why does body temperature rise at night

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by Emmanuel Rodriguez, M. D. , M. P. H. Q. В Why does a fever sometimes get higher at night? A. В The answer to that is pretty simple: Body temperature, whether youвre sick or well, just gets higher later in the day. But the explanation behind that answer has to do with all sorts of things. A small gland at the base of the brain called theВ hypothalamus Your bodyвs В vital functions The temperature of yourВ surroundings The hypothalamus is your bodyвs built-in thermostat. By secreting hormones in small pulses, it communicates with your other vital organs, carefully regulating your body temperature close to a set temperature of 98. 6 degrees Fahrenheit. If you produce excess heat by exercising, your hypothalamus reduces your temperature by increasing the blood flow to your skin (basically, drawing more heat out of your body) and by making you sweat. On the other hand, if you go out into the cold, your hypothalamus tries to increase your temperature by causing you to shiver. When you have a fever, the hypothalamus has reset your body temperature to one thatвs higher than normal. В It does this for an unclear reason. Some people think fever helps the bodyвs immune system fight the infection because some bacteria donвt thrive on higher temperatures. Home remedies + science = do-it-yourself survival medicine! Get prepared for disasters with.


Your temperature usually follows a built-in 24-hour cycle. Its lowest point is between 3 and 6 a. m. , followed by a peak between 4 and 11 p. m. Your hypothalamus has its own 24-hour hormone-secretion pattern. We donвt know the reason for this so-called circadian rhythm, but to some extent the day/night light cycle helps regulate it. The things the body does during the day (heartbeat, muscle movements, breathing) involve a release of heat energy, causing your core body temperature to warm up as the day progresses. This explains why your temperature increases toward the end of the day under normal conditions. However, this cycle still happens when you have a fever. В The difference is that now, the temperature elevation is more obvious since youвre already starting from a higher temperature than normal. There are exceptions to this cycle. Outside factors that can dampen the evening temperature-elevation include older age; certain medical conditions, such as diabetes; and the use of some common drugs, such as acetaminophen (Tylenol) or aspirinвall of which affect the functioning of the hypothalamus. Board certified in internal medicine, В EMMANUEL RODRIGUEZ, M. D. , M. P. H. , В is an infectious-disease specialist with NorthReach Internal Medicine Clinic in Marienette, Wis. , and attending physician and hospital epidemiologist with Bay Area Medical Center. (Subscribe to updates below. ) Bushfires are quite appropriately dominating our nationБs concerns during the current Australian heatwave.


But for many, the struggle to sleep through soaring temperatures is a personal inferno that dominates conversation around offices and homes across the country. Sleep and body control of temperature ( ) are intimately connected. Core body temperature follows a 24-hour cycle linked with the sleep-wake rhythm. Body temperature decreases during the night-time sleep phase and rises during the wake phase. Sleep is most likely to occur when core temperature decreases, and much less likely to occur during the rises. Our hands and feet play a key role in facilitating sleep as they permit the heated blood from the central body to lose heat to the environment through the skin surface. The sleep hormone melatonin plays an important part of the complex loss of heat through the peripheral parts of the body. At sleep onset, core body temperature falls but peripheral skin temperature rises. But temperature changes become more complex during sleep as our temperature self-regulation varies according to sleep stage. has shown how environmental heat can disturb this delicate balance between sleep and body temperature. An ambient temperature of 22к or 23к Celsius is ideal. Any major variation in this leads to disturbance of sleep with reduced slow wave sleep (a stage of sleep where the brainБs electrical wave activity slows and the brain БrestsБ), and also results in less dreaming sleep (rapid eye movement or REM sleep). Indeed during REM sleep, our ability to regulate body temperature is impaired so in a clever sort of way the body БavoidsБ this stage of sleep during extreme cold or heat.


A heat wave may cause several nights of fragmented sleep with less slow wave and REM sleep. This will certainly cause a correct perception of bad, restless sleep with consequent negative effects on mood and alertness. In theory, it may also have subtle effects such as problems with complex memory retention, higher judgement (poorer decision making and increased risk-taking behaviour), blood pressure control and regulation of glucose in the body. The clear message is this: if youБre going to make some big decisions during a heatwave, sleep in a carefully controlled air-conditioned environment. But apart from air-conditioning, what can you do to sleep better during a heatwave? Sleeping in the lateral position (on your side) with less contact with the mattress may be good but the body tends to do this anyway during sleep, in response to rising temperatures. Cooling the central body with a wet cloth or towel makes sense. A cool shower may also help. It is important to avoid doing anything too strenuous in the hours before bed-time as this will make it harder for the body temperature to fall during sleep. And when you wake up hot, sticky and irritated because you donБt have air-conditioning or believe such devices are environmentally unsound, remember those fighting bushfires - it could be a lot worse.

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