25-hydroxy vitamin D levels are associated with childhood asthma in a population-based study in Peru

Associations between vitamin D status and biomarkers linked with inflammation in patients with asthma: a systematic review and meta-analysis of interventional and observational studies

BACKGROUND

Numerous studies indicate an association between vitamin D status and inflammatory biomarkers in patients with asthma, but findings are inconsistent. This review aims to summarize the relationship between serum vitamin D status, assessed by 25-hydroxyvitamin D (25(OH)D) level, and inflammatory biomarkers in children and adults with asthma.

METHODS

A literature search of interventional and observational studies on 25(OH)D up to November 2022 was conducted across six electronic databases. Outcomes of interest included a range of inflammatory biomarkers classified in four categories: T helper 2 (Th2) pro-inflammatory, non-Th2 pro-inflammatory, anti-inflammatory, and non-specific biomarkers. Study characteristics were extracted and risk of bias was evaluated using the American Academy of Nutrition and Dietetics tool. Meta-analysis was conducted on studies with a low risk of bias, while narrative reporting was used to present the direction of associations (positive, no association, or negative) for each biomarker, overall and within the low-risk studies.

RESULTS

We included 71 studies (3 interventional, 68 observational) involving asthma patients. These studies investigated the association between serum 25(OH)D and Th2 pro-inflammatory biomarkers (N = 58), non-Th2 pro-inflammatory biomarkers (N = 18), anti-inflammatory biomarkers (N = 16), and non-specific biomarkers (N = 10). Thirteen (18.3%) studies, 50 (70.4%), and 8 (11.3%) were at high, moderate, and low risk of bias, respectively. In all studies, irrespective of risk of bias, the most frequently reported finding was no significant association, followed by a negative association between 25(OH)D and pro-inflammatory biomarkers and a positive association with anti-inflammatory biomarkers. In low-risk studies, one biomarker could be meta-analysed. The pooled estimate for 25(OH)D and serum IgE showed a negative association (β (95% CI)= - 0.33 (-0.65 to - 0.01); I2 = 88%; N = 4 studies). A negative association between 25(OH)D and blood eosinophils was also observed in the largest of three studies, as well as with cathelicidin (LL-37) in the only study reporting it. For other biomarkers, most low-risk studies revealed no significant association with 25(OH)D.

CONCLUSION

Serum 25(OH)D is negatively associated with serum IgE and possibly with blood eosinophils and LL-37, supporting an in vivo immunomodulatory effect of 25(OH)D. Future research should employ rigorous methodologies and standardized reporting for meta-analysis aggregation to further elucidate these associations.

Association between serum 25-hydroxyvitamin D and asthma: Evidence from the National Health and Nutrition Examination Survey (NHANES) 2011-2018

BACKGROUND AND OBJECTIVE

Asthma is a heterogeneous respiratory disease characterized by airway hyper-responsiveness and reversible airflow blockage. There is ongoing debate about the impact of vitamin D on asthma. This research is focused on investigating the correlation between serum levels of 25-hydroxyvitamin D and asthma.

METHODS

This cross-sectional study comprised 22,708 eligible participants. Data on asthma and serum 25-hydroxyvitamin D levels from the National Health and Nutrition Examination Survey (NHANES) 2011-2018 were analyzed. Serum 25-hydroxyvitamin D levels were the main factor, with the presence of asthma as the outcome variable. Weighted logistic regression was utilized to investigate the relationship between serum levels of 25-hydroxyvitamin D and asthma, while accounting for factors such as age, gender, race, length of time in US, annual family income, education level, high-density lipoprotein, low-density lipoprotein, triglycerides, and cholesterol.

RESULTS

Upon adjusting all variables in model III, epi-25-hydroxyvitamin D3 displayed a negative correlation with current asthma at the lower quartile Q1 (0.784, [0.697 to 0.922]), Q2 (0.841, [0.729 to 0.946]), Q3 (0.396, [0.240 to 0.653]) when compared to the highest quartile Q4 level. However, no significant difference was observed between asthma and 25-hydroxyvitamin D2, as well as 25-hydroxyvitamin D3.

CONCLUSIONS

In the U.S. population, elevated levels of epi-25-hydroxyvitamin D3 are correlated with an increased risk of developing existing asthma. However, it is important to interpret this finding carefully given the constraints of cross-sectional studies.

A 12-week double-blind randomised controlled trial investigating the effect of dietary supplementation with 5000 μg/d (125 µg/d) vitamin D in adults with asthma

Vitamin D deficiency has previously been linked to higher rates of exacerbation and reduced lung function in asthmatics. Previous randomised controlled trials investigating the effect of vitamin D supplementation have mainly focused on children with asthma. Trials involving adults have typically used bolus dosing regimens, and the main outcomes have been patient-focused without investigating underlying inflammation. The present study aimed to conduct a 12-week placebo-controlled randomised controlled trials administering a daily 5000 μg (125 µg) vitamin D3 supplement to adults with mild to moderate asthma. A total of 32 participants were randomised to receive either the 5000 μg vitamin D3 supplement or an identical matching placebo. The primary outcome of the study was lung function measured by the ratio of FEV1:FVC (effect size 2·5) with secondary outcomes including asthma symptoms and inflammatory biomarkers. There was a small but statistically significant higher increase in the mean (±sd) ratio of FEV1:FVC from baseline to post-intervention in the vitamin D group (+0·05 ± 0·06) compared with the placebo group (+0·006 ± 0·04, P = 0·04). There was no effect of the intervention on asthma control test scores, or the inflammatory biomarkers measured. There was a moderate, significant association between baseline plasma 25(OH)D concentration and baseline plasma IL-10 (r = 0·527, P = 0·005) and TNF-α (r = −0·498. P = 0·008) concentrations. A daily vitamin D3 supplement led to slightly improved lung function in adult asthmatics and may be a useful adjunct to existing asthma control strategies, particularly for individuals with suboptimal vitamin D status.

Basis of preventive and non-pharmacological interventions in asthma

Asthma is one of the most common atopic disorders in all stages of life. Its etiology is likely due to a complex interaction between genetic, environmental, and lifestyle factors. Due to this, different non-pharmacological interventions can be implemented to reduce or alleviate the symptoms caused by this disease. Thus, the present narrative review aimed to analyze the preventive and non-pharmacological interventions such as physical exercise, physiotherapy, nutritional, ergonutritional, and psychological strategies in asthma treatment. To reach these aims, an extensive narrative review was conducted. The databases used were MedLine (PubMed), Cochrane (Wiley), Embase, PsychINFO, and CinAhl. Asthma is an immune-mediated inflammatory condition characterized by increased responsiveness to bronchoconstrictor stimuli. Different factors have been shown to play an important role in the pathogenesis of asthma, however, the treatments used to reduce its incidence are more controversial. Physical activity is focused on the benefits that aerobic training can provide, while physiotherapy interventions recommend breathing exercises to improve the quality of life of patients. Nutritional interventions are targeted on implement diets that prioritize the consumption of fruits and vegetables and supplementation with antioxidants. Psychological interventions have been proposed as an essential non-pharmacological tool to reduce the emotional problems associated with asthma.

