Exhaustion measured by the SF-36 vitality scale is associated with a flattened diurnal cortisol profile

Parents' work demands on next day's cortisol awakening response - the moderating role of family-to-work conflict

BACKGROUND

Constant availability, overtime and feeling overwhelmed by work can impact employees' wellbeing and their biological stress responses. Especially working parents often struggle to balance the demands of their work and family life and were found to be distracted from their work due to family responsibilities. The Family-to-Work Conflict (FWC) indicates the extent to which participating in work is made difficult by family demands. Recent studies have found associations between FWC and biological outcomes such as the Cortisol Awakening Response (CAR), a measure of an individual's Hypothalamic-Pituitary-Adrenal (HPA)-axis activity. This diary study investigates the effect of parental work demands on next day's cortisol response as well as the moderating role of FWC and the mediating role of fatigue.

METHODS

Over the course of five consecutive days (from Monday to Friday), 168 observations were made on a total of 42 parents. Participants had at least one child and worked a minimum of 20 hours per week. Salivary cortisol samples were obtained immediately, 15 and 30 minutes after awakening each day. Work demands, FWC and fatigue were assessed using standardized questionnaires. Within-person effects were examined using multilevel modeling and mediation analyses.

RESULTS

Our results indicate that there are no main effects of work demands on next day's cortisol response. The multilevel analysis revealed that FWC predicts lower wakening cortisol levels and confirmed FWC as an increasing moderator between work demands and next day's HPA-axis activity. Further, work overload was found to increase fatigue, which in turn leads to higher CAR on the following day. This indicates that fatigue mediates the relationship between work demands and CAR. Our findings add to a growing body of research demonstrating further predictors for HPA-axis activity and emphasise the importance of considering family related demands when investigating biological outcomes for working parents.

Diurnal cortisol secretion and health-related quality of life in healthy older people

Several studies have demonstrated that a dysregulated hypothalamic-pituitary-adrenal (HPA) axis is related to worse health status (e.g., depression, posttraumatic stress, or diabetes, among others). However, less is known about the association between the individual's perception of their own health status and HPA-axis functioning in healthy older people. The aim of the present study was to examine the relationship between HPA-axis functioning and health-related quality of life (HRQoL) in healthy older people. To do this, 140 healthy older people (69 men and 71 women) from 56 to 76 years old collected eight saliva samples on two consecutive weekdays to measure the diurnal cortisol cycle (i.e. awakening cortisol levels, cortisol awakening response (CAR), overall morning cortisol levels, change in the cortisol levels during the day, and bedtime cortisol levels). In addition, they completed the SF-36 questionnaire to obtain a measure of HRQoL (i.e. reflecting physical and mental functional health status). Results showed that higher awakening and bedtime cortisol levels and the CAR were associated with a better perception of both physical and mental health. In addition, the wake-to-bed cortisol slope was only positively related to physical health. No sex differences were found. These findings suggest that the awakening and bedtime cortisol levels and the CAR are the most relevant indices of diurnal cortisol secretion for understanding the relationship between HPA-axis functioning and HRQoL status in older people.

Evaluating the Reliability and Validity of the Children's Vitality-Relaxation Scale

This study developed the Children's Vitality-Relaxation Scale (CVRS) by revising the adult version of the Restoration Outcome Scale (ROS). The CVRS was translated and culturally adapted into Korean, and its reliability and validity were evaluated in a cross-sectional, descriptive design study. Data collected from 181 elementary school students in grades 4‒6 were used to test the validity and reliability of the CVRS. Exploratory factor analysis, Pearson's correlation, known-groups comparison, and Cronbach's alpha were used for analysis. The factor analysis indicated a two-factor structure, and all factor loadings were above 0.40. The CVRS was a seven-point Likert scale consisting of eight items, which were classified as "vitality" (four items) and "relaxation" (four items). The external construct validity with the PANAS, PSS, and SRI was acceptable. In the known-groups comparison, the CVRS score was significantly higher for boys than for girls, and the CVRS score for high-income students was higher than low-income students. The Cronbach's α for the scale was 0.84 and ranged from 0.72-0.87 for the subscales. Results showed that the CVRS is a valid and reliable scale with acceptable psychometric characteristics in Korean children. The scale can be used to measure children's affect in various settings.

