STRUGGLING to fall asleep at night? It may be time to ditch your mobile phone after nightfall. The largest study to link disrupted sleep with mental health issues has recommended devices should not be used after 10pm if you want to get a decent night’s sleep. That means no more aimlessly scrolling through Facebook in bed, watching YouTube clips or sleeping with the TV on.
The study, published in The Lancet Psychiatry, found people who do so are more likely to suffer from mood problems and rate themselves as less happy than those who switch off entirely in the hours leading up to bedtime. The authors, who examined the circadian rhythms of 91,000 middle-aged people, used wearable monitors to determine how far the subjects were from the ideal condition of an active day and a restful night. It found people on their mobile phones late at night were more likely to have poor sleep hygiene, which could affect mood and overall wellbeing.
Senior study author Professor Daniel Smith from the University of Glasgow told The Times that people with abnormal sleep patterns were likely to experience more fluctuation in their mood, as well as depression or bipolar disorder.
“Everyone who has ever stepped off a long-haul flight or had children knows that even a couple of nights’ poor sleep can be pretty bad for your mood and thinking ability,” he said. “I don’t think it’s unreasonable to say this is another piece of evidence that might suggest we should all be more mindful of our natural rhythms of activity and rest.”
The solution?
Don’t carry your phone to bed with you. At 10pm, leave it charging in another room or just switch it off until morning. And not only that — also try to engage in restfulness in the hours leading up to sleep. “It’s not just what you do at night, it’s what you do during the day — trying to be active during the day and inactive in darkness. Especially in the winter, making sure you get out in the morning in the fresh air is just as important in getting a good night’s sleep as not being on your mobile phone.”
Background
Disruption of sleep and circadian rhythmicity is a core feature of mood disorders and might be associated with increased susceptibility to such disorders. Previous studies in this area have used subjective reports of activity and sleep patterns, but the availability of accelerometer-based data from UK Biobank participants permits the derivation and analysis of new, objectively ascertained circadian rhythmicity parameters. We examined associations between objectively assessed circadian rhythmicity and mental health and wellbeing phenotypes, including lifetime history of mood disorder.
Methods
UK residents aged 37–73 years were recruited into the UK Biobank general population cohort from 2006 to 2010. We used data from a subset of participants whose activity levels were recorded by wearing a wrist-worn accelerometer for 7 days. From these data, we derived a circadian relative amplitude variable, which is a measure of the extent to which circadian rhythmicity of rest–activity cycles is disrupted. In the same sample, we examined cross-sectional associations between low relative amplitude and mood disorder, wellbeing, and cognitive variables using a series of regression models. Our final model adjusted for age and season at the time that accelerometry started, sex, ethnic origin, Townsend deprivation score, smoking status, alcohol intake, educational attainment, overall mean acceleration recorded by accelerometry, body-mass index, and a binary measure of childhood trauma.
Findings
We included 91 105 participants with accelerometery data collected between 2013 and 2015 in our analyses. A one-quintile reduction in relative amplitude was associated with increased risk of lifetime major depressive disorder (odds ratio [OR] 1·06, 95% CI 1·04–1·08) and lifetime bipolar disorder (1·11, 1·03–1·20), as well as with greater mood instability (1·02, 1·01–1·04), higher neuroticism scores (incident rate ratio 1·01, 1·01–1·02), more subjective loneliness (OR 1·09, 1·07–1·11), lower happiness (0·91, 0·90–0·93), lower health satisfaction (0·90, 0·89–0·91), and slower reaction times (linear regression coefficient 1·75, 1·05–2·45). These associations were independent of demographic, lifestyle, education, and overall activity confounders.
Interpretation
Circadian disruption is reliably associated with various adverse mental health and wellbeing outcomes, including major depressive disorder and bipolar disorder. Lower relative amplitude might be linked to increased susceptibility to mood disorders.
Funding
Lister Institute of Preventive Medicine.
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