2024-01-08 15:48:00
A cold snap is hitting mainland France this week: negative temperatures are expected for the morning of Tuesday January 9 in almost the entire country. Several prefectures have moreover activated their “very cold” plan: Cantal, Côtes-d’Armor, Haut-Rhin, Ile-de-France, Maine-et-Loire, Meurthe-et-Moselle, Paris… The North and East of the country are particularly concerned.
What is the extreme cold plan?
Each year, between November 1 and March 31, state services and MétéoFrance monitor the occurrence of cold waves and, in particular, the drop in temperature. “felt temperature”when the effects of the wind accentuate the feeling of cold. Beyond a certain threshold, special attention must be paid to homeless people because the cold puts their lives in danger.
Four levels of vigilance
Vert : the temperature felt is below -5° and emergency accommodation centers are not yet saturated.Jaune : the cold lasts several days. The temperature felt is between -5 and -10°, emergency accommodation centers are saturated.Orange : the temperature felt is between -10 and -18°, emergency accommodation centers are saturated.Rouge : the temperature felt is below -18°, emergency accommodation centers are saturated.
Depending on the situation, additional reception places can be opened for welcome the homeless. It is recommended that the entire population contact 115 (telephone platform centralizing available places) or the number of emergencies, 15to help anyone in difficulty.
How the body defends itself once morest the cold
When it is cold, the body has two reactions to protect itself: producing heat and, at the same time, trying to lose as little heat as possible.
Different mechanisms are at play.
The muscles begin to move. The simple act of moving, jumping or running warms the body thanks to the energy released by the muscles in action. The tremors and chillswhich correspond to involuntary muscle contractions, help us resist the cold.
The “goosebumps” is a skin defense reflex. When the hairs rise, they form a protective down. Instinctively, we also tend to curl up to expose as little body surface area as possible to the cold.
The cold represents a stress for the human body. In response, the brain secretes catecholamines, neurotransmitters, which send a signal to the blood vessels to contract. “In a cold environment, the vasoconstriction phenomenon (narrowing of the diameter of small blood vessels) reduces blood flow and thus causes a reduction in heat loss from the skin. observes Emmanuelle Turpin-Legendre, head of studies in the Men at Work department at INRS (National Institute for Research and Safety).
The extremities are particularly sensitive to this phenomenon: “The extremities, whether the mains where the feet, have a large skin surface area. In addition, the hands or feet are far from the trunk and its deep organs, a part of the body that physiological mechanisms preserve so that it keeps its internal temperature close to 37°C for as long as possible, to the detriment of the extremities. less essential for survival”, she continues.
The caliber of the blood vessels being narrowed, the heart will have to make an effort extra to propel blood throughout the body. This is why, when it is cold, the heart rate increases, blood pressure is higher, oxygen consumption is higher.
Higher mortality than in the event of a heatwave
THE cold waves remain the cause of a higher number of deaths (from all causes) than heatwave episodes, according to several studies:
that of Public Health France, published in December 2017 in the Weekly epidemiological bulletin . The analysis of deaths over a period of ten years (2000-2010) shows that 3.9% of mortality is attributable to cold and 1.2% to heat; or that published in October 2021 in The Lancet Planetary health : the majority of deaths in the world are due to too low temperatures (8.52%, or 67 deaths per 100,000 inhabitants) and much less due to extreme heat (0.91%, or 7 deaths per 100,000 inhabitants) ( source 1).
Schematically, the heatwave hits quickly and hard, but on a smaller number of people; while the effects of cold are measured over time and on a larger population.
Hypothermia: what symptoms? what to do ?
These chain reactions of the body to the cold have only one goal: to maintain the core body temperature around 37 degrees. If it falls below 35 degrees, we are talking regarding hypothermia. Below 32°C, vital functions are no longer properly ensured.
