The role of latitude, ultraviolet radiation exposure and vitamin D in childhood asthma and hayfever: an Australian multicenter study

Association between serum Vitamin D levels and asthma severity and control in children and adolescents

OBJECTIVE

To assess the association of serum Vitamin D (vitD) levels with asthma control and severity in children and adolescents in different seasons of the year.

METHOD

Longitudinal, prospective study with 7- to 17-year-old children and adolescents diagnosed with asthma. All participants underwent two assessments conducted in opposite seasons of the year which included a clinical assessment, a questionnaire for classification of asthma control (Asthma Control Test), spirometry, and blood collection to measure serum vitD levels.

RESULTS

In total, 141 individuals with asthma were evaluated. The mean vitD was lower in females (p = 0.006) and sunlight exposure appears not to be an influencing factor for vitD levels. We found no differences in mean vitD of patients with controlled and uncontrolled asthma (p = 0.703; p = 0.956). However, the severe asthma group had lower mean Vitamin D than the mild/moderate asthma group for both assessments (p = 0.013; p = 0.032). In the first assessment, the group with vitD insufficiency had a higher prevalence of severe asthma (p = 0.015). Vitamin D was positively correlated with FEV₁ in both assessments (p = 0.008; p = 0.006) and with FEF_25-75% in the first assessment (p = 0.038).

CONCLUSION

In a tropical climate zone, there is no evidence of association between seasonality and serum vitD levels or between serum vitD levels and asthma control in children and adolescents. However, vitD and lung function were positively correlated and the group with vitD insufficiency had a higher prevalence of severe asthma.

A Community Based Randomized Controlled Trial to See the Effect of Vitamin D Supplementation on Development of Diabetes Among Women with Prediabetes Residing in A Rural Community of Northern India

Background:

The primary objective of this study was to intervene with vitamin D supplementation in rural-based women with pre-diabetes (impaired fasting glucose or impaired glucose tolerance) to prevent development of type 2 diabetes (T2DM).

Methods:

This was an open-label randomized placebo-controlled trial conducted in rural women with pre-diabetes and vitamin D deficiency (Clinicaltrials.gov NCT02513888). Women aged 20-60 years with pre-diabetes were selected from rural Haryana (north India) and followed up for two years. A semi-structured questionnaire was used to collect information on socio-demographic and behavioral details, like sun exposure, dietary habits, etc., The intervention group received vitamin D supplementation while control group received lactose granules as placebo. Equal doses of calcium carbonate were given to both the groups.

Results:

A total of 132 participants were recruited in the study (58 each in the intervention and control groups). It was observed that there was no statistical significance in the incidence of diabetes in the control group as compared to the intervention group at the end of 2 years (P = 0.701).

Conclusion:

Though during the first year there was some delay in development of DM in the intervention group but at the end of two years there was no significant effect of vitamin D supplementation in delaying the incidence of diabetes in these women after two years.

Trial registration:

(Clinicaltrials.gov NCT02513888).

Climatic factors are associated with asthma prevalence: An ecological study using English quality outcomes framework general practitioner practice data

Asthma is a complex disease with multiple environmental factors proposed to contribute to aetiology. Geographical analyses can shed light on the determinants of asthma. Ultraviolet radiation has been associated with asthma prevalence in past ecological studies. We have increased the detail of examining the association between asthma and ultraviolet radiation with addition of the variables of temperature, relative humidity and precipitation. An ecological study was designed to investigate meteorological factors associated with asthma prevalence in England. Data from the 2005 quality outcomes framework were used to determine the prevalence of asthma in primary care in England. This information was supplemented with indicators of obesity and smoking of the General Practitioner practice and population (by age and sex), deprivation and ethnicity at lower super output level from the 2001 and 2011 census. Annual mean meteorological data was attained from the Met Office and Joint Research Centre. We used a multiple linear regression to examine individual and multiple climatic factors through a principal components analysis. We tested for an association with asthma prevalence, after taking into account the spatial autocorrelation of the data. Asthma prevalence from general practice surgeries in England was 5.88% (95% CI 5.83 to 5.92). In the highest ultraviolet radiation weighted by the pre-vitamin D action spectrum (UV_vitd) quartile (2.12 to 2.50 kJ/m²/day), asthma had a 5% reduction in prevalence; compared to the lowest quartile here (0.95 (95% CI 0.92 to 0.98)). Similar reductions were found in the higher temperature 0.93 (95% CI 0.90 to 96). The opposite was found with relative humidity 1.09 (95% CI 1.05 to 1.12). A combination of high temperature and UVvitd highlighted postcode districts in the South East of England with a climate beneficial to low asthma prevalence. The South West of England represented a climate which had both beneficial and detrimental associations with asthma development. Climate is associated with asthma prevalence in England. Understanding the contribution of multiple climatic factors and the relationship with the indoor environment could help to explain the population distribution of asthma.

