Importance of Body Temperature and Aging.

How to manage when external factors challenge our body temperature.

Right now, if you were to take your temperature with a thermometer, it would probably read at about 37 degrees Celsius or 98.6 Fahrenheit. As warm-blooded mammals, humans maintain a relatively consistent core body temperature. However, its degree may be altered by both internal and external factors. Thus, measuring a person’s temperature can provide useful information about their health. This topic is all you need to know about body temperature and the optimal temperature ranges for newborns, children, adults, and the elderly.

When we talk about how hot or cold someone is, we typically imply their core body temperature (the inside of the head, chest, and abdominal cavity). The surface temperature, often known as the body shell temperature, is another component. It is the sum of the external environment and the internal body temperature and is thus a measurement of the skin’s sensitivity.

body temperature vs core temperature

In contrast to the body’s core temperature, the human skin temperature ranges from around 28°C to 37°C. Reviewing the scientific literature, the average core body temperature for each age group is listed below.

Age Oral
  • 0–12 months


  • Children


  • Adults


  • Adults over age 65


Your internal temperature may be 1 degree Fahrenheit (0.6 degrees Celsius) greater or lower than the above parameters.

Factors Influencing Change in Body Temperature.

Furthermore, even in a single individual, core body temperature varies constantly, all day long, depending on the individual’s mood and metabolic rate. A variety of internal and environmental variables affect body temperature.

  • During The Day:Body temperature

Throughout the day, the core body temperature changes between 0.5 and 1 °C. The term for these regular changes is “Diurnal rhythm.” It is often at its lowest early in at 3 a.m. and gradually rises when an individual awakens, reaching its highest point at 6 p.m. This fluctuation coincides with the amount of metabolic activity, which is lowest during sleep and gradually increases throughout the day.

  • During Sleep: Each person’s body temperature reaches a low point in the early morning at a different time. While you sleep, your body and mind go through a number of distinct stages. Dream sleep, or rapid eye movement sleep (REM), is a state in which the body is extremely active. However, a 2019 study indicated that during this time period, humans are unable to control their body temperature. The study participants reported more REM sleep when the room was at a comfortable temperature.
  • Basal Body Temperature: An individual’s lowest resting core temperature when asleep is known as their basal body temperature. The most accurate time to take a person’s basal temperature is first thing in the morning when they wake up. Women’s basal temperature varies with the phase of the menstrual cycle.
  • Site Of Measurement: Temperature measurements vary based on the measuring place. Here are some fundamental criteria for comprehending how temperature measurements may differ across the most popular measurement locations. In general, an axillary temperature is 0.3°C to 0.6°C [0.5°F to 1°F] lower than an oral temperature, whereas a rectal temperature is 0.3°C to 0.6°C [0.5°F to 1°F] higher.
  • Exercise/Physical Exertion: Muscles create heat as they function. The amount your body temperature rises during exercise depends on the activity’s intensity and how much heat you dissipate.
  • Stress: An elevated core temperature is a common physiological response to emotional or physical stress. A rise in core body temperature is mediated by the stress hormones cortisol and adrenaline. The body’s adaptive reaction to stressors causes a rise in temperature. Adrenaline, the hormone responsible for the “fight or flight” response, triggers the liver to produce more heat and also causes other compensatory modifications. Because it is both huge and very metabolically active, the liver significantly affects core body temperature.
  • Meals: Typically, there is a minor rise in body temperature immediately after eating. Between 20 and 30 minutes after eating indicates that your metabolic rate has increased to promote digestion. This is especially true for high-calorie meals, as the body releases a great deal of heat energy when digesting its food.
  • Caffeine: Caffeine increases heart rate, metabolism, and respiration at even modest levels, which in turn raises blood pressure and body temperature. This is because vasodilation in the organs occurs at the same time as a mild narrowing of blood vessels in the brain, resulting in a sensation of warmth and a decrease in subjective weariness.

The average body temperature changes during different phases of life,

In Children: Most babies and children have temperatures between 36.5 and 37.5 ° Celsius. A baby’s body surface area is more than its body weight, which causes its temperature to be higher. Additionally, due to their bodies increased metabolic activity, heat is produced. Even though children have more brown adipose tissue (brown fat), which is used to make heat, they cool down much faster when exposed to cold air than older children and adults. This also means that they cannot regulate their body temperature. The   temperature could go down for a number of reasons, such as being exposed to very cold temperatures or other things.

In Women: It has been studied that the menstrual cycle affects women of childbearing age’s core temperature. Consequently, in the second half of the menstrual cycle (after ovulation), the temperature rises by approximately 0.4 °C as a result of the hormone progesterone, before returning to a normal level with the onset of menstruation. Progesterone’s thermogenic action allows for an assessment of fertility by measurement of the basal body temperature on days when conception is likely.

How We Control Our Body Temperature.

The preservation of a steady body temperature is vital for human metabolic function. When the body temperature is too low, metabolism ceases to function. On the other hand, if the temperature is too high, important proteins are destroyed. It is also important to know that the temperature is not always indicative of illness if the temperature of the body is above or below normal. Our internal temperature can be affected by age, sex, time of day, and degree of activity.

