Lt. Gen. (Retd) Mahmud Ahmed Akhtar
It has been noted by researchers that “we are running cooler, on an average”. Fever is a very common symptom and sign in clinical practice. The older physicians noted rise of body temperature by the sense of touch – later by counting rise of pulse. Later, medical science discovered the mechanism of rise and fall of body temperature and its controlling center in the brain. Pathological conditions like rise of temperature, low-grade, moderate, high-grade rises (hyperpyrexia), heat stroke, continuous fever, resting, intermittent etc. was used as a clinical sign in diagnosing different types of clinical diagnosis, planning relevant investigations and treatment. This was more important in tropical and sub-tropical countries.
Lt. Gen. (Retd) Mahmud Ahmed Akhtar
In the older days, clinicians used fever as a clinical sign. Later scientific world, predominantly the western, made advance in clinical medicine even in the tropical and sub-tropical region of the globe. The third world, lacking resources, may not be able to make sophisticated researches in subjects like genetics, molecular biology etc., but can do in clinical field, which sadly, isn’t done. In peptic ulcer research, Dr Iry, a general medicine practitioner, did the pioneering research. Hospital working physician has seen peptic ulcer patients with complications while Dr Iry saw peptic ulcer patients in earlier stages, also mild ones, changing concepts of peptic ulcer as only the severe disease. The study of average values like blood pressure and lab values could be good subjects for research studies in Pakistan.
Over the past few decades, evidence has been mounting that the average human body temperature is not really 98.6 Degrees Fahrenheit. Instead, most people’s baseline is a little bit cooler, says Don G Smith, a medical journalist writing in daily New York Times.
The standard of 98.6 Degrees Fahrenheit (37 Degrees Celsius) was established over 150 years ago by the German physician Dr Carl Wunderlich, who reportedly took over a million measurements from 25,000 people. Temperature ranged from 97.2 to 99.5 Degrees Fahrenheit (36.2 to 37.5 Degrees Celsius) and the average was 98.6 Degrees Fahrenheit. Dr Wunderlich also established 100.5 Degrees Fahrenheit as “probably febrile”.
However, a study was published in September that evaluated the temperatures of more than 126,000 people from 2008 to 2017 that average is closer to 97.9 Degrees Fahrenheit. Other modern-day studies reported similar numbers. Experts who study body temperatures have different opinions about why we have become cooler over time and whether that matters when it comes to evaluating fever and diagnosing infection.
Why the Standard is off Base
Some researchers say it may just be a measurement issue. Dr Wunderlich might have assessed temperatures using different methods and standards than the ones we use today. One account report that he used a footlong thermometer that went into a person’s armpit.
Many factors that influence a body temperature reading, the most significant being from which body part do you take it. Reliability of rectal temperatures are higher than oral temperatures, which in term have higher reliability than the readings taken from skin. Body temperature is also influenced by the time of day, whether it is hot or cold outside and even whether the person has had something to eat or drink. Readings can also vary from thermometer to thermometer depending upon how they are calibrated.
Comparing historical and modern data gives one a hodgepodge mixture of observations, said Dr Philip Mackowiak, an emeritus professor of medicine at the University of Maryland School of Medicine, who in 1992 paper was one of the first researchers to scrutinize Dr Wunderlich’s concludes. The drop in temperature may be a true phenomenon, he added, but there is no way of knowing because the data are so varied.
Other experts think that humans really have gotten cooler over the past 100 years. Our temperatures have really declined over the last 150 years, which might be because we are lucky to be healthier than we used to be, said Dr Julie Parsonnet, a professor of medicine, epidemiology and population health at Stanford Medicine who led the September study on body temperature. For instance, it could be that many people in Dr Wunderlich’s sample had many highly elevated temperatures from low-grade inflammations.
Better treatment of infections, improved dental care and the development and use of medications (like statins have many actions including anti-inflammatory in addition to lipid-lowering effect) may have contributed to decline in inflammation since the 19th century, which in turn, lowered peoples’ average temperature, said Dr Parsonnet.
Regardless of the reason, the experts believe that 98.6 Degrees Fahrenheit should no longer be considered the universal human temperature standard. But instead of shifting the average temperature down, it should be given as a range, said Dr Waleed Javaid, a professor of medicine at Mount Sinai in New York City, who published a 2019 review paper on body temperature. A range would account for the natural variability in temperature that occurs due to gender and age. Women tend to run slightly warmer than men and older adults run cooler than younger people. Additionally, everyone’s body temperature fluctuates throughout the day, i.e., is typically lowest in the morning and highest in the late afternoon.
There is a range for heart rate. There is a range for blood pressure and temperature has a range too.
What counts as a Fever?
If we redefine “normal” body temperature, then what registers as abnormal? The US Center for Disease Control and Prevention says that temperature of 100.4 Degrees Fahrenheit and above is a fever. A roughly two-degree increase from 98.6. but if the average human temperature is lower, it is possible that the temperature indicating fever may be lower as well. A personalized approach to fever where doctors compare each patient against their own baseline so that low-grade fevers are not missed in people who run cooler.
There is an example of a patient aged 80 years suffering from sub-acute bacterial endocarditis went undiagnosed for several months for the patient never registered as feverish. Her temperature was around 98.6 but her treating doctor assessed that was normal for her age. This individualized approach would be normal.
There is a range for heart rate. There is a range for blood pressure and temperature too has a range. One should not be concerned about the possibility of low-grade fevers being missed because of the current temperature standards. Instead of changing the definition of a fever, the solution may be to place less of an emphasis on fever overall and to think it as a one sign amongst many, something many physicians already do. This advice applies to patients as well as physicians.
If temperature is very high, that is important information but the temperature is not the only one to look into it. It is well known principle of clinical medicine that for diagnosis of disease, all signs and symptoms should be considered.
