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Monitoring of need for recovery and prolonged fatigue within the working population: Evaluation of reliability and agreement over time.

BACKGROUND
Need for recovery (NFR) and prolonged fatigue are two important concepts for monitoring short- and long-term outcomes of psychological job demands within employees. For effective monitoring it is, however, important to gain insight in the reproducibility of the instruments that are used.


OBJECTIVE
The objective was to assess reproducibility of the NFR scale and Checklist Individual Strength (CIS), measuring NFR and prolonged fatigue respectively, in the working population.


METHODS
Longitudinal data from the Maastricht Cohort Study (MCS) study was used, capturing 12,140 employees from 45 different companies at baseline. A 'working' and 'returning to work' sample was conceived for different intervals; 4-month, 1-year, and 2-year.


RESULTS
Reliability, assessed with the interclass correlation, was high within employees with a stable work environment for the NFR scale (0.78) and CIS (0.75). The smallest detectable change, assessing the agreement, was 41.20 for the NFR scale and 31.10 for the CIS.


CONCLUSIONS
Reliability was satisfactory for both the NFR scale and CIS. The agreement of both scales to detect a changes within employees was, however, less optimal. It is, therefore, suggested that, ideally, both instruments are placed within a broader range of instruments to effectively monitor the outcomes of psychological job demands.