Specific insomnia symptoms impact cognition later in life

Difficulty starting sleep had the greatest impact on cognition later in life compared with other symptoms of insomnia, according to study findings from nearly 2,500 patients presented at the virtual SLEEP 2021 meeting.

Researchers first published the findings in Sleep, the journal of the Sleep Research Society, and presented recently at the society’s annual meeting, which is being held virtually.

“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,” Afsara Zaheed, a clinical science graduate student in the department of psychology at the University of Michigan, said in a press release. “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.”

Zaheed and colleagues examined which specific insomnia symptoms indicated performance in five cognitive domains 14 years later and whether depressive symptoms and/or vascular diseases mediated these relationships. The study included 2,496 adults aged 51 years and older in the Health and Retirement Study. Participants first reported insomnia symptoms in 2002 — which the researchers classified as study baseline — with four self-reported items about how often the patients had difficulty falling asleep, nighttime waking, early waking and feeling rested after waking. The researchers evaluated cognition in 2016 as part of the Harmonized Cognitive Assessment Protocol and operationalized with five factor scores on episodic memory, executive function, language, visuoconstruction and processing speed.

Multiple regressions controlled for sociodemographic factors and baseline global cognitive performance. The researchers also tested whether observed relationships were explained by self-reported depressive symptoms and/or vascular diseases, such as hypertension, heart disease, diabetes and/or stroke in 2014, accounting for baseline values.

The researchers found that only difficulty falling asleep in 2002 correlated with cognition in 2016. Zaheed and colleagues reported that more frequent difficulty with falling asleep predicted worse episodic memory, executive function, language and processing speed performance, but not visuoconstruction. They also found that these relationships were mediated by depressive symptoms and vascular diseases in 2014 for all areas except for episodic memory. Only depressive symptoms influenced the association with memory, according to the study results.

After accounting for these mediating factors, Zaheed and colleagues found that the direct impact of difficulty with falling asleep persisted for episodic memory, executive function and language but not processing speed.

“These results are important given the lack of currently available treatments for late-life cognitive disorders, like Alzheimer’s disease and other dementias,” Zaheed said in the press release. “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.”

Reference:

SLEEP 2021. Having trouble falling asleep predicts cognitive impairment in later life. Available at: https://www.sleepmeeting.org/having-trouble-falling-asleep-predicts-cognitive-impairment-later-life/. Accessed June 10, 2021.