Exogenous supplementation of melatonin, one of the key hormones governing circadian rhythm, is indicated for treatment of circadian rhythm sleep disorders¹ and, despite insufficient evidence,² is widely used as an over-the-counter sleep aid. Evidence of antioxidant and anti-inflammatory properties of melatonin³ has prompted investigation of its therapeutic value in multiple diseases.⁴ Although melatonin is generally regarded as safe, adverse effects have been reported, and data on long-term use and high-dose use are scarce.⁵ The heterogeneity in over-the-counter formulations⁶ further supports the need for a broader understanding of consumption of exogenous melatonin in the population.

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder, characterized by recurrent upper airway obstruction during sleep, resulting in intermittent hypoxia, increased sympathetic activation, and sleep deficiency. Over the past 2 decades, there has been a robust body of evidence to support a strong link between OSA and cardiometabolic diseases. Obesity is an important risk factor for OSA. Observational studies indicate that OSA is a strong risk factor for the development of hypertension and diabetes. Moreover, clinical and experimental studies support a causal role of OSA in hypertension and impairments in glucose metabolism, beyond excess weight. Notably, OSA is particularly underdiagnosed and undertreated in women, which may heighten the cardiometabolic risk. OSA is often overlooked during pregnancy and has been linked to adverse cardiometabolic outcomes in observational studies. In randomized clinical trials, treatment of OSA with continuous positive airway pressure reduces blood pressure in individuals with hypertension, but the beneficial effects of continuous positive airway pressure on glycemic outcomes are less convincing. Inconsistent cardiometabolic response to OSA treatment can be partly explained by failure to consider heterogeneity in OSA and variable continuous positive airway pressure adherence among diverse populations. In this review, we summarize the relationships between OSA and cardiometabolic conditions with a particular focus on obesity, hypertension, and diabetes. We review the current knowledge on the heterogeneity in OSA and discuss potential underlying mechanisms for impairments in blood pressure and glucose metabolism in OSA. We also provide a clinical perspective for OSA management considering current research gaps and emerging approaches for the prevention and treatment of cardiometabolic disease.

Sleep apnea is very common in patients with cardiovascular disease, especially in patients with hypertension. Over the last few decades a number of discoveries have helped support a causal relationship between the two and even resistant hypertension. The role neurogenic mechanisms play has gathered more attention in the recent past due to their immediate bedside utility. Several innovative discoveries in pathogenesis including those exploring the role of baroreflex gain, cardiovascular variability, chemoreceptor reflex activation and the sympathetic nervous system have emerged. In this review, we discuss the epidemiology of sleep apnea and hypertension and the pathogenic mechanisms contributing to neurogenic hypertension. Furthermore, recent management strategies in addition to continuous positive airway pressure (CPAP), such as upper airway stimulation and renal denervation that target these pathogenic mechanisms, are also discussed.

Background: Rest-activity rhythm (RAR), a manifestation of circadian rhythms, has been associated with morbidity and mortality risk. However, RAR patterns in the general population and specifically the role of demographic characteristics in RAR pattern have not been comprehensively assessed. Therefore, we aimed to describe RAR patterns among non-institutionalized US adults and age, sex, and race/ethnicity variation using accelerometry data from a nationally representative population. Methods: This cross-sectional study was conducted using the US National Health and Nutrition Examination Survey (NHANES) 2011–2014. Participants aged ≥20 years who were enrolled in the physical activity monitoring examination and had at least four 24-h periods of valid wrist accelerometer data were included in the present analysis. 24-h RAR metrics were generated using both extended cosinor model (amplitude, mesor, acrophase and pseudo-F statistic) and nonparametric methods (interdaily stability [IS] and intradaily variability [IV]). Multivariable linear regression was used to assess the association between RAR and age, sex, and race/ethnicity. Results: Eight thousand two hundred participants (mean [SE] age, 49.1 [0.5] years) were included, of whom 52.2% were women and 67.3% Whites. Women had higher RAR amplitude and mesor, and also more robust (pseudo-F statistic), more stable (higher IS) and less fragmented (lower IV) RAR (all P_trend < 0.001) than men. Compared with younger adults (20–39 years), older adults (≥ 60 years) exhibited reduced RAR amplitude and mesor, but more stable and less fragmented RAR, and also reached their peak activity earlier (advanced acrophase) (all P_trend < 0.001). Relative to other racial/ethnic groups, Hispanics had the highest amplitude and mesor level, and most stable (highest IS) and least fragmented (lowest IV) RAR pattern (P_trend < 0.001). Conversely, non-Hispanic blacks had the lowest peak activity level (lowest amplitude) and least stable (lowest IS) RAR pattern (all P_trend < 0.001). Conclusions: In the general adult population, RAR patterns vary significantly according to sex, age and race/ethnicity. These results may reflect demographic-dependent differences in intrinsic circadian rhythms and may have important implications for understanding racial, ethnic, sex and other disparities in morbidity and mortality risk.