Daytime napping is associated with retinal microcirculation: a large population-based study in China

Abstract

Study Objectives To investigate the association between daytime napping and retinal microcirculation. Methods This is a cross-sectional study from a prospective population-based cohort. 2,662 participants were recruited after quota sampling. Information on napping was collected through face-to-face interviews. Retinal vascular calibers (RVCs), including central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arterio-to-venous ratio (AVR), were obtained from fundus photography. Multivariate regression and restricted cubic spline curve were performed to determine the association between RVCs and daytime napping duration. Results 56.4% participants reported daytime napping regularly. Compared to no nap, daytime nap was related to higher CRAE, with nap duration of 0.5–1 h showing the most significant association. 0.5–1 h daytime nappers displayed an average of 4.18 µm (95% confidence interval [CI] 2.45–5.91, p < 0.001) wider CRAE than non-nappers after adjustment. No significant association was found between CRVE and daytime napping. Moreover, individuals with 0.5–1 h daytime napping had a lower risk for AVR reduction (odds ratio [OR] 0.70, 95% confidence interval [CI] 0.56–0.86, p = 0.001) than non-nappers. Similar association persisted in non-hypertensive population. Restricted cubic spline indicated a J-shaped relationship between AVR reduction and nap duration. Conclusion Retinal microcirculation was positively associated with self-reported 0.5–1 h daytime napping. Better indicators of retinal microcirculation were probably related to nap duration in a J-shaped manner. Also, the possibly beneficial role of 0.5–1 h daytime napping on retinal microcirculation might be independent of clinically diagnosed vascular diseases.

Daytime napping, comorbidity profiles, and the risk of sarcopenia in older individuals

“…The inflammation, oxidative stress, and microvascular impairment were three crucial pathophysiological causes of developing sarcopenia ( Cruz-Jentoft and Sayer, 2019 ). The current studies suggested that optimal daytime napping can lead to stress-release effects secondary to sleep deprivation, decline immuno-inflammatory effects consecutive to sleep restriction, and ameliorate microvascular health ( Faraut et al, 2017 ; Liu et al, 2022 ). These changes, secondary to optimal daytime napping, potentially reverse the pathophysiological causes of developing sarcopenia.…”

“…We found that daytime napping <30 min or ≥120 min were associated with the increased risk of sarcopenia compared with 60 min. The beneficial effects of daytime napping on health conditions were presumed to have the correlation with sleep architecture and usually took place in nonrapid eye-movement (NREM) sleep dominated by parasympathetic activity ( Liu et al, 2022 ). When napping duration is more than 60 min, individuals may have rapid eye-movement sleep dominated by sympathetic activity.…”

“…When napping duration is more than 60 min, individuals may have rapid eye-movement sleep dominated by sympathetic activity. Slow-wave sleep in NREM sleep (mainly including stages 3 and 4 of sleep) can inhibit hypothalamic–pituitary adrenal axis and decrease cortisol release and catecholamine production caused by sympathetic activity ( Liu et al, 2022 ). Sleep architecture is usually in stages 1 and 2 of sleep for individuals who napped for <30 min, which has no significant benefit for health conditions due to the absence of slow-wave sleep.…”