The association between insomnia and cognitive decline: A scoping review.

OBJECTIVE

This study aimed to investigate the association between insomnia and cognitive decline to provide insights for clinical interventions and future research.

METHODS

The PubMed, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases were systematically searched to identify studies on the association between insomnia and cognitive decline published within the last decade. The quality of the included studies was evaluated, followed by data extraction and summary analysis.

RESULTS

A total of 36 studies were included in the review. Both subjective and objective measures were utilized across 12 indices to assess sleep status, while cognitive function was evaluated using 5 scales and 34 tests. The results revealed a significantly increased risk of cognitive decline or Alzheimer's disease among patients with insomnia, alongside notable impairments in attention, memory, visuospatial abilities, executive function, and verbal memory. Comprehensive assessments of cognitive domains were more sensitive in detecting group differences compared to assessments of specific cognitive sub-functions. Furthermore, MRI analyses showed reduced gray matter volumes in regions such as the prefrontal cortex, cingulate gyrus, temporal lobe, and hippocampus, together with reduced integrity of the white matter in patients with insomnia.

CONCLUSIONS

The findings indicate a potentially bidirectional relationship between insomnia and cognitive decline, suggesting that each may influence and exacerbate the other. Insomnia may increase the risk of cognitive decline and appears to be associated with reduced gray matter volume and compromised white matter integrity in the brain, which could potentially lead to declines in attention, memory, visuospatial abilities, executive function, and verbal memory. Conversely, cognitive decline may contribute to the onset of insomnia, further deteriorating sleep quality. However, further research is necessary to fully comprehend this intricate relationship.