L.G.P.M. van Amelsvoort

An epidemiological approach to study fatigue in the working population: the Maastricht Cohort Study

In 1998, a large scale prospective cohort study of prolonged fatigue in the working population was started in the Netherlands. The ultimate goal of this Maastricht Cohort Study was to identify risk factors involved in the aetiology and natural course of prolonged fatigue in the working population and to develop preventive measures and treatments that can be used in occupational health settings. In this paper, a conceptual model for epidemiological research on prolonged fatigue is presented. This model is the basis for the Maastricht Cohort Study. Alongside the model and design, the characteristics of the study population, the prevalence and one year cumulative incidence of prolonged fatigue, as well as its relation with secondary health outcomes (psychological distress, need for recovery, and burnout) are presented. Furthermore, model, design, and the presented results are discussed.

Fatigue as a risk factor for being injured in an occupational accident: results from the Maastricht Cohort Study

Aims: To determine whether fatigue and need for recovery are risk factors for being injured in an occupational accident. Methods: These associations were investigated within the Maastricht Cohort Study of “Fatigue at Work”, a prospective cohort study of employees from a wide range of companies and organisations. For 7051 employees information was available on fatigue as measured with the Checklist Individual Strength (CIS), need for recovery as measured with the VBBA, and possible confounding factors such as age, smoking, alcohol consumption, educational level, shift work, and work environment. Information on the risk factors was collected in May 1999 and January 2000, before the occurrence of the occupational accidents. The incidence of being injured in an occupational accident was inventoried over the year 2000. A total of 108 employees reported having been injured in an occupational accident in 2000. Results: For the highest CIS fatigue score tertile a for age, gender, educational level, smoking, shift work, and work environment, adjusted relative risk for being injured in an occupational accident of 1.29 (95% CI: 1.03 to 2.78) was found compared to the lowest tertile, and for the highest tertile of need for recovery a relative risk of 2.28 (95% CI: 1.41 to 3.66) was found. Conclusions: Fatigue and need for recovery were found to be independent risk factors for being injured in an occupational accident. This means that in the push back of occupational accidents, fatigue, and even more importantly need for recovery, need special attention.

Work–family conflict as a risk factor for sickness absence

Objectives: (1) To study both cross-sectional and prospective relationships between work–family conflict and sickness absence from work; (2) to explore the direction of the relationships between the different types of conflict (work–home interference and home–work interference) and sickness absence; and (3) to explore gender differences in the above relationships. Methods: Data from the Maastricht Cohort Study were used with six months of follow up (5072 men and 1015 women at T6). Work–family conflict was measured with the Survey Work–Home Interference Nijmegen (SWING). Sickness absence was assessed objectively through individual record linkage with the company registers on sickness absence. Results: In the cross-sectional analyses, high levels of work–family conflict, work–home interference, and home–work interference were all associated with a higher odds of being absent at the time of completing the questionnaire, after controlling for age and long term disease. Differences in average number of absent days between cases and non-cases of work–home interference were significant for men and most pronounced in women, where the average number of absent days over six months follow up was almost four days higher in women with high versus low–medium work–home interference. Conclusions: A clear relation between work–family conflict and sickness absence was shown. Additionally, the direction of work–family conflict was associated with a different sickness absence pattern. Sickness absence should be added to the list of adverse outcomes for employees struggling to combine their work and family life.

Work schedules and fatigue: a prospective cohort study

Aims: (1) To describe the prevalence of fatigue among employees in different work schedules (day work, three-shift, five-shift, and irregular shift work); (2) to investigate whether different work schedules are related to increasing fatigue over time, while taking into account job title and job characteristics; and (3) to study fatigue among shift workers changing to day work. Methods: Data from nine consecutive four-monthly self administered questionnaires from the Maastricht Cohort Study on Fatigue at work (n = 12 095) were used with 32 months of follow up. Day and shift workers were matched on job title. Results: The prevalence of fatigue was 18.1% in day workers, 28.6% in three-shift, 23.7% in five-shift, and 19.1% in irregular shift workers. For three-shift and five-shift workers substantial higher fatigue levels were observed compared to day workers at baseline measurement. In the course of fatigue over the 32 months of follow up there were only small and insignificant differences between employees in different work schedules. However, among employees fatigued at baseline, fatigue levels decreased faster over time among five-shift workers compared to fatigued day workers. Shift workers changing to day work reported substantially higher fatigue levels prior to change, compared to those remaining in shift work. Conclusions: Substantial differences in fatigue existed between day and shift workers. However, as no considerable differences in the course of fatigue were found, these differences have probably developed within a limited time span after starting in a shift work job. Further, evidence was found that fatigue could be an important reason for quitting shift work and moving to day work. Finally, in the relation between work schedules and fatigue, perceived job characteristics might play an important role.

