Impacts of serum vitamin D levels on sleep and daytime sleepiness according to working conditions

The role of interaction between vitamin D and VDR FokI gene polymorphism (rs2228570) in sleep quality of adults

To evaluate association of vitamin D with sleep quality in adults and the influence of VDR-gene polymorphism FokI (rs2228570;A > G). Cross-sectional population-based study in adults, conducted in Brazil. The outcome was sleep-quality, evaluated by the Pittsburgh Sleep Quality Index. Vitamin D was determined by indirect electrochemiluminescence and classified as deficiency (VDD), 25(OH)D < 20 ng/mL in a healthy population or 25(OH)D < 30 ng/mL for groups at risk for VDD. FokI polymorphism in the VDR-gene was genotyped by qPCR and classified as homozygous wild (FF or AA), heterozygous (Ff or AG), or homozygous mutant (ff or GG). Multivariate logistic analysis was used to estimate the association between vitamin D and FokI polymorphism with sleep-quality. In a total of 1674 individuals evaluated, 53.6% had poor-sleep-quality, 31.5% had VDD, and the genotype frequency of the FokI polymorphism was 9.9% FF, 44.6% Ff, and 45.5% ff. In multivariate analysis, individuals with VDD had 1.51 times the chance of poor-sleep-quality, and individuals with the ff genotype had 1.49 times the chance of poor-sleep-quality (OR:1.49;95%CI:1.05-2.12) when compared to individuals with the FF or Ff genotype. In the combined analysis, individuals with VDD and ff genotype had more chance of poor-sleep-quality than individuals with sufficient vitamin D and genotype Ff or FF (OR:2.19;95%CI:1.27-3.76). Our data suggest that VDD and VDR FokI gene polymorphism are associated with poor-sleep-quality, and combining the two factors increases the chance of poor-sleep-quality compared to separate groups.

Serum Calcium and Magnesium Levels, Not 25-Hydroxyvitamin D, Are Associated With Sleep Quality in Airline Pilots

INTRODUCTION

Despite the vulnerability of airline pilots (APs) to sleep disturbances, the biological underpinnings responsible for this phenomenon are still not entirely elucidated. However, there is an increasing amount of evidence indicating an association between 25-hydroxyvitamin D, Ca2+, and Mg2+ levels and sleep health. In this cross-sectional study, we sought to examine the potential associations between serum levels of these biomarkers and the occurrence of poor sleep among APs.

METHODS

 We examined a convenience sample of 100 male APs who underwent the Pittsburgh Sleep Quality Index (PSQI) to assess their sleep quality. Those who scored 5 or higher on the PSQI were labeled as poor sleepers. Serum levels of 25-hydroxyvitamin D, Ca2+, and Mg2+ were quantified in all participants.

RESULTS

 Out of the 100 APs, 58 (58%) and 42 (42%) were classified as good and poor sleepers, respectively, based on the PSQI scores. We defined vitamin D deficiency as serum 25-hydroxyvitamin D levels below 10 ng/mL and insufficiency as levels ranging from 10 to 30 ng/mL. The results revealed no significant differences in serum levels of 25-hydroxyvitamin D between the two groups, and there was no evidence of vitamin D deficiency or insufficiency. However, poor sleepers exhibited significantly lower levels of both Mg2+ (1.8 ± 0.1 mg/dL versus2.0 ± 0.1 mg/dL, respectively) and Ca2+ (8.5 ± 0.4 mg/dL versus9.1 ± 0.5 mg/dL, respectively) compared to good sleepers (P < 0.001 for both). Logistic regression analysis identified both Mg2+ and Ca2+ as independent biomarkers associated with poor sleep quality in APs (P < 0.001 for both).

CONCLUSION

Lower serum concentrations of Mg2+ and Ca2+, not 25-hydroxyvitamin D, may be associated with poor sleep in APs.

Association between diet, mental health and sleep quality in university students during the COVID-19 pandemic: a systematic review

OBJECTIVES

To evaluate recently published scientific evidence and synthesize the results of observational studies that examine the association between diet, mental health, and sleep quality in university students during the COVID-19 pandemic.

CONTENT

An electronic search of scientific literature published in 2021 and up to 2 years ago was performed using keyword search, with focus on observational studies published in PubMed, MEDLINE and Web of Science. It included: active university students of both sexes during the COVID-19 pandemic.