Vitamin D Status in Egyptian Children With Allergic Rhinitis

Objective: This study aimed to assess the serum levels of vitamin D in an Egyptian cohort of children with allergic rhinitis (AR) and to evaluate any correlation of vitamin D status with the disease severity. Patient and methods: One hundred twenty children with AR and 100 healthy children were included in our study. We studied the serum levels of vitamin D 25(OH)D and 1,25(OH)2D in all participants. The associations between vitamin D levels and clinical characteristics of AR were examined. Results: In AR group, the serum levels of calcium, (25(OH)D and 1,25(OH)2D levels were significantly lower (p < .0001, p < .001, and p < .0001, respectively) in AR children than in controls. Furthermore, the mean 25-OHD3 levels in patients with moderate/severe AR were significantly lower than those with mild AR (p < .001). We found significant negative correlations between mean 25(OH)D levels and total nasal symptom score (r = -.62, p = .002) and total immunoglobulin E levels (r = -.27, p = .013) in AR group. Conclusions: Vitamin D deficiency is a frequent finding among Egyptian children with AR when compared to the healthy group. A significant inverse association was observed between vitamin D levels and AR disease severity.

The Role of Vitamin D in Respiratory Allergies Prevention. Why the Effect Is so Difficult to Disentangle?

Asthma and allergic rhinitis are the most common chronic childhood diseases with an increasing prevalence worldwide. There is an urgent need to look for methods of preventing allergic diseases from an early age. The relationship between vitamin D status and allergic diseases has been discussed in several studies recently. 25-hydroxyvitamin D (25(OH)D) is suggested to affect the development and/or severity of asthma and allergic rhinitis. Observational studies have seemed to confirm that vitamin D deficiency may contribute to an increase in allergy and asthma. Following interventional studies, however, have yielded ambiguous results. In this review, we describe recent findings regarding 25(OH)D impact on allergic diseases and provide a systematic analysis of the causes of great variability of the achieved results in different studies.

Predictive role of IL-17A/IL-10 ratio in persistent asthmatic patients on vitamin D supplement

Asthma is an airway inflammatory disorder. Vitamin (Vit) D is a potent immuno-modulator. It suppresses Interleukin (IL)-17 and induces IL-10. This study aims to investigate the role of IL-17A and IL-10 in predicting asthma control in case of Vit D supplementation. Seventy-nine patients enrolled in this study (42 patients received Vit D supplement and 37 patients did not receive the supplement). The enrolled patients were assessed at the beginning of this study and after 3 months. At the end of the study, there was a significant improvement in pulmonary function parameters in the Vit D supplemented group when compared to both the baseline values and the non-supplemented group. There was a significant decrease in serum IL-17A levels and a significant increase in serum IL-10 levels in comparison with the baseline values (p < 0.0001). The highest correlation of FEV1% improvement percentage was associated with the baseline IL-17A/IL-10 ratio (r = 0.65; p < 0.0001). The IL-17A/IL-10 ratio at a cutoff ≥ 2.66 had a sensitivity of 72.2% and a specificity of 83.3%. The IL-17A/IL-10 ratio had an adjusted odds ratio = 4.66 (p = 0.04). Vit D supplementation reduces the serum IL-17A levels and elevates the serum IL-10 levels in persistent asthmatic patients. So, Vitamin D can be used as an adjunct therapy side by side with the conventional asthma therapy. The IL-17A/IL-10 ratio seems to be a possible predictive biomarker for asthma improvement in patients depending on Vit D supplementation.

