The team also collected information about work absence due to sickness from the Social Insurance Institution of Finland. This records all absences due to sickness that last over 10 days.

Information of participants’ sleep behavior and patterns was collected by questionnaires, and the researchers obtained data on their health from physical exams carried out by field physicians.

The study analyzed a nationally representative survey of 3,760 men and women in Finland. The participants were aged 30-64 when they joined the study, and were followed for an average of 7 years.

A report on the study, led by Dr. Tea Lallukka, a specialized researcher at the Finnish Institute of Occupational Health in Helsinki, is published in the journal Sleep.

A new study finds that people who regularly get 7 to 8 hours a night of restful, uninterrupted sleep, are the least likely to be absent from work due to sickness.

The results show that the risk of being absent from work due to sickness for 10 days or more rose sharply among people who said they slept less than 6 hours or more than 9 hours a night.

When they analyzed the results further, the team found those who slept between 7 and 8 hours a night had the lowest risk of sickness absence. For men the optimal sleep duration was 7 hours 46 minutes, and for women it was 7 hours 38 minutes.

Feeling more tired than others, waking very early, using sleeping pills, and experiencing symptoms of insomnia, were also linked to a significant rise in working days lost to sickness absence.

Dr. Lallukka says we should be promoting optimal sleep duration because very long and very short sleep seem to be linked to health problems and subsequent sickness absence:

“Those sleeping 5 hours or less, or 10 hours or more, were absent from work every year for 4.6 to 8.9 days more, as compared to those with the optimal sleep length,” she says, and adds:

“Insomnia symptoms should be detected early to help prevent sickness absence and deterioration in health, well-being and functioning. Successful prevention of insomnia not only promotes health and work ability among employees, but it can also lead to notable savings in reduced sickness absence costs.”

The team also estimates that the direct cost of sickness absence to government and employers could drop by up to 28% by fully addressing problems with workers’ sleep patterns.

The National Institute for Health and Welfare, the Academy of Finland and the Finnish Work and Environment Fund provided funds for the research.

In July 2014, Medical News Today learned about a study of Chinese people aged 55 and over that found insufficient sleep speeds up brain aging.