SUMMARY AND OUTLOOK

The 5 studies included in this review showed that there have been significant changes in both mental health and eating habits during the COVID-19 pandemic. The conclusion, there is an association between mental health and sleep quality in university students, resulting in an alteration of sleep hours and poor sleep. Furthermore, an association between mental health and diet quality is also observed, producing an increase in caloric intake or in the number of meals during the day.

Severe Vitamin D Deficiency-A Possible Cause of Resistance to Treatment in Psychiatric Pathology

In the last few years, vitamin D functions have been studied progressively, and along with their main role in regulating calcium homeostasis, the potential function in the nervous system and the link between different psychiatric disorders and vitamin D deficiency have been revealed. The discovery of vitamin D receptors in multiple brain structures, like the hippocampus, led to the hypothesis that vitamin D deficiency could be responsible for treatment resistance in psychiatric diseases. The aim of this study was to analyze the current knowledge in the literature regarding vitamin D deficiency among individuals afflicted with psychiatric disorders and assess the potential therapeutic benefits of vitamin D supplementation. A systematic search was conducted on the PubMed database for articles published in the last five years (2016-2022) in English, focusing on human subjects. Results show that vitamin D deficiency has implications for numerous psychiatric disorders, affecting mood and behavior through its influence on neurotransmitter release, neurotrophic factors, and neuroprotection. It also plays a role in modulating inflammation, which is often elevated in psychiatric disorders. In conclusion, vitamin D deficiency is prevalent and has far-reaching implications for mental health. This review underscores the importance of exploring the therapeutic potential of vitamin D supplementation in individuals with psychiatric disorders and highlights the need for further research in this complex field.

Attenuation of homeostatic sleep response and rest-activity circadian rhythm in vitamin D deficient mice

The link between vitamin D deficiency (VDD) and sleep disturbances has long been suggested. However, the direct causality between VDD, sleep disturbances, and circadian rhythm remains unclear. We aimed to characterize sleep-wake behavior and circadian rhythms in an animal model of VDD. VDD was induced by feeding vitamin D-deficient chow, and we analyzed sleep and circadian rhythm parameters. During light period, VDD mice exhibited reduced wake with more frequent wake bouts and increased NREM sleep time. However, during dark period, the wake EEG power spectrum peaked at theta band frequency, and slow-wave energy was suppressed in mice with VDD. Rest-activity analyses revealed increased circadian period, lower wheel counts, and more frequent and short activity bouts during VDD. Combining sleep and circadian data, we found significantly suppressed activities during the hours with a wake duration shorter than 30 minutes. Moreover, mice in VDD state exhibited a negative correlation between wake theta power and hourly wheel-running counts during dark period. Our data point to a direct link between VDD and disturbances in sleep and rest-activity circadian rhythm, featuring frequent wake bouts during the sleeping phase, reduced sleep pressure build-up in dark period, and reduced activity levels due to increased susceptibility to sleepiness.

Vitamin D status, sleep patterns, genetic susceptibility, and the risk of incident adult-onset asthma: a large prospective cohort study

Introduction

Vitamin D has been known to be associated with asthma, particularly in children, while the evidence among adults is limited and inconclusive. This study aimed to investigate the association between serum, vitamin D concentrations, and the incidence of adult-onset asthma and also the modified effect caused by sleep patterns and genetic risks.

Methods

A prospective cohort study with 307,872 participants aged between 37 and 73 years was conducted based on the UK Biobank, with a median follow-up of 12 years. The Cox proportional hazard model was applied to evaluate the association between vitamin D status and incident adult-onset asthma, and the modified effect was investigated by conducting stratified analysis according to sleep pattern score and genetic risk score, and subgroup analyses were performed by sex, age, BMI, and smoking status as well.

Results

Individuals with optimal vitamin D concentration were associated with 11.1% reduced risk of incident asthma compared to those participants with deficient vitamin D (HR = 0.889; 95% CI: 0.820-0.964; p = 0.005). Moreover, stratification analysis demonstrated that the protective effect of vitamin D on asthma risk was modified by sleep patterns or genetic susceptibility, with the strongest protective effect being observed in the subpopulation with a moderate sleep pattern (HR = 0.883; 95% CI: 0.797-0.977; p = 0.016) and a moderate genetic risk (HR = 0.817; 95% CI: 0.711-0.938; p = 0.004). In subgroup analyses, the protective effect of optimal vitamin D levels was only significant among men, individuals younger than 60 years of age, overweight individuals, and current or previous smokers.

