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Original Studies |
Center for Psychobiological and Psychosomatic Research, University of Trier (B.M.K., J.H., D.H.H., O.T.W., K.-M.P., C.K.), Trier, Germany; the Department of Psychiatry and Psychotherapy, Semmelweis University of the Medical Sciences (E.V.), Budapest, Hungary; and the Department of Psychiatry, University of Göttingen (J.P.), Göttingen, Germany
Address all correspondence and requests for reprints to: Dr. Clemens Kirschbaum, Center for Psychobiological and Psychosomatic Research, University of Trier, Dietrichstrasse 1011, 54290 Trier, Germany. E-mail: kirschba{at}uni-trier.de
| Abstract |
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After a 2-week treatment with 50 mg DHEA daily or placebo, 75 men and women (mean age, 67.6 yr) were exposed to the Trier Social Stress Test (TSST). The TSST is a brief psychosocial stress that consists of a free speech and mental arithmetic task in front of an audience. The results show that the TSST induced significant increases in ACTH, salivary free cortisol, total plasma cortisol, norepinephrine, and heart rates (all P < 0.0001) as well as decreased positive affect in the elderly (P = 0.0009). Men showed larger stress responses in ACTH (P = 0.004), salivary free cortisol (P = 0.044), and plasma total cortisol (P = 0.076) compared to women. No sex differences were observed in norepinephrine, epinephrine, or heart rate responses. In contrast to ACTH and cortisol response differences, women reported that they were significantly more stressed by the TSST than men (P = 0.0051).
Women treated with DHEA showed ACTH stress responses similar to those of men, but significantly enhanced compared to those of women taking placebos (P < 0.009). No other stress response differences emerged between DHEA and placebo groups. Finally, DHEA treatment did not result in an improvement of subjective well-being.
We conclude that elderly men show larger HPA responses than women to psychosocial stress, as studied in the TSST. Estrogen effects on hypothalamic CRF-producing neurons might be responsible for these sex differences.
| Introduction |
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Early studies by Kitay (1, 2) have shown that sex steroids, especially estradiol, exert a potentiating effect on the HPA axis in animals. A similar influence of estradiol in healthy young men was recently reported by this laboratory (10), supporting the view of a substantial influence of sex steroids on HPA activity. As aging is characterized by significantly decreasing gonadal steroid levels, investigations of potential sex differences in HPA responses to psychosocial stress in the elderly are warranted.
The present report describes the responsiveness of the HPA axis and the sympathetic nervous system to the Trier Social Stress Test (TSST), a potent psychosocial stress protocol in healthy elderly men and women. In addition, the effects of a 2-week treatment with the sex hormone precursor dehydroepiandrosterone (DHEA) on HPA responses were studied.
| Subjects and Methods |
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Thirty-nine healthy male (67.4 ± 0.9 yr) and 36 healthy postmenopausal female (67.6 ± 0.8 yr) participants underwent a comprehensive medical examination for past or current health problems. Subjects with psychiatric, endocrine, cardiovascular, other chronic diseases or those medicated with psychoactive drugs, ß-blockers, estrogens, or glucocorticoids were excluded from participation. Ten smokers, who reported smoking less than 15 cigarettes/day, were included. In each experimental condition there were 2 or 3 smokers, respectively. The mean body mass index was 25.8 ± 0.4 (± SEM) for men and 25.5 ± 0.6 (± SEM) for women. The study protocol was approved by the ethics committee of the University of Trier.
Hormonal treatment
The present experimental study applied a placebo-controlled,
double blind design. For 2 weeks, 40 subjects took 50 mg DHEA daily
(Prasteron, Audor Pharma, Regensburg, Germany), whereas 35 sex-, age-,
and body mass index-matched controls received placebo (see Table 1
). One DHEA capsule contained 50 mg DHEA
and lactose; placebo capsules contained lactose only. Subjects were
instructed to take the capsules at bedtime each day.