To function effectively, the human body must maintain a temperature within a restricted range of around 1.6 degrees Celsius or 3 degrees Fahrenheit. Outside of this range, neurons and muscles and organs function less effectively. Even cellular proteins might be impacted. Therefore, the body exerts great effort to maintain a safe temperature by sweating in hot weather and restricting blood vessels in cold weather.

This is done with the help of a special mechanism called thermoregulation. Thermoregulation is the process by which the body maintains a steady internal temperature by adjusting the rate of heat generation to match the rate of heat loss. Sensors in the central nervous system (CNS) transmit information to the hypothalamus when the body’s internal temperature fluctuates. In response, it transmits messages to many organs and bodily systems. They reply via several techniques.

If the body requires cooling, several systems are activated:

  • The perspiration produced by our sweat glands cools our skin as it evaporates. This helps reduce inner body temperature.
  • Vasodilation causes the vessels beneath the skin to become wider. This boosts blood flow to the skin, which is colder — away from the body’s core, which is warmer. This allows the body to radiate away excess heat.

If the body wants to warm up, the following systems are activated:

  • Vasoconstriction narrows the blood vessels under the skin. This reduces blood flow to the skin, preserving heat close to the body’s core.
  • Muscles, organs, and the brain create heat in a number of ways via thermogenesis. For instance, muscles can generate heat by shivering.
  • The thyroid gland secretes hormones that raise the metabolism, a process known as hormonal thermogenesis. This raises the quantity of energy and heat that our body generates.

To summarize, the hypothalamus is the region of your brain in charge of these kinds of things. Too much cold causes the blood vessels to constrict and the muscles to twitch in an effort to maintain body temperature. Moreover, your body sends a signal to start sweating when it gets too hot.

Thanks to the balance of heat generation, heat conservation, and heat dissipation, the human body’s core temperature (about 36.5 °C to 37.4 °C) remains generally steady throughout the day. The thermostat of the body responds to alterations in blood flow, activity, and external temperature. The ambient temperature at which an unclothed adult still feels comfortable, i.e. is not too cold and not too warm for him, is referred to as the thermoneutral zone or “comfort zone” and is around 27 °C to 32 °C.

But sometimes the body systems don’t work in the same manner and cause either very high or very low temperatures of the body,


When the internal temperature of the body increases above 37.5 degrees Celsius, hyperthermia sets in. In this situation, the body’s internal thermoregulation is inhibited, thus the core temperature does not rise to its predetermined level also known as “set-point”.  However, when a person has a fever, the hypothalamus raises the body’s set-point temperature. This rise in body temperature is an effort by the body to fight off a disease or infection.

In addition to an elevated body temperature, hyperthermia expresses itself through signs such as reddened, hot, firstly often dry skin, an increased respiratory rate, heart palpitations (tachycardia), and sometimes changes in consciousness. Rarely, do seizures or febrile convulsions develop as complications.

When someone has a fever, the thermometer may show a reading that is significantly higher than usual. The American College of Critical Care has defined it as a temperature of 100.9°F (38.3°C) or above. In most people, a fever is diagnosed when the temperature rises more than 2 degrees Fahrenheit (1.1 degrees Celsius).

The highest human body temperature is 108.14 F. At greater temperatures, proteins get denatured and the brain sustains irreparable damage.


Hypothermia describes a decrease in the core body temperature below 35 °C. Depending on the temperature and concomitant symptoms, there are four phases of hypothermia,

  • Defensive stage (excitation), 35-32 °C: No loss of consciousness, but restlessness, trembling, breathlessness, hypertension, and fast heartbeat.
  • Exhaustion stage (adynamia), 32-30 °C: Indifference and confusion; irregular and shallow breathing; slower heartbeat and lowered blood pressure; increased muscular and joint stiffness.
  • Unconsciousness; mydriasis (dilation of the pupils); weak breathing; acute slowing of the pulse; low blood pressure.
  • Below 27 °C, apparent death (vita reducta): Possible respiratory arrest; heart: ventricular fibrillation or stoppage of cardiac activity.

A common misconception is that hypothermia only occurs when people are exposed to cold temperatures for too long. Hypothermia, however, is not limited to the outdoors. There are several causes of hypothermia. For instance, a thermoregulatory system that is only partially functional may be responsible for a dramatic decrease in body temperature, malnutrition, a slowed metabolism, sickness or injury, a diminished or nonexistent capacity to generate heat through cold shaking, vasodilation, and perspiration in a cold environment, as well as substantial fluid or blood losses with surgery or accident.  Hypothermia poses a particular threat to infants and the elderly.

