Predictors of outcome in fatigued employees on sick leave

Abstract

Objective

The main objective of this study was to identify predictors of fatigue caseness, work resumption and chronic fatigue syndrome (CFS)-like caseness in a sample of fatigued employees on sick leave.

Methods

For 12 months, 151 fatigued employees on sick leave, 44% of whom met research criteria for CFS at baseline, were followed. Measures included fatigue, health aspects, psychological problems, burnout, causal attributions and self-efficacy. Logistic regression analysis was used to determine associations between predictor variables at baseline and outcome at follow-up.

Results

After 12 months, 43% of the patients were no longer fatigue cases, and 62% had resumed work. Recovery from fatigue caseness was predicted by stronger psychological attributions and other perception-related factors, whereas work resumption was predicted by lower age, male sex, CFS-like caseness and less cognitive difficulties. Lower physical functioning scores were predictive of (the development of) CFS-like caseness.

Conclusion

Recovering from persistent fatigue and work resumption seem to result from different underlying processes and do not necessarily fall together. As many factors associated with outcome in fatigue reflect illness perception, the prevention of persistent fatigue and CFS may partly be achieved by the modification of perception.

Introduction

Fatigue is a common complaint in the general, primary care and working population, with a reported prevalence varying from 7% to 45% [1], [2], [3]. In most cases, fatigue lacks a clear somatic cause [4] and appears to be a functional symptom [5], [6]. Fatigue can best be understood as a continuum, ranging from mild complaints frequently seen in the community to severe, disabling fatigue like chronic fatigue (syndrome; [1]). When fatigue becomes severe and persistent, it may lead to long-term sick leave [7] and work disability [8].

In the present study, we report predictors of outcome in a sample of persistently fatigued employees absent from work on sick leave. To our knowledge, predictors of outcome have never been studied in this particular group of patients. The study sample was originally selected to assess the efficacy of brief cognitive behaviour therapy (CBT) by general practitioners in fatigued employees on sick leave. Despite favourable effects of CBT for chronic fatigue syndrome (CFS) in previous studies [9], [10], CBT had no detectable effect on the course and duration of fatigue and absenteeism compared with usual GP care [11]. One explanation for this finding might be that impairment in our sample was too advanced for a short treatment in a primary care setting. At baseline, 44% of the patients already met research criteria for CFS [12].

Previously, we studied the relation between persistent fatigue among employees and CFS and found that the two conditions share many characteristics [13]. Interesting in this context is the potential role of causal attributions. Studies have shown that outcomes in CFS patients are predicted by the extent to which patients attribute their illness to a somatic or psychological cause [14], [15], [16], [17], [18], [19], [20]. In a recent study, Chalder et al. [21] found that fatigue caseness and social disability after CBT or counselling were predicted by stronger somatic causal attributions in a sample of fatigued primary care patients, 28% of whom met research criteria for CFS [12].

We examined the role of several factors, among which causal attributions, as predictors of outcome after 1 year. Outcome was defined in terms of (recovery from) fatigue caseness, work resumption and CFS-like caseness (meeting research criteria for CFS) at follow-up. As fatigued employees who meet criteria for CFS may differ from fatigued employees who do not meet CFS criteria in important clinical ways [13], we hypothesized that different predictors of outcome would be found in CFS-like cases and non-CFS cases at baseline.