of 15. However, the highest incidence is among Scots who have never been abroad. Their fair skin puts them at risk from the sun at home. The Met Office provides a forecast of ultraviolet light levels in different regions through the summer, taking account of sun position, cloud cover and the level of ozone in the atmosphere, using a scale developed by the World Health Organisation.

It is also planning to extend its alert service for people with respiratory problems, which for the last three years has run only during the winter, through the summer months as well, linked to levels of atmospheric pollution. "A lot of people get exacerbations of their symptoms in summer linked to high temperatures and poor air quality. We will run the alert service through the year," Mr Elliott said.

Pollen levels play havoc with the health of the millions of hay fever sufferers in summer, but these are not included in Met office forecasts – yet. Pollen forecasts are issued by the National Pollen Research Unit at the University of Worcester but Mr Elliott said he hoped to include them in Met Office forecasts "in the future".

Climate change

The biggest impact of weather on health is seen in the global effects of climate change. Storms, floods, heatwaves and other "extreme events" are expected to become more common. Malaria and similar tropical diseases may spread beyond their current geographical limits as temperatures rise.

The Met Office is an acknowledged world leader in the science of climate change but has only recently begun to research the health impact. It has linked up with the Peninsula Medical School based in Plymouth to investigate the health effects.

Mr Elliott said: "My personal view is that the two big areas of importance in climate change are the economic impact and the health impact. Everything else is a side issue."

The weather and illness: Facts and figures

* In the last five years‚ more than 130‚000 people over 65 have died from cold-related illnesses during the winter months in Britain.

* In the winter of 1999/2000, around 48,440 excessive deaths were recorded in England and Wales, based on a comparison with a non-winter period. This was the highest in 25 years, exacerbated by seasonal flu.

* As many as a third of people in the UK suffer symptoms of SAD, a mood disorder thought to be caused by a lack of light, most common in people between the ages of 18 and 30.

* Sun-related skin cancer is the most common cancer among 15 to 34-year-olds.

* A study by Cancer Research UK in August 2009 revealed that more than 50 per cent of British people who suffered sunburn last summer did so while in the UK.

* The number of hay fever sufferers has quadrupled in Britain in the last 50 years and stands at around 12 million. About 95 per cent of sufferers in the UK are allergic to grass pollen.

* The UK has one of the highest rates of asthma. More than 50 per cent of people with asthma also have hay fever.

* Hay fever sufferers drop at least one exam grade because it hits in spring and summer.

Rhiannon Bury