In addition to chills, goosebumps and numbness in the extremities, other signs can gradually appear and signal the onset of hypothermia: speech disorders, confusionloss of judgment, loss of energy, somnolence…
Faced with a person in a situation ofhypothermiafor example following falling into icy water, you must immediately remove your wet clothes, warm yourself with blankets and hot drinks, and call for help by dialing 15 or 112.
Cold snap: what are the risks for the heart?
The heart is undoubtedly the organ that suffers the most from the cold. Due to vasoconstriction, he tires more quickly. As the caliber of the arteries is narrowed, the risk of tearing the arterial wall increases. A clot that breaks loose in the coronary arteries can cause a heart attack.
Under the influence of the cold, high blood pressure flare-up can also have serious consequences: stroke or rupture of a cerebral aneurysm.
“In the cold, increased heart rate, blood pressure and increased oxygen requirements can lead to decompensation in patients who have a history of cardiovascular disease : heart attack, angina pectoris, or heart failure”, observes Professor Alain Furber, cardiologist and president of the French Cardiology Federation.
This heart fragility in the face of cold has been confirmed by several studies. Thus, the one carried out in December 2022 in 27 different countries (source 2): a period of extreme cold can lead to 1% additional deaths linked to a cardiovascular problem such as stroke or heart attack. This ratio is four times higher than during periods of extreme heat.
Why pollution is an additional risk
The effects of cold are potentiated during pics de pollution. In winter, the boilers (and more particularly those that run on fuel oil or wood) operate at full speed, releasing fine particles into the atmosphere which penetrate deep into the body. These affect not only the lungs, but also the heart and blood vessels. Consequence: the risk of heart attack increases.
Tobacco + stress + cold: an explosive cocktail
THE smokers must be particularly vigilant during cold periods because tobacco exacerbates vasoconstrictionthus multiplying the risk of heart attack.
The typical situation is the stressed person who goes out to smoke a cigarette in the cold. This is the worst cocktail because tobacco and stress lead, like the cold, to a spasm of the arteries. Professor Furber, cardiologist.
In case of extreme cold, a greater risk of asthma attack
Exposed to a cold, dry air (especially during a pollution peak), the bronchi react by contracting. This bronchospasm can trigger an asthma attack.
The first precaution to take is to cover your nose and mouth with a scarf to warm the air you inhale. Another piece of advice: anticipate cold spells by talking to your doctor. It is often enough to take the right treatment at the right time to avoid asthma attack.
Frostbite and frostbite: what are the differences?
L’angel mainly affects the hands and feet. Fingers or toes become red, swollen and painful, but the lesion remains superficial. Conversely, gelure is a deep lesion that can lead to amputation. For prevention, you must equip yourself well and layer on protective layers. For example: wear silk gloves under leather gloves, or put on two pairs of socks, making sure they are not too tight so as not to hinder blood circulation.
The cold facilitates the circulation of viruses
L’winter is prone to epidemics with its attendant flu, colds, gastroenteritis and other bronchiolitis. A list to which must be added, since the beginning of 2020, Covid-19. The cold promotes the circulation of viruses, particularly respiratory viruses. Cold, dry air dries out and can damage the mucous membrane of the nose, which constitutes our first defense barrier once morest respiratory infections.
And as it’s cold, we go outside less, preferring to stay confined in enclosed spaces. Ideal conditions for the transmission of viruses.
In this context, we better understand the importance of barrier gestures : cough and sneeze into your elbow, blow your nose into a disposable tissue, ventilate the rooms regularly, wear a mask to protect yourself and others, wash your hands frequently with soap and water or hydroalcoholic gel, stay at distance from each other. These simple gestures and behaviors protect us once morest Covid-19, but also once morest all contagious microbes.
Faulty heating: beware of the risk of carbon monoxide poisoning
Every year, around a hundred people die following inhaling carbon monoxide (CO) and nearly 3,000 are poisoned, according to Public Health France. Three quarters of accidents take place in winter. The CO is a toxic gas, undetectable since it is colorless and odorless. It is issued when heaters have poor draft or are defective. Fuels like gazthe boisthe coalthe fuel oil, gasoline or oil can release CO. Hence the importance of maintaining and checking every year the correct operation of its boiler, of all heating appliances and ducts chimneys. It is also necessary to ensure that the ventilations are not obstructed.