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Each subject reported twice to the laboratory. The first appointment, between 08000930 h, included a medical examination, distribution of capsules, and completion of a mood questionnaire (see below). Two weeks later, subjects were exposed to the psychological stressor at the second appointment, between 09001330 h. After catheter insertion and a rest period of 45 min, a mood questionnaire (see below) was completed, and subjects were interviewed about any symptoms experienced in response to the DHEA/placebo treatment. After the resting period, the first blood and saliva samples were collected. Thereafter, subjects were confronted with the TSST (11), which consists of a free speech and mental arithmetic task of 13-min duration performed in front of an audience. Additional blood and saliva samples were obtained 1, 10, 20, 30, 45, 60, 90, and 120 min after stress exposure. Mood and perceived stressfulness were assessed by visual analog scales (VAS; see below) after stress exposure.
Assessment of well-being, mood, and perceived stress
The German self-rating depression scale was employed to measure the extent of depression (12). Three subjects (self-rating depression scale scores >48) were excluded from all statistical analyses, because of a possible impact of depression on HPA responses (13).
Nine items were used to investigate possible changes in physical or psychological conditions after the 2-week treatment, including stress resilience, well-being, quality of sleep, stressfulness of daily activities, quality of sex, relaxation, pain, general activity, and level of concentration. At the first appointment, momentary mood was assessed with a German mood questionnaire (14). This questionnaire measures elevated vs. depressed mood, wakefulness vs. sleepiness, and calmness vs. restlessness. At the second appointment, momentary mood was assessed before and after the stress task. Nine VASs were employed for participants ratings of the stressfulness of the TSST.
Blood and saliva sampling
At both laboratory appointments, basal blood samples were obtained for measurement of basal gonadal steroids. During the second appointment, one blood sample and one saliva sample were collected directly before starting the stress exposure. The remaining eight samples were collected 1, 10, 20, 30, 45, 60, 90, and 120 min after cessation of stress. Saliva was collected by the subjects, using Salivette (Sarstedt, Rommelsdorf, Germany) collection devices.
Biochemical analyses
Two basal blood samples (before and after treatment) were used to measure DHEA sulfate (DHEA-S; by enzyme-linked immunosorbent assay, IBL, Hamburg, Germany), androstendione plasma levels (by RIA, IBL), estradiol and free testosterone levels (by RIAs, Biermann, Bad Nauheim, Germany), and total testosterone levels (by RIA, IBL). The free cortisol concentration in saliva was measured using a time-resolved immunoassay with fluorometric detection as described in detail previously (15). The total plasma cortisol was measured with a RIA (IBL). ACTH was determined with a two-site chemiluminescence assay (Nichols Institute, Bad Nauheim, Germany). Norepinephrine and epinephrine were assayed by high performance liquid chromatography, as previously described (16). Inter- and intraassay coefficients of variance were below 12% and 10%, respectively, for all analytes.
Heart rate
Heart rates were measured continuously at 1-min intervals with electrocardiogram precision employing wireless transmission (Sport Tester Profi, Polar Instruments, Gross-Gerau, Germany). Heart rate responses were computed from 10 min before stress exposition to 10 min after cessation of stress.
Statistical analyses
ANOVAs for repeated measures were used to analyze endocrine and
heart rate responses to the stressor. To control for different baseline
levels, hormone samples obtained directly before the stress exposition
were treated as covariates. All reported results were corrected by
Greenhouse-Geisser procedure where appropriate. Newman-Keuls
post-hoc tests were applied for significant effects. For all
analyses, the significance level was
= 5%. Correlations were
computed by Pearson product-moment correlations. Factor analyses
(principal component, varimax oblique) and reliability analyses were
employed to create the scale "stressfulness" based on items of the
VAS. A
2 test was used to analyze whether the subjects
were able to correctly identify the content of the received capsules.
