Cold Weather and You

February 03, 2011

Two-thirds of the United States has been under a winter storm watch this week, at one point Houston was colder than Detroit. In Kansas, they've somewhat affectionately dubbed the huge weather mass 'The Blizzard of Oz.'  One thing is for sure, there are a lot of cold people in the U.S. So why do we all react to cold with shivering or chattering teeth?  To create heat. This reaction is driven by the hypothalamus, a small gland in the brain that acts as a thermostat.  Thanks to the hypothalamus, the body's reaction to heat loss is speedy and automatic.  A minor drop of temperature in the body kicks off immediate reactions: muscles shiver to create heat and blood vessels in the skin constrict to prevent excessive heat loss, both of these reactions are dedicated to protecting the body's 'core' system. To guarantee well-being, the body’s core temperature needs to be maintained at around 98°F. The body's core includes vital organs such as the heart, lungs, liver, brain, and kidneys which perform required functions for the body. Skin, the muscles, arms and legs are all considered peripheral, which is why your hands, nose or feet may be very cold without causing immediate danger to survival.  In a cooler environment, you lose heat until the periphery reaches the same temperature as the surroundings, then the heat flow stops and the core's heat level is preserved. Cold's effect on the thermoregulatory center in the hypothalamus that influences appetite is also worth mentioning. Prolonged exposure to cold increases appetite as the body uses more energy to generate heat and maintain temperature. The increased appetite also serves to increase the fat stores that insulate the body from heat loss. This helps explain ‘winter fat.’  In this regard, a consistent fitness regimen will help maintain a healthy metabolism while avoiding those extra pounds! Weather extremes also create additional stress on the cardiovascular system.   In a cold environment, blood vessels constrict to preserve heat, which means the heart has to work harder to move blood through the narrower vessels. Several surveys of blood donors indicate that blood pressure rises when temperature drops, published figures showed increases of between 12 and 18mmHg. This small increase isn't significant for a healthy person, however if a person is suffering from high blood pressure or heart disease, they should take precautions.  Remember, a heart under strain requires a high volume of oxygen-rich blood and narrow vessels do restrict the supply.  If you fit this description, pay attention for the symptoms of angina. Lower temperatures also cause an almost immediate change to the composition of the blood that persists for up to two days. This change is an increase of particles in the blood, such as platelets, red blood cells, fibrinogen and cholesterol, which make the blood thicker. The thicker blood with constricted blood vessels increase the risk of blood clotting that could lead to blocked blood vessels. Add heavy snow shovelling and you're in a very dangerous situation. Hospital emergency departments register a significant increase of patient numbers after heavy snowfall. In fact, data collected from patients fitted with heart defibrillators show a strong relationship between weather extremes and heart diseases. Researchers found that heart rhythm abnormalities are more frequent on days with either very high or very low outside air temperatures. While some patients reacted immediately to temperature changes, others’ reactions were delayed by two to three days! There is no doubt that cold weather increases the risk of heart or circulatory disease, but remember ‘cold’ is relative. The mortality rate during Hawaii’s winter increases by 22 per cent, a figure similar to some cold climate regions. Take care of yourself in this cold weather!  Moderate the amount of time you spend outside when the temperatures are dangerous, and dress well.

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