Impact of One Year of Shift Work on Cardiovascular Disease Risk Factors

The purpose of the study was to investigate whether the reported increased cardiovascular disease risk in shift workers could be explained by changes in cardiovascular risk factors. In a cohort of 239 shift and 157 daytime workers, 1-year changes in biological and lifestyle cardiovascular risk factors were monitored between the start of a new job and 1 year later. Both body mass index and low-density lipoprotein/high-density lipoprotein cholesterol ratio decreased significantly in shift workers compared with daytime workers (body mass index change: −0.31 and +0.13 kg/m2; low-density lipoprotein/high-density lipoprotein ratio change: −0.33 and −0.13 respectively). Cigarettes smoked per day increased significantly in shift compared with daytime workers (+1.42 and −1.03, respectively). Therefore, only for smoking, an unfavorable change was observed. This may explain, at most, only a part of the excess cardiovascular disease risk reported in shift workers.

Health problems and psychosocial work environment as predictors of long term sickness absence in employees who visited the occupational physician and/or general practitioner in relation to work: a prospective study

Aims: To determine whether psychosocial work environment and indicators of health problems are prospectively related to incident long term sickness absence in employees who visited the occupational physician (OP) and/or general practitioner (GP) in relation to work. Methods: The baseline measurement (May 1998) of the Maastricht Cohort Study, a prospective cohort study among 45 companies and organisations, was used to select employees at work who indicated having visited the OP and/or GP in relation to work. Self report questionnaires were used to measure indicators of health problems (presence of at least one long term disease, likeliness of having a mental illness, fatigue) and psychosocial work environment (job demands, decision latitude, social support, job satisfaction) as predictors of subsequent sickness absence. Sickness absence data regarding total numbers of sickness absence days were obtained from the companies and occupational health services during an 18 month period (between 1 July 1998 and 31 December 1999). Complete data were available from 1271 employees. Results: After adjustment for demographics and the other predictors, presence of at least one long term disease (OR 2.36; 95% CI 1.29 to 4.29) and lower level of decision latitude (OR 1.69; 95% CI 1.22 to 2.38) were the strongest predictors for sickness absence of at least one month. A higher likelihood of having a mental illness, a higher level of fatigue, a lower level of social support at work, and low job satisfaction were also significant predictors for long term sickness absence, but their effect was less strong. Conclusion: In detecting employees at work but at risk for long term sickness absence, OPs and GPs should take into account not only influence of the psychosocial work environment in general and level of decision latitude in particular, but also influence of indicators of health problems, especially in the form of long term diseases.

Need for recovery after work and the subsequent risk of cardiovascular disease in a working population

Background: A high need for recovery after work can be regarded as a short term adverse effect of working day stressors and the person’s inability to cope and recover. Consequently, it might be an intermediate factor between job stressors and cardiovascular disease (CVD). Aim: To investigate, in a longitudinal study, the relation between need for recovery and subsequent CVD. Methods: Data from the Maastricht Cohort Study of 12 140 workers were used, with 42 incident self reported CVD cases during 32 months of follow up. Cox proportional hazards analysis was used to calculate age, gender, smoking status, and educational level adjusted relative risks. Results: The adjusted relative CVD risk for the second compared to the first tertile of the need for recovery score was 1.22 (95% CI: 0.49 to 3.04), and for the third compared to the first tertile was 3.16 (95% CI: 1.34 to 7.48). When need for recovery was entered as continuous score, an adjusted relative risk per SD increase of 1.54 (95% CI: 1.15 to 2.03) was found. Additional adjustment for several work related factors as job demands, did not notably change the observed relation between need for recovery and CVD. Moreover, the increased risk for subjects reporting high job demands (1.38 per SD increase; 95% CI: 1.02 to 3.92) decreased substantially after adjustment for need for recovery. Conclusion: The results show that need for recovery is a strong predictor of subsequent cardiovascular disease and might be an intermediate factor between job stressors and cardiovascular disease.

