Aging does not impair temperature regulation in humans
750-Word Counterpoint Summary
BPK 432
Fall 2016
November 28 2016
Emily Lee
Bryan Lee
BPK 432-Counterpoint Presentation 750 Word Summary
Aging does not impair temperature regulation in humans
Emily Lee
Bryan Lee
The hypothesis for our counterpoint presentation is that aging does not impair
temperature regulation in humans. The opposing point hypothesis is that aging does impair
temperature regulation in humans.
Supporting evidence:
Armstrong and Kenny conducted an experiment to investigate how age was related in
passive heat exposure. For this study, the subjects were matched for VO2max, height, weight,
adiposity and skinfold thickness. Heat acclimation reduced the initial rectal temperature and
mean body temperature in both the young and the elderly groups. However, there were no age
differences in skin temperature, rectal temperature and mean body temperature during the
passive heat exposure in both pre- and post- heat acclimation states. When chest sweating rate
was plotted against mean body temperature, there was also no difference between the young and
old groups before and after the heat acclimation [1].
Sweating is an important aspect in human thermoregulation and Drinkwater et al. looked
at the relation between aging and sweating in women. Young and old women subjects were
matched for body surface area for the study. The rectal temperature thresholds for sweating at the
arms were 36.9 ± 0.1
for both young and older groups. The authors measured sweating rates at
five different sites which were the arm, chest, back, thigh and abdomen. When they were all
averaged, there were no significant differences between the age groups. Both age groups
displayed similar sweat electrolyte levels and evaporative heat loss pattern as well. Rectal
temperature was similar throughout the experiment and it reached a plateau at 37.2
and 37.1
for young and older women respectively [2].
Similar results were seen in Bernstein et al. study during the three-hour exposure at 76 oF.
Mean skin temperatures for young and aged subjects towards the end of the exposure were 90.0
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BPK 432-Counterpoint Presentation 750 Word Summary
Aging does not impair temperature regulation in humans
Emily Lee
Bryan Lee
o
F and 89.2 oF respectively. Evaporative water loss for the young and the aged groups were 0.339
gm/m2/min and 0.257 gm/m2/min respectively. As the numbers indicate, there were no
significant differences in mean skin temperatures and evaporative water loss between the age
groups [3].
A study conducted by Wagner and Horvath showed that there were no significant
differences in rectal temperature in younger and older groups at a thermoneutral temperature of
28 . The older women group maintained a constant core temperature during cold exposures and
surprisingly, younger women were only able to maintain constant rectal temperature during cold
exposure at 20
. Males, on the other hand, had declined rectal temperature during cold
exposures. The slope of figure 1, which indicated the rate of temperature decline, during the 10
exposure were identical for young women, men and older men. Metabolic rate, which produces
heat, were constant for all groups at 28
. These results demonstrate that older individuals are
able to maintain constant body temperature and even perform better than younger subjects in
some cases [4].
Opposing evidence critiques:
Frank et al. studied the differences in thermoregulatory response to the cold environment
between the aged and young group. They measured the core temperature at the tympanic
membrane using thermocouple probes. Vasomotor activity was measured by laser Doppler
flowmetry at the tip of the left index finger and concentration of norepinephrine and epinephrine
was also measured from venous blood. They found that the older group had lower core
temperature threshold for vasoconstriction and total body oxygen consumption than younger
group. Their maximum intensities were also lower than the younger group, concluding that the
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BPK 432-Counterpoint Presentation 750 Word Summary
Aging does not impair temperature regulation in humans
Emily Lee
Bryan Lee
thermoregulatory efficiency decreases with age [5]. A limitation to this study is that due to the
technical problems with the blood flow measurements, the values were not obtained in two older
subjects and one younger subject. This might have influenced the results and skewed the data
because almost 20% of the data have not been obtained.
Smith et al, examined age related alterations in the relation between regional sweating
and skin blood flow to thermal and pharmacological stimuli. Four microdialysis fibers were used
in nine young subjects and eight aged subjects during two experimental protocol: acetylcholine
dose response and whole body heating. The study concluded that the aged group had
significantly lower sweating threshold and observed vasomotor and sudomotor dysfunction.
However, the limitations are that the microdialysis might have blocked the sweat glands at the
skin site being measured and they were not able to detect this. Moreover, there were females and
males in each group but the sex differences were not taken into account [6].
Conclusion
Aging is a complicated process and it cannot be an independent factor for
thermoregulation impairment. Studies that have matched for confounding factors provided
positive evidences for our counterpoint hypothesis that aging does not impair temperature
regulation in humans.
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BPK 432-Counterpoint Presentation 750 Word Summary
Aging does not impair temperature regulation in humans
Emily Lee
Bryan Lee
References
1. Armstrong, C. G., & Kenney, W. L. (1993). Effects of age and acclimation on responses
to passive heat exposure. Journal of Applied Physiology, 75(5), 2162–2167.
2. Drinkwater, B. L., Bedi, J. F., Loucks, A. B., Roche, S., & Horvath, S. M. (1982).
Sweating sensitivity and capacity of women in relation to age. Journal of Applied
Physiology, 53(3), 671–676.
3. Bernstein, L. M., Johnston, L. C., Ryan, R., Inouye, T., & Hick, F. K. (1956). Body
Composition as Related to Heat Regulation in Women. Journal of Applied Physiology,
9(2), 241–256.
4. Wagner, J. A., & Horvath, S. M. (1985). Influences of age and gender on human
thermoregulatory responses to cold exposures. Journal of Applied Physiology, 58(1),
180–186.
5. Frank, S. M., Raja, S. N., Bulcao, C., & Goldstein, D. S. (2000). Age-related
thermoregulatory differences during core cooling in humans. American Journal of
Physiology-Regulatory, Integrative and Comparative Physiology, 279(1), R349-R354.
6. Smith, C. J., Alexander, L. M., & Kenney, W. L. (2013). Nonuniform, age-related
decrements in regional sweating and skin blood flow. American Journal of PhysiologyRegulatory, Integrative and Comparative Physiology, 305(8), R877-R885.
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