Conclusion

Increased serum vitamin D levels were associated with a lower risk of incident adult-onset asthma, and this association was modified by sleep patterns and genetic predisposition to some extent.

Influence of sunlight on the association between 25-hydroxyvitamin D levels and sleep quality in Brazilian adults: A population-based study

OBJECTIVES

This study aimed to evaluate the association of vitamin D with sleep quality during the COVID-19 pandemic and the influence of daily sunlight on this association.

METHODS

This cross-sectional, population-based study among adults stratified by multistage probability cluster sampling was conducted from October to December 2020 in the Iron Quadrangle region of Brazil. The outcome was sleep quality, evaluated by the Pittsburgh Sleep Quality Index. Vitamin D (25-hydroxyvitamin D) concentrations were determined by indirect electrochemiluminescence and a deficiency was classified as 25(OH)D < 20 ng/mL. To assess sunlight, the average daily sunlight exposure was calculated and was classified as insufficient when less than 30 min/d. Multivariate logistic analysis was used to estimate the association between vitamin D and sleep quality. A directed acyclic graph was used to select minimal and sufficient sets of adjustment variables for confounding from the backdoor criterion.

RESULTS

In a total of 1709 individuals evaluated, the prevalence of vitamin D deficiency was 19.8% (95% CI, 15.5-24.9%), and the prevalence of poor sleep quality was 52.5% (95% CI, 48.6-56.4%). In multivariate analysis, vitamin D was not associated with poor sleep quality in individuals with sufficient sunlight. Moreover, in individuals with insufficient sunlight, vitamin D deficiency was associated with poor sleep quality (odds ratio [OR], 2.02; 95% CI, 1.10-3.71). Furthermore, each 1-ng/mL increase in vitamin D levels reduced the chance of poor sleep quality by 4.2% (OR, 0.96; 95% CI, 0.92-0.99).

CONCLUSIONS

Vitamin D deficiency was associated with poor sleep quality in individuals with insufficient exposure to sunlight.

Shift Work and Serum Vitamin D Levels: A Systematic Review and Meta-Analysis

Vitamin D deficiency and insufficiency are highly prevalent conditions worldwide due to several factors, including poor sun exposure. Shift workers may be exposed to the risk of hypovitaminosis D due to fewer opportunities for sunlight exposure compared to day workers. A systematic review of the PubMed, SCOPUS, and EMBASE databases was conducted according to the Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) statement to investigate the effect of shift work on vitamin D levels. Mean differences (MD) and 95% confidence intervals (CI) of serum 25-OH-D levels in shift workers and non-shift workers were calculated. A total of 13 cross-sectional studies were included in the meta-analysis. We found significantly lower levels of serum 25-OH-D in shift workers compared with non-shift workers (MD: −1.85, 95% CI [−2.49 to −1.21]). Heterogeneity among included studies was high (I2 = 89%, p < 0.0001), and neither subgroup analysis nor meta-regression were able to identify specific sources of the heterogeneity that may be related to the different characteristics of shift work among studies. The monitoring of serum vitamin D levels and prompt correction of any deficiencies should be considered in shift workers. Notably, since a large part of the observations are derived from Koreans, larger epidemiological studies are needed in other populations.

Lower Serum Calcium Levels Associated with Disrupted Sleep and Rest–Activity Rhythm in Shift Workers

Vitamin D deficiency is prevalent in many developed countries, and several studies suggest that vitamin D plays an essential role in brain function. A recent study showed that vitamin D deficiency was closely associated with daytime sleepiness and shorter sleep time. The relationshipbetween vitamin D levels and calcium levels is well established, and calcium level regulates slow-wave sleep generation. It is conceivable that the sleep disturbance in vitamin D deficiency may be due to an altered calcium level. Nonetheless, calcium levels, sleep disturbances, and activity rhythms have not been investigated directly. Therefore, we hypothesized that calcium and vitamin D levels might be important in regulating sleep and activity rhythm, and we analyzed the correlation with calcium levels by actigraphy analysis. Interestingly, a negative correlation was found between calcium level and sleep latency, total sleep time, use of sleep medicine, and daytime dysfunction among shift workers. In contrast, non-shift workers showed a negative correlation between the calcium level and the circadian phase. These findings suggest that low serum calcium levels may disrupt sleep–wake control and rest–activity rhythm, even if they are within the normal range.

