Normal Body Temperature : Rethinking the normal human body temperature
The 98.6° F "normal" benchmark for body temperature comes to us from Dr. Carl Wunderlich, a 19th-century German physician who collected and analyzed over a million armpit temperatures for 25,000 patients. Some of Wunderlich's observations have stood up over time, but his definition of normal has been debunked, says the April issue of the Harvard Health Letter. A study published years ago in the Journal of the American Medical Association found the average normal temperature for adults to be 98.2°, not 98.6°, and replaced the 100.4° fever mark with fever thresholds based on the time of day.
Now, researchers at Winthrop University Hospital in Mineola, N.Y., have found support for another temperature truism doctors have long recognized: Older people have lower temperatures. In a study of 150 older people with an average age of about 81, they found that the average temperature never reached 98.6°. These findings suggest that even when older people are ill, their body temperature may not reach levels that people recognize as fever. On the other hand, body temperatures that are too low (about 95°) can also be a sign of illness.
The bottom line is that individual variations in body temperature should be taken into account, reports the Harvard Health Letter. Ideally, you and your doctor should have enough temperature measurements at various times of day to establish a baseline for you. Short of this, recognize that 98.6° isn't the benchmark that we've long believed it to be.