A Meta-Analysis on Vitamin D Supplementation and Asthma Treatment

Background

Vitamin D, as an immunomodulator, may be related to the therapeutic effect of asthma patients, but the research in this area is still controversial. The aim of this meta-analysis was to analyze the role of vitamin D supplementation in the treatment of asthma patients.

Materials and Methods

Randomized Controlled Trials (RCTs) of vitamin D supplementation in asthma were searched in PubMed, EMBASE, and the Cochrane library. Primary outcomes were forced expiratory volume in one second (FEV1), asthma exacerbations, Asthma Control Test scores (ACT scores), and fractional exhaled nitric oxide (FENO).

Results

A total of 10 RCTs were included, including 1,349 patients. Vitamin D supplementation didn't affect the ACT scores (SMD = 0.04, 95% CI = -0.13 to 0.21, P = 0.87), FEV1 (SMD = 0.04, 95% CI = -0.35 to 0.43, P < 0.01) and FENO (SMD = -0.01, 95% CI = -0.22 to 0.20, P = 0.27), but reduced the rate of asthma exacerbations (RR = 0.69, 95% CI = 0.41 to 0.88, P < 0.01), especially in subgroups of children (RR = 0.46, 95% CI = 0.30 to 0.70, P = 0.83) and follow up time less than 6 months (RR = 0.45, 95% CI = 0.32 to 0.63, P = 0.95). Additionally, though there was only one study included in the subgroup, it significantly enhanced FEV1 at the last visit for patients whose FEV1 baseline value was less than 70% (SMD = 0.94, 95% CI = 0.47 to 1.41).

Conclusion

Vitamin D supplementation can reduce asthma exacerbations, especially in children, and within 6 months of follow up time. In addition, vitamin D has a positive effect on improving FEV1 of patients whose FEV1 baseline value is less than 70%, but more RCTs are still needed to support this conclusion.

Systematic Review Registration

[https://inplasy.com], identifier [10.37766/inplasy20 22.6.0049].

Asthma and vitamin D in Brazilian adolescents: Study of Cardiovascular Risks in Adolescents (ERICA)

OBJECTIVE

To evaluate the association between asthma prevalence and serum levels of vitamin D in Brazilian adolescents.

METHODS

This was a cross-sectional, school-based study involving adolescents between 12-17 years of age from four large Brazilian cities located at different latitudes (Fortaleza, Rio de Janeiro, Brasília, and Porto Alegre). Information on asthma diagnosis, lifestyle, and sociodemographic characteristics was collected by means of self-administered questionnaires. Serum concentrations of calcifediol were dichotomized as sufficient (≥ 20 ng/mL) or insufficient/deficient (< 20 ng/mL) levels. Bivariate analyses were carried out between vitamin D levels and prevalence of active asthma (AA), as well as other variables in study, using the chi-square test. Generalized linear models were configured to analyze potential confounding factors (p < 0.20).

RESULTS

Between 2013 and 2014, 1,053 adolescents were evaluated. The prevalences of AA and insufficient/deficient levels of calcifediol were 15.4% and 21%, respectively. There were no statistically significant associations between AA and hypovitaminosis D. The prevalences of AA and vitamin D insufficiency were, respectively, 2.34 (95% CI, 1,28-4.30) and 3.22 (95% CI, 1.75-5.95) times higher in Porto Alegre than in Rio de Janeiro, regardless of possible confounding factors. However, no significant associations were found between the prevalence of AA and vitamin-D-related variables in any of the cities.

CONCLUSIONS

No association was found between AA and low levels of vitamin D in adolescents living at different latitudes in Brazil.

Effect of age and body mass index on vitamin D level in children with asthma in Riyadh

Vitamin D deficiency prevalence in children has been rising. Low 25-hydroxyvitamin D3 (25(OH)D3) levels contribute to poor asthma control in children. This study assessed 25(OH)D3 levels in children with asthma from Riyadh with respect to anthropometrics, dietary, and lifestyle variables. Children with asthma (n, 60; 2–17 years) were assessed for serum 25-hydroxy vitamin D3 (25(OH)D3) level and body anthropometrics (weight, height, and body mass index [BMI]). Vitamin D dietary intake, sun exposure, and sociodemographic data were collected using a structured questionnaire. Thirty-one children (52%) had a 25(OH)D3 level < 50 nmol/L, 15 of whom (25%) had a level < 30 nmol/L. 25(OH)D3 level was significantly negatively correlated with age (P < 0.05), weight (P < 0.02), and height (P < 0.05). Children with a 25(OH)D3 level < 30 nmol/L had a significantly higher BMI than children with insufficient and sufficient vitamin D levels (P < 0.01). There was no significant effect of sex on 25(OH)D3 level. Higher 25(OH)D3 level was associated with a greater body area exposure to the sun. This study found that > 50% of the children with asthma had below sufficiency vitamin D levels. The vitamin D screening and supplementation of older and overweight children with asthma is recommended.

The role of nutrition in asthma prevention and treatment

Asthma is a chronic respiratory condition characterized by airway inflammation and hyperreactivity. Prevalence has continued to rise in recent decades as Western dietary patterns have become more pervasive. Evidence suggests that diets emphasizing the consumption of plant-based foods might protect against asthma development and improve asthma symptoms through their effects on systemic inflammation, oxidation, and microbial composition. Additionally, increased fruit and vegetable intake, reduced animal product consumption, and weight management might mediate cytokine release, free radical damage, and immune responses involved in the development and course of asthma. The specific aim of this review paper is to examine the current literature on the associations between dietary factors and asthma risk and control in children and adults. Clinical trials examining the mechanism(s) by which dietary factors influence asthma outcomes are necessary to identify the potential use of nutritional therapy in the prevention and management of asthma.

Translating vitamin D transcriptomics to clinical evidence: Analysis of data in asthma and chronic obstructive pulmonary disease, followed by clinical data meta-analysis

Vitamin D (VitD) continues to trigger intense scientific controversy, regarding both its bi ological targets and its supplementation doses and regimens. In an effort to resolve this dispute, we mapped VitD transcriptome-wide events in humans, in order to unveil shared patterns or mechanisms with diverse pathologies/tissue profiles and reveal causal effects between VitD actions and specific human diseases, using a recently developed bioinformatics methodology. Using the similarities in analyzed transcriptome data (c-SKL method), we validated our methodology with osteoporosis as an example and further analyzed two other strong hits, specifically chronic obstructive pulmonary disease (COPD) and asthma. The latter revealed no impact of VitD on known molecular pathways. In accordance to this finding, review and meta-analysis of published data, based on an objective measure (Forced Expiratory Volume at one second, FEV₁%) did not further reveal any significant effect of VitD on the objective amelioration of either condition. This study may, therefore, be regarded as the first one to explore, in an objective, unbiased and unsupervised manner, the impact of VitD levels and/or interventions in a number of human pathologies.

