Abstract: Ten studies fulfilled the inclusion criteria. Six CBA studies reported on interventions relating to temporal flexibility: self-scheduling of shift work (n = 4), flexitime (n = 1) and overtime (n = 1). The remaining four CBA studies evaluated a form of contractual flexibility: partial/gradual retirement (n = 2), involuntary part-time work (n = 1) and fixed-term contract (n = 1). The studies retrieved had a number of methodological limitations including short follow-up periods, risk of selection bias and reliance on largely self-reported outcome data. Four CBA studies on self-scheduling of shifts and one CBA study on gradual/partial retirement reported statistically significant improvements in either primary outcomes (including systolic blood pressure and heart rate; tiredness; mental health, sleep duration, sleep quality and alertness; self-rated health status) or secondary health outcomes (co-workers social support and sense of community) and no ill health effects were reported. Flexitime was shown not to have significant effects on self-reported physiological and psychological health outcomes. Similarly, when comparing individuals working overtime with those who did not the odds of ill health effects were not significantly higher in the intervention group at follow up. The effects of contractual flexibility on self-reported health (with the exception of gradual/partial retirement, which when controlled by employees improved health outcomes) were either equivocal or negative. No studies differentiated results by socio-economic status, although one study did compare findings by gender but found no differential effect on self-reported health outcomes. The findings of this review tentatively suggest that flexible working interventions that increase worker control and choice (such as self-scheduling or gradual/partial retirement) are likely to have a positive effect on health outcomes. In contrast, interventions that were motivated or dictated by organisational interests, such as fixed-term contract and involuntary part-time employment, found equivocal or negative health effects. Given the partial and methodologically limited evidence base these findings should be interpreted with caution. Moreover, there is a clear need for well-designed intervention studies to delineate the impact of flexible working conditions on health, wellbeing and health inequalities.

Plain-language summary: Flexible working arrangements, such as flexitime and teleworking, are becoming more common in industrialised countries but the impacts of such flexibility on employee health and wellbeing are largely unknown. This review examined the health and wellbeing effects of flexible working arrangements which favour the worker as well as those dictated by the employer (for example, fixed-term contracts or mandatory overtime). Ten controlled before and after studies were found which evaluated the effects of six different types of flexible working arrangement on employee health and wellbeing: self-scheduling (n = 4); flextime (n = 1); overtime (n = 1); gradual retirement (n = 2); involuntary part-time (n = 1) and fixed-term contract (n = 1). Self-scheduling of shift interventions and employee controlled partial/early retirement were found to improve health (including systolic blood pressure and heart rate; tiredness; mental health, sleep duration, sleep quality and alertness; and self-rated health status) and/or wellbeing (co-workers' social support and sense of community) and no ill health effects were observed. The studies of overtime working, flexitime and fixed-term contracts found no significant effects on physical, mental or general health or on any of the wellbeing outcomes examined. Importantly, however, the study on overtime failed to provide detailed information on either the amount or duration of overtime worked, so it is therefore difficult to draw any conclusions regarding the effects of overtime on workers' health and wellbeing. Overall, these findings seem to indicate that flexibility in working patterns which gives the worker more choice or control is likely to have positive effects on health and wellbeing. However, given the small number of studies included in the review and their methodological limitations, caution should be applied to this conclusion. Well-designed studies are therefore needed to further explain the relationship between flexible working and health and wellbeing.