Infant Feeding, Vitamin D and IgE Sensitization to Food Allergens at 6 Years in a Longitudinal Icelandic Cohort

Nordic Nutrition Recommendations (NNR) recommend exclusive breastfeeding until 6 months, partial breastfeeding until 1 year or longer and irrespective of breastfeeding, avoiding solid foods before 4 months. Strong evidence was found for benefits of breastfeeding regarding growth and infections but limited/inconclusive evidence regarding atopic disease and asthma. Vitamin D is of special interest in the Nordic diet. The aim of this prospective study was to compare infant feeding and vitamin D between immunoglobulin E (IgE) sensitized (n = 14) and non-sensitized (n = 130) children at 6 years. Information on diet and vitamin D supplement use were collected with dietary recall (<5 months), 1-d food records (5 and 6 months) and 3-d weighed food records (12 months and 6 years). Serum-specific IgE-antibodies against milk, egg, cod, wheat, soy and peanut (cut-off specific IgE ≥ 0.35 kUA/L) were measured at 6 years and serum 25-hydroxyvitamin D at 12 months and 6 years. At 4 months, 57% of IgE sensitized vs. 23% of non-sensitized children (p < 0.01) had received solid food. At 12 months, IgE sensitized children had a lower intake of vitamin D (median (25th, 75th percentiles): 3.9 μg/d (3.2, 7.2) vs. 8.1 μg/d (4.4, 12.3), p = 0.03) and at 6 years, fewer used vitamin D supplements regularly (23% vs. 56%, p = 0.03). Introduction of solid foods prior to 4 months increased the odds of IgE-sensitization, OR = 4.9 (95%, CI = 1.4–16.6) and vitamin D supplement at 6 years decreased the odds of IgE-sensitization, OR = 0.2 (95%, CI = 0.1–0.98), adjusting for maternal smoking. These observations support the NNR in their recommendation against introducing complementary solid foods before the age of 4 months. Furthermore, they support encouraging vitamin D intake for young children at northern latitudes.

Risk effects of high and low relative humidity on allergic rhinitis: Time series study

BACKGROUND

The relationship between environmental factors and allergic rhinitis (AR) has become a focal point recently. However, few studies have investigated the adverse effects of both high relative humidity (RH) and low relative humidity. Moreover, the laged effect and disease burden of RH on AR were also neglected.

OBJECTIVES

To explore the association of both high and low RH on daily AR hospital outpatients, and to quantify the corresponding disease burden attributable to RH.

METHODS

In our study, we define 95th as high RH and 5th as low RH. A distributed lag non-linear model (DLNM) combined with a Poisson generalized linear regression model were applied to analyze the relationship between RH and hospital outpatients for AR. All patients were retrieved from Anhui Provincial Children's Hospital (n = 37,221) from January 2015 to December 2016. Daily meteorological and air pollutant data were collected by Hefei Meteorological Bureau and Environmental Protection Agency. Subgroup analyses were conducted by gender and occupational groups.

RESULTS

Acute adverse effects of high and low RH on AR were explored respectively, with an increase of daily AR outpatients when encountered high and low RH. The low RH presented a risk effect at current day and lasted up to the eighth day. However, high RH began to appear a risk effect on the fourth day. Notably, the fraction of hospital outpatients attributable to low RH was 5.22% (95% CI: 1.92%, 8.33%) and high RH was 4.07% (95% CI: 1.13%, 7.30%) in the backward perspective. Additionally, male and students apparent to be more sensitive to the effects of low RH.

CONCLUSION

This study suggests that both high and low RH are potential trigger for AR hospital outpatients in Hefei, China. Our studies might offer valuable messages to health practitioners and useful direction to decisions-makers respectively.