The Vitamin D Receptor Gene Polymorphisms in Asthmatic Children: A Case-Control Study

Background: The association between vitamin D receptor (VDR) polymorphisms and the risk of asthma remains unclear. This study aimed to investigate the effect of VDR gene polymorphisms and VDR mRNA expression levels on respiratory function, nitric oxide levels in expiratory air, and serum vitamin D levels in children with asthma. Materials and Methods: The study included 80 healthy children (control group) and 100 asthmatic children (asthma group) between the age of 5 and 18 years. The VDR genotypes (ApaI, TaqI, and FokI) and VDR mRNA levels were determined in all groups. Results: There was no statistically significant difference in vitamin D levels between the asthma group and the control group (P > 0.05). A significant association was found between both genotype (CC) of the TaqI polymorphism [odds ratio (OR) = 0.2, 95% confidence interval (CI) (0.07-0.5), P = 0.003] and genotype (CA) of ApaI polymorphisms [OR = 0.2, 95% CI (0.07-0.8), P = 0.02], and asthma risk. In addition, when single-nucleotide polymorphism allelic frequencies between asthma and control groups were compared there is no significant association (P > 0.05). When compared to control group, VDR mRNA expression in asthma group decreased in genotypes CC and CA of ApaI and in genotypes TT and TC of TaqI (P < 0.05). Conclusion: The results provide supporting evidence for an association between TaqI and ApaI polymorphisms and asthma susceptibility.

Complex relationships between vitamin D and allergic sensitization among Puerto Rican 2-year-old children

BACKGROUND

In the United States, Puerto Ricans have a higher prevalence of asthma than other Latino ethnicities. Low vitamin D levels for children living in northern climates could be a factor.

OBJECTIVE

To assess serum 25-hydroxyvitamin D [25(OH)D] distributions (a marker of vitamin D) and associations among vitamin D, allergic sensitization, early wheeze, and home/demographic factors.

METHODS

Puerto Rican infants born in New York City, with a maternal history of atopy, were enrolled in a birth cohort. Blood was collected at age 2 years (n = 154; 82 males and 72 females). Serum 25(OH)D and immunoglobulin E (IgE) (indoor allergen-specific and total) were determined using immunoassays. Home/demographic characteristics and respiratory symptoms were assessed by questionnaire.

RESULTS

The median concentration of 25(OH)D was 22.6 ng/mL; 32% were at risk of deficiency or inadequacy (<12 or 12-19 ng/mL). Serum 25(OH)D levels were lower in the heating (a surrogate for less sun exposure in colder months) compared with nonheating (26.1 vs 22.7 ng/mL, P = .02) season, but were not associated with allergen-specific IgE levels or with level of acculturation (measured by maternal birthplace). However, low 25(OH)D levels (below median) were associated with high total IgE >100 IU/mL (P = .01). Also, 25(OH)D concentrations differed between children who attended daycare and those who did not (21.8 vs 24.5 ng/mL; t test, P = .02). Serum 25(OH)D was not associated with wheeze or asthma by 2 years of age (P = .43).

CONCLUSION

Vitamin D deficiency, possibly linked with allergic pathways, may partially explain the trajectory for disproportionate asthma burden among Puerto Ricans, especially those born and raised in colder climates.

Factors Associated with Vitamin D Status Among Korean Female Adolescents

PURPOSE

The prevalence of vitamin D deficiency among female adolescents in South Korea is the highest in East Asia. Therefore, this study aims to identify factors associated with vitamin D status among female adolescents in South Korea.

DESIGN AND METHODS

This cross-sectional descriptive study was conducted using a data set from the fifth Korean National Health and Nutrition Examination Survey (2010-2012). Participants comprised 734 female adolescents aged 12-18 years. A general linear model using a complex samples design was employed.

RESULTS

The mean vitamin D level of the participants was 14.90 ng/mL. Among these participants, 87.6% had a vitamin D deficiency. As their age increased by one year, their vitamin D level decreased by 0.47 ng/mL. Female adolescents with a low household income had vitamin D levels lower by 1.88 ng/mL than those with a high household income. Vitamin D levels in female adolescents who skipped lunch was lower by 3.41 ng/mL than those who had lunch.

CONCLUSION

The prevalence of vitamin D deficiency among female adolescents in South Korea is considerable. The findings suggest that age, socioeconomic status, and skipping a meal were associated with vitamin D status in female adolescents, but physical activity was not.

PRACTICE IMPLICATIONS

As the findings of this study indicate, older female adolescents and those from lower household incomes may be at higher risk for lower levels of Vitamin D. Counseling female adolescents as to dietary measures to avoid vitamin D deficiency is advised. Preventive health for at risk female adolescents includes provision of health education and counseling.

Vitamin D was not associated with survival or cerebrospinal fluid cathelicidin levels in children with bacterial meningitis

AIM

Vitamin D deficiency impairs the immunological system and has been associated with worse outcomes of infectious diseases, but its role in bacterial meningitis remains unknown. We investigated whether serum 25-hydroxyvitamin D concentrations related to disease outcomes and to cerebrospinal fluid (CSF) cathelicidin concentrations in childhood bacterial meningitis.

METHODS

All consecutively enrolled patients in a clinical trial on childhood bacterial meningitis in Latin America in 1996-2003 were considered, and 142 children, with a median age of seven months who had a confirmed bacterial aetiology and frozen serum available for further analyses, were included in this study. Serum 25-hydroxyvitamin D concentrations were determined with a chemiluminescence immunoassay analyser, while CSF cathelicidin was measured by enzyme-linked immunosorbent assay.

RESULTS

The median serum 25-hydroxyvitamin D concentration was 96 (range 19-251) nmol/L. No relationship was found with patient survival, but children with any neurological sequelae had lower serum 25-hydroxyvitamin D levels than children without sequelae. Serum 25-hydroxyvitamin D was unrelated to cathelicidin concentrations in CSF.

CONCLUSION

Although serum 25-hydroxyvitamin D in children with bacterial meningitis was not associated with survival or CSF cathelicidin concentrations, its relationship with more detailed disease outcomes warrants further study.

