Falling temperatures require the body to adapt. The heart, in particular, will have to put in an extra effort. In a healthy person, regulation will be done without difficulty. But the cold can be formidable for the most fragile. How to protect yourself? Our advices.

Cold, wave:, what, the, risks?

When it is cold, the body has two reactions to protect itself: to generate heat and, at the same time, to try to lose as little as possible.

 Different mechanisms are in play:

 The muscles start to move. The simple act of moving, jumping or running warms the body with the energy released by the working muscles. Tremors and chills, which are involuntary contractions of muscles, help us resist the cold.

 “Goosebumps” are the skin's defense reflex. When the hairs rise, they form a protective down. Instinctively, we also tend to curl up to expose as little body surface as possible to the cold.

 The cold is stressful for the human body. In response, the brain secretes catecholamines, neurotransmitters, which send a signal to blood vessels to constrict. "In a cold environment, the phenomenon of vasoconstriction (narrowing of the diameter of small blood vessels) decreases blood flow and thus causes a decrease in heat loss in the skin", observes Emmanuelle Turpin-Legendre, head of studies at Men at Work department at INRS (National Institute for Research and Safety).

 The extremities are particularly sensitive to this phenomenon: "The extremities, whether it is the hands or the feet, have a significant skin surface. In addition, the hands or feet are far from the trunk and its deep organs, part of the body that the physiological mechanisms preserve so that it keeps as long as possible its internal temperature close to 37 °, and this to the detriment of the extremities less essential to survival ", she continues.

 As the caliber of the blood vessels is narrowed, the heart will have to work extra hard to force blood throughout the body. Therefore, when it is cold, the heart rate increases, blood pressure is higher, oxygen consumption is higher.

Hypothermia: a dangerous situation

  These chain reactions have one purpose: to keep the core body temperature around 37 degrees. If it drops below 35 degrees, it is called hypothermia. Below 32 ° C, vital functions are no longer properly provided.

When faced with a person in a hypothermic situation, for example after a fall in ice-cold water, one should immediately remove his wet clothes, warm him with blankets and hot drinks, and call for help by dialing 15 or 112.

Higher mortality than in the event of a heat wave

  Cold waves are the cause of a higher number of deaths (all causes) than heat wave episodes, as shown by a study by Public Health France, published in the Weekly Epidemiological Bulletin of December 12, 2017. L he analysis of deaths over a ten-year period (2000-2010) in 18 different metropolitan areas shows that 3.9% of mortality is attributable to cold and 1.2% to heat. Basically, the heat wave hits hard and fast, but on a smaller number of people; while the effects of cold are measured over time and over a larger population.  

A risk for the heart in the event of a cold snap

  The heart is arguably the organ that suffers the most from the cold. Because of the vasoconstriction, it gets tired more quickly. As the caliber of the arteries is narrowed, the risk of tearing the arterial wall increases. A clot that breaks off in the coronary arteries can cause a heart attack. 

 Under the effect of cold, a surge of high blood pressure can also have serious consequences: stroke or rupture of a brain aneurysm.

"In the cold, the increase in heart rate, blood pressure and increased oxygen requirements can lead to decompensation in patients with a cardiovascular history: infarction, angina, or heart failure", observes Prof. Alain Furber, cardiologist and president of the French Federation of Cardiology.

Pollution, an additional risk

  The effects of cold are potentiated during pollution peaks. In winter, boilers (and more particularly those that run on oil or wood) operate at full speed, releasing fine particles into the atmosphere that penetrate deep into the body. These affect not only the lungs, but also the heart and vessels. Consequence: The risk of heart attack increases. 

Tobacco + stress + cold: an explosive cocktail 

 Smokers should be particularly vigilant in cold weather because tobacco exacerbates vasoconstriction, thus increasing the risk of heart attack.

             “The typical situation is the stressed person going out to smoke a cigarette in the cold. This is the worst cocktail because tobacco and stress, like the cold, lead to a spasm of the arteries ", underlines Professor Furber.

Caution for asthmatics

When exposed to 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 inhaled air.

  Another tip: anticipate cold spells by talking to your doctor. Often, taking the right treatment at the right time is enough to prevent an asthma attack.

Frostbite and frostbite: it's not the same

 Frostbite mainly affects the hands and feet. The fingers or toes become red, swollen, and painful, but the lesion remains superficial. Conversely, frostbite is a deep injury that can lead to amputation. In prevention, you have to be well equipped and overlay the 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 interfere with blood circulation.

