Chronic insomnia disorder (INS) is a condition that affects many individuals, particularly older adults and females. This study, published in the journal Sleep, investigates the effects of sex and chronic insomnia on neurophysiological markers of sleep quality, specifically sleep spindles and slow-wave activity (SWA). Understanding these differences is crucial, as they may explain the higher prevalence of insomnia in females.
Study Objectives
The primary aim of the research was to examine how sex and chronic insomnia disorder influence spindle and SWA beyond the effects of aging. The researchers sought to uncover the mechanistic differences that contribute to the increased vulnerability to insomnia in females.
Materials and Methods
The study involved 222 adults aged 18 to 82, including 119 individuals diagnosed with chronic insomnia disorder (71% female) and 103 healthy sleepers (61% female). After a habituation night, participants underwent one night of sleep assessment using polysomnography. Key metrics such as spindle density, slow oscillation (SO) density, relative sigma power, and SWA were analyzed during NREM sleep.
Results
The findings revealed that age, chronic insomnia disorder, and sex each uniquely contributed to NREM oscillatory activity. Specifically, chronic insomnia disorder was associated with a reduction in spindle and SO density, while sex differences accounted for variations in SWA. Notably, SWA was generally higher in females, but this difference was not statistically significant within the insomnia or healthy sleeper groups.
Moreover, female participants with chronic insomnia disorder reported the highest levels of insomnia severity and exhibited lower sigma power compared to their male counterparts. Deficits in spindle and SO density were also observed in female INS relative to female healthy sleepers, as well as in male INS compared to male healthy sleepers.
Conclusions
The study concludes that the combination of reduced sigma power in females with chronic insomnia disorder, along with lower spindle and SO density compared to female healthy sleepers, may contribute to greater insomnia severity in females. These findings highlight the importance of considering sex differences in the assessment and treatment of insomnia.
What this study does not show
This study does not establish a causal relationship between the observed neurophysiological markers and insomnia severity, nor does it provide insights into potential treatment options based on these findings.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Not established
- Clinical utility: Not established