Association of vitamin D receptor expression with inflammatory changes and prognosis of asthma

The expression level of vitamin D receptor in patients with asthma was investigated to study the association between vitamin D receptor and inflammatory changes in asthma. Thirty patients with bronchial asthma treated in the Tianjin Hospital of ITCWM Nankai Hospital were selected as the experimental group, while 30 healthy individuals were selected as the control group. The mRNA expression level of vitamin D receptor in blood was detected via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The protein expression level of vitamin D receptor in blood was detected via western blot analysis and the levels of inflammatory factors were detected via enzyme-linked immune sorbent assay (ELISA). Correlations between the expression level of vitamin D and inflammatory factors were studied via Pearsons analysis. Finally, the prognoses of patients were recorded and analyzed. The results showed that the mRNA and protein expression levels of vitamin D receptor in the experimental group were significantly lower than those in control group (P<0.01). The content of 25-(OH) D₃ in serum in the experimental group was significantly lower than that in the control group (P<0.01). The contents of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum in the experimental group were obviously higher than those in the control group, but the contents of IL-10 and transforming growth factor-β (TGF-β) were obviously lower than those in the control group (P<0.01). Moreover, the correlation analysis revealed that IL-6 and TNF-α were negatively correlated with the expression of vitamin D receptor (P<0.05), whereas IL-10 and TGF-β were positively correlated with the expression of vitamin D receptor (P<0.05). In conclusion, the expression of vitamin D receptor is positively correlated with the levels of pro-inflammatory factors. Moreover, the vitamin D receptor affects the prognosis and recovery of lung function of patients with asthma.

Finding a Better Solution for Asthma Control in Children

Asthma is a chronic respiratory condition that is very common among children. With proper management and follow-ups, this condition can be easily controlled in a child. However, there are several factors that are negatively influencing a proper care of asthmatic children throughout the world. In this mini-review, the roles of the parents, the schools and the child himself were analyzed and several possible solutions to improve those hurdles were discussed.

The association of serum 25-OH vitamin D with asthma in Saudi adults

The study aimed to assess the differences and associations of serum 25 (OH)D levels in Saudi adults with and without asthma. A total of 1070 Saudi adults aged 22 to 28 years (359 with known asthma and 711 matched nonasthmatic controls) were selected randomly from the Riyadh Cohort, Saudi Arabia. Serum 25(OH)D serum levels were measured. Asthma diagnosis was taken from questionnaires. In all participants, 359 (33.6%) were known asthmatic and 711 (66.5%) were nonasthmatic. The overall incidence of vitamin D deficiency (serum 25(OH)D <25 nmol/L) was 29.6% in controls and 35.6% in asthma group (P = .01). The asthma group have a significantly lower serum 25(OH)D than the control group (P = .01) but lost significance after adjusting for age, body mass index (BMI), and sex. Nonasthmatic and asthmatic females had a higher incidence of vitamin D deficiency (33% and 46%) than nonasthmatic and asthmatic males (17% and 33%). Vitamin D deficiency is significantly high among Saudi adults with asthma, but more so among women. Whether vitamin D deficiency exacerbates asthma attack remains to be proven in this population.

Associations of Serum Nitric Oxide with Vitamin D and Other Metabolic Factors in Apparently Healthy Adolescents

Introduction

Nitric oxide (NOx) is an important biomolecule which interacts with other molecules including 25(OH)D to mediate various metabolic pathways. Interactions and associations of NOx with 25(OH)D have been well studied both in vitro and in vivo, yet associations in apparently healthy adolescents have never been studied.

Methods

A total of 740 (245 boys and 495 girls) apparently healthy Saudi adolescents aged 10-17 years were included in this cross-sectional study, to determine the associations of NOx with 25(OH)D and other biomarkers in Saudi adolescents. Serum NOx, 25(OH)D, and other biochemical and anthropometric parameters were measured following standard protocols and manufacturers' guidelines.

Results

NOx level was significantly higher in boys than girls (p<0.001). In all subjects, NOx showed a significant inverse correlation with 25(OH)D. After stratification according to sex however this significant association was observed only in boys and not in girls. NOx was also significantly associated with BMI, serum triglycerides, and systolic blood pressure in all subjects.

Conclusion

The significantly inverse association of NOx and 25(OH)D among apparently healthy adolescents is influenced by sex and further strengthens the extraskeletal role of 25(OH)D in maintaining endothelial homeostasis in this age group, particularly in boys. Whether vitamin D correction can influence NOx production over time among adolescents remains to be proven.

Kawasaki disease: a comprehensive review

Kawasaki disease is an acute systemic vasculitis that was first reported in 1961. Over the last 5 decades multiple papers have been published to further understand this disease. The diagnosis of Kawasaki disease is made based on the clinical findings. Atypical Kawasaki disease includes patients who do not meet all the criteria for diagnosis. The main complication of Kawasaki disease is coronary aneurysm, and the treatment is intravenous immunoglobulin and aspirin. A second dose of immunoglobulin is given if the patient does not improve, and several other treatment options have been proposed over the last few years as second and third line options.

Prevalence and Associated Risk Factors of Bronchial Asthma in Children in Santo Domingo, Dominican Republic

Background

Bronchial asthma is an important health problem worldwide. There is insufficient data on the prevalence of bronchial asthma among school children in Santo Domingo, Dominican Republic.

Objective

The objective of this study is to assess the prevalence of asthma and its related risk factors among school children in Santo Domingo, Dominican Republic.

Materials and methods

A cross-sectional study using a modified questionnaire was conducted in Santo Domingo among 600 children aged three to 11 eleven years. The prevalence of asthma and its associated risk factors such as birth order, family history of asthma, family history of allergy, exposure to pets at home, exposure to tobacco smoke, and source of fuel used at home were collected. The relevant data collected was analyzed using the Statistical Package for the Social Sciences (SPSS) 24.0. (IBM Corp., Armonk, NY) software.

Results

The prevalence of asthma was found to be 22.0%. Age, family history of asthma, family history of allergy, exposure to tobacco smoke, and birth order showed statistical significance. The source of fuel used at home, gender, and exposure to pets were not statistically significant to be considered as risk factors associated with asthma in the population studied.

Conclusion

With an asthma prevalence of 22.0% in the pediatric population, the Dominican Republic has one of the highest national rates of asthma in the pediatric population in Latin America. Proper education, screening, and prevention can help lower the burden of this disease economically and socially.

Seasonal variation of asthma control, lung function tests and allergic inflammation in relation to vitamin D levels: a prospective annual study

Introduction

There are scarce data about the role of vitamin D (vitD) in asthma control related to seasons and other confounders.

Aim

To investigate the seasonal relationship between vitD levels and asthma control, lung function tests (LFTs) and cytokines during a 1-year period, among 7–17-year-old asthmatic children.

Material and methods

Thirty patients with asthma with house dust mite monosensitization were evaluated 3 monthly about the previous month’s health and vitD related lifestyle factors and asthma control test (ACT), spirometry and bronchial provocation test for a year. Serum vitD, vitD binding protein (VDBP), total IgE levels, absolute eosinophil and Treg counts and cytokine levels were simultaneously measured. The seasonal changes of vitD and other parameters and the relationship between 120 pooled data sets of vitD and major outcomes were evaluated.