ASTHMA - comparing the impact of vitamin D versus UVR on clinical and immune parameters

The incidence of asthma has increased markedly since the 1960s and is currently estimated to affect more than 300 million individuals worldwide. A number of environmental factors are implicated in asthma pathogenesis, one of which is vitamin D. Vitamin D deficiency is a global health concern and has increased in parallel with asthma incidence. Epidemiological studies report associations between low vitamin D status, assessed as circulating levels of 25-hydroxyvitamin D, with asthma incidence, severity, exacerbations and responses to treatment. This has led to clinical studies to test whether increasing the levels of vitamin D improves asthma management. Despite being highly variable in dosing regimens, design and outcomes, meta-analyses suggest overall positive outcomes with respect to reduced asthma exacerbations and steroid requirements. The primary mechanism for increasing vitamin D levels in the body is through exposure of the skin to the ultraviolet B (UVB) component of ultraviolet radiation (UVR), most commonly from sun exposure. However, only a limited number of studies investigating the impact of UVR on the asthmatic response have been performed; these generally report on the impact of latitude as a surrogate of sun exposure, or address this in animal models. To the best of our knowledge no comprehensive trials to assess the impact of UVB radiation on asthma outcomes have been performed. Within this review we discuss observational and clinical studies in this field, and innate and adaptive immune mechanisms through which UVR and vitamin D may impact respiratory health, and asthma. We highlight the heterogeneity of asthmatic disease, which is likely to impact upon the efficacy of interventional studies, and briefly overview more recent findings relating to the impact of vitamin D/UVR on the development of asthma.

Prevalence of pollen-induced allergic rhinitis with high pollen exposure in grasslands of northern China

BACKGROUND

The aim of this study was to investigate the prevalence of epidemiologic and physician-diagnosed pollen-induced AR (PiAR) in the grasslands of northern China and to study the impact of the intensity and time of pollen exposure on PiAR prevalence.

METHODS

A multistage, clustered and proportionately stratified random sampling with a field interviewer-administered survey study was performed together with skin prick tests (SPT) and measurements of the daily pollen count.

RESULTS

A total of 6043 subjects completed the study, with a proportion of 32.4% epidemiologic AR and 18.5% PiAR. The prevalence was higher in males than females (19.6% vs 17.4%, P = .024), but no difference between the two major residential and ethnic groups (Han and Mongolian) was observed. Subjects from urban areas showed higher prevalence of PiAR than rural areas (23.1% vs 14.0%, P < .001). Most PiAR patients were sensitized to two or more pollens (79.4%) with artemisia, chenopodium, and humulus scandens being the most common pollen types, which were similarly found as the top three sensitizing pollen allergens by SPT. There were significant regional differences in the prevalence of epidemiologic AR (from 18.6% to 52.9%) and PiAR (from 10.5% to 31.4%) among the six areas investigated. PiAR symptoms were positively associated with pollen counts, temperature, and precipitation (P < .05), but negatively with wind speed and pressure P < .05).

CONCLUSION

Pollen-induced AR (PiAR) prevalence in the investigated region is extremely high due to high seasonal pollen exposure, which was influenced by local environmental and climate conditions.

Serum vitamin D profile of Nigerian children with asthma: Association with asthma severity and control

OBJECTIVE

Childhood asthma is a chronic inflammatory airway disorder with increasing prevalence even in Africa. Vitamin D, with anti-inflammatory and immune-modulatory properties, may have effects on the severity and level of symptoms control in childhood asthma. We aimed to assess the serum vitamin D levels in children with asthma as related to disease severity and control in a tropical region.

METHODS

A hospital based comparative cross sectional study was conducted in western Nigeria. Serum vitamin D (25-OH-D) levels of all the children, assayed using high-performance liquid chromatography (HPLC), were compared to the various disease severity and levels of asthma control as well as between the asthmatic and non-asthmatic children.

