Healthy sleep duration linked to less sick time from work

Results show that the risk of an extended absence from work due to sickness rose sharply among those who reported sleeping less than 6 hours or more than 9 hours per night. Further analysis found that the optimal sleep duration with the lowest risk of sickness absence from work was between 7 and 8 hours per night: 7 hours, 38 minutes for women and 7 hours, 46 minutes for men. Insomnia-related symptoms, early morning awakenings, feeling more tired than others, and using sleeping pills also were consistently associated with a significant increase in workdays lost due to sickness.

"Optimal sleep duration should be promoted, as very long and very short sleep indicate health problems and subsequent sickness absence," said principal investigator Tea Lallukka, PhD, specialized researcher at the Finnish Institute of Occupational Health. "Those sleeping five 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."

The study results are published in the September issue of the journal Sleep.

"Insufficient sleep -- due to inadequate or mistimed sleep -- contributes to the risk for several of today's public health epidemics, including cardiovascular disease, diabetes and obesity. Getting at least seven hours of nightly sleep is a key to overall health, which translates to less sick time away from work," said American Academy of Sleep Medicine President Dr. Timothy Morgenthaler, a national spokesperson for the Healthy Sleep Project. The "Sleep Well, Be Well" campaign was launched earlier this year to increase awareness of the importance of sleep as one of the three pillars of a healthy lifestyle.

The study involved a nationally representative survey of 3,760 men and women in Finland who had been working at any time in the prior year. Participants were 30-64 years old at baseline. Sleep characteristics were determined by questionnaire, and health measures were derived from physical examination conducted by field physicians. Data for work absences due to sickness were gathered from the Social Insurance Institution of Finland, which tracks all sickness absences lasting more than 10 days. The average follow-up period was seven years.

A novel statistical method developed by study co-authors Tommi Härkänen, PhD, and Risto Kaikkonen, MSc, was used to predict adjusted average sickness absence days per working year. Additional statistical estimates found that the direct costs of sickness absence to the Finnish government and employers could decrease by up to 28 percent if sleep disturbances could be fully addressed.

"Insomnia symptoms should be detected early to help prevent sickness absence and deterioration in health, well-being and functioning," said Lallukka. "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 study was supported by the National Institute for Health and Welfare, the Academy of Finland and the Finnish Work and Environment Fund.