Results

Mean vitD levels, forced expiratory volume in 1 s (FEV₁%) and ACT score were lowest in winter and highest in summer. Pooled vitD levels were positively correlated with pooled ACT scores, Treg counts, FEV₁% values and VDBP levels and negatively with total immunoglobulin E (IgE) and interleukin-4 (IL-4) levels and bronchodilator response. VitD levels were positively associated with ACT score, and FEV₁% value and negatively with serum IgE level and bronchodilator response after adjusting for confounders.

Conclusions

This study revealed that asthma control measures, LFTs and IgE levels were significantly related to serum vitD levels, independent from age, body mass index, inhaled corticosteroid use, sun exposure and season among asthmatic children. Vitamin D levels showed a positive correlation with Treg counts and a negative correlation with Th2 type cytokines.

Non-musculoskeletal benefits of vitamin D

The aim of this study is to determine and critically evaluate the plausible relationships of vitamin D with extra-skeletal tissues in humans. Severe vitamin D deficiency results in rickets in children and osteomalacia in adults; these beneficial effects in the musculoskeletal system and certain physiological functions are well understood. Nevertheless, mounting reports support additional beneficial effects of vitamin D, outside the musculoskeletal system. This review explores the recent advances in knowledge about the non-skeletal effects of vitamin D. Peer-reviewed papers were extracted from research databases using key words, to assess correlations between vitamin D and extra-skeletal diseases and conditions. As per the guidelines of the Preferred Reporting Items for Systematic Reviews (PRISMA); general interpretations of results are included; taking into consideration the broader evidence and implications. This review summarizes current knowledge of the effects of vitamin D status on extra-skeletal tissues with special attention given to relationships between vitamin D status and various diseases commonly affecting adults; the effects of intervention with vitamin D and exposure to sunlight. Evidence suggests that vitamin D facilitates the regulation of blood pressure; and cardiac; endothelial; and smooth muscle cell functions; playing an important role in cardiovascular protection. In addition; 1,25(OH)₂D improves immunity; subdues inflammation; and reduces the incidence and severity of common cancers; autoimmune diseases and infectious diseases. Almost all adequately powered; epidemiological and biological studies that use; adequate doses of vitamin D supplementation in D-deficient populations have reported favorable outcomes. These studies have concluded that optimizing 25(OH)D status improves the functionality of bodily systems; reduces comorbidities; improves the quality of life; and increases survival. Although accumulating evidence supports biological associations of vitamin D sufficiency with improved physical and mental functions; no definitive evidence exists from well-designed; statistically powered; randomized controlled clinical trials. Nevertheless, most studies point to significant protective effects of vitamin D in humans when the minimum 25(OH)D serum level exceeds 30ng/mL and is maintained throughout the year.

Developments in the field of clinical allergy in 2015 through the eyes of Clinical and Experimental Allergy

In the second of two papers, we describe developments in the field of clinical allergy as documented by Clinical and Experimental Allergy in 2015. Epidemiology, clinical allergy, asthma and rhinitis are all covered.

Associations between serum 25(OH)D concentrations and prevalent asthma among children living in communities with differing levels of urbanization: a cross-sectional study

Background

Prior evidence suggests that vitamin D deficiency may increase the risk of asthma and atopy and impair pulmonary function in children.

Methods

In this cross-sectional analysis nested in a case-control study, we analyzed serum 25(OH)D concentrations in 413 children with asthma and 471 children without asthma living in two geographically adjacent study communities (Pampas and Villa El Salvador). We measured total and antigen-specific IgE levels, pulmonary function, asthma control, and exhaled nitric oxide.

Results

Mean 25(OH)D concentrations were 25.2 ng/mL (SD 10.1) in children with asthma and 26.1 ng/mL (SD 13.7) in children without asthma (p = 0.28). Vitamin D deficiency (25(OH)D < 20 ng/ml) was more common in Pampas than in Villa El Salvador (52.7% vs. 10.5%; p < 0.001). In the overall study population, a 10 ng/ml decrease in serum 25(OH)D concentrations was not significantly associated with odds of asthma (OR 1.09, 95% CI: 0.94 to 1.25). However, vitamin D deficiency was associated with a 1.6-fold increase in odds of asthma in the overall cohort (95% CI: 1.14 to 2.25). After stratifying by site, a 10 ng/mL decrease in serum 25(OH)D concentrations was associated with 18% higher odds of having asthma in Pampas (OR = 1.18, 95% CI 1.02 to 1.38), whereas there was no significant association between 25(OH)D concentrations and asthma in Villa El Salvador (OR = 0.95, 95% CI 0.87 to 1.05). Combined data from these geographically adjacent populations suggests a possible threshold for the relationship between 25(OH)D levels and asthma at approximately 27.5 ng/ml. Serum 25(OH)D concentrations were not clearly associated with asthma control, total serum IgE, atopy, or airway inflammation.

Conclusion

Serum 25(OH)D concentrations were inversely associated with asthma in one study community with a high prevalence of deficiency. Studies are needed to investigate a possible threshold 25(OH)D concentration after which higher vitamin D levels show no further benefit for asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s40733-017-0033-2) contains supplementary material, which is available to authorized users.

Free 25(OH)D concentrations are associated with atopy and lung function in children with asthma

BACKGROUND

Evidence suggests free mono-hydroxyvitamin D (25[OH]D) concentrations are more strongly linked to certain outcomes than total concentrations; however, no studies have examined the relation between free 25(OH)D and respiratory or allergic disease.

OBJECTIVE

To examine associations between total and free 25(OH)D concentrations and asthma outcomes.

METHODS

We quantified total and free 25(OH)D concentrations in 137 Peruvian children with asthma and 152 children without asthma and examined associations with asthma outcomes.

RESULTS

Mean age ± SD was 13 ± 2.5 years, and 50.2% were boys. Mean total and measured free 25(OH)D concentrations were 29 ± 9.5 ng/mL and 5.0 ± 1.3 pg/mL, respectively. Lower free but not total 25(OH)D concentrations were significantly associated with atopy in all children (total, odds ratio [OR] 1.3 per 10-ng/mL decrease, 95% confidence interval [CI] 0.95-1.7, P = .12; vs free, OR 1.3 per 1-pg/mL decrease, 95% CI 1.0-1.6, P = .02) and children with asthma (total, OR 1.1 per 10-ng/mL decrease, 95% CI 0.75-1.7, P = .57; vs free, OR 1.6 per 1-pg/mL decrease, 95% CI 1.0-2.5, P = .04). Free but not total 25(OH)D levels were significantly associated with pre-bronchodilator forced expiratory volume in 1 second (total, 0.11 L, -0.12 to 0.34, P = .34; vs free, 0.20 L, 0.021-0.39, P = .03) and forced vital capacity (total, 0.13 L, -0.12 to 0.37, P = .31; vs free, 0.22 L, 0.026-0.42, P = .03) Z-scores in children with asthma.

