Why do seniors have less fever?

In fact, it’s not that the elderly have less fever. However, as they naturally have a “cooler” body, the increase in body temperature is often not perceived or seen as a symptom of something more serious in this age group.

As we age, the average body temperature tends to get lower — the difference can reach 1ºC compared to adults and teenagers.

In other words: if the older individual is normally at 36ºC and, on a certain day, it passes to 37.1ºC, this may already represent a feverish condition — even if the diagnosis of fever only occurs at around 38ºC in the youngest.

This confusion, in turn, can hinder and delay the diagnosis of common or more serious diseases from the sixth decade of life onwards, such as urinary tract infections and pneumonia.

Contrary to what happens with children, therefore, fever should not be seen as the main symptom among the elderly, point out the geriatricians heard by BBC News Brasil.

In this group, discomforts such as prostration, difficulty with balance, mental confusion and frequent falls can be the first signs of an illness.

Paying attention to these and other signs, in addition to monitoring the temperature from time to time, are ways to make the early detection of various problems and start treatment.

But why does this change in temperature happen?

Low thermometer

Two articles published by Santa Casa de São Paulo in 2010 investigated this issue in depth.

By analyzing hundreds of records, the researchers concluded that the average temperature of a healthy young adult is 37ºC — and this normal range varies between 36.3ºC and 37.5ºC.

In the elderly, the average is 36.1ºC, with a variation of 0.21ºC for more or less.

The studies also point out that there is a “decrease of 0.15ºC in temperature for each decade of life”.

But what is behind this natural cooling of the body? Doctors explain that there are three main reasons for this.

The first has to do with the natural changes of aging: metabolism is reduced, there is less muscle mass, blood vessels become tighter, the nervous system loses some of its ability to retain heat…

“We have a kind of thermostat in the hypothalamus, one of the regions of the brain. It controls our body temperature”, explains geriatrician Marcelo Altona, from Hospital Israelita Albert Einstein, in São Paulo.

“During the aging process, this ‘natural thermostat’ can be altered”, he adds.

The doctor Marco Túlio Cintra, vice president of the Brazilian Society of Geriatrics and Gerontology, points out that, often, the hypothalamus continues to function properly during aging.

In these cases, the change in temperature involves the simple loss of heat to the environment.

“The elderly have more difficulty in retaining heat in the body, due to changes that occur in the skin and fat cells”, he adds.

Second, this group is more often affected by diseases that affect temperature regulation, such as diabetes, neurological disorders, malnutrition, and sarcopenia (progressive loss of muscle mass).

In addition, the use of some medications and immobility related to locomotion problems also influence this process.

Third, the very difficulty in measuring temperature in this age group can lead to underestimated results (when the number that appears on the thermometer is lower than reality).

This is because the areas of the body where the mercury thermometer is placed change over the years.

In the armpit, excess sweat, skin folds and fat can get in the way. The same occurs in the ear, if there is a buildup of wax in the ear canal.

In the mouth, the lack of some teeth, problems with salivation or the difficulty of keeping the thermometer stable are complicating factors.

In the anus, the last alternative on the list, the barrier is the lack of convenience of introducing the instrument there.

One option is the more modern digital devices, which measure the forehead — but they are more expensive and you have to be careful to change the battery when necessary.

confusion in sight

The difficulty in measuring properly — or the lack of knowledge about what is the normal limit of temperature in aging — can pose a threat to health.

This is because an elderly person may have pneumonia or another serious illness and, because they do not have a temperature considered high, do not undergo a medical evaluation.

This confusion delays the diagnosis of diseases that, if detected early, would have a less invasive and more effective treatment, such as pneumonia and urinary infections.

“Contrary to what happens with children, fever is not among the main symptoms of infection in the elderly. Often, they have a normal temperature or even hypothermia”, warns Cintra.

“The caregiver and the older individual themselves need to be aware of other signs, such as prostration, change in balance, mental confusion, frequent falls… In many cases of urinary tract infection over 60, the only sign is an increase in accidents and falls”, he reports.

“If the average temperature of an elderly person is 35.5ºC or 36ºC, and he has 36.9ºC or 37ºC, this is already a sign that he needs to be monitored more closely”, points out Altona.

“In very frail people or with very advanced ages, small changes in vital signs, such as temperature, blood pressure and heart rate, already require some greater care”, says the specialist.

One guideline that may be helpful for some individuals involves taking a continuous temperature record.

By using the thermometer once a fortnight, or once a month, it is possible to know what the average healthy temperature is — and to notice when the body is warmer than normal.

That is: if the individual is always at 36ºC and, on a certain day, appears with 37.2ºC, this can represent a warning sign depending on the case, even if this is not considered a fever in other age groups.

But Cintra considers that this monitoring must be very well guided and strictly follow the guidelines of the health professional and the thermometer manufacturer.

“Measuring fever all the time can be an unnecessary source of stress”, he points out.

“This habit is useful in some cases, but it is not suitable for everyone”, he adds.

When suggested, these regular temperature measurements should always be taken at the same location on the body and with the same device, if possible.

This text was originally published on the BBC News Brazil website.