Megan Brooks

June 08, 2017

BOSTON — A person's emotional functioning may suffer with prolonged exposure to sleep restriction, new research shows.

"We found that exposure to 3 weeks of sleep restriction and recovery as commonly experienced in society today contributes to an overall blunting of emotional intensity," presenter Keeyon Olia, clinical research student, Department of Neurology, Sleep & Inflammatory Systems Laboratory, Beth Israel Deaconess Medical Center and Harvard University, Boston, Massachusetts, told Medscape Medical News.

"This is an important finding because blunted affect can lead to anhedonia and emotion regulation difficulties, which are heavily implicated in a variety of disorders, such as depression and generalized anxiety, schizophrenia, and so on," said Olia.

The late-breaking study was presented here at SLEEP 2017: 31st Annual Meeting of the Associated Professional Sleep Societies.

Blunted Response to Positive Images

The literature is divided on whether sleep restriction causes heightened or blunted emotional reactivity, with some studies showing heightened emotional reactivity with restricted sleep and others showing diminished emotional expressiveness, Olia said.

The researchers investigated changes of affective responses to emotional photographs using a 3-week-long in-laboratory model mimicking a pattern of sleep restriction during the work week with recovery sleep on the weekend.

Fourteen healthy adults (7 women) aged 18 to 55 years completed two 25-day stays in the Harvard Catalyst Clinical Research Center. Participants completed a control stay, with an 8-hour sleep opportunity every night, and a sleep restriction stay, with 3 cycles including 5 nights of 4-hour sleep opportunity and 2 nights of 8-hour sleep opportunity.

For emotion testing, participants were presented 30 photographs — 11 positive, 14 neutral, 5 negative — during baseline and day 4 of each week. The pictures are from the International Affective Picture System, a validated database designed to provide a standardized set of pictures for studying emotion and attention that has been widely used in psychological research.

The participants were asked to rate their affective valence (how positive or negative) and emotional intensity (strength of emotion) for each photograph using the self-assessment manikin.

The researchers used a repeated-measures mixed-model analysis to assess the effects of repeated sleep restriction compared with control sleep on ratings of valence and intensity.

There was no significant condition effect on ratings of affective valence.  However, participants reported less intense reactions to photographs throughout the sleep restriction stay compared with the control stay (P < .10 for interaction effect), reaching significance during the third week of sleep restriction (P < .05).

"Sleep restriction led to an overall blunted emotional intensity, and this was primarily seen in response to positive images. It was not seen in response to neutral images or in response to negative images," Olia said.

"The blunting effect was relatively small, about 1 unit on a 7-unit scale, so it's not a huge effect, but it's there and in a very healthy young population," he noted. "We don't know yet what the clinical significance of this is, so future studies will be really important in a larger population."

"Identifying these correlations," Olia added, "are relatively easy, but taking the next step and explaining the neurobiological mechanisms that are driving these correlations will be much more difficult."

Rapidly Evolving Field

Reached for comment, Ana Krieger, MD, medical director of the Center for Sleep Medicine at Weill Cornell Medicine and New York-Presbyterian in New York City, said, "This study is interesting in showing that sleep disruption may dampen positive affect and that may have a modulatory effect on our emotions. It might put us at risk for impaired emotional regulation, which could be in the spectrum of a disorder, like symptoms of depression."

"We don't know what the long term effects are," cautioned Dr Krieger, "but it's definitely concerning because what we are learning is that sleep is part of a whole process and the neurotransmitters that get us to sleep are the same ones that, in one way or another, modulate our cognitive function, our emotions, our state of mind in terms of mood and balance of brain activities."

"The field is rapidly evolving and providing us with a better understanding of all the nuances of sleep and the variability there is in cognitive regulation and neuronal regulation as well," said Dr Krieger. "The bottom line is we do need to learn more about what the differential effects are on the neuronal pathways in people that have disrupted sleep or people that just don't sleep enough. Those are two different dysfunctions."

Shalini Paruthi, MD, spokesperson for the American Academy of Sleep Medicine, noted that "many studies have looked at sleep deprivation and the things that you tend to lose with sleep loss, and mood and emotional regulation are one of the first things to suffer."

"Getting at least 7 hours of sleep, preferably more, and on a regular basis is very important for everyone," said Dr Paruthi, co-director of the Sleep Medicine and Research Center at St. Luke's Hospital in St. Louis, Missouri.

The study was supported by grants from the National Institutes of Health and the National Center for Research Resources to the Harvard Clinical and Translational Science Center. The authors, Dr Paruthi, and Dr Krieger have disclosed no relevant financial relationships.

SLEEP 2017: 31st Annual Meeting of the Associated Professional Sleep Societies. Abstract LBA-1. Presented June 5, 2017.

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