CONCLUSION

Atopy, forced expiratory volume in 1 second, and forced vital capacity were more strongly linked to free than to total 25(OH)D concentrations, suggesting the free form might be more relevant in modulating allergic disease risk and pulmonary function in children with asthma.

Vitamin D deficiency among smear positive pulmonary tuberculosis patients and their tuberculosis negative household contacts in Northwest Ethiopia: a case-control study

Background

Vitamin D is a fat-soluble vitamin that increases the immunity against tuberculosis (TB), decreases the re-activation of latent TB and reduces the severity of active TB disease. Epidemiological studies on the prevalence of vitamin D deficiency, and its association with TB showed inconsistent results in different countries. This study was aimed to determine the prevalence of vitamin D deficiency and its association with TB in Northwest Ethiopia.

Methods

A case–control study was conducted among smear positive pulmonary tuberculosis patients and their household contacts without symptoms suggestive of TB. Study participants were recruited at 11 TB diagnostic health facilities in North and South Gondar zones of Amhara region between May 2013 and April 2015. The spot-morning-spot sputum samples and 5 ml blood sample were collected prior to commencing TB treatment for the diagnosis of TB and serum vitamin D assay, respectively. The diagnosis of TB was performed using smear microscopy and GeneXpert. Serum vitamin D level was analyzed using VIDAS 25 OH Vitamin D Total testing kits (Biomerieux, Marcy I’Etoile, France) on mini VIDAS automated immunoassay platform. Vitamin D status was interpreted as deficient (<20 ng/ml), insufficient (20–29 ng/ml), sufficient (30–100 ng/ml) and potential toxicity (>100 ng/ml).

Results

Of the total study participants, 134 (46.2%) were vitamin D deficient, and only 56 (19.3%) had sufficient vitamin D level. A total of 59 (61.5%) TB patients and 75 (38.7%) non TB controls were vitamin D deficient. Results of multivariate logistic regression analyses showed a significantly higher vitamin D deficiency among tuberculosis cases (p < 0.001), females (p = 0.002), and urban residents (p < 0.001) than their respective comparison groups. Moreover, age groups of 35–44 (p = 0.001), 45–54 (p = 0.003) and ≥55 (p = 0.001) years had significantly higher vitamin D deficiency compared with age group <15 years.

Conclusions

Vitamin D deficiency is highly prevalent among TB patients and non TB controls in Ethiopia where there is year round abundant sunshine. Study participants with tuberculosis, females, older age groups, and urban residents had significantly higher prevalence of vitamin D deficiency. These findings warrant further studies to investigate the role of vitamin D supplementation in the prevention and treatment of tuberculosis in high TB burden countries like Ethiopia.

Vitamin D Insufficiency and Asthma in a US Nationwide Study

BACKGROUND

Vitamin D insufficiency (a serum 25-hydroxy vitamin D level of <30 ng/mL) has been associated with asthma morbidity.

OBJECTIVE

To examine vitamin D insufficiency, asthma, and lung function among US children and adults.

METHODS

Using data from the National Health and Nutrition Examination Survey from 2001 to 2010, we examined vitamin D insufficiency and (1) current asthma or wheeze in 10,860 children (6-17 years) and 24,115 adults (18-79 years) and (2) lung function in a subset of participants. Logistic or linear regression was used for the multivariable analysis, adjusting for age, sex, race/ethnicity, income, body mass index, smoking, and C-reactive protein level.

RESULTS

Vitamin D insufficiency was associated with current asthma (odds ratio, 1.35; 95% CI, 1.11-1.64) and current wheeze in children, as well as with current wheeze in adults (odds ratio, 1.17; 95% CI, 1.04-1.31). After stratifying the analysis by race/ethnicity and (in adults) current smoking, vitamin D insufficiency was associated with current asthma and wheeze in non-Hispanic white children only; in adults, vitamin D insufficiency was associated with current wheeze in non-Hispanic whites and blacks. Vitamin D insufficiency was also associated with lower FEV1 and forced vital capacity in children and adults. When analyzing each National Health and Nutrition Examination Survey wave separately, vitamin D insufficiency prevalence was 72% to 76% from 2001 to 2006, and then decreased from 2007 to 2010 (64%-65%); interestingly, asthma prevalence decreased for the first time from the period 2007 to 2008 (8.2%) to the period 2009 to 2010 (7.4%).

CONCLUSIONS

We show racial/ethnic-specific associations between vitamin D insufficiency and current asthma or wheeze in children and adults. Moreover, we report parallel recent decrements in the prevalence of vitamin D insufficiency and asthma.

A new sensitive LC/MS/MS analysis of vitamin D metabolites using a click derivatization reagent, 2-nitrosopyridine

There is an increased demand for comprehensive analysis of vitamin D metabolites. This is a major challenge, especially for 1α,25-dihydroxyvitamin D [1α,25(OH)2VitD], because it is biologically active at picomolar concentrations. 4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) was a revolutionary reagent in dramatically increasing sensitivity of all diene metabolites and allowing the routine analysis of the bioactive, but minor, vitamin D metabolites. A second generation of reagents used large fixed charge groups that increased sensitivity at the cost of a deterioration in chromatographic separation of the vitamin D derivatives. This precludes a survey of numerous vitamin D metabolites without redesigning the chromatographic system used. 2-Nitrosopyridine (PyrNO) demonstrates that one can improve ionization and gain higher sensitivity over PTAD. The resulting vitamin D derivatives facilitate high-resolution chromatographic separation of the major metabolites. Additionally, a liquid-liquid extraction followed by solid-phase extraction (LLE-SPE) was developed to selectively extract 1α,25(OH)2VitD, while reducing 2- to 4-fold ion suppression compared with SPE alone. LLE-SPE followed by PyrNO derivatization and LC/MS/MS analysis is a promising new method for quantifying vitamin D metabolites in a smaller sample volume (100 µL of serum) than previously reported methods. The PyrNO derivatization method is based on the Diels-Alder reaction and thus is generally applicable to a variety diene analytes.

25-Hydroxyvitamin D concentrations, asthma and eczema in childhood: The generation R study

BACKGROUND & AIMS

A role of vitamin D in the development of respiratory and allergic disease in children remains unclear. It may be likely that vitamin D has an effect on airway inflammation, but only few studies examined the effect in children. We aimed to examine whether serum 25-hydroxyvitamin D (25(OH) vitamin D) concentrations are associated with the fraction of exhaled nitric oxide (FeNO), airway interrupter resistance (Rint), physician diagnosed asthma ever, wheezing and eczema in a population-based cohort study in 6 year old children.