RESULTS

A total of 206 children (103 asthmatics and 103 non-asthmatics) were recruited with a mean (SD) age of 6.6 (3.7) years. The majority (82.5%) of the children with asthma had mild intermittent form, 63.1% had well controlled symptoms while 33.0% and 3.9% had partly controlled and uncontrolled symptoms, respectively. None of the children were deficient in vitamin D. The mean (SD) serum vitamin D levels of the children with asthma (49.2 [7.2] ng/mL) was significantly lower than those without asthma (51.2 [6.9] ng/mL, P = 0.043). Varying degrees of asthma severity and levels of symptoms control were not affected by serum vitamin D levels.

CONCLUSION

Children with asthma in Nigeria had marginally but significantly lower mean serum vitamin D levels when compared with their counterparts without asthma. However, serum vitamin D level does not seem to be associated with childhood asthma severity and control in these children with normal serum vitamin D levels.

Altitude above 1500 m is a major determinant of asthma incidence. An ecological study

BACKGROUND

Previous studies suggest an inverse correlation between asthma and altitude. In the present work, we performed an in-depth analysis of asthma incidence in the 758 Mexican counties covered by the largest medical institution in the country (∼37.5 million insured subjects), and evaluated its relationships with altitude and other factors.

METHODS

Asthma incidence in each county was calculated from new cases diagnosed by family physicians. Other variables in the same counties, including selected diseases, geographical variables, and socioeconomic factors, were also obtained and their association with asthma was evaluated through bivariate and multivariate analyses.

RESULTS

Median asthma incidence was 296.2 × 100,000 insured subjects, but tended to be higher in those counties located on or near the coast. When asthma incidence was plotted against altitude, a two-stage pattern was evident: asthma rates were relatively stable in counties located below an altitude of ∼1500 m, while these rates progressively decreased as altitude increased beyond this level (r_S = -0.51, p < .001). Multivariate analysis showed that, once each variable was adjusted by the potential influence of the others, asthma incidence was inversely correlated with altitude (standardized β coefficient, -0.577), helminthiasis (-0.173), pulmonary tuberculosis (-0.130), and latitude (-0.126), and was positively correlated with acute respiratory tract infection (0.382), pneumonia (0.289), type 2 diabetes (0.138), population (0.108), and pharyngotonsillitis (0.088), all with a p ≤ .001.

CONCLUSION

Our study showed that altitude higher than ∼1500 m comprises a major factor in determining asthma incidence, with the risk of new-onset asthma decreasing as altitude increases. Other less influential conditions were also identified.

Do sufficient vitamin D levels at the end of summer in children and adolescents provide an assurance of vitamin D sufficiency at the end of winter? A cohort study

BACKGROUND

The changes in serum 25-hydroxyvitamin D (25(OH)D) in adolescents from summer to winter and optimal serum vitamin D levels in the summer to ensure adequate vitamin D levels at the end of winter are currently unknown. This study was conducted to address this knowledge gap.

METHODS

The study was conducted as a cohort study. Sixty-eight participants aged 7-18 years and who had sufficient vitamin D levels at the end of the summer in 2011 were selected using stratified random sampling. Subsequently, the participants' vitamin D levels were measured at the end of the winter in 2012. A receiver operating characteristic (ROC) curve was used to determine optimal cutoff points for vitamin D at the end of the summer to predict sufficient vitamin D levels at the end of the winter.

RESULTS

The results indicated that 89.7% of all the participants had a decrease in vitamin D levels from summer to winter: 14.7% of them were vitamin D-deficient, 36.8% had insufficient vitamin D concentrations and only 48.5% where able to maintain sufficient vitamin D. The optimal cutoff point to provide assurance of sufficient serum vitamin D at the end of the winter was 40 ng/mL at the end of the summer. Sex, age and vitamin D levels at the end of the summer were significant predictors of non-sufficient vitamin D at the end of the winter.

CONCLUSIONS

In this age group, a dramatic reduction in vitamin D was observed over the follow-up period. Sufficient vitamin D at the end of the summer did not guarantee vitamin D sufficiency at the end of the winter. We found 40 ng/mL as an optimal cutoff point.