A circulation of viruses facilitated by the cold 

 Winter is ripe for epidemics with its trail of flu, colds, gastroenteritis and other bronchiolitis. A list to which must be added, since early 2020, the Covid-19. The cold promotes the circulation of viruses, especially respiratory viruses. Cold, dry air dries up and can damage the lining of the nose, which is our first defense against respiratory infections.

And since 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: coughing and sneezing into your elbow, blowing your nose in a disposable tissue, regularly ventilating the rooms, wearing a mask to protect yourself and others, wash your hands frequently. water and soap or hydroalcoholic gel, stay away from each other. These simple actions and behaviors protect us against Covid-19, but also against all contagious germs.

  Defective heating and carbon monoxide poisoning

Each year, a hundred people die after inhaling carbon monoxide (CO) and nearly 3,000 are poisoned, according to Public Health France. Three-quarters of accidents happen in winter. CO is a poisonous gas, undetectable because it is colorless and odorless. It is issued when the heaters have poor draft or are defective. Fuels such as gas, wood, coal, fuel oil, gasoline or petroleum can emit CO. Hence the importance of maintaining and checking the proper functioning of your boiler, all heating devices and chimney flues every year. It is also important to make sure that the ventilations are not blocked.

In the event of CO poisoning symptoms (headaches, fatigue, nausea), the first reflex is to ventilate the room widely, evacuate the room and call for help (15 or 112 for emergencies). Carbon monoxide poisoning can affect several people at the same time. As a preventive measure, it may be useful to install a CO detector in your home. 

To find out more, Public Health France has made available a brochure: "The dangers of carbon monoxide, to understand". 

 Practicing physical activity in the cold

 Doing sports, it warms up! However, physical exercise in the cold puts the body to the test. The body tires and dehydrates faster because it must both fight against the cold and make a physical effort. 

Caution should be exercised, especially in people with asthma and in cases of cardiovascular disease (high blood pressure, history of heart attack or stroke, etc.). Especially during a pollution peak.

 To protect yourself, it is important to dress well by choosing textiles that are insulating and capable of absorbing perspiration. Wool that swells with moisture is not the best choice.

 Before starting any physical exercise, you should warm up slowly for a few minutes. The muscles and heart will be better prepared for the effort. "Warming up will cause vasodilatation of the skin and muscles, which will compensate for the vasoconstriction caused by the cold," explains Prof. Furber.

Another tip: don't forget to hydrate. Indeed, the cold dries out the body. Basically, a good hydration will facilitate the work of the muscles and maintain a correct blood pressure. "We need water as much in winter as in summer," says the cardiologist.

Finally, when the outside temperature drops below -5°C, it's best to avoid brutal and intense physical effort outdoors. Indoor sport also has its advantages.

Eat well and stay hydrated in the cold

Digestion produces heat in the body. This shows the importance of a good diet in periods of extreme cold. To provide fuel, there is nothing like low-glycemic index foods that facilitate the regular release of glucose (energy source) into the body, avoiding "fuel strokes". Pasta, legumes, wholemeal bread, fruits and vegetables fit this profile.

 Soups are ideal because they provide vitamins, minerals and warmth at the same time. 

Alcohol should be avoided. Grog or mulled wine brings a false sense of comfort. Alcohol dilates the blood vessels, which promotes heat loss. "Its action will lift the protective mechanism of vasoconstriction", remarks Pr Furber. Instead of increasing, the body temperature "decreases by half a degree for every 50 grams of alcohol consumed" according to the Anpaa (National Association for Prevention in Alcohol and Addiction). It should also be noted that alcohol accelerates dehydration of the body, which is already accentuated by the cold. It also lowers the vigilance threshold, which can be dangerous in periods of extreme cold.  

Dress warmly

Several layers of clothing provide good protection from the cold. The first one, close to the body, will absorb perspiration and prevent moisture from cooling the skin. The second layer must be insulating, knowing that the effects of cold and wind are cumulative. 

In a document intended for people working in cold thermal conditions, the INRS gives an example of this "felt temperature". Thus, on a winter day at -10°C with a wind speed of 30 km/h, the sensation felt on the skin is equivalent to an outside temperature of -19.5°C.  

A garment that is well designed against the cold must have enough layers to be insulating, without being too thick so as not to hinder movement, as Laurence Robert, head of studies in the Process Engineering Department at INRS explains: "One solution consists of creating thick fabrics by assembling two or more thin fabrics together to form the envelope of a wadding. The aim is to create a layer and to make this air as "calm" as possible inside, static air being a very good thermal insulator ".

In addition to warm and suitable clothing, you should also think about covering your extremities because feet and hands are particularly sensitive to the cold. 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 large scarf and a hat will do the trick!