Dear Editor,
We are pleased to address the suggestion of Hui Chen and colleagues that further consideration of circadian rhythms might provide insight into the relationship between obstructive sleep apnea (OSA) and metabolic syndrome (MS) reported in the letter.
The common pathophysiology among metabolic syndrome, obstructive sleep apnea, and hypertension may be the reason for the joint effect observed by our work.1 A key factor in the causal link between OSA with these CVD risk factors may be the abnormal circadian rhythm. We are well aware of that day‐night time autonomic nervous system (ANS) function is closely associated with circadian rhythm in normal subjects and many pathological conditions.2, 3 Considering the importance of ANS for circadian rhythms, we should pay more attention to evaluate the alteration of role of ANS in OSA population. In night time, patients with sleep‐disordered breathing (SDB) may be predisposed to arrhythmias because of alterations in sympathetic and parasympathetic nervous system activity occurring with SDB associated hypoxemia, acidosis, and arousal.4, 5 Autonomic dysfunction in OSA patients may be related not only to the factors above but also to the metabolic condition in OSA, since as some high quality of works reported that the impaired autonomic control may stem from injury to central and peripheral neuron resulting from metabolic damage and in turn the autonomic dysfunction could lead to further metabolic morbidity later in life and even mortality.6, 7, 8 Substantial evidence exists to support the strong associations between ANS dysfunction and hypertension and CVD such as coronary heart disease and mortality.9, 10 Thus, it will be important to gain further insights into the relative contributions of the various sleep measures traditionally collected in nocturnal polysomnography and the metabolic condition in OSA for day‐night circadian rhythms and the underling pathophysiology involved in ANS dysfunction.
DISCLOSURES
None.
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