The Association of Sleep Quality and Vitamin D Levels in Hemodialysis Patients

Background

To date, hemodialysis (HD) is the most common therapy for chronic kidney disease (CKD) patients. However, it causes different complications such as sleep disorders. Sleep regulation is connected to vitamin D; hence, its deficiency might influence the quality and duration of sleep. This study is aimed at evaluating the correlation of sleep quality and vitamin D levels in 80 HD patients.

Methods

This cross-sectional study was performed on 80 hemodialysis patients admitted to 29 Bahman hospitals in Tabriz, Iran. Before beginning of dialysis, serum 25 (OH) D levels were assessed among patients and the sleep patterns and sleep quality of patients were accurately calculated by the Pittsburgh sleep quality index (PSQI) standard questionnaire.

Results

Our results showed that 22 HD patients (27.5%) had severe sleep disorders. In addition, it was found that serum levels of vitamin D had significant correlation with sleep quality (r = −0.341, p = 0.002) in general, even after adjusting confounding factors such as calcium (Ca), phosphate (P), and parathyroid hormone (PTH) level. In poor sleepers (PSQI ≤ 5), a negative correlation was observed between the levels of vitamin D and PSQI score (r = −0.397, p = 0.004). PSQI scores in the normal range of PTH (r = −0.377, p = 0.006) and in >600 pg/ml of PTH (r = −0.675, p = 0.011) had a correlation with vitamin D levels. The level of vitamin D was the single independent predictor of sleep efficiency (β coefficient = −0.386, p = 0.001).

Conclusion

The present project reported that the positive effect of vitamin D is associated with sleep disorder in HD patients. In future studies, normal levels of Ca and P should be considered along with normal vitamin D levels among the included patients.

Vitamin D and sleep duration: Is there a bidirectional relationship?

Vitamin D contributes to numerous physiological processes within the body but primarily calcium and bone homeostasis. Emerging evidence highlights a novel role for vitamin D in maintaining and regulating optimal sleep. Sleep is a known regulator of bone health, highlighting the interconnectedness between vitamin D concentrations, sleep duration and bone metabolism. It is possible that the relationship between sleep length and vitamin D is bidirectional, with vitamin D playing a role in sleep health and conversely, sleep affecting vitamin D levels. Nevertheless, limited information on the direction of the interaction is available, and much remains to be learned concerning the complex relationship between insufficient sleep duration and vitamin D deficiency. Given the potential to implement interventions to improve sleep and vitamin D supplementation, understanding this relationship further could represent a novel way to support and improve health.

Assessment of vitamin D, exercise, and lipid profile associated with excessive daytime sleepiness in school children

Previous research reported associations of excessive daytime sleepiness (EDS) with a low vitamin D level, obesity, and sexual maturity. The aim of this study was to identify the association and rank the importance of these with EDS. This study examined 618 children who were 10-12 year-old. The pediatric daytime sleepiness scale (PDSS) was used to evaluate EDS and sleep patterns. EDS was defined as a total PDSS score above 17. We ranked the importance of the relationship of these factors with EDS using random forest analysis. EDS (n = 111, 18%) was positively associated with more advanced pubertal stage in girls, chronic cough, urticaria, and allergic rhinitis. Multivariable analysis with adjustment for confounding indicated that children with low level of 25-hydroxyvitaminD₃ (25(OH)D₃ (<20 ng/mL) and high-density lipoprotein-cholesterol (HDL-C) (<40 mg/dL) levels had an increased risk of EDS (25(OH)D₃:adjusted odds ratio [aOR] = 1.73; 95% confidence interval [CI]: 1.06 to 2.81; P = 0.028; HDL-C: aOR = 2.84; 95% CI: 1.05 to 7.68; P = 0.039). Random forest analysis indicated that 25(OH)D₃ level, exercise, and body mass index (BMI) were over three. This study indicated high levels of 25-(OH)D₃ and HDL-C and performing regular exercise decreased the risk of EDS.