CHARLOTTE, N.C. – , preliminary findings from a pilot study of objective and subjective cognitive measures have shown.
The pilot study underscored the important role of objective sleep measures to better understand discrepancies when patients’ own reports of everyday cognitive function don’t align with objective cognitive profiles, Amy Costa, MA, a graduate student in psychology at the University of Missouri-Columbia, said in reporting the results at the annual meeting of the Associated Professional Sleep Societies.
Amy Costa
“Between our previously published paper and these new pilot results, we’re reporting evidence that suggests sleep is playing a role between the objective and subjective cognition relationship,” Ms. Costa said in an interview. “It is possible that these older adults who are sleeping poorly may be worse at understanding how well they’re doing cognitively. That’s really important for doctors. For example, if we can’t diagnose someone with mild cognitive impairment or Alzheimer’s disease or other types of dementia earlier, then we can’t intervene as quickly.”
Sleep efficiency, cognition, and patient complaints
These findings are in agreement with those Ms. Costa and colleagues recently published in the Journal of Clinical Sleep Medicine, she said.
The current pilot study included 35 older adults with an average age of 69 years who had insomnia complaints. They completed one night of home-based polysomnography – specifically with the Sleep Profiler PSG2TM – and a battery of cognitive tests. Their average sleep deficiency was 57%, “indicating potentially pretty severe insomnia,” Ms. Costa said.
“We found that sleep efficiency – that is the percentage of time spent sleeping while in bed – moderated the association between self reports and objective measures of cognitive distractibility,” Ms. Costa said in reporting the results. “In other words, our findings suggest that individuals with lower sleep efficiency who are performing the worst cognitively have the least amount of complaints. Basically, this can be thought of as that they are overestimating their cognitive performance.”
Sleep stage versus working memory and distractibility
The pilot study also focused on how the percentage of lighter-stage sleep, or N1 sleep, moderated the associations between working memory, as measured by Sternberg performance, and memory, distractibility, and blunders measured with the Cognitive Failures Questionnaire.
At the highest percentage of N1 sleep, worse working memory was associated with fewer complaints about memory, distractibility, and blunders, Ms. Costa said.
“The percentage of lighter-stage N1 sleep and sleep efficiency moderated the association between cognitive flexibility and distractibility,” Ms. Costa said. At the lowest percentage of N1 sleep, worse cognitive flexibility was associated with more distractibility, while at the highest percentage of N1 sleep worse cognitive flexibility showed a reverse effect; it was linked to less distractibility. The lowest percentage of sleep efficiency showed an association between worse cognitive flexibility and less distractibility, but the highest percentage of SE showed an association between worse cognitive flexibility and more distractibility.
“So in terms of evaluating their cognitive performance, the worse working memory was associated with more blunder complaints in individuals with the lowest percentage of N1,” she said. “So whenever individuals were spending less time in N1, they were able to better recognized their cognitive ability.”
She added, “Overall, more light and more fragmented sleep moderated the association between worse objective and less cognitive complaints, suggesting that these individuals might be overestimating their cognitive abilities.”
The findings indicate that evaluation of objective sleep should consider objectively measured N1 and sleep efficiency to better understand when subjective cognitive complaints and neurophysiological/objective cognitive profiles don’t align, she said.