Management

Longer working hours impairs mental function

By Will Campbell ⋅ March 12, 2009 ⋅  Printable version ⋅

working late?

A study by the Finish Institute of Occupation Health using the Whitehall II data, has concluded that longer working hours is leading to a widespread decline in the cognitive function of employees. The paper Long working hours and cognitive function:the Whitehall II study used the data from over 2,200 civil servants and compared their cognitive function with working hours, in the first large scale prospective study on the association of these factors.

Survey data

The Whitehall II survey started in 1985, and covered and initial population of 10,308 UK civil servants, who have been the subject of follow up surveys at regular intervals thereafter. An initial survey of cognitive function was carried out in 1997-99, and followed up in 2002-04, and workers were sorted by their working hours into normal (35-40), average (41-55) and very long (more than 55). There were five standard tests of cognitive function, fluency, vocabulary, reasoning, comprehension and recall. The responses were modelled, taking into account other factors, such as age, sex, marital status, employment status and conditions as well as personal health factors.

Working Hours

Of those surveyed, 39 percent reported working 35-40 hours per week, giving 61 percent working more than normal hours, with 8% of the population working more than 55 hours per week. Those workers in the “very long hours” category were more likely to be male, married, higher occupational grade, experience more psychological stress, have shorter sleep patterns and a higher alcohol intake. Comparisons were made on various models, but a statistical significance was found on cognitive ability.

Cognitive function

At the initial study, those workers who reported more than 55 hours work per week have lower vocabulary score at the first assessment, and also at the follow up, when compared to those workers in the 35-40 hours per week group. They also showed lower scores on the reasoning test during the follow up.

The results were shown to be cumulative, and the longer the working hours per week, the lower the score in the cognitive tests. Employees with longer working hours also reported more symptoms of depression and mental illness.

Conclusion

The conclusion to the report is that there is a link between longer working hours and cognitive ability in middle aged workers. Dr Marianna Virtanen, one of the authors, said “the disadvantages of working overtime should be taken seriously… …the differences in aspects of cognitive function between employees working longer hours and those working normal hours is similar in magnitude to that of smoking, a risk factor for dementia”.

Some questions have been raised about the strength of the claims regarding dementia, focusing on the short time between follow up studies as being insufficient to draw such conclusions, however, the authors intend to continue with the study in the future - “It is particularly important to examine whether the effects are long-lasting and whether long working hours predict more serious conditions such as dementia” said Professor Mika Kivimaki.

Tags: overtime, Stress