MedicalResearch.com Interview with: Tea Lallukka, PhD Finnish Institute of Occupational Health & University of Helsinki, Hjelt Institute, Department of Public Health University of Helsinki, Finland Medical Research: What are the main findings of the study? Dr. Lallukka: Our study used nationally representative survey data linked with register data on medically certified sickness absence among working -aged Finnish women and men. We showed consistent associations between insomnia symptoms, sleep duration, and being tired and sickness absence. The follow-up lasted around 7 years. Sickness absence days were derived from comprehensive registers from the Social Insurance Institution of Finland. The associations were broadly similar among women and men. Furthermore, they remained even after considering key correlates of sleep and sickness absence including socioeconomic position, working conditions, health behaviors, obesity, and mental and physical health. Health data were derived from physical examination conducted by field physicians. These data are more objective, and help provide more robust evidence. We further covered all key sleep disturbances and sleep duration for more comprehensive understanding about the contribution of sleep to sickness absence. Finally, a novel method developed by the authors (Härkänen & Kaikkonen) allowed us to estimate the difference in sickness absence days per working year among those reporting and not reporting different sleep disturbances. Using the difference in days absent from work, we were further able to estimate the hypothetical direct costs of sickness absence highlighting notable societal significance of sleep. Thus, a large part of all costs of sickness absence are attributable to poor sleep. For example, those sleeping 5 hours or less or 10 hours or more, were absent from work ca 5-9 days more, as compared to those with optimal sleep length. The optimal sleep length with the lowest risk of sickness absence was 7 hours 46 minutes for men and 7 hours 38 minutes for women. (more…)