NEW YORK NURSE: May 2010
by Gina Myers, PhD, RN, CNR-PC
You may have heard it said that the older you get, the colder you get. How true is this? A recent systematic review by Lu, Leasure & Dai (2009) identifies a change in the longstanding belief that normal temperature for all adults is 98.6 °F. A systematic review is a type of literature review that searches many databases to find research conducted on a chosen topic. A group of reviewers then evaluates the studies that are found and summarizes the findings to help us learn the best evidence available on a topic (Melnyk & Fineout-Overholt, 2005).
An extensive search of seven Western and Chinese scientific databases was done to find articles that would help determine the normal body temperature in people age 60 and older (older adults). The researchers also wanted to learn the differences in temperature with regard to where it was taken and with what device, and the existence of temperature variability with time of day or time of year. Initially, their search found 290 articles. These were narrowed down after the researchers reviewed each study’s abstract. They excluded articles that did not report group means, looked at both afebrile and febrile patients, did not identify older adults, and gathered data through retrospective chart review. After this screening, there were 22 articles that were included. All studies were reviewed and appraised by two different research nurses; any disagreement in evaluation was resolved by a third researcher. The number of subjects in the studies ranged from 18 to 1,020; the majority were obtained using convenience sampling. They were selected from the community, nursing homes, and hospital settings. Non-invasive temperature measurements using a variety of sites (oral, rectal, tympanic, urine and axillary) were included in this review.
After appraising the studies, researchers conducted a meta-analysis to assess temperature data across all of the studies. Meta-analysis is a way to take the results from a number of small studies and statistically pool them together as if they were all part of one large study, giving strength to the findings (Melnyk & Fineout-Overholt, 2005). Using this methodology, the researchers looked for variations in temperature with regard to age, measurement site, device used, and time of day and year.
After combining the results, researchers found that normal body temperature in older adults shows a variation across body measurement sites. Averages for each site are as follows: rectal 98.8°F, tympanic 98.3°F, urine 97.6°F, oral 97.4°F, and axillary 97.1°F. The authors note that normal readings for older adults determined from this study are lower than the normal temperature readings typically reported in nursing textbooks, regardless of site taken. Specifically, the temperature of the older population is 0.7°F lower than adults for rectal temperature, 0.3°F lower for tympanic, 1.2°F lower for oral temperature and 0.6 lower for axillary temperature. Also noteworthy is that the rectal temperature is 1.4°F higher than oral. This difference is greater than the typical estimate of 1°F indicated in nursing textbooks. Further, temperature was 0.7°F higher in the afternoon compared to the morning. Changes in season did not seem to have much of an influence on temperature, with only a 0.2°F difference.
The authors note limitations to these findings. Many of the studies included were 10 years old or older, and were done with mercury thermometers, which are no longer available. Many had samples sizes less than 100, with temperature being measured only once. The time of day the temperature was taken was also inconsistent. Future studies to determine the accurate sites for temperature measurement in the older population, as well as the reliable methods of temperature measurement were suggested.
It is important for nurses to understand the unique aspects of caring for the older population. The first is to be aware of the differences that exist in normal temperature for older adults in comparison to those who are younger. The variation in temperature between measurement sites is also essential. The authors propose that clinicians think again when initiating treatment for abnormal temperatures. Due to the normal aging process, the lower normal temperature range could possibly lead to a blunted fever response (Tai et al, 2002), suggesting a different approach to the treatment of temperature elevation in the older adult. Also, it is important to consistently measure temperature with the same device and site to obtain the most accurate trend data. This will decrease the incidence of considerable temperature changes, which would cause concern. Last, bathing older patients in the evening when they are warmer, may be a good practice change to consider. Although temperature may be considered a subtle difference, it is one piece of the puzzle that leads to a reliable patient assessment.
Lu, S., Leasure, A., & Dai, Y. (2009). A systematic review of body temperature variations in older people. Journal of Clinical Nursing, 19, 4-16.
Melnyk, B., & Fineout-Overholt, E. (2005). Evidence-based practice in nursing & healthcare: A guide to best practice. Philadelphia: Lippincott, Williams & Wilkens.
Tai, S., Guller, V., Gurevich, A., & Levi, S. (2002). Fever of unknown origin in the elderly. Journal of Internal Medicine, 252, 295-304.