Study design
The present cross-sectional observational study is the first (baseline) assessment of a 3-year longitudinal cohort study including 11 equally spaced (i.e., 3 months) consecutive surveys between 2012 and 2014. All data in the present paper were collected using paper-and-pencil questionnaires that were returned by mail. The study protocol was approved by the Regional Ethical Review Board in Lund, Sweden (reg. no. 2012/298). All participants gave written informed consent when they entered the study.
Participants
A total of 1355 occupationally active individuals (57 % women), with a mean age of 41.1 years (SD 6.7 years; range 27 − 52), were included. At baseline, 54 % had at least three years of university studies, 13 % shorter university studies, 16 % upper secondary school, 16 % lower secondary school, and less than 1 % reported elementary school. The vast majority were employees (90 %), 6 % were self-employed, and 4 % combined self-employment with outside employment. Occupational activity on at least a full-time basis (40 h/week) was reported by 83 %, while 16 % worked 75 − 99 % of full time, and 1 % worked 50 − 75 % of full time (occupational activity from employment < 70 % of full time was accepted in case additional work as self-employed was reported; n = 4). A marginal group (3 %) temporarily worked less than full time owing to parallel activities, such as studies or parental leave, or to partial unemployment.
Identification of participants
Participants were selected in two sampling rounds (Fig. 1) entailing a pool of responders to a health questionnaire and a supplementary sample from the general population. The target was to obtain circa 1500 individuals who had a relatively long education, were likely to have worked several years in their profession, but who were not approaching retirement. In addition, participants should be in good health, thus without previous somatic or psychiatric disorder, as indicated in their self-reports.
Sampling from the health questionnaire
Given our intention to identify the earliest signs of ED, and based on our previous clinical experience of ED cases, we strove to include employees in active work who had a relatively long educational background, assuming such individuals would be engaged in complex and demanding work. This approach was judged to increase the likelihood of prospectively finding individuals with accumulated and prolonged stress reactions that may lead to ED. Access was granted to a database consisting of 28,198 responders to a population survey of lifestyle and health in southern Sweden conducted in 2008 [24]. The inclusion criteria were: 27 − 52 years of age, at least a 2-year upper secondary school education, a Scandinavian language as native language, and no apparent somatic or psychiatric disorder or drug abuse. An invitation letter and a baseline questionnaire were sent to the 3774 eligible individuals, asking them to reply to a similar questionnaire every three months during a 3-year period. The invitation letter requested that participants be gainfully employed (at least 75 % of full time), had no period of long-term full-time sick leave for the past six months, had no chronic disease or prescribed daily medication. In total, 947 individuals returned the baseline questionnaire with the informed consent sheet and were thus included as potential participants.
Sampling from the general population
Additional individuals were invited who were on the Scania University Hospital population register, which covers all inhabitants in the southernmost county of Sweden, Scania (Skåne). The inclusion criteria were: 27 − 52 years of age, Swedish residence and born in Sweden, and not already identified in the above health questionnaire sample (information relevant to the other selection criteria were not available for this sample). Thereafter, a randomized sample of citizens living in the major southern Swedish cities of Lund and Malmo, and their vicinity, was drawn. Given our intention to obtain circa 500 additional participants, and an expected participation rate of 10 − 15 %, 4025 eligible individuals were mailed the invitation letter and the baseline questionnaire. In total, 453 individuals returned the baseline questionnaire with the informed consent sheet, and were thus included as potential participants.
Final criteria for inclusion
The 1400 returned baseline questionnaires with properly filled in consent sheets were subjected to further scrutiny. Individuals who had a somatic disease, daily medication with psychotropic drugs, excessive alcohol intake, who worked only part time, or had recently been prescribed a longer full-time sick leave were excluded (n = 45). Thus the final study sample comprised 1355 individuals.
Measures
Inventories for screening exhaustion disorder (ED)
Lund University Checklist for Incipient Exhaustion (LUCIE)
The development of LUCIE is described in Additional file 1 and the questionnaire sheet in Additional file 2. In short, LUCIE consists of 28 items (statements) covering 6 domains: (a) sleep and recovery (3 items), (b) separation between work and spare time (4 items), (c) sense of community and support in the workplace (2 items), (d) managing work duties and personal capabilities (5 items), (e) private life and spare time activities (3 items), and (f) health complaints (11 items). Responses to all items were made on a 4-point scale: 1 = not at all, 2 = somewhat, 3 = quite a bit, 4 = very much. The distinctiveness of the dimensions was verified using a principal component analysis (Additional file 1). Cronbach’s alpha ranged from 0.67 to 0.87 on the domain subscales, and was 0.92 on the full scale (n = 1355).
