Within-person fluctuations in wellbeing and task-specific work ability.

PURPOSE: To research within-person fluctuations in occupational health, work ability and wellbeing, we need new measurement strategies. We studied absolute agreement for weekly measurements of task-specific work ability and relationships between wellbeing, work demands and personal factors and task-specific work ability over time.

METHODS: Forty-eight Dutch academic researchers answered questions during 12 consecutive weeks. Physical and mental work demands, indicators of wellbeing and task-specific work ability in each week were measured. Intra-class correlation coefficients (ICC) for absolute agreement between task-specific work ability measures were calculated. For application in individual workers, an ICC > 0.90 was regarded as suitable. Multilevel models were used to relate both time-invariant and time-varying predictors to task-specific work ability.

RESULTS: Multiple measurements increased the reliability. Absolute agreement, however, did not reach the optimal level, except for the task 'ability to conduct data analyses' which had an ICC value of 0.95 (95% CI 0.91-0.98). Individuals' leisure time physical activity (p = 0.03) and relational (p = 0.02) and social (p = 0.02) wellbeing were related to their average task-specific work ability. Weekly physical demands (p = 0.01) and personal (p = 0.04) and general wellbeing (p = 0.03) were related to weekly fluctuations in work ability.

CONCLUSIONS: We demonstrated intra-individual variability in repeated assessments of task-specific work ability, pointing to the need for multiple measurements when characterizing work ability. The finding that some time-invariant and time-varying predictors can be related to the estimate of aspects of task-specific work ability and its fluctuations is helpful in understanding the dynamics of this concept.