Exhaustion measured by the SF-36 vitality scale is associated with a flattened diurnal cortisol profile
Introduction
Exhaustion can be described as a condition characterized by fatigue and loss of strength or vitality. The possible association between exhaustion and reduced activity in the hypothalamo–pituitary–adrenal (HPA) axis is increasingly discussed (Nicolson and van Diest, 2000; Raison and Miller, 2003; Fries et al., 2005). This notion is mainly derived from studies concerning different clinically established disorders exhibiting hypocortisolaemic features (e.g. posttraumatic stress disorder, chronic fatigue syndrome, fibromyalgia, atypical depression) in which fatigue constitutes a prominent characteristic (Yehuda et al., 1991; Demitrack and Crofford, 1998; Gold and Chrousos, 1999). The aetiology of the decreased HPA activity in hypocortisolaemic disorders has been disputed (Cleare, 2004a, Cleare, 2004b), but since disturbances in the HPA axis are intimately associated with physiological stress response systems, HPA hypoactivity is frequently considered a possible feature of chronic stress (Demitrack and Crofford, 1998; McEwen, 1998; Heim et al., 2000). This view thus contrasts with the more traditional view that stress is characterized by an increased activation of the HPA axis, and it is hypothesised that HPA hyporesponsiveness would constitute a later phase in the chronic stress process, subsequent to an initial period of stress-induced HPA hyperactivity (McEwen, 1998; Fries et al., 2005).
In normal (non-clinical) populations, cortisol patterns indicating hypoactivity in the HPA axis have been observed in association with chronic stress (e.g. Caplan et al., 1979; Goenjian et al., 1996; Adam and Gunnar, 2001; Ranjit et al., 2005). In a study of medically healthy individuals it was shown that cortisol levels that were substantially suppressed due to severe chronic stress returned to normal after termination of the stressful period (Zarkovic et al., 2003). Chronic stress thus seems to exert a “direct” effect on the HPA axis in reducing its activity, i.e. without being mediated by disease. In these studies the potential link between exhaustion and cortisol was not considered. Most research concerning this relationship has been performed by means of using measures of “burnout”—which include exhaustion as one of several dimensions—but the summarised findings of cortisol in burnout have not yet been conclusive (Mommersteeg et al., 2006). Moreover, the measure of “vital exhaustion”, developed for prediction of myocardial infarction (Appels et al., 1987), has been shown to correlate with attenuated cortisol response and reduced diurnal cortisol variation (Kristenson et al., 1998; Sjögren et al., 2006). It should be noted that the construct of vital exhaustion contains dimensions of both exhaustion and depression (Appels, 1980; Appels et al., 2000; Prescott et al., 2003; McGowan et al., 2004) and cortisol levels associated with vital exhaustion can therefore be regarded as a reflection of a combination of physiological patterns in these two conditions. In a study of particular interest concerning cortisol patterns in exhaustion, the vital exhaustion measurement was used in order to screen for exhaustion after which depressed participants were excluded from the study (Nicolson and van Diest, 2000), thereby ensuring that the reported findings concern exhaustion and not depression. The study was performed on a sample of healthy working males, and a tendency towards overall lower levels of cortisol was found in exhausted individuals compared with controls.
The purpose of the present study was to further explore cortisol patterns in exhaustion as assessed in a non-patient population. For the assessment of exhaustion the SF-36 vitality scale was utilised. Exhaustion measured by this scale has been shown to be differentiable from measures of depression and anxiety (Lindeberg et al., 2006), which would seem valuable considering evidence of increased HPA activity and elevated cortisol levels in depression and anxiety disorders (Gillespie and Nemeroff, 2005; Abelson et al., 2007).
The study objective was to elucidate whether exhaustion measured by the SF-36 vitality scale in a working population was associated with differences in salivary cortisol concentrations and in the diurnal variation of salivary cortisol (cortisol variability). Our primary hypothesis was to find lowered cortisol variability and suppressed concentrations of cortisol (indicating HPA axis hypoactivity) in exhausted individuals compared with non-exhausted.
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Participants and design
The study sample consisted of 78 individuals, 57 females and 21 males, who participated in a follow-up assessment of a cohort study concerning possible predictors of work-related ill-health. The initial cohort (N=437) was identified in the year 2001 and was recruited from five different work-sites including manual and non-manual employees (Hansen et al., 2006). The work-sites were recruited on the basis of possible high workload and were identified in collaboration with the local Labour
Results
Twenty respondents (26%) scored 16 or above on the inverted SF-36 vitality score and were thereby designated as belonging to the exhausted group. Fifty-eight respondents scored below 16 and were thus defined as non-exhausted. Descriptive characteristics of the exhausted and non-exhausted groups are shown in Table 1. Age was slightly lower and BMI was slightly higher in the exhausted group. Daily smoking was fairly evenly distributed between groups, and saliva cortisol was sampled at similar
Discussion
The results of this study showed that exhausted individuals exhibited a flattened diurnal cortisol profile compared with non-exhausted. The flattened profile was due to lowered cortisol levels in the morning whereas evening cortisol did not differ between the groups. Overall cortisol levels thus tended towards being lower in exhausted individuals but these differences were not statistically significant.
A recent meta-analytic review (Miller et al., 2007) revealed that low morning cortisol and
Role of the funding source
Funding for this study was provided by The Swedish Research Council and Swedish Council for Working Life and Social Research. The funding sources had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.
Conflict of interest
We declare that we have no conflicts of interest.
Acknowledgements
We thank The Swedish Research Council and The Swedish Council for Working Life and Social Research for financial support.
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