Insomnia Symptoms Associated with Self-Reported & Objective Cognition Scores

Amy Costa

Insomnia among older patients may indicate risk of worsened cognition—both objectively and self-reported, according to findings from a new study.

In data from a new analysis, a team of investigators from the University of Missouri reported that insomnia symptoms impact the relationship between clinically-observed and self-reported cognition. More intricately, poor sleep health was associated with lesser ratings for both objective and self-observed cognition.

Investigators led by Amy N. Costa, a PhD student in the department of psychological services at Missouri, sought to assess the interactive links between objective cognitive domains including processing and attention/processing speed, verbal episode memory and inductive reasoning and subjective sleep characteristics with self-reported cognition among older adults with insomnia.

It’s previously established that individuals with insomnia are at increased risk of cognitive impairment—with evidence supporting but not proving the theory that sleep fragmentation may influence “the discrepant relationship between objective and subjective cognition.”

“An additional goal of the study was to understand what specific cognitive domains were associated with self-reported cognition,” investigators wrote. “We hypothesized worse sleep would interact with objective cognitive performance in their associations with self-reported cognitive ratings, given previous findings in middle-aged and older adults without insomnia.”

Costa and colleagues recruited patients from a larger randomized, controlled trial examining the effects of a behavioral therapy for insomnia in older adult patients. They used patient data from 14 days of baseline prior to the 4-week intervention analysis. Eligible patients for their assessment were ≥65 years old, having met criteria for insomnia, and no reported use of prescription nor over-the-counter sleep medication for ≥1 month.

The investigators analyzed patients’ baseline daily sleep diaries, which included self-reported measures of total sleep time (TST), sleep onset latency (SOL), wake after sleep onset (WASO), and sleep efficiency. They additionally observed patients’ recorded cognition ratings on a 0-100 scale (with “100” indicating very good cognition), as well as daily cognitive task scores for letter series (indicating reasoning), word list delayed recall (indicating verbal memory), the Symbol Digit Modalities Test (SDMT; indicating attention/processing speed) and number copy (indicating processing speed).

They determined independent and interactive associations between average objective cognition or sleep and average self-reported cognition through multiple regressions for each cognitive task. Investigators controlled data for age, education and patient depression status.

The assessment included 51 paitents. Mean patient age was 68.9 years old; 70.6% were female. Nearly two-thirds (60.8%) reported not using sleep medication. Mean TST sleep scores were 364.25 minutes; mean SOL was 60.49 minutes; mean WASO was 60.49. Mean self-reported cognition scores were 53.76.

Investigators observed an interactive association between SDMT performance and TST with self-reported cognition; insomnia patients with the least TST had a congruent relationship between such scores and self-reported cognition. The team additionally observed an interactive relationship between SDMT, WASO and sleep efficiency scores and self-reported cognition in patients with either average-to-longest WASO or average-to-shortest sleep efficiency.

“The hypothesis that poor sleep would interact with objective cognition in its associations with self-reported cognition was supported, and consistent with prior work showing the moderating impact of sleep on the objective cognition/metacognition relationship,” the team wrote. “However, the direction of this association differed from our prior findings in middle-aged and older adults without insomnia, which showed that the relationship between objective cognition and subjective memory complaints was discrepant.”

Costa and colleagues concluded that insomnia symptoms among older patients may play a pivotal role in the relationship between objective and self-reported cognition. They suggested future analyses look into this association in cognitively impaired older adults with sleep complications.

“Understanding how sleep problems play into the relationship of objective cognition and self-reported cognition will better help clinicians to understand when the relationship converges or diverges,” they concluded.

The study, “Self-reported cognition in older adults with insomnia: Associations with sleep and domain specific cognition,” was published online in Journal of Sleep Research.