Psychological distress, fatigue and long-term sickness absence: prospective results from the Maastricht Cohort Study.

Objective: Little is known about psychological distress as a risk factor for the onset of long-term sickness absence and even less about the influence of fatigue in this relationship. Methods: We examined the relationship between psychological distress and the onset of long-term sickness absence during 18 months of follow-up while considering fatigue. Analyses were based on 6403 employees participating in the Maastricht Cohort Study. Results: Psychological distress was related to the onset of long-term sickness absence (women relative risk 1.45, 95% confidence interval = 1.23–1.72; men 1.33, 1.21–1.46). Adjustment for fatigue weakened the associations, particularly in women. Caseness analyses revealed different effects of psychological distress and fatigue in the onset of long-term sickness absence in men and women. Conclusion: The findings underline the need for interventions aiming at psychological distress and, depending on the gender, also at fatigue, to reduce the risk of long-term sickness absence.

Changes in frequency of premature complexes and heart rate variability related to shift work.

OBJECTIVES To investigate whether an increased risk of cardiovascular disease might be caused by increased arrhythmogeneity and by unfavourable changes in autonomic cardiac control the changes in the occurrence of premature complexes (PVCs) and in heart rate variability (HRV) were studied in subjects who started to work in shifts. METHODS 1 Year changes in frequency of PVCs and HRV were measured in 49 shift workers and 22 control subjects working in daytime. All respondents were starting in a new job in integrated circuit or waste incinerator plants. RESULTS The incidence of PVC increased significantly in shift workers over the 1 year follow up, compared with daytime workers. The frequency of ventricular extrasystoles increased in 48.9% of the shift workers, and in 27.3% of the daytime workers. The Spearman correlation coefficient between the number of nights worked and the change in PVCs was 0.33 (p=0.004). A small non-significant unfavourable change in HRV was found in both the shift and daytime workers. CONCLUSIONS A change in arrhythmogeneity, but not in cardiac autonomic control, might explain the increased risk of cardiovascular disease in shift workers.

Prevention of long-term sickness absence and major depression in high-risk employees: a randomised controlled trial

Objectives To examine the efficacy of early intervention on the prevention of long-term sickness absence and major depression among employees at high risk of future sickness absence and with mild to severe depressive complaints. Methods Randomised controlled trial conducted among employees working in an office environment. 139 employees were identified both at high risk of future sickness absence and with mild to severe depressive complaints through screening. Subsequently, they were randomly assigned to the intervention group (n=69) or the control group (n=70). Objective sickness absence was analysed at 12 and 18 months of follow-up. Depressive complaints were assessed by the Beck Depression Inventory (BDI-II) at baseline, and at 6 and 12 months of follow-up. Results Intention-to-treat analyses showed a significant difference in total sickness absence duration between the intervention (27.5 calendar days (SD 44.7)) and control group (50.8 days (SD 75.8)) over 12 months of follow-up, a reduction of 46% (p=0.017). The intervention group showed a non-significantly lower proportion of long-term sickness absence spells compared with the control group (p=0.127). Statistically significant and clinically relevant differences in depressive complaints were found after both 6 months (p=0.001) and 12 months (p=0.005) of follow-up, in favour of the intervention group. Relative risk reductions (RRR) were 19.2% and 19.8% respectively. Sickness absence data were available for all participants over 18 months of follow-up. Questionnaire data were available for 99 (at 6 months) and 90 participants (at 12 months). No adverse events or side effects occurred. Conclusions Early intervention in employees with mild to severe depressive complaints and high risk of future long-term sickness absence proved to be effective in preventing/reducing both sickness absence and depressive complaints.