The trait and occasion components of fatigue and their association with sickness absence.

OBJECTIVE: Fatigue is an important health outcome in public and occupational health care. To correctly understand and treat high levels of (prolonged) fatigue it is important to disentangle the state of fatigue into a time-varying (occasion) and -invarying (trait) component. Not only for understanding of the construct itself over time but also for its relation with (health) outcomes such as sickness absence.

METHODS: Longitudinal data (n=2316) from the Maastricht Cohort Study (MCS) study was used, which assessed fatigue across 4-month intervals using the Checklist Individual Strength (CIS).

RESULTS: It was found that the occasion component explains 27.60% (95%-CI [25.80%; 29.40%]) of the variance of fatigue and the trait component 71.00% (95%-CI [69.00%; 72.90%]). The trait component was, furthermore, found to be a significant predictor of sickness absence.

CONCLUSION: Fatigue has a considerable time-invariant component. As this component is also related with other adverse health outcomes, preventive measures and interventions should take the difference between the occasion and trait component of fatigue into account.