Salivary Cortisol Profiles of Children with Hearing Loss

OBJECTIVES

It has long been speculated that effortful listening places children with hearing loss at risk for fatigue. School-age children with hearing loss experiencing cumulative stress and listening fatigue on a daily basis might undergo dysregulation of hypothalamic-pituitary-adrenal (HPA) axis activity resulting in elevated or flattened cortisol profiles. The purpose of this study was to examine whether school-age children with hearing loss show different diurnal salivary cortisol patterns than children with normal hearing.

DESIGN

Participants included 32 children with mild to moderate hearing loss (14 males; 18 females) and 28 children with normal hearing (19 males; 9 females) ranging in age from 6 to 12 years. Saliva samples were obtained six times per day on two separate school days. Cortisol levels were measured by mass spectrometric detection after liquid-liquid extraction. Salivary cortisol levels between children with hearing loss and children with no hearing loss over the course of the day were examined with hierarchical linear modeling using mixed model statistical analysis. Between-group comparisons were also computed for the area under the curve, an analytical approach for calculating overall cortisol secretion throughout the day.

RESULTS

Significant differences in the cortisol awakening response (CAR) were observed between children with hearing loss and children with normal hearing; however, no differences were observed between the two groups subsequent to the cortisol awakening response (60-min postawakening, 10:00 A.M., 2:00 P.M., and 8:00 P.M.). Compared with children with normal hearing, children with hearing loss displayed elevated cortisol levels at awakening and a reduced growth in cortisol secretion from awakening to 30-min postawakening. No significant differences in overall cortisol secretion throughout the day were found between groups (area under the curve). Finally, cortisol levels increased with increasing age for children with hearing loss but not for children with normal hearing.

CONCLUSIONS

Results of this preliminary study indicate a possible dysregulation in HPA axis activity in children with hearing loss characterized by elevated salivary cortisol levels at awakening and a diminished increase in cortisol from awakening to 30-min postawakening. The pattern of elevated cortisol levels at awakening is consistent with some studies on adults with burnout, a condition characterized by fatigue, loss of energy, and poor coping skills. These findings support the idea that children with hearing loss may experience increased vigilance and need to mobilize energy promptly in preparation for the new day.

Prospective Associations of the Short Form Health Survey Vitality Scale and Changes in Body Mass Index and Obesity Status

OBJECTIVES

The objectives of the current study were to prospectively investigate the predictive value of the vitality scale of the Short Form Health Survey for changes in body mass index and development of obesity.

METHODS

The study population comprised 2864 (81.5%) men and 648 (18.5%) women from the Metropolit Project and the Danish Longitudinal Study on Work, Unemployment and Health, who participated in a follow-up examination in 2009-2011 corresponding to a follow-up period of 3-7 years. Associations of vitality with body mass index and obesity were investigated separately for men and women in linear and logistic regression models adjusting for age, baseline body mass index, education, physical activity, smoking, and obesity-related diseases.

RESULTS

Vitality was significantly associated with change in body mass index among men (p < 0.001) and women (p < 0.05) gaining weight after adjusting for age, baseline body mass index, education, physical activity, smoking, and obesity-related diseases. No significant associations of vitality with BMI change were observed among individuals maintaining or losing weight during the follow-up period. Furthermore, vitality significantly predicted development of obesity among women.

CONCLUSION

The study indicates that vitality is of predictive value for increases in BMI over time among individuals gaining weight and may further predict the development of obesity among women. This identification of poor vitality as a potential risk indicator for weight gain and development of obesity may be beneficial in clinical practice.

Adrenal fatigue does not exist: a systematic review

BACKGROUND

The term "adrenal fatigue" ("AF") has been used by some doctors, healthcare providers, and the general media to describe an alleged condition caused by chronic exposure to stressful situations. Despite this, "AF" has not been recognized by any Endocrinology society, who claim there is no hard evidence for the existence. The aim of this systematic review is to verify whether there is substantiation for "AF".

METHODS

A systematic search was performed at PUBMED, MEDLINE (Ebsco) and Cochrane databases, from the beginning of the data until April 22nd, 2016. Searched key words were: "adrenal" + "fatigue", "adrenal" + "burnout", "adrenal" + "exhaustion", "hypoadrenia", "burnout" + "cortisol", "fatigue" + "cortisol", "clinical" + "burnout", "cortisol" + "vitalility", "adrenal" + "vitality", and "cortisol" + "exhaustion". Eligibility criteria were: (1) articles written in English, (2) cortisol profile and fatigue or energy status as the primary outcome, (3) performed tests for evaluating the adrenal axis, (4) absence of influence of corticosteroid therapy, and (5) absence of confounding diseases. Type of questionnaire to distinct fatigued subjects, population studied, tests performed of selected studies were analyzed.