Temperature drop and the risk of asthma: a systematic review and meta-analysis

The relationship between asthma and temperature changes remains controversial. The aim of this study was to investigate the association between temperature changes and the risk of asthma. A total of 26 studies (combined total number of subjects N > 26 million), covering 13 countries and Costa Rica, were identified by using a series of keywords in different combinations and searching the papers in PubMed, EMBSEA, Web of Science, MEDLINE, AIM, LILACS, and WPRIM before February 2016. Most of the papers were published in English. Random-effects meta-analyses were performed to evaluate the effect of temperature drop on risk of asthma. Several secondary analyses were also calculated based on stratification for different age, season, latitude, and region on risk of asthma. The odds ratio (OR) estimate between temperature drop and asthma was 1.05 (95% CI 1.02, 1.08) in the meta-analysis. For children, the overall OR was 1.09 (95% CI 1.03, 1.15). Dose-effect analyses showed stronger associations in asthma risk for each 1°1 °C decrement in short-term temperature (OR 1.055, 95% CI 1.00, 1.11). Further stratifications showed that winter (OR 1.03, 95% CI 1.01, 105) and low latitude (OR 1.72, 95% CI 1.23, 2.41) have a statistically significant association with the increased risk of asthma. Exposure of people to short-term temperature drop (per 1 °C decrement) was significantly associated with the risk of lower respiratory tract infections (LRTI) with asthma (OR 1.02, 95% CI 1.00, 1.04). Results suggest an adverse effect of temperature drop on asthma risk, especially in children and low-latitude areas. It may be opportune to consider the preventive actions against temperature drop, including simple face masks, to decrease the risk of asthma.

Ambient ultraviolet radiation exposure and hepatocellular carcinoma incidence in the United States

BACKGROUND

Hepatocellular carcinoma (HCC), the most commonly occurring type of primary liver cancer, has been increasing in incidence worldwide. Vitamin D, acquired from sunlight exposure, diet, and dietary supplements, has been hypothesized to impact hepatocarcinogenesis. However, previous epidemiologic studies examining the associations between dietary and serum vitamin D reported mixed results. The purpose of this study was to examine the association between ambient ultraviolet (UV) radiation exposure and HCC risk in the U.S.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database provided information on HCC cases diagnosed between 2000 and 2014 from 16 population-based cancer registries across the U.S. Ambient UV exposure was estimated by linking the SEER county with a spatiotemporal UV exposure model using a geographic information system. Poisson regression with robust variance estimation was used to calculate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for the association between ambient UV exposure per interquartile range (IQR) increase (32.4 mW/m2) and HCC risk adjusting for age at diagnosis, sex, race, year of diagnosis, SEER registry, and county-level information on prevalence of health conditions, lifestyle, socioeconomic, and environmental factors.

RESULTS

Higher levels of ambient UV exposure were associated with statistically significant lower HCC risk (n = 56,245 cases; adjusted IRR per IQR increase: 0.83, 95% CI 0.77, 0.90; p < 0.01). A statistically significant inverse association between ambient UV and HCC risk was observed among males (p for interaction = 0.01) and whites (p for interaction = 0.01).

CONCLUSIONS

Higher ambient UV exposure was associated with a decreased risk of HCC in the U.S. UV exposure may be a potential modifiable risk factor for HCC that should be explored in future research.

A Review on the Role of Vitamin D in Asthma

Asthma, a major public health issue, is one of the most common diseases affecting millions of population globally. It is a chronic respiratory disease characterized by increased airway inflammation and hyper-responsiveness. Vitamin D is of particular interest in asthma due to its immunomodulatory effects. Serum 25-hydroxyvitamin D is found to be associated with a wide range of pulmonary diseases, including viral and bacterial respiratory infections, asthma, and cancer. Several researches have reported positive associations between vitamin D and asthma. On the other hand, others have reported contrasting effects of vitamin D on asthma.

This review provides an examination of current epidemiologic and experimental evidence of a causal association between vitamin D status and asthma or asthma exacerbations, including its probable protective mechanism. Most of the evidence regarding vitamin D and asthma is reported by observational studies. Therefore, results from the experimental trials of vitamin D supplementation are important as they can provide evidence for future recommendations about the significance of vitamin D for asthma. Moreover, the trials can be effective in assessing the correct dosage and safety of vitamin D supplementation when given in diverse age groups such as children, teenagers, and adults for prevention and treatment of asthma.