The LUCIE items were derived from qualitative analyses of patient interviews and patient narratives concerning the prodromal stages of ED as well as through systematic analyses of the patients’ journal data (n = 92). The scoring builds on two algorithms that generate two supplementary indicators: the Stress Warning Scale (SWS) and the Exhaustion Warning Scale (EWS). Each scale ranges from 0 to 100 (for a detailed description on the calculation of scale scores see Additional file 1). A SWS score ≤ 17.00 (‘the green zone’) is intended to indicate no or negligible lasting stress symptoms. A SWS score between 17.01 and 38.50 (‘the yellow zone’) suggests possible slight lasting stress symptoms. A SWS score ≥ 38.51 (‘the red zone’) indicates mild to moderate lasting stress symptoms. If the SWS score reaches the red zone, it is advisable to also check the supplementary EWS score, which covers more serious symptoms of lasting stress, thus suggesting exhaustion. An EWS score ≤ 21.50 (‘the EWS green zone’) indicates that signs of exhaustion are absent or negligible, while a score exceeding 21.50 (‘the EWS red zone’) suggests severe lasting stress symptoms that might indicate ED. In practice, the combination of SWS and EWS scores provides a four-step ranking of incremental stress symptomatology:
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1.
Step 1-GG (SWS green zone and EWS green zone) = no or negligible lasting stress symptoms
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2.
Step 2-YG (SWS yellow zone and EWS green zone) = possible slight lasting stress symptoms
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3.
Step 3-RG (SWS red zone and EWS green zone) = mild to moderate lasting stress symptoms, but less severe than ED
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4.
Step 4-RR (SWS red zone and EWS red zone) = lasting stress symptoms of a severity indicating possible ED.
Because the other theoretically plausible combinations of scores (i.e., SWS green zone or SWS yellow zone in combination with EWS red zone score) are extremely rare these four ranking steps serve as a useful simplification. Thus, in cases where a person obtains a high SWS score, the EWS measure will work as sorting mechanism by indicating whether the stress symptomatology reaches an intensity that is also indicative of ED (step 4), or one that is more benign in nature (step 3).
Karolinska exhaustion disorder scale (KEDS)
KEDS is a recently developed tool for screening for the presence of ED [17]. It contains 9 items, covering (1) ability to concentrate, (2) memory, (3) physical stamina, (4) mental stamina, (5) recovery, (6) sleep, (7) hypersensitivity to sensory impressions, (8) experience of demands, and (9) irritation and anger. Each item has seven response alternatives, ranging from 0 − 6, where higher values reflect more severe symptoms. Verbal anchors are provided for the scale steps 0, 2, 4 and 6, but not for 1, 3 and 5. The sum of item scores constitutes the outcome, which may vary between 0 to 54. A sum of item scores ≥ 19 is considered to indicate possible ED [17]. Cronbach’s alpha was 0.86.
Self-reported exhaustion disorder scale (s-ED)
The s-ED scale consists of 4 items, one of which consists of 6 sub-items. Its aim is to assess exhaustion in compliance with the Swedish National Board of Health and Welfare (NBHW, 2003) criteria for ED (Table 1) [16]. A classification of s-ED requires that the respondent reply “Yes” to the statements A, B and D (see Table 1) as well as confirm the presence of at least four of the six symptoms specified in C. For statement D, an affirmative reply can be graded with the two alternatives “Yes, a little” and “Yes, pronounced,” which defines the severity of the condition in terms of “light/moderate s-ED” or “pronounced s-ED,” respectively.
Inventories pertaining to the burnout concept
Shirom-melamed burnout questionnaire (SMBQ)
The SMBQ [19] is a psychologically oriented measure that is based on Hobfoll’s Conservation of Resources Theory, but only as regards energy resources [25, 26]. The SMBQ assesses burnout using 22 items in four domains: (a) “Physical Fatigue,” (b) “Cognitive weariness,” (c) “Tension,” and (d) “Listlessness.” Responses to the items were made on a 7-point scale ranging from 1 ‘Never or almost never’ to 7 ‘Always or almost always.’ Five items require reversed scoring. The mean score of each domain was used as the outcome, and the score SMBQ-Global-22 is represented by the mean of all 22 items. An alternative SMBQ-Global-18, excluding the “Tension” domain, as suggested by Lundgren-Nilsson et al., was also explored [27]. Cronbach’s alpha ranged from 0.76 to 0.94 on the domain subscales and on the Global-22 scale and the Global-18 scale, 0.96 and 0.95, respectively.