RESULTS

From 3,470 articles found, 58 studies fulfilled the criteria: 33 were carried in healthy individuals, and 25 in symptomatic patients. The most assessed exams were "Direct Awakening Cortisol" (n = 29), "Cortisol Awakening Response" (n = 27) and "Salivary Cortisol Rhythm" (n = 26).

DISCUSSION

We found an almost systematic finding of conflicting results derived from most of the studies methods utilized, regardless of the validation and the quality of performed tests. Some limitations of the review include: (1) heterogeneity of the study design; (2) the descriptive nature of most studies; (3) the poor quality assessment of fatigue; (4) the use of an unsubstantiated methodology in terms of cortisol assessment (not endorsed by endocrinologists); (5) false premises leading to an incorrect sequence of research direction; and, (6) inappropriate/invalid conclusions regarding causality and association between different information.

CONCLUSION

This systematic review proves that there is no substantiation that "adrenal fatigue" is an actual medical condition. Therefore, adrenal fatigue is still a myth.

Unstimulated cortisol secretory activity in everyday life and its relationship with fatigue and chronic fatigue syndrome: a systematic review and subset meta-analysis

The hypothalamic-pituitary-adrenal (HPA) axis is a psychoneuroendocrine regulator of the stress response and immune system, and dysfunctions have been associated with outcomes in several physical health conditions. Its end product, cortisol, is relevant to fatigue due to its role in energy metabolism. The systematic review examined the relationship between different markers of unstimulated salivary cortisol activity in everyday life in chronic fatigue syndrome (CFS) and fatigue assessed in other clinical and general populations. Search terms for the review related to salivary cortisol assessments, everyday life contexts, and fatigue. All eligible studies (n=19) were reviewed narratively in terms of associations between fatigue and assessed cortisol markers, including the cortisol awakening response (CAR), circadian profile (CP) output, and diurnal cortisol slope (DCS). Subset meta-analyses were conducted of case-control CFS studies examining group differences in three cortisol outcomes: CAR output; CAR increase; and CP output. Meta-analyses revealed an attenuation of the CAR increase within CFS compared to controls (d=-.34) but no statistically significant differences between groups for other markers. In the narrative review, total cortisol output (CAR or CP) was rarely associated with fatigue in any population; CAR increase and DCS were most relevant. Outcomes reflecting within-day change in cortisol levels (CAR increase; DCS) may be the most relevant to fatigue experience, and future research in this area should report at least one such marker. Results should be considered with caution due to heterogeneity in one meta-analysis and the small number of studies.

Cortisol patterns are associated with T cell activation in HIV

Objective

The level of T cell activation in untreated HIV disease is strongly and independently associated with risk of immunologic and clinical progression. The factors that influence the level of activation, however, are not fully defined. Since endogenous glucocorticoids are important in regulating inflammation, we sought to determine whether less optimal diurnal cortisol patterns are associated with greater T cell activation.

Methods

We studied 128 HIV-infected adults who were not on treatment and had a CD4⁺ T cell count above 250 cells/µl. We assessed T cell activation by CD38 expression using flow cytometry, and diurnal cortisol was assessed with salivary measurements.

Results

Lower waking cortisol levels correlated with greater T cell immune activation, measured by CD38 mean fluorescent intensity, on CD4⁺ T cells (r = −0.26, p = 0.006). Participants with lower waking cortisol also showed a trend toward greater activation on CD8⁺ T cells (r = −0.17, p = 0.08). A greater diurnal decline in cortisol, usually considered a healthy pattern, correlated with less CD4⁺ (r = 0.24, p = 0.018) and CD8⁺ (r = 0.24, p = 0.017) activation.

Conclusions

These data suggest that the hypothalamic-pituitary-adrenal (HPA) axis contributes to the regulation of T cell activation in HIV. This may represent an important pathway through which psychological states and the HPA axis influence progression of HIV.

