A genetic predisposition to sleep 5 or fewer hours per night is associated with a significantly higher risk for subsequent depression. However, a genetic propensity to depression is not associated with suboptimal sleep patterns later on, new research shows.
The analysis included participants in the English Longitudinal Study of Ageing (ELSA), a prospective cohort study of a representative UK sample (mean age, 65 years) that is assessed biennially.
Researchers collected data on sleep duration and depression through nurse home visits and computer-assisted personal interviews and used combined ELSA waves from 2004 to 2008, when collection of genetic data began.
Using genome-wide association studies from the UK Biobank, the authors constructed polygenic scores (PGSs) to predict an individual’s genetic risk over an average of 8 years for a disease or outcome, overall sleep duration, short sleep (≤ 5 hours nightly), long sleep (≥ 9 hours of sleep nightly), and depression.
The analysis included two analytic samples; one involved 6521 persons to determine the role of baseline sleep on depression (assessed using the Center for Epidemiologic Studies Depression Scale) at follow-up, and the other involved 6070 persons to determine the role of baseline depression on suboptimal sleep at follow-up.
After adjustments, including for age and sex, a 1–standard deviation increase in PGS for short sleep was associated with an increase of 14% in odds of developing depression during the follow-up period (odds ratio [OR], 1.14; P = .008).
There was no significant association of the PGS for sleep duration (P = .053) or long sleep (P = .544) with the onset of depression.
There were no significant associations between PGS for depression and future overall sleep duration, short sleep, and long sleep by the end of the follow-up, suggesting that different mechanisms underlie the relationship between depression and subsequent onset of suboptimal sleep in older adults.
Several sensitivity analyses — including additional adjustment for socioeconomic, environmental and behavioral factors — upheld the findings of the main analysis, highlighting the robustness of the results.
The study showed that common genetic markers for short sleep play an important role in the incidence of depression in older adults, the authors note, adding that the new findings “support a growing view that short-sleep is more salient to the experience of depression than long sleep” across the lifespan.
The study was led by Odessa S. Hamilton, Department of Behavioural Science and Health, University College London, United Kingdom. It was published online October 20 in Translational Psychiatry.
There are probably intraindividual differences in sleep duration that were not assessed in the study. The depression scale used may be indicative of subclinical depression and not major depressive disorder. The phenotypic sensitivity analyses did not account for comorbidities or medications that can affect sleep duration and depression.
ELSA is funded by the National Institute on Aging and by a consortium of UK government departments coordinated by the National Institute for Health and Care Research. The authors report no relevant conflicts of interests.
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