Estimating costs of lost productivity – examples of methodological shortcomings from an evaluation related to long-term sickness absence
Background: The Swedish Agency for Health Technology Assessment and Assessment of Social Services (SBU) was commissioned by the government to evaluate positive and negative effects of different ways for healthcare to manage individuals on long-term sickness absence, or at risk of becoming so. The commissioning also included an analysis of health economic aspects.
Objectives: The purpose of this sub-study was to critically assess the methods for calculating costs of lost production seen in the health economic studies identified within the evaluation.
Methods: A systematic literature review was performed to identify randomised controlled trials and associated health economic studies of health care interventions related to long-term sickness absence. The evaluation was restricted to the most common causes of long-term sick absence in Sweden. Health economic studies that met the study inclusion criteria were critically assessed by two SBU health economists using SBU's checklist for trial-based health economic studies. Independent individual assessments were followed by a consensus assessment where the studies were rated as having high, medium or low quality with respect to health economic methodology.
Results: A total of 22 health economic studies were identified, the majority conducted in the Nordic countries and the Netherlands. In twelve of the studies, the health economic analyses were assessed as having low methodological quality. The most common reason was flaws in how costs of lost production had been calculated. In some cases, sickness benefits were assumed to be equivalent to costs of lost production, even though they constitute a transfer payment and not a cost. In other cases, the economic value of lost production and sickness benefits were summed, leading to double counting.
Conclusions: Costs of lost production are a key health economic aspect in the context of long-term sickness absence. The fact that more than half of the health economic studies identified within the evaluation had methodological flaws in how costs for lost production were calculated indicates that the concepts and established methods are difficult to grasp, and that expertise within health economics should be involved in studies that include health economic analyses.
Patient, public and/or healthcare consumer involvement: None.