Physical therapy and psychological intervention normalize cortisol levels and improve vitality in women with endometriosis

There is as yet no effective treatment for endometriosis. The objective of this study was to evaluate the effectiveness of submitting women with endometriosis and chronic pelvic pain to a therapeutic protocol involving physical and psychological therapy. Twenty-six female volunteers were submitted to a treatment protocol consisting of 2.5-h sessions, once a week for 10 weeks. We applied a Visual Analogue Scale, the Perceived Stress Questionnaire (PSQ), and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Morning, afternoon, and evening levels of cortisol were determined in saliva samples. The PSQ scores were significantly lower after treatment, whereas the scores for the SF-36 vitality and physical functioning domains were significantly higher. Salivary cortisol levels were higher after treatment in the samples collected in the morning, but not in those collected in the afternoon or evening. The post-treatment cortisol levels were similar to those reported for healthy women. There were positive correlations between vitality, role emotional, social functioning, and mental health, and negative correlations to perceived stress. In conclusion, the physical and psychological intervention protocol applied in this study to women suffering of endometriosis was effective in reducing perceived stress, normalizing cortisol levels, increasing vitality and improving physical functioning.

Exhaustion predicts coronary heart disease independently of symptoms of depression and anxiety in men but not in women

OBJECTIVE

Exhaustion is hypothesised to be a risk-factor for coronary heart disease (CHD), but as such its independence from emotional states, in particular depression, has not been established in previous investigations. This study aimed to explore the unique contribution of exhaustion, independent from symptoms of depression and anxiety, to CHD development.

METHODS

The study sample was 5061 men and 6734 women from the Malmö Shoulder and Neck Study cohort examined in 1993-96. Exhaustion was measured by the SF-36 vitality scale. Symptoms of depression and anxiety were measured by the General Health Questionnaire. 571 first coronary events were ascertained through record linkage until 2005. Cox regression analysis was used to assess the contribution of exhaustion to CHD.

RESULTS

In age-adjusted analysis exhaustion predicted coronary events in a non-linear way in both men (HR=1.49, 95% CI 1.06-2.11 in the highest exhaustion category) and women (HR=1.78, 95% CI 1.23-2.58 in the second highest exhaustion category). After adjustment for traditional risk-factors for CHD and socioeconomic status, the effect was attenuated and statistically significant only in women. However, further adjustment for symptoms of depression and anxiety strengthened the association between exhaustion and CHD in men (HR=1.62, 95% CI 1.05-2.50), whereas in women, exhaustion no longer predicted CHD.

CONCLUSION

In age-adjusted analysis, exhaustion predicted CHD in both men and women, but its independence from depression and anxiety was demonstrated only in men. Further studies on the topic are required. A larger focus on potential gender differences should seem warranted in future research.

Relationship between commuting and health outcomes in a cross-sectional population survey in southern Sweden

BACKGROUND

The need for a mobile workforce inevitably means that the length of the total work day (working and traveling time) will increase, but the health effects of commuting have been surprisingly little studied apart from perceived stress and the benefits of physically active commuting.

METHODS

We used data from two cross-sectional population-based public health surveys performed in 2004 and 2008 in Scania, Sweden (56% response rate). The final study population was 21, 088 persons aged 18-65, working > 30 h/week. Duration (one-way) and mode of commuting were reported. The outcomes studied were perceived poor sleep quality, everyday stress, low vitality, mental health, self-reported health, and absence from work due to sickness during the past 12 months. Covariates indicating socioeconomic status and family situation, overtime, job strain and urban/rural residency were included in multivariate analyses. Subjects walking or cycling to work < 30 min were used as a reference category.

RESULTS

Monotonous relations were found between duration of public transport commuting and the health outcomes. For the category commuting > 60 min odds ratios (ORs) ranged from 1.2 - 1.6 for the different outcomes. For car commuting, the relationships were concave downward or flat, with increasing subjective health complaints up to 30-60 min (ORs ranging from 1.2 - 1.4), and lower ORs in the > 60 min category. A similar concave downward relationship was observed for sickness absence, regardless of mode of transport.

CONCLUSIONS

The results of this study are concordant with the few earlier studies in the field, in that associations were found between commutation and negative health outcomes. This further demonstrates the need to consider the negative side-effects of commuting when discussing policies aimed at increasing the mobility of the workforce. Studies identifying population groups with increased susceptibility are warranted.