METHODS

Serum 25(OH) vitamin D concentration was assessed in 3815 children. 25(OH) vitamin D concentrations ≥75 nmol/L were considered as sufficient, between 50 and 75 nmol/L as insufficient, and <50 nmol/L as deficient. FeNO and Rint were measured at the research center. Data on physician diagnosed asthma, wheezing, and eczema were obtained by parent-reported questionnaires.

RESULTS

In comparison with sufficient 25(OH) vitamin D concentration, deficient concentrations were associated with elevated FeNO of ≥25 ppb (OR: 2.54; 95% CI: 1.34-4.80). In addition, deficient and insufficient 25(OH) vitamin D concentrations were associated with a lower Rint (Z-score: -1.26; 95% CI: -1.66 to -0.85) (ß: -0.75; 95% CI: -1.08 to -0.42), and increased risks of eczema (OR: 1.65; 95% CI: 1.13-2.41) (OR: 1.44; 95% CI: 1.06-1.95). Insufficient 25(OH) vitamin D concentration were associated with a decreased risk of physician diagnosed asthma ever (OR: 0.59; 95% CI: 0.38-0.94).

CONCLUSIONS

Our results indicate that lower 25(OH) vitamin D levels are associated with elevated FeNO levels, but lower Rint values. Lower 25(OH) vitamin D levels are also associated with a decreased risk for asthma diagnoses but an increased risk for eczema.

Biomarkers for the Phenotyping and Monitoring of Asthma in Children

An important issue in relation to the utility and reliability of biomarkers for asthma monitoring is how asthma is defined and characterized. What kind of asthma, or at what stage of the disease is a particular biomarker supposed to add information? Often, the purpose, or usefulness of a biomarker is not made clear. Diagnosis, severity evaluation, and monitoring are all different clinical uses for a biomarker, and confusion may arise when a biomarker is suitable for one of these but not another. When the utility of available biomarkers are discussed, these different roles need to be clarified. Our opinion is that there are four aspects of relevance to asthma, for which biomarkers are required: to diagnose allergies, to evaluate inflammation in the airways, to evaluate hyper-responsiveness, and for certain measures of lung function, such as lung clearance index. These types of biomarkers are needed for the phenotyping and monitoring of asthma. Another important role for biomarkers is, as mentioned above, to monitor asthma in order to follow treatment effects on inflammation and hyper-responsiveness as objective adjuncts to the patients' own symptom reports and lung function. This review will mainly focus on biomarkers that reflect airway inflammation. In spite of the numerous studies that have been conducted, we still have to remember that the value of biomarkers available for routine use, such as eosinophil counts in blood and sputum and exhaled nitric oxide, have to be interpreted in relation to reported symptoms and lung function. Measures of bronchial hyper-responsiveness, performed either by direct (methacholine challenge) or indirect (exercise or mannitol challenge) methods, could be considered biomarkers but will not be included in this review. On the other hand, diagnosing allergy is not usually useful for monitoring asthma although it is of fundamental importance for the interpretation of most biomarkers that are suitable for monitoring. We have therefore included the different approaches for diagnosing and evaluating allergic sensitization in this review.

Particularities of allergy in the Tropics

Allergic diseases are distributed worldwide and their risk factors and triggers vary according to geographical and socioeconomic conditions. Allergies are frequent in the Tropics but aspects of their prevalence, natural history, risk factors, sensitizers and triggers are not well defined and some are expected to be different from those in temperate zone countries. The aim of this review is to investigate if allergic diseases in the Tropics have particularities that deserve special attention for research and clinical practice. Such information will help to form a better understanding of the pathogenesis, diagnosis and management of allergic diseases in the Tropics. As expected, we found particularities in the Tropics that merit further study because they strongly affect the natural history of common allergic diseases; most of them related to climate conditions that favor permanent exposure to mite allergens, helminth infections and stinging insects. In addition, we detected several unmet needs in important areas which should be investigated and solved by collaborative efforts led by the emergent research groups on allergy from tropical countries.

Association of vitamin D receptor gene polymorphisms and vitamin D levels with asthma and atopy in Cypriot adolescents: a case-control study

Background

Polymorphisms in the vitamin D receptor (VDR) gene have been studied in immune-related disorders either as independent contributors or in combination with vitamin D concentration. Vitamin D and VDR have been independently linked to asthma susceptibility. We investigated whether VDR variants were associated independently or in relation to vitamin D levels with asthma in Cypriot adolescents.

Methods

We studied 190 current wheezers, 69 of which were categorized as active asthmatics and 671 healthy controls. We determined three VDR genotypes (BsmI, TaqI, ApaI) and measured serum 25(OH)D levels. Logistic regression and stratified analyses by the presence of hypovitaminosis D (≤20 ng/ml) were used to evaluate the association of the VDR variants with asthma.

Results

The distribution of TaqI genotypes was significantly different between controls and current wheezers (p = 0.030) or active asthmatics (p = 0.014). The tt genotype was over-represented in wheezers (19.2 %) and asthmatics (21.3 %) compared to respective controls (12.9 %). No difference was observed between controls, current wheezers and active asthmatics in the genotypic distribution of BsmI and ApaI polymorphic sites. After stratification by the presence of hypovitaminosis D, a significant association was detected between tt genotype of TaqI polymorphism with wheezing (OR: 1.97, 95 % CI: 1.12, 3.46) and asthma (OR: 2.37, 95CI%: 1.02, 5.52) only in those with normal vitamin D levels (>20 ng/ml) but not in subjects with low vitamin D.

Conclusions

The minor TaqI genotype of VDR is associated with asthma in Cypriot adolescents. This polymorphism may contribute to asthma susceptibility primarily under conditions of normal vitamin D levels (>20 ng/ml).

Electronic supplementary material

The online version of this article (doi:10.1186/s40248-015-0025-0) contains supplementary material, which is available to authorized users.

Asthma in Latin America

Consistent with the diversity of Latin America, there is profound variability in asthma burden among and within countries in this region. Regional variation in asthma prevalence is likely multifactorial and due to genetics, perinatal exposures, diet, obesity, tobacco use, indoor and outdoor pollutants, psychosocial stress and microbial or parasitic infections. Similarly, non-uniform progress in asthma management leads to regional variability in disease morbidity. Future studies of distinct asthma phenotypes should follow-up well-characterised Latin American subgroups and examine risk factors that are unique or common in Latin America (eg, stress and violence, parasitic infections and use of biomass fuels for cooking). Because most Latin American countries share the same barriers to asthma management, concerted and multifaceted public health and research efforts are needed, including approaches to curtail tobacco use, campaigns to improve asthma treatment, broadening access to care and clinical trials of non-pharmacological interventions (eg, replacing biomass fuels with gas or electric stoves).

