Academic journal article Scandinavian Journal of Work, Environment & Health

The Joint Association of Sleep Duration and Insomnia Symptoms with Disability Retirement - a Longitudinal, Register-Linked Study

Academic journal article Scandinavian Journal of Work, Environment & Health

The Joint Association of Sleep Duration and Insomnia Symptoms with Disability Retirement - a Longitudinal, Register-Linked Study

Article excerpt

Haaramo P, Rahkonen 0, Lahelma E, Lallukka T. The joint association of sleep duration and insomnia symptoms with disability retirement - a longitudinal, register-linked study. ScandJ Work Environ Health. 2012;38(5):427435. doi:10.5271/sjweh.3269

Objective The aim of this study was to examine the joint association of sleep duration and insomnia symptoms with subsequent disability retirement.

Methods Baseline survey data were collected in 2000-2002 from 40-60-year-old employees of the City of Helsinki, all working at baseline. Baseline data were linked with disability retirement data until the end of 2010, obtained from the Finnish Centre for Pensions registers (N=6042). Sleep duration and self-reported insomnia symptoms (non-restorative sleep and difficulties in initiating and maintaining sleep) were derived from the baseline surveys. All-cause disability retirement (N=561 ) and the most prevalent diagnostic groups - musculoskeletal diseases (43%) and mental disorders (26%) - were examined. Cox regression analysis was used to yield hazard ratios (HR) with 95% confidence intervals (95% CI).

Results A joint association of sleep duration and insomnia symptoms with disability retirement was found, implying a higher risk for those with frequent insomnia symptoms. HR for all-cause disability retirement ranged among those with frequent symptoms from 2.02 (95% CI 1 .53-2.68, sleeping 7 hours) to 3.92 (95% CI 2.57-5.97, sleeping <5 hours). Adjusting for sociodemographic, work, and health-related factors attenuated the associations, which nevertheless remained. The associations were similar for the two diagnostic groups, although stronger for those with mental disorders.

Conclusion Frequent insomnia symptoms dominate the joint association of sleep duration and insomnia symptoms with subsequent disability retirement. Examining exclusively sleep duration would provide an incomplete understanding of the consequences of poor sleep.

Key terms difficulty in initiating sleep; difficulty in maintaining sleep; mental disorder; musculoskeletal disease; non-restorative sleep; sleep disorder; sleep problem.

Sleep duration and insomnia symptoms - such as difficulties in initiating and maintaining sleep as well as non-restorative sleep - are two complementary and interrelated characteristics of sleep. However, the relationship between the two is not linear and previous studies have shown them to be individual indicators with divergent effects (1). Therefore, on the one hand, this calls for separate examinations of the independent effects of sleep duration and insomnia symptoms, and, on the other hand, an examination of their joint effects.

Several studies on the association between sickness absence, which reflects work disability, and insomnia symptoms have been previously conducted [see eg, (2)]. The association between sleep and disability retirement - indicating permanent deterioration of work ability - has been less studied so far. No prior studies have examined the joint association of sleep duration and insomnia symptoms with disability retirement or other indicators of work disability. An association has been found between insomnia symptoms and disability retirement in some recent studies (1, 3-6). In line with these studies, a previous study by our group confirmed the association between insomnia symptoms and subsequent disability retirement, taking into account various types of symptoms and different disability diagnoses (7). Only one Norwegian study has examined the association between sleep duration and disability retirement (1). Following a large sample of 40- 45-year-old participants for four years, the study found that only long sleep duration was associated with all-cause disability retirement. As previous studies have shown that both sleep duration and insomnia symptoms are associated with subsequent disability retirement, it is presumable that by jointly examining these two key characteristics of sleep, we will gain a deeper understanding of the association between sleep and disability retirement. …

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