As middle-aged women warned of cold water swimming dangers, what are the winter health risks?

• Winter cold water swimmers, particularly middle-aged women, have been warned it can lead to a dangerous lung condition

• A healthy woman in her 50s, who is a triathlete and experienced outdoor swimmer, was recently rushed to hospital after suddenly developing fluid in her lungs during a night swim in a quarry

• Doctors say she developed swimming-induced pulmonary oedema and risk factors include swimming in cold temperatures as well as being female and older

• Read the full article for tips on how to stay safe in cold water and worrying symptoms to look out for

Cold water swimmers have been warned about the health risks of taking the plunge in chilly winter temperatures, after a fit and healthy woman in her 50s developed swimming-induced pulmonary oedema (SIPE) during a late night swim in a quarry.

Medical experts said swimmers should be told more about the risks of SIPE which is also regularly seen in scuba divers. Symptoms include difficulty breathing due to fluid accumulation in the lungs, low oxygen levels in the body and a cough.

Read more: Wild swimming: The best places to swim in the United Kingdom

With many women over 40 and 50 using cold water swimming as a way to get fit, boost their mood in midlife and also deal with difficult symptoms of the menopause, it will come as a blow to hear that factors increasing the risk of SIPE include age, being female, long-distance swimming in cold temperatures, as well as having high blood pressure and pre-existing heart disease.

The patient, who hasn't been named, was rescued and spent the night in hospital, coughing up blood and hyperventilating, but thankfully has since made a full recovery.

This latest health warning follows a public alert issued by Parliament Hill Lido, in Hampstead Heath, north London, in November urging inexperienced swimmers to "be careful" and not to stay in the water too long after at least one person a day fell ill during one chilly week before Christmas.

The unheated outdoor pool is open to members of the public 365 days a year. It's one of many open air facilities across the UK in use throughout winter, catering for the growing number of enthusiasts seeking the 'euphoric high' outdoor swimming can provide. But the latest case is a reminder that there can be significant health risks, even for experienced swimmers.

The most common risk is of course hypothermia, which led Parliament Hill Lido to plead via via an Instagram post an "PLEASE SHORTEN YOUR SWIM!!" with an accompanying image of the recorded low pool temperature, as part of its warning.

"The water temperature has dropped like a stone and is now sitting around 8. This is significantly colder than it was just a week ago, yet a number of swimmers are still trying to stay in the water for as long as they did last week.

"This week, the lifeguards have dealt with at least one hypothermic swimmer EVERY DAY, and they are becoming concerned that people are not taking the temperature seriously.

"Please look out for yourself and other swimmers and please don’t stay in the water too long.

Watch: Boost wellness with mindful swimming

"Also. Don’t rely on the sauna to warm you up. The extremes of temperature can be dangerous and have led to multiple incidents this week.

"Enjoy your swim, but please be careful….."

One social media user and swimmer responded with their tips on how to handle the drop in temperature.

"I swam there in April several times and was so worried for those dipping between the sauna and the cold pool," they wrote. "I swim in the ocean and am always mindful of the water temperature, entering gradually and reducing exposure as the temperatures plummet. @The Wild Swim Store have lots of advice."

Read more: Teacher endures freezing temperatures to go wild swimming every day for a year

Cold water swimming – whether in pools, lakes or the sea – has grown in popularity in recent years, with Wim Hof, or 'The Iceman one of its key pioneers. It's thought to have health benefits associated with helping metabolism, inflammation, swelling and sore muscles, sleep, immunity, energy levels and mental wellbeing.

One study in 2018 explored whether it's an effective treatment for 'major depressive disorder', analysing one particular case. A 24-year-old woman who had been treated for the condition since she was 17, wanted to be medication-free after the birth of her daughter. Weekly open cold water swimming led to an immediate improvement in mood after each swim and a sustained and gradual reduction in symptoms, and then a careful, staggered reduction in medication. A year later, she was still able to remain medication-free.

But while there may be obvious pros, even in a lifeguard-protected facility, there is still the risk of hypothermia to consider, as well as cold shock, incapacitation (becoming physically helpless in water), and cramp.

One of the Lido pool workers told The Telegraph, "Over recent years it has become more and more fashionable to swim in cold water and that has meant we have had more and more people doing it.

"But not everyone is experienced and undertaking proper acclimatisation [getting used to cold water]. And not everyone knows the signs [of hypothermia] – as soon as you start feeling a tingle you really should get out."

They advised that the number of the pool temperature (which should be displayed) equates to the time it's safe to spend in the water.

Read more: Study launched into benefits of wild swimming as antidepressant alternative

What are the signs of hypothermia?

Hypothermia is a dangerous drop in body temperature below 35°C (the norm is around 37°C), which is a medical emergency that should be treated in hospital, and sometimes in intensive care, according to the NHS.

Signs and symptoms include:

• shivering

• pale, cold and dry skin (skin and lips may appear blue)

• slurred speech

• slow breathing

• tiredness or confusion

A baby with hypothermia may be cold to touch and their skin red, floppy, or unusually quiet and sleepy, refusing to feed.

Go to A&E or call 999 if you or someone has any of the above, or alert someone that you need help.

Read more: Cooling off? Here's how to stay safe around water

While you're waiting for assistance, you can move the person indoors or somewhere sheltered, wrap them in a blanket, sleeping bag or dry towel, make sure their head is warm, give them a warm non-alcoholic drink and some sugary food if they're fully awake. Make sure you keep them alert by talking to them and always ensure you or someone stays with them.

Don't use a hot bath, hot water bottle or heat lamp to warm them up; don't rub their arms, legs, feet or hands and don't give them any alcohol.