Association between vitamin D deficiency and insufficiency and the risk of childhood asthma: evidence from a meta-analysis

OBJECTIVE

Whether vitamin D deficiency and insufficiency are associated with childhood asthma remains unclear. Thus, we conducted a meta-analysis to summarize the evidence from epidemiological studies of vitamin D deficiency and insufficiency and the risk of childhood asthma.

METHODS

Pertinent studies were identified by searching of PubMed and Web of Knowledge. The random effect model was used to combine the results. Meta-regression and subgroups analyses were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Egger's regression asymmetry test.

RESULTS

Finally, 14 articles with 15 studies including 3424 cases for vitamin D deficiency and 9 articles with 10 studies including 2756 cases for vitamin D insufficiency were included in this meta-analysis. The relative risk (95% confidence interval) of childhood asthma risk for vitamin D deficiency was 1.684 (1.321-2.148), and the associations were significant in America and Europe. Significant association of childhood asthma between vitamin D insufficiency and childhood asthma risk was found overall [1.577 (1.230-2.023)] and the subgroups of America, Europe and Asia. No evidence of significant publication bias between vitamin D deficiency and insufficiency and childhood asthma risk were found.

CONCLUSIONS

Results from this meta-analysis suggested that vitamin D deficiency and insufficiency might increase the risk of childhood asthma.

Myopia and daylight in schools: a neglected aspect of public health?

A century ago, it was widely believed that high levels of daylight in classrooms could prevent myopia, and as such, education departments built schools with large windows to try to stop children becoming short-sighted. This practice continued until the 1960s, from which time myopia was believed to be an inherited condition. In the years that followed, less emphasis was placed on preventing myopia. It has since become more common, reaching epidemic levels in east Asia. Recent research strongly suggests that the amount of light children get as they grow determines whether they will develop short sight; however, evidence that daylight in classrooms prevents myopia is lacking. Given the rapid increase in prevalence among school children worldwide, this should be investigated.

Vitamin D as an adjunctive therapy in asthma. Part 2: A review of human studies

Vitamin D deficiency (VDD) is highly prevalent worldwide, with adverse effects on bone health but also potentially other unfavorable consequences. VDD and asthma-incidence/severity share many common risk factors, including winter season, industrialization, poor diet, obesity, dark skin pigmentation, and high latitude. Multiple anatomical areas relevant to asthma contain both the enzyme responsible for producing activated vitamin D and the vitamin D receptor suggesting that activated vitamin D (1,25-dihydroxyvitamin D) may have important local effects at these sites. Emerging evidence suggests that VDD is associated with increased airway hyperresponsiveness, decreased pulmonary function, worse asthma control, and possibly decreased response to standard anti-asthma therapy. However the effect is inconsistent with preliminary evidence from different studies suggesting vitamin D is both beneficial and detrimental to asthma genesis and severity. Current evidence suggests that supplementation with moderate doses of vitamin D may be appropriate for maintenance of bone health in asthmatics, particularly steroid users. However emerging data from an increasing number of randomized, controlled, intervention studies of vitamin D supplementation in pediatric and adult asthma are becoming available and should help determine the importance, if any of vitamin D for asthma pathogenesis. The purpose of this second of a two-part review is to review the current human literature on vitamin D and asthma, discussing the possible consequences of VDD for asthma and the potential for vitamin D repletion as adjunct therapy.

The role of dendritic cells and monocytes in the maintenance and loss of respiratory tolerance

Promoting tolerance to inhaled antigens is an active area of study with the potential to benefit the millions of Americans currently suffering from respiratory allergies and asthma. Interestingly, not all individuals with atopy are symptomatic, arguing that sensitization alone does not lead to an allergic clinical phenotype. Respiratory dendritic cells (rDCs), classically associated with inducing inflammatory responses, can actively promote tolerance. Tolerance can be broken when inflammatory stimuli, including viral infections and other environmental exposures, inhibit rDC-mediated tolerance by allowing innocuous antigen to be presented to initiate type-2 immunity. Importantly, rDCs are composed of multiple subsets, each with a unique response to an inhaled antigen that can lead to either tolerance or inflammation. In this review, we will discuss how rDC subsets actively maintain tolerance or, alternatively, break tolerance in response to environmental cues.

Serum 25(OH)D concentrations and atopic diseases at age 10: results from the GINIplus and LISAplus birth cohort studies

Background

Vitamin D is well recognized for its role in skeletal health and its involvement in the modulation of the immune system. In the literature, controversial results are reported for atopic diseases. Thus, we investigated the association between vitamin D status and the prevalence of atopic diseases.

Methods

Serum 25-hydroxy-vitamin D (25(OH)D) concentrations were measured in a sample of 2815 10-years old children from two German birth cohort studies. Self-reported physician-diagnosed eczema, hay fever or allergic rhinitis, and asthma were used as outcome variables as well as specific IgE positivity against common allergens. We applied logistic regression models, deriving adjusted odds ratio estimates (aOR) and 95% confidence intervals (CI).

Results

For asthma and hay fever or allergic rhinitis, no associations existed with serum 25(OH)D concentrations. We observed a significant positive relationship between serum 25(OH)D levels and eczema at age 10 (aOR = 1.09, CI = 1.01-1.17, per 10 nmol/l increase in serum 25(OH)D levels) and for the lifetime prevalence of eczema (aOR = 1.05, CI = 1.01-1.09). Specific IgE positivity for food allergens (aOR = 1.07, CI = 1.02-1.11) and aeroallergens (aOR = 1.05, CI = 1.01-1.08) at age 10, as well as lifetime prevalence, was significantly related to the vitamin D status.

Conclusion

In this study we found no indication that higher blood 25(OH)D levels are associated with decreased risk for any of the atopic outcomes in children. However, we observed a positive association of serum 25(OH)D concentrations with eczema and detectable specific IgE. Due to the given limitations of our study, the clinical relevance of these findings needs further clarification.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-014-0286-3) contains supplementary material, which is available to authorized users.

Vitamin D and asthma-life after VIDA?

The vitamin D hypothesis postulates that lower vitamin D levels are causally associated with increased asthma risk and asthma severity. Multiple epidemiological studies have shown an inverse relationship between circulating vitamin D levels (in the form of 25-hydroxy vitamin D) and asthma severity and control and lung function. However, in the recently published vitamin D and asthma (VIDA) study, vitamin D supplementation failed to show an improvement in asthma control in adults. This article reviews the current epidemiological and trial evidence for vitamin D and asthma and explores some of the possible alternative explanations for previous findings (including "reverse causation" and the importance of studying children and adults). We also address some of the unique challenges of conducting vitamin D trials and potential ways to address them. Finally, I will argue for further clinical trials of vitamin D in asthma, especially in children, using knowledge gained from the VIDA trial.