Exploring the link between vitamin D deficiency and obstructive sleep apnea: A comprehensive review.

Despite the high prevalence and significant health burden of obstructive sleep apnea (OSA), its underlying pathophysiology remains incompletely understood. This comprehensive review explores the emerging connection between vitamin D deficiency and OSA, discusses potential mechanisms underlying this association, and explores the therapeutic implications of these findings. Recent research has consistently highlighted the high incidence of vitamin D deficiency among patients with OSA, which often occurs independently of geographical location. This suggests that factors beyond lack of sunlight exposure may be involved. This review also discusses how reduced vitamin D may be associated with more severe manifestations of OSA. In addition, it explores the potentiality of using vitamin D supplements as a therapeutic strategy for OSA, noting that some studies have found improvements in sleep quality and a reduction in OSA severity. Potential mechanisms are proposed, including the role of vitamin D deficiency in promoting inflammation, oxidative stress, hypoxia, impairing immune function, muscle function, and gene polymorphism of vitamin D receptors, all of which could contribute to the pathogenesis of obstructive sleep apnea. The paper underscores the need for future research to validate these observations, to determine optimal vitamin D supplementation dosage and duration, to explore potential side effects and risks, and to investigate potential interactions with other treatments.

FBG wavelength demodulation based on a radio frequency optical true time delay method.

A new fiber Bragg grating (FBG) wavelength shift demodulation method based on optical true time delay microwave phase detection is proposed. We used a microwave photonic link (MPL) to transport a radio frequency (RF) signal over a dispersion compensation fiber (DCF). The wavelength shift of the FBG will cause the time delay change of the optical carrier that propagates in an optical fiber with chromatic dispersion, which will result in the variation of the RF signal phase. A long DCF was adopted to enlarge the RF signal phase variation. An IQ mixer was used to measure the RF phase variation of the RF signal propagating in the MPL, and the wavelength shift of the FBG can be obtained by the measured RF signal phase variation. The experimental results showed that the wavelength shift measurement resolution is 2 pm when the group velocity dispersion of the DCF is 79.5 ps/nm and the frequency of the RF signal is 18 GHz. The demodulation time is as short as 0.1 ms. The measurement resolution can be improved simply by using a higher frequency of the RF signal and a longer DCF or larger chromatic dispersion value of the DCF.