Association between Loss of Sleep-specific Waves and Age, Sleep Efficiency, Body Mass Index, and Apnea-Hypopnea Index in Human N3 Sleep

Abstract

Sleep spindles (SS) and K-complexes (KC) play important roles in human sleep. It has been reported that age, body mass index (BMI), and apnea-hypopnea index (AHI) may influence the number of SS or KC in non-rapid-eye-movement (NREM) 2 (N2) sleep. In this study, we investigated whether the loss of SS or KC is associated with the above factors in NREM 3 (N3) sleep. A total of 152 cases were enrolled from 2013 to 2017. The correlations between the number of SS or KC in N3 sleep and participants' characteristics were analyzed using Spearman rank correlation. Chi-squared test was used to assess the effects of age, sleep efficiency, and BMI on the loss of N3 sleep, N3 spindle and N3 KC. Our results showed that there were negative correlations between the number of SS in N3 sleep with age, BMI, and AHI (P < 0.001), and similar trends were found for KC as well. The loss of SS and KC in N3 sleep was related with age, BMI, and AHI (P < 0.01), as was the loss of N3 sleep (P < 0.01). However, sleep efficiency was not related with the loss of N3 sleep, SS and KC in N3 sleep (P > 0.05). The present study supports that age, BMI, and AHI are all influencing factors of SS and KC loss in human N3 sleep, but sleep efficiency was not an influencing factor in the loss of N3 sleep and the loss of SS and KC in N3 sleep.

Sleep Spindle Characteristics in Obstructive Sleep Apnea Syndrome (OSAS)

“…Next, we also found significant associations between a higher spindle density and a lower AHI in N3, and between a longer spindle duration and a lower AHI in N2. Similarly, Li et al (36) reported a significant association between a higher number of sleep spindle in N3 and a lower AHI, independently of sleep efficiency. Likewise, Madaeva et al (40) reported significant associations between more favorable spindle characteristics and a lower AHI, a higher SaO2, and a lower total arousal index.…”

“…As regards sleep stages, studies reported significant differences in sleep spindle characteristics between individuals with and without OSAS during all NREM stages but not during REM (33,35,36). Himanen et al (37) observed an increased spindle frequency at the end of the night among healthy controls, but not among individuals with OSAS.…”

The association between obstructive sleep apnea and sleep spindles in middle-aged and older men: a community-based cohort study

“…Previous small studies consistently reported decreased overall spindle density (11)(12)(13)(14)(15)(16) Hz, number/min), frontal slow spindle density (11)(12)(13) Hz, number/min), centroparietal fast spindle density (13)(14)(15)(16) Hz, number/min), and overall spindle frequency in clinical samples of patients with OSA compared to age-or gender-matched controls [4,[10][11][12]. Some evidence also suggests spindle abnormalities partly improve with OSA therapy [12,13].…”

“…Spindle frequency (Hz), amplitude (µV 2 ), overall density (11)(12)(13)(14)(15)(16), slow density (11)(12)(13), and fast density (13-16 Hz) (number of spindle events/artifact-free sleep minutes) were calculated for N2 and N3 sleep. Frequency was calculated as the average number of spindle cycles per second, whereas amplitude was calculated by measuring from the base to the maximum height of the spindle.…”

“…Some evidence also suggests spindle abnormalities partly improve with OSA therapy [12,13]. Furthermore, several small studies showed associations of a greater number of obstructive breathing episodes with reduced spindle deceleration and decreased spindle density [14][15][16].…”