Utrecht work engagement scale (UWES-9)
The UWES-9 [20] was used to assess work engagement, which is theoretically considered the opposite of burnout. Three aspects of work engagement were assessed using 9 items; the three aspects were: vigor, dedication, and absorption. Each aspect was assessed using three items; responses were made on a 7-point scale with labels ranging from “Never” (score 0) to “Always” (score 6). Results are reported as the mean value of each aspect, and as a grand total mean of all items. Cronbach’s alpha ranged from 0.82 to 0.87 on the aspects, and was 0.93 on the total scale.
Inventories pertaining to work conditions, private life, and family-to work interference
The job content questionnaire (JCQ)
A Swedish 26-item version of the Job Content Questionnaire (JCQ) [21] was used to assess perceived psychological job demands, job control and job support. The 9 psychological job demands items concern conflicting demands, how hard the workers work, and organizational constraints on task completion. The 9 job control items concern possibilities to make decisions about work (subscale: decision authority, 3 items) as well as the required skill level and possibilities to be creative (subscale: skill discretion, 6 items). The 8 job support items differentiate between instrumental and emotional aspects as well as support from leaders (subscale: manager support; 4 items) and from colleagues (subscale: co-worker support; 4 items) [21]. Each item was given as a statement, where the subject’s response indicated degree of agreement. Responses to the psychological job demands and job control items were made on a 4-point scale (1–4): 1 = totally disagree, 2 = disagree, 3 = agree and 4 = totally agree. Responses to the support items were made on a 5-point scale (0–4): 0 = missing supervisor/colleagues, 1 = totally disagree, 2 = disagree, 3 = agree and 4 = totally agree. For respondents indicating “missing supervisor/colleagues,” support scores were not calculated. Cronbach’s alpha ranged from 0.78 to 0.79 for the main categories job demands, job control and job support, while the subscale alpha values varied between 0.61 and 0.83.
Circumstances in private life
Private stress One item was created to estimate to what extent factors and circumstances outside work burdened the respondents. The question read “Would you agree that you have recently felt stressed or mentally strained due to problems or demands outside work?” and responses were made on a 4-point scale: 1 = Not at all, 2 = To some extent, 3 = Quite a lot, and 4 = Not applicable. The ‘not applicable’ option was recoded to “1” prior to analyses. Thus the score ranged from 1 to 3, with higher scores indicating more stress.
Family to work interference This was measured using four items [22]. Two items covered time-based interference, and the other two covered strain-based interference. The unidirectional assessment only considered the influence of the family on work [28]. Responses were made on a 4-point scale indicating agreement: 0 = not at all, 1 = to some degree, 2 = to a large degree, 3 = and does not apply. The “does not apply” option was recoded to zero, and the sum of scores on the four items was used as a family-to-work interference index (range 0-8). Higher scores indicated greater interference. Cronbach’s alpha was 0.67.
Inventory pertaining to the concept of personality traits
The big five inventory (BFI)
The Big Five personality dimensions–Neuroticism (N), Extraversion (E), Openness (O), Agreeableness (A), and Conscientiousness (C) [29]–were measured using the 44-item BFI [23]. The items of the BFI are short and easily understandable phrases, and each BFI item is rated on a 5-point scale indicating degree of agreement: 1 = “Disagree strongly,” 2 = “Disagree a little,” 3 = “Neither agree nor disagree,” 4 = “Agree a little” and 5 = “Agree strongly.” For each Big Five dimension, the mean score of the 8 to 10 items covering the specific dimension was used as an outcome measure. Cronbach’s alpha for the dimensions were: N = 0.79; E = 0.86; O = 0.79; A = 0.73; C = 0.75.
Statistical analysis
The statistical analysis was performed using the IBM SPSS 22.0 software. Two-tailed p-values ≤ 0.05 were considered statistically significant. Kappa statistics and Spearman rank correlations (both with bootstrap estimated 95 % confidence intervals (95 % CI) in order to compensate for ties) were used to estimate the degree of agreement and association between LUCIE, KEDS, and s-ED. For the Kappa statistics, we also conducted sensitivity analyses (i.e., tested the robustness of our result by examining narrower subsets of the study sample by excluding observations that, from a theoretical perspective, may be considered different). Accordingly, and because (a) LUCIE is intended to assess early stages of exhaustion and (b) to estimate agreement between the categories indicating more severe signs of exhaustion, we also conducted analyses in which individuals classified as belonging to the middle steps of the LUCIE 4-step ranking were excluded. For continuous scale scores, non-parametric Kruskal-Wallis tests were used to evaluate whether groups of participants defined by their LUCIE classification differed with regard to their reporting in the other inventories. For nominal or category data, between-group comparisons were made using Pearson’s Chi-square test.