Summary: People who have trouble falling asleep at night are at increased risk of cognitive decline within fourteen years compared to those with other forms of insomnia, a new study reports.
A study of nearly 2,500 adults found that having trouble falling asleep, as compared to other patterns of insomnia, was the main insomnia symptom that predicted cognitive impairment 14 years later.
Results show that having trouble falling asleep in 2002 was associated with cognitive impairment in 2016. Specifically, more frequent trouble falling asleep predicted poorer episodic memory, executive function, language, processing speed, and visuospatial performance.
Further analysis found that associations between sleep initiation and later cognition were partially explained by both depressive symptoms and vascular diseases in 2014 for all domains except episodic memory, which was only partially explained by depressive symptoms.
“While there is growing evidence for a link between insomnia and cognitive impairment in older adults, it has been difficult to interpret the nature of these associations given how differently both insomnia and cognitive impairment can present across individuals,” said lead author Afsara Zaheed, a graduate student in clinical science within the department of psychology at the University of Michigan.
“By investigating associations between specific insomnia complaints and cognition over time using strong measures of cognitive ability, we hoped to gain additional clarity on whether and how these different sleep problems may lead to poor cognitive outcomes.”
Insomnia involves difficulty falling asleep or staying asleep, or regularly waking up earlier than desired, despite allowing enough time in bed for sleep. Daytime symptoms include fatigue or sleepiness; feeling dissatisfied with sleep; having trouble concentrating; feeling depressed, anxious, or irritable; and having low motivation or energy.
The study analyzed data from the Health and Retirement Study, which involved 2,496 adults who were at least 51 years of age.
In 2002 they reported the frequency of experiencing insomnia symptoms. In 2016 the participants’ cognition was assessed as part of the Harmonized Cognitive Assessment Protocol and operationalized with a comprehensive neuropsychological battery tapping episodic memory, executive function, language, visuoconstruction, and processing speed. Analyses controlled for sociodemographics and baseline global cognitive performance.
“These results are important given the lack of currently available treatments for late-life cognitive disorders, like Alzheimer’s disease and other dementias,” said Zaheed.
“Sleep health and sleep behaviors are often modifiable. These results suggest that regular screening for insomnia symptoms may help with tracking and identifying people with trouble falling asleep in mid-to-late life who might be at risk for developing cognitive impairments later in life. Additional intervention research is needed to determine whether intervening on insomnia symptoms can help prevent or slow the progression of cognitive impairments in later life.”
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537 Insomnia Symptoms and Subsequent Cognitive Performance in Older Adults: Are Depressive Symptoms and Vascular Disease Mediators?
Alzheimer’s disease and related dementias (ADRD) are growing public health concerns, and poor sleep may represent a modifiable risk factor. However, there is limited research on insomnia as a predictor of subsequent performance in different cognitive domains and mechanisms that might underlie domain-specific associations. The current study examined: (1) which insomnia symptoms predicted performance across five cognitive domains 14 years later, and (2) whether depressive symptoms and/or vascular diseases mediated these associations.
Participants included 2,496 adults aged 51+ in the Health and Retirement Study. Insomnia symptoms in 2002 (i.e., “baseline”) were quantified by four self-reported items on frequency of trouble falling asleep, nighttime awakenings, early awakenings, and feeling rested upon awakening. Cognition was assessed in 2016 as part of the Harmonized Cognitive Assessment Protocol and operationalized with five factor scores corresponding to episodic memory, executive function, language, visuoconstruction, and processing speed. Multiple regressions examined associations between baseline insomnia symptoms and subsequent cognitive performance, controlling for sociodemographics and baseline global cognitive performance. Mediation models tested whether associations were explained by self-reported depressive symptoms and/or vascular diseases (i.e., hypertension, heart disease, diabetes, and/or stroke) in 2014, controlling for baseline values.
Only trouble falling asleep in 2002 was associated with cognition in 2016. Specifically, more frequent trouble falling asleep predicted poorer episodic memory, executive function, language and processing speed performance, but not visuoconstruction. These associations were mediated by depressive symptoms and vascular diseases in 2014 for all domains except episodic memory; only depressive symptoms mediated the association involving memory. After accounting for these mediators, direct effects of trouble falling asleep remained for episodic memory, executive function and language, but not processing speed.
Difficulty with sleep initiation may be more consequential for later-life cognition than other insomnia symptoms. Depressive symptoms and vascular diseases may partially drive these associations. We speculate that sleep-onset insomnia could mean less total sleep, immune dysfunction, or endocrine effects that worsen mood, vascular health, and cognition. Remaining associations indicate that additional research is needed to characterize other mechanisms through which sleep initiation problems could contribute to later impairments in frontal and temporal cognitive systems, which are implicated early in ADRD.