Salivary cortisol, stress, and health in primary caregivers (mothers) of children with cerebral palsy

This study evaluated level of salivary cortisol and perceived burden, stress and health of mothers and primary caregivers of children (4-11 years of age) with cerebral palsy (purpose group, n=37) and those for mothers of children of the same age without developmental problems (control group, n=38). Anthropometric and socioeconomic data were collected from the participants, who also completed the perceived stress questionnaire, the Burden Interview and the 36-Item Short Form Health Survey (SF-36). Cortisol level was assayed in saliva samples collected at various times in a single day and the area under the cortisol curve was then determined. Both groups presented low socioeconomic level and high, although equivalent, perceived stress index. However, the purpose group showed lower cortisol levels, as well as lower scores for many of the SF-36 domains related to physical well-being (physical functioning, role-physical, vitality, and general health) and social functioning. Nevertheless, bodily pain was also reported to be lower. For the control group, the area under the cortisol curve correlated negatively with mental health and social functioning. For the purpose group, where the burden is greater, no such correlation was found. It was concluded that mothers of healthy children leaving in unfavorable socioeconomic conditions face high levels of stress with the hypothalamus-pituitary-adrenal cortex axis function preserved. However, to the mothers of children with cerebral palsy, who live in even worse socioeconomic conditions and also have the burden of caring for a disabled child, the level of stress was overwhelming, to an extent that it impaired the hypothalamus-pituitary-adrenal cortex axis function, as well as reflecting negatively on certain aspects of their physical and psychological well-being. This must receive consideration during the treatment of the child, an approach which is in line with present day tendencies towards family-centered models of assistance to disabled children.

Cortisol awakening response and nighttime salivary cortisol levels in healthy working Korean subjects

PURPOSE

Cortisol awakening response (CAR) and nighttime cortisol levels have been used as indices of adrenocortical activity. However, population-based statistical information regarding these indices has not been provided in healthy subjects. This study was carried out to provide basic statistical information regarding these indices.

MATERIALS AND METHODS

Cortisol levels were measured in saliva samples collected immediately upon awakening (0 min), 30 min after awakening and in the nighttime on two consecutive days in 133 healthy subjects.

RESULTS

We determined the mean [standard deviation (SD)], median (interquartile range) and 5th-95th percentile range for each measure and auxiliary indices for CAR, i.e., the secreted cortisol concentration within 30 min of awakening (CARscc) and absolute and relative increases in cortisol level within 30 min of awakening (CARi and CARi%, respectively). We also determined these values for auxiliary indices derived from nighttime cortisol level, i.e., the ratio of cortisol level 30 min after awakening (CA(₃₀ min)) to nighttime level (CA(₃₀ min)/NC), as well as absolute and relative decreases in cortisol levels from CA(₃₀ min) to nighttime (DCd and DCd%, respectively). We found no significant differences in cortisol level for any time point or in auxiliary indices between collection days, genders and ages.

CONCLUSION

The provided descriptive information and statistics on the CAR and nighttime cortisol level will be helpful to medical specialists and researchers involved in hypothalamus- pituitary-adrenal axis assessment.

Cortisol variability and self-reports in the measurement of work-related stress

We examined whether a high cortisol awakening response (CAR) and low cortisol decline over the day (CDD) are related to self-reported work stress and well-being, and whether there are gender differences in these relationships. Three hundred eighty-three working men and women responded to a survey measuring job stress factors, mastery at work, symptoms and well-being. Salivary cortisol was sampled at awakening, after 45 min and at 21:00, from which the variables CAR and CDD were defined. A high CAR was associated with lower perceived job control and work mastery, and poorer well-being. Low CDD was associated only with higher job demands, but the self-report scores showed a number of interactions between cortisol group and gender. Among women, those showing a low CDD, compared with those with a higher CDD, had more favourable scores on a number of job stress factors and symptom load. In contrast, among men, a similar comparison showed those with low CDD to have poorer scores on job stress factors and symptom load. We conclude that individuals displaying high CAR or low CDD differ from those not displaying these cortisol profiles in self-report of work stress and well-being, and that gender differences appear in these relationships.

The SF-36 component summary scales and the daytime diurnal cortisol profile

PURPOSE

Higher daytime cortisol output has been associated with higher levels of perceived stress and worse mental and physical health outcomes. Hypothalamic-pituitary-adrenal (HPA) axis dysregulation, such as elevated secretion of daytime cortisol, occurs in many mental and physical illnesses. However, the nature of the association between functional health status and daytime cortisol production has not been established.

