Study Links Healthy Sleep Duration to Less Sick Time Away From Work

New research suggests that sleeping seven to eight hours per night is associated with the lowest risk of absence from work due to sickness. The results underscore the importance of the “Sleep Well, Be Well” campaign of the National Healthy Sleep Awareness Project, a collaboration between the Centers for Disease Control and Prevention, American Academy of Sleep Medicine, Sleep Research Society and other partners.

Results show that the risk of an extended absence from work due to sickness rose sharply among those who reported sleeping less than six hours or more than nine hours per night. Further analysis found that the optimal sleep duration with the lowest risk of sickness absence from work was between seven and eight hours per night: seven hours, 38 minutes for women and seven 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,” says 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,” says 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 to 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,” says 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.