In case of poisoning symptomsI CO (headaches, fatigue, nausea), the first reflex is to ventilate the room widely, evacuate the room and call emergency services (15 or 112 for emergencies). Carbon monoxide poisoning can affect several people at the same time. For prevention, it may be useful to install a CO detector in your home.
To find out more, Public Health France provides a brochure: “The dangers of carbon monoxide, to understand”.
Can you do sports when it’s cold?
Exercising warms you up! However, thephysical exercise practiced in the cold puts the body under severe strain. The body gets tired and dehydrates more quickly since he must both fight once morest the cold and exert physical effort.
Caution is necessary, particularly in people with asthma and in cases of cardiovascular disease (high blood pressure, history of heart attack or stroke, etc.). Even more so during a pollution peak.
To protect yourself, it is important to get dressed by choosing insulating textiles capable of absorbing perspiration. Wool that swells with moisture is not the best choice.
Before embarking on any physical exercise, you should warm up quietly for a few minutes. The muscles and the heart will be better prepared for the effort. « L’warming up will cause vasodilation in the skin and muscles which will compensate for vasoconstriction due to the cold. explains Professor Furber.
Another tip: don’t forget to hydrate. In fact, the cold dries out the body. Basically, good hydration will facilitate muscle work and maintain correct blood pressure. “We need water as much in winter as in summer,” reminds the cardiologist.
Finally, when the outside temperature drops below -5°C, it is better to give up brutal and intense physical efforts outdoors. Indoor sport also has its advantages.
What diet to combat the cold?
Digestion produces heat in the body. This shows the importance of a good food during periods of extreme cold. To provide fuel, nothing like the low glycemic index foods which facilitate the regular release of glucose (energy source) in the body, avoiding “pump surges”. THE pastaTHE legumesthe pain completTHE fruits and the vegetables match this profile.
THE soups are ideal since they provide vitamins, minerals and heat at the same time.
In terms of drinks
Alcohol should be avoided. THE grog where the hot wine bring a false sense of comfort. In fact, alcohol dilates blood vessels which promotes heat loss. “Its action will lift the protective mechanism of vasoconstriction”, remarks Professor Furber. Instead of increasing, body temperature “decreases by half a degree for every 50 grams of alcohol consumed” according to Anpaa (National Association for Prevention in Alcoholism and Addictology). You should also know that alcohol accelerates dehydration of the body, while this is already accentuated by the cold. It also lowers the threshold of vigilance, which can be dangerous in periods of extreme cold.
How to dress warmly
Several layers of clothing allow to protect yourself from the cold. The first, close to the body, will absorb perspiration and prevent humidity from cooling the skin. The second must be insulating, knowing that the effects of cold and wind are cumulative.
In a document intended for people who work in cold thermal conditions, the INRS gives an example of this ” felt temperature “. Thus, on a winter day at -10°C with a 30 km/h wind, the sensation felt on the skin is equivalent to an outside temperature of -19.5°C.
And well-designed clothing once morest the cold must have enough layers to be insulating, without being too thick so as not to hinder movements, as explained by Laurence Robert, research manager in the Process Engineering department at INRS: “One solution is to create thick fabrics by putting together two or more thin fabrics to form the envelope of a wadding. The goal is to create a layer and make this air there as “calm” as possible at the same time. interior, static air being a very good thermal insulator.
In addition to warm, suitable clothing, you should also remember to cover your extremities because your feet and hands are particularly sensitive to the cold. THE mittens are more effective than gloves.
Without forgetting the head. The INRS reports that “nearly 30% of body heat is evacuated through the skull and mouth”. A big scarf and a hat will do the trick!
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