METHODS

Healthy adult volunteers (n=68, 45 females) provided saliva samples 3, 6, 9 and 12 h after waking, for two consecutive days, in everyday settings. Bivariate correlations between log salivary cortisol concentrations were calculated, and the SF-36 component summary scores were calculated. Latent growth curve modeling was used to model the daytime profile and adjust for covariates (age, sex and waking time).

RESULTS

Higher PCS scores were not associated with cortisol three hours after waking (cortisol intercept), or the diurnal decline (cortisol slope). Higher MCS scores were correlated with faster cortisol decline across the day (r=-.31, P<.01) but not with cortisol intercepts. In a latent growth curve model adjusting for age, sex and waking time, the association was no longer statistically significant.

CONCLUSIONS

Large scale epidemiological studies involving salivary cortisol would benefit from measuring SF-36 component summary scores. Cortisol intercepts and slopes may be differentially related to the PCS and MCS, although greater statistical power is needed to test this hypothesis more fully. Associations between daytime cortisol and the PCS or MCS could reflect the regulatory competence of bodily systems, common causes or unmeasured confounding factors.

Conflict between the work and family domains and exhaustion among vocationally active men and women

Exhaustion is consistently found to be more prevalent in women than in men. Women suffer from job strain more often, which may constitute a partial explanation for this phenomenon, but experienced shortcomings in combining work and family demands may also contribute to ill health. The aim of this study was to investigate, and analyse by gender, how work-related and family-related factors, as well as the interface between them, i.e. work-to-family conflict (WFC) and family-to-work conflict (FWC), are related to exhaustion. The study was cross-sectional with self-administered questionnaires assessing exposures and outcome with previously well-validated instruments. The participants were 2726 men and 2735 women, aged 45-64, vocationally active, and residing in Malmö, Sweden. Sixteen percent of the women and 8% of the men considered themselves exhausted. WFC, FWC, job strain, and low job support were all strongly correlated to exhaustion in both genders. In the multivariate analyses, adjusting for other work and family risk factors, WFC and FWC remained statistically significant risk factors for exhaustion in both men and women. Job strain, low job support, and having a somatic disorder were also independently associated with exhaustion. While WFC was more prevalent among men, it was more strongly associated with exhaustion in women than in men. In women, WFC and FWC contributed to a larger part of the explanatory power of the model, which amounted to 22% of the variance in women and 14% in men. The results imply that the concept of 'work stress' should be regarded in a wider context in order to understand gender related issues of exhaustion among vocationally active individuals.

Cortisol secretion and fatigue: associations in a community based cohort

The association between fatigue and reduced activity in the hypothalamo-pituitary-adrenal (HPA) axis has been described. However the temporal association between fatigue and HPA activity is under debate. We examine whether alterations in cortisol secretion play a role in the development of fatigue or whether changes occur later as a consequence of fatigue in a longitudinal cohort study of 4299 community dwelling adults (mean age 61). Cortisol secretion was measured from saliva samples collected waking, waking + 0.5, 2.5, 8, 12 h and bedtime at phase 7 (2003-2004) of the Whitehall II study. Fatigue was measured at phase 6 (2001), phase 7 and phase 8 (2006) of the Whitehall II study. Three elements of secretion were examined: waking cortisol, the cortisol awakening response and diurnal slope in cortisol secretion. Fatigue was determined using the vitality sub-scale of the Short Form-36. A wide variety of co-variates were measured. We find that fatigue measured at phase 6 was not associated with cortisol secretion at phase 7. At phase 7, low waking cortisol levels and a flat slope in diurnal cortisol secretion were associated with fatigue independently of co-variates. In participants low or free of fatigue at phase 7 low waking cortisol and flatter slope in cortisol secretion were associated with new-onset fatigue at phase 8 (for example, odds ratio for lowest vs. highest tertile of waking cortisol 1.50; 95% confidence intervals, 1.08, 2.09 after adjusting for all co-variates). In conclusion, we find that low waking salivary cortisol and a flat slope in cortisol secretion is associated with fatigue. Cortisol is also associated with future onset of fatigue suggesting that changes in cortisol secretion are etiologic or occur early in the genesis of fatigue.