Changes in physical or psychological well-being were determined both
for the total sample and for each sex separately by Kruskal-Wallis
ANOVAs. The nominal
level was adjusted by Bonferroni correction for
multiple comparisons. All results shown are the mean ±
SEM.
| Results |
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ANOVAs revealed significant sex differences for salivary free cortisol
and ACTH stress responses (ACTH: F = 7.60; P =
0.0041; salivary free cortisol: F = 2.98; P =
0.044) and a trend for plasma total cortisol (F = 2.28;
P = 0.076). Men showed significantly higher ACTH
concentrations at 1, 10, 20, and 90 min as well as higher salivary free
cortisol concentrations 10 and 20 min after cessation of stress (all
P < 0.05). Norepinephrine, epinephrine, or heart rate
responses did not differ between sexes (Fig. 1
).
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A factor analysis clustered seven items to the factor perceived
stressfulness (task was strenuous, free speech was difficult,
arithmetic task was difficult, stressful, novel, uncontrollable, and
threatening). The reliability of the resulting factor was
= 0.90
(Cronbachs
). Men and women differed significantly in perceived
stressfulness of the TSST, with women reporting to be more stressed
(F = 8.37; P < 0.0051; Fig. 2
). There was no significant sex
difference in the amount of perceived challenge or the perceived
importance of individual performance.
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2 = 0.50; P = NS; Table 2
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| Discussion |
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The present results show that the applied psychosocial stress protocol (TSST) induces significant activation of the HPA axis and the sympathetic nervous system in elderly subjects, which resemble the responses observed in children and younger adults (11, 19). More important, this is the first study to report clear-cut sex differences in HPA responsiveness to psychosocial stress in elderly individuals. In accord with previous results obtained in younger adults (7), elderly men showed higher ACTH and cortisol stress responses than age-matched postmenopausal women. This was rather surprising, because women reported that they were more stressed by the TSST than did men with a comparable level of need for achievement. As none of the other subjective ratings assessed in this study revealed any sex differences, it appears more likely that endocrine rather than psychological factors might be responsible for the observed HPA responses. One of the prime candidates for explaining sex differences in HPA stress responsiveness is obviously the gonadal steroids. Among them, estradiol exerts a strong stimulatory influence on the axis in several animal species (20, 21, 22, 23, 24, 25), with important modulatory effects on mineralocorticoid and glucocorticoid receptors (26, 27, 28, 29, 30). Moreover, estradiol may directly enhance CRF gene transcription in the hypothalamus through binding to estrogen-responsive elements on the CRF gene (31). Testosterone, on the other hand, could exert similar effects after being metabolized to estrogens by aromatization in both brain and peripheral tissues (32, 33, 34, 35). Although women appear to be more sensitive at the pituitary and adrenal levels (3, 4, 5, 6), the higher testosterone and estradiol levels of elderly men may explain the enhanced ACTH and cortisol responses after suprapituitary stimulation.
Short term treatment with DHEA seems to increase the HPA response in
women. In our study, DHEA-substituted women showed "male-like"
endocrine stress profiles. The enhanced ACTH stress responses were
probably caused by DHEA-induced elevations of estradiol levels in this
group of women. However, other mechanisms could provide alternative
explanations for the present observation. An enhanced ACTH stress
response after DHEA treatment could be a consequence of the influence
of DHEA and DHEA-S on the
-aminobutyric acidA receptor
system in the central nervous system (36, 37, 38). This may lead to
increased secretion of vasopressin (39), which, in turn, acts
synergistically with CRF on corticotrophs. Moreover, DHEA treatment did
not alter mood or well-being, which is in line with previous findings
of this laboratory (40, 41, 42).
In conclusion, marked sex differences in HPA responses to psychosocial stress persist across a wide age range. As in younger adults, elderly men showed higher HPA responsiveness than women to a public speaking and mental arithmetic task. In contrast to antiglucocorticoid effects observed in rodents, a brief treatment with DHEA appears to enhance the pituitary stress responses in women.
| Footnotes |
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Received September 16, 1997.
Revised January 8, 1998.
Accepted January 16, 1998.
| References |
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-Aminobutyric acid
antagonists stimulate vasopressin release from organ-cultured
hypothalamo-neurophyseal explants. Endocrinology. 120:15761580.[Abstract]
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