Emotional memory fades overnight in patients with obstructive sleep apnea
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Patients with obstructive sleep apnea showed impaired emotional memory after one night of sleep, according to study results published in Annals of the American Thoracic Society.
Further, less time spent in REM sleep, as well as fragmented sleep, are linked to troubles in general memory and accurate memory of emotional images, according to researchers.
“The study brings awareness to addressing mood symptoms frequently comorbid with OSA,” Ina Djonlagic, MD, assistant professor of neurology in the division of sleep medicine at Harvard Medical School, told Healio. “A clinician may find it helpful to point out the effect that OSA can have on emotional memory processing as a means of promoting adherence to treatment.”
In a single-center study, Djonlagic and colleagues analyzed 26 patients (mean age, 42.5 years; 10 women) newly diagnosed with OSA and 24 healthy matched control patients (mean age, 37 years; 13 women) to see if those with OSA experience impaired sleep-dependent memory consolidation, especially in their memory for emotional content.
Prior to their polysomnographically recorded sleep, participants completed the emotional tradeoff task which involved studying 64 encoded scenes on neutral backgrounds, including 32 with negative objects and 32 with neutral objects, for 5 seconds each. Researchers noted an example of a negative object would be a spider, whereas a neutral object example would be a chipmunk.
Researchers then had participants perform a recognition test when they woke up with previously seen and new objects and backgrounds. Thinking about what they looked at before sleeping, participants had to determine if the objects and backgrounds shown separately from one another were the same, similar or new compared with the ones they studied.
In the recognition test, researchers showed 32 same, similar and new objects, all including 16 negative and 16 neutral objects, and 32 same, similar and new backgrounds.
Using these results, memory retention of objects was individually assessed for negative and neutral and in terms of objects and backgrounds.
Results from the retention test showed shortfalls in recognition memory of patients with OSA compared with control patients.
In these patients, the ability to identify the items they saw previously as the same or as similar items, defined as overall recognition, was weakened for all scene elements (negative and neutral objects and scene backgrounds). However, in both the healthy controls and those with OSA, negative components had larger object-background difference in memory compared with neutral components, according to researchers.
“We were surprised to find the emotional trade off effect preserved, which is the ability to remember emotional [negative] scenes at the ‘expense’ of remembering backgrounds,” Djonlagic told Healio. “While OSA patients showed overall worse recognition compared to healthy controls, some elements of emotional processing were preserved, which suggests that there are robust memory systems designed to prioritize emotional memory during sleep which can withstand the deleterious effects of OSA during the consolidation period.”
Looking at specific recognition — or correctly recognizing the same items as the same — researchers found that patients with OSA only showed memory impairment for negative objects.
Both successful overall and specific memory recognition correlated with more rapid eye movement (REM) sleep, and overall recognition additionally correlated with sleep efficiency for both patients with OSA and healthy patients.
“Future OSA treatment trials should include emotional memory processing as one of the outcome measures,” Djonlagic told Healio.
This study by Djonlagic and colleagues contributes to previous literature on the impact REM sleep has on emotional memory and brings attention to the mental health of patients with OSA, according to an accompanying editorial by Andrew W. Varga, MD, PhD, Anna E. Mullins, PhD, and Korey Kam, PhD, of the Mount Sinai Integrative Sleep Center in the division of pulmonary, critical care, and sleep medicine, and Friedman Brain Institute at Icahn School of Medicine at Mount Sinai.
“The potential broader significance of this work relates to interactions between OSA and mental health, as emotional memory likely has relevance to several psychiatric disorders, particularly depression and post-traumatic stress disorder,” Varga, Mullins and Kam wrote. “The seeming importance of metrics of REM sleep toward emotional memory raises questions about the potential importance of REM-predominant OSA, which can be overlooked as clinically unimportant, especially if the overall AHI does not suggest clinically meaningful disease. Notably, individuals with REM-related OSA displayed worse depression and total mood disturbance subscale scores on the [Profile of Mood Scale] than individuals without OSA or even combined non-REM and REM OSA.”
For more information:
Ina Djonlagic, MD, can be reached at idjonlag@bidmc.harvard.edu.