Meaning Hypothermia is a condition in which the core body temperature falls below the bare minimum required to sustain essential metabolic processes. The warming or increasing body temperature is hyperthermia. It takes place when the body absorbs or generates more heat than it loses.
Reasons • Exhaustion or extended exposure to cold temperatures can cause frostbite.
• Remaining in icy waters for long spans.
• Wearing damp clothing in cold weather.
•Prolonged exposure to hot, dry environments
• Dressing in tight or heavy clothes in a hot environment.
• Having a condition that impairs your ability to perspire.
• Extreme dehydration or fluid loss
Symptoms • Slow, shallow or altered breathing
• Confusion
• Shivering
• Pale skin
• Drowsiness
• Slurred or mumbled speech
• Red cold skin (turns blue in later stages)
• Thirst
• Dizziness
• Nausea
• Sweating
• Dilated blood vessels
Treatment • Try drinking fluids that are warm
• Moving to a warmer environment •Rewarming externally
• Passive cooling
• Resting in a shaded and cold area
• Limiting clothes
• Drinking cold fluids
• Air conditioning

Body Temperature & Aging.  

As with most physiological performance characteristics, the ability of endotherms to thermoregulate reduces with age. Both the ability to preserve or disperse heat and thermogenesis are impaired by ageing. Temperatures decline by about 0.1 to 0.15 °C for every decade of a person’s life.

Causes include decreased thermoregulation and decreased release of pyrogens (substances that cause fever). We also naturally lose subcutaneous fat, which means our bones and organs have less cushioning and protection. People over the age of 65 often have a normal body temperature below 98.6 degrees Fahrenheit (37 degrees Celsius). According to several scientific studies, adults over the age of 64 have a harder time adjusting to sudden temperature changes than their younger counterparts.

It is extremely challenging to discover infections in the elderly because of their low baseline and their muted immune responses. According to the results of the study, those between the ages of 65 and 75 had higher average body temperatures than those between the ages of 75 and 85 and those older than 85. Age changes the distribution of fat, muscle, skin, and sweat glands. Around 30% of the elderly no longer develop a fever despite the presence of a serious illness.

Aging is not necessarily a factor in a person’s heightened vulnerability to temperature. The following are some more potential triggers:

  • Hypothyroidism
  • Anaemia
  • Atherosclerosis
  • Diabetes
  • Cardiovascular problems
  • Drug reactions

Why is this important? A limited capacity to regulate internal body temperature during heat or cold stress might increase the likelihood of developing hyperthermia or hypothermia. hypothermia is a very serious risk for elders. The National Institute on Aging reports that A body temperature of 95 degrees Fahrenheit or less in a senior citizen can lead to a variety of health issues, such as a heart attack, renal difficulties, liver damage, or even worse.”

Moreover, coping with these problems might strain the cardiovascular system, which is weakened with age. Thus, caution should be maintained when older people encounter combined problems of temperature and cardiovascular control.

What other changes occur in the elderly? Have a look at this article for more insight into aging.

Measuring Body Temperature.

Depending on the purpose and required precision, several measurement methods and instruments are utilized.

The two most common types of thermometers used to take a body temperature are the contact thermometer and the non-contact thermometer. Although mercury thermometers (expansion thermometers) were the gold standard for measuring body temperature for quite some time, electronic thermometers and those using infrared sensor technologies are quickly replacing them, especially after COVID -19 Outbreak. Typically, the temperature is monitored within the ear, (orally) behind the tongue, in the armpit, rectally (preferred for children/babies), or on the forehead.

There is also an ingestible thermometer capsule, and each of these several thermometer kinds produces somewhat different average temperatures.

The following readings are considered accurate for measuring with any of these thermometers,

5 1

Tips To Maintain Body Temperature.

Here are some general tips to maintain

1. Hydration is Important: Our thirst reflex lessens as we age. Regardless of the weather, it is important to consume ample amounts of liquids according to a study. Someone who weighs 150 pounds, for instance, should aim for 75–150 ounces of water daily. On hot days, one should stay away from alcoholic beverages and caffeine.

2. Building muscle: It has been well documented that building muscles can get thermoregulation to work better. Aerobic and endurance exercise training improves the body’s thermoregulatory responses, leading to less physiological stress and greater cardiovascular and exercise capacity in warm and hot environments.

3. Dress Properly: In cold weather, when venturing outside in chilly weather, scarves and hats are essential for warding off the cold. Also, layering is safe as it can be removed if an elder feel overheated. In hot weather, use of air conditioner and fans, covering curtains and blinds, and staying out of direct sunlight during the day are all tried and true methods for keeping one comfortable in summer.

4. Track the Weather: Consider the heat index in the summer and the wind chill in the cold. Local health officials will issue heat alerts for the elderly and small children when the heat index rises above a certain level.

5. Review Medications: If you are taking any medication, it is ample to consult with your doctor to see if you are more likely to suffer any changes in temperatures due to it. Certain drugs, or adjustments to dose, may be discouraged or required by your doctor during certain seasonal changes.

Body temperature is an important marker of human health, along with pulse rate, respiration rate, oxygen saturation, and blood pressure. The proper core body temperature is needed to maintain metabolic activities. The body maintains a steady temperature of 36.5 to 37.4 °C. A deviation up or down might signal health problems.


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Being a Doctor by profession, Aimen is passionate about helping people get better health in their lives. Aimen enjoys her research on Prime With Time subjects and strives to create better awareness of the problems and changes related to women's health.
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