Mortality and temperature inversely proportional

In a 46-page document released by the director of InVS Gilles Brucker, it is clear that we have more to fear from large temperature drops as heat waves. "In absolute terms, the cold is more deadly than the heat," it is argued, the mortality associated with it is indeed much larger than the few annual deaths from hypothermia homeless.

According to different data, mortality increases almost linear as the temperature decreases. Example, in January 1985, France has experienced a wave of unprecedented cold has led to significant mortality (13%) mainly due to myocardial infarction (17%), stroke (54%) and pneumonia (208% ). For one region Ile-de-France (the sixth of the French population), the excess of deaths was 1039 compared to January of the previous four years.

Adverse effects occur when the thermoregulatory system is deficient or when the heat stress is too high. In addition, a wind of 90km / h associated with a temperature of -10 ° C has a multiplier effect. It causes the same feeling that a temperature of -30 ° C in calm weather.

Immediately "vasoconstriction and associated phenomena can lead to rupture of atherosclerotic plaques and promote arterial thrombosis," reads the report. In the coronary arteries spasm related to cold associated with a possible thrombosis and increased demand for myocardial oxygen promotes, among those at risk, the occurrence or worsening of angina, or even a myocardial infarction if complete stenosis. Warning, the effect is not necessarily immediate. The interval between the cold wave and death can be 7 to 14 days.

"In the brain, these same mechanisms (hypertension, hyperviscosity and thrombosis) may be the origin of accidents, stroke, especially ischemic type," the report said.

In addition, the cold air inhalation irritant to mucous membranes and the containment of the population, conducive to the spread of germs, are possible explanations for the increase recorded in winter conditions. Respiratory infections account for about 25% of the excess winter mortality with a delayed effect from 15 to 30 days.

Besides hypothermia, the report also cites endocrine diseases or asthma and a very indirect way, the increased risk of carbon monoxide poisoning caused by heating deficient risk.