Although working very long hours is linked to an increased risk of certain types of health and safety problems for particular groups of industrial employees, the report's authors assert that other factors – such as previous health problems – have a much stronger effect on overall worker health, safety and productivity.
"Our results challenge the assumption that each hour of work above 40 hours steadily increases health and safety risks and reduces productivity," said Harris Allen Jr., Ph.D., lead author of the report. "In fact, no adverse effects were found until the 60-hour-per-week mark."
Even when workers reached the 60-hour-per-week mark, Allen noted that "the effects were limited to an increased risk of workers' compensation episodes for hourly female employees with a history of workers comp' episodes and to an increased risk of new musculoskeletal diagnoses for older workers."
"Our results also raise the possibility that policies like the European Union's Working Time Directive – with across-the-board restrictions that severely obstruct the capacity to work longer hours – may themselves be too blunt and onerous in today's increasingly competitive marketplace," Allen said.
Researchers Analyzed Data on Nearly 2,800 Workers
Using a database of information on a sample of nearly 2,800 workers representing a heavy manufacturer, Allen and colleagues analyzed the effects of work hours on a broad range of health, safety and productivity outcomes. At the time of the study, the company had a policy of strongly encouraging but not mandating overtime, resulting in an employee average of more than 43 work hours per week.
According to the researchers, while employees in the above subgroups working 60 or more hours posted a higher rate of injuries and other health problems, those with other job and demographic characteristics working 60 or more hours per week did not show this added risk. Nor did employees working more "moderate" overtime (48 to 59 hours) face more risk, regardless of their job and demographic characteristics.
The researchers found that working overtime did not increase the risk of physical or mental health problems. Overtime also was unrelated to "presenteeism" (days the employee was at work but performing at less than full capacity).
According to the researchers, the number of work hours mattered much less in accounting for employee outcomes than factors whose origins preceded the number of hours worked: compensation type, demographics and, particularly, prior diseases and health status.
Findings Contradict Previous Research
Previous studies have suggested that long work hours directly affect the risk of health and safety problems – the more hours worked per week above 40, the greater the risk.
In the European Union, a policy called the Working Time Directive limits average work hours to no more than 48 per week. The researchers assert that such policies may pose a challenge for private-sector employers – especially those whose operations are structured in ways that are maximized when employees work overtime.
"Although work hours are a factor, they should be considered alongside previous health and other factors that comprise the larger context within which employee health, productivity and safety outcomes are determined," said William Bunn, M.D., co-author of the report. "On both the research and policy fronts, more emphasis needs to be focused on prior health and other antecedents to the number of hours worked that better predict employee safety, lost productivity and future health."