Temporal Trends in Satellite-Derived Erythemal UVB and Implications for Ambient Sun Exposure Assessment

Ultraviolet radiation (UVR) has been associated with various health outcomes, including skin cancers, vitamin D insufficiency, and multiple sclerosis. Measurement of UVR has been difficult, traditionally relying on subject recall. We investigated trends in satellite-derived UVB from 1978 to 2014 within the continental United States (US) to inform UVR exposure assessment and determine the potential magnitude of misclassification bias created by ignoring these trends. Monthly UVB data remotely sensed from various NASA satellites were used to investigate changes over time in the United States using linear regression with a harmonic function. Linear regression models for local geographic areas were used to make inferences across the entire study area using a global field significance test. Temporal trends were investigated across all years and separately for each satellite type due to documented differences in UVB estimation. UVB increased from 1978 to 2014 in 48% of local tests. The largest UVB increase was found in Western Nevada (0.145 kJ/m2 per five-year increment), a total 30-year increase of 0.87 kJ/m2. This largest change only represented 17% of total ambient exposure for an average January and 2% of an average July in Western Nevada. The observed trends represent cumulative UVB changes of less than a month, which are not relevant when attempting to estimate human exposure. The observation of small trends should be interpreted with caution due to measurement of satellite parameter inputs (ozone and climatological factors) that may impact derived satellite UVR nearly 20% compared to ground level sources. If the observed trends hold, satellite-derived UVB data may reasonably estimate ambient UVB exposures even for outcomes with long latency phases that predate the satellite record.

Spatiotemporal exposure modeling of ambient erythemal ultraviolet radiation

BACKGROUND

Ultraviolet B (UV-B) radiation plays a multifaceted role in human health, inducing DNA damage and representing the primary source of vitamin D for most humans; however, current U.S. UV exposure models are limited in spatial, temporal, and/or spectral resolution. Area-to-point (ATP) residual kriging is a geostatistical method that can be used to create a spatiotemporal exposure model by downscaling from an area- to point-level spatial resolution using fine-scale ancillary data.

METHODS

A stratified ATP residual kriging approach was used to predict average July noon-time erythemal UV (UV_Ery) (mW/m²) biennially from 1998 to 2012 by downscaling National Aeronautics and Space Administration (NASA) Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) gridded remote sensing images to a 1 km spatial resolution. Ancillary data were incorporated in random intercept linear mixed-effects regression models. Modeling was performed separately within nine U.S. regions to satisfy stationarity and account for locally varying associations between UV_Ery and predictors. Cross-validation was used to compare ATP residual kriging models and NASA grids to UV-B Monitoring and Research Program (UVMRP) measurements (gold standard).

RESULTS

Predictors included in the final regional models included surface albedo, aerosol optical depth (AOD), cloud cover, dew point, elevation, latitude, ozone, surface incoming shortwave flux, sulfur dioxide (SO₂), year, and interactions between year and surface albedo, AOD, cloud cover, dew point, elevation, latitude, and SO₂. ATP residual kriging models more accurately estimated UV_Ery at UVMRP monitoring stations on average compared to NASA grids across the contiguous U.S. (average mean absolute error [MAE] for ATP, NASA: 15.8, 20.3; average root mean square error [RMSE]: 21.3, 25.5). ATP residual kriging was associated with positive percent relative improvements in MAE (0.6-31.5%) and RMSE (3.6-29.4%) across all regions compared to NASA grids.

CONCLUSIONS

ATP residual kriging incorporating fine-scale spatial predictors can provide more accurate, high-resolution UV_Ery estimates compared to using NASA grids and can be used in epidemiologic studies examining the health effects of ambient UV.

Associations of maternal and fetal 25-hydroxyvitamin D levels with childhood lung function and asthma: the Generation R Study

BACKGROUND

Exposure to low levels of vitamin D in fetal life might be a risk factor for childhood asthma.

