Association Between Insomnia And Mortality Is Only Evident Among Long Sleepers
Received 5 July 2019
Accepted for publication 7 October 2019
Published 13 November 2019 Volume 2019:11 Pages 333—342
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Dr Sutapa Mukherjee
Anna Karin Hedström,1 Rino Bellocco,2 Weimin Ye,3 Ylva Trolle Lagerros,4 Torbjörn Åkerstedt5
1Department of Clinical Neuroscience and Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; 2Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden, and Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy; 3Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; 4Department of Medicine, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden, and Obesity Center, Academic Specialist Center, Stockholm Health Services, Stockholm, Sweden; 5Stress Research, Stockholm University, Stockholm, Sweden, and Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
Correspondence: Anna Karin Hedström
Institute of Environmental Medicine, Karolinska Institutet Box 210, Stockholm 17177, Sweden
Background: Previous studies investigating the relationship between insomnia and mortality have been inconsistent.
Purpose: We aimed to assess whether nocturnal insomnia symptoms and non-restorative sleep are associated with all-cause mortality and whether they modify the associations between short and long sleep duration and all-cause mortality.
Patients and methods: The present report is based on a prospective cohort study of 39,139 participants with a mean follow-up time of 19.6 years. Cox proportional hazard models with attained age as timescale were used to estimate overall mortality hazard ratios (HRs) with 95% confidence intervals (CI) for different categories of sleep duration and insomnia symptoms.
Results: Both difficulty initiating sleep and daytime sleepiness were independently associated with increased mortality among those with sleep duration of 9 hrs or more (HR 1.51, 95% CI 1.11–2.07 and HR 1.37, 95% CI 1.03–1.82). Mortality increased with increasing severity of difficulties initiating sleep (p for trend 0.04) and daytime sleepiness (p for trend 0.01) among the long sleepers. None of the insomnia symptoms were associated with mortality among those who reported sleep duration of 8 hrs or less.
Conclusion: Long sleep in combination with difficulties initiating sleep and daytime sleepiness, possibly due to psychiatric or physical disorders, was thus associated with increased mortality, whereas long sleep without difficulties falling asleep or daytime sleepiness was not associated with mortality. Our study emphasizes the need to take nocturnal insomnia symptoms and daytime sleepiness into consideration when assessing the influence of sleep duration on mortality. Additional research is needed to elucidate the relationship between long sleep, insomnia and related psychiatric and physical disorders.
Keywords: prospective cohort study, sleep quality, sleep duration
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