OBJECTIVE

We examined whether 25-hydroxyvitamin D levels in mid-gestation and at birth were associated with higher airway resistance and inflammation, and increased risks of wheezing and asthma in school-age children.

METHODS

We performed a population-based prospective cohort study among 3130 mothers and their children. Maternal blood samples in mid-gestation and umbilical cord blood samples at birth were used to determine 25-hydroxyvitamin D levels. At age of 6, airway resistance (Rint) was measured by interrupter technique and airway inflammation by fractional exhaled nitric oxide (FENO) using NIOX chemiluminescence analyser. Wheezing and asthma were prospectively assessed by annual questionnaires until age 6.

RESULTS

Maternal levels of 25-hydroxyvitamin D in mid-gestation were not associated with Rint, FeNO, wheezing patterns, or asthma. Children in the lowest tertile of 25-hydroxyvitamin D levels at birth had a higher Rint (Z-score (95% confidence interval [95% CI]): -0.42 (-0.84, -0.01), P-value for trend< 0.05), compared to those in the highest tertile group. The effect estimate attenuated when child's current 25-hydroxyvitamin D level was taken into account [Z-score (95% CI): -0.55 (-1.08, 0.01)].

CONCLUSION AND CLINICAL RELEVANCE

Low levels of 25-hydroxyvitamin D at birth were associated with a higher airway resistance in childhood. Additional adjustment for child's current 25-hydroxyvitamin D level reduced the effect size of the association. Further studies are needed to replicate these findings and to examine mechanisms underlying the observed association and the long-term consequences.

Vitamin D pathway regulatory genes encoding 1α-hydroxylase and 24-hydroxylase are dysregulated in sinonasal tissue during chronic rhinosinusitis

BACKGROUND

Vitamin D deficiency is associated with many inflammatory respiratory disease states. However, serum vitamin D concentrations may not reflect tissue-specific availability. In this study we sought to assess the local expression of genes essential in vitamin D regulation in chronic rhinosinusitis (CRS).

METHODS

A cross-sectional study of adult patients undergoing endoscopic sinus surgery was performed. Patients were defined as having CRS with polyps (CRSwNP) or without polyps (CRSsNP), or normal sinus mucosa. Sinus mucosal biopsies were assessed using quantitative polymerase chain reaction to determine expression of genes encoding the vitamin D receptor (VDR), 25-hydroxylase (CYP2R1), 1α-hydroxylase (CYP27B1), and 24-hydroxylase (CYP24A1). Expression levels correlated with serum 25(OH)D [sum 25(OH)D₂  and 25(OH)D₃ ], the 22-item Sinonasal Outcome Test (SNOT-22), and Nasal Symptom Score (NSS). Separate analyses were performed for patients grouped by tissue eosinophilia.

RESULTS

Thirty-one patients were assessed (age 49.47 ± 18.14 years, 48.4% female), including 8 CRSsNP, 10 CRSwNP, and 13 controls. CRSsNP and CRSwNP mucosa exhibited decreased CYP27B1 compared with controls (0.0437 [Interquartile range (IQR) 0.0999] vs 0.3260 [IQR 2.9384] vs 0.6557 [IQR 1.1005], p = 0.039), whereas CYP24A1 was upregulated (0.8522 [IQR 1.3170] vs 1.2239 [IQR 4.4197] vs 0.1076 [IQR 0.1791], p = 0.025). CYP24A1 was upregulated in both non-eosinophilic CRS and eosinophilic CRS (1.1337 [IQR 2.3790] vs 0.9555 [IQR 3.2811] vs 0.1076 [IQR 0.1791], p = 0.033). Significant correlations were observed between NSS and CYP2R1 (r = -0.432, p = 0.022), CYP24A1 (r = 0.420, P = 0.026), and VDR (r = 0.425, p = 0.024), although no correlations with serum 25(OH)D were observed.

CONCLUSIONS

The local regulation of vitamin D in sinonasal tissue during CRS may be independent of serum 25(OH)D levels. Vitamin D may be dysregulated at multiple levels, with decreased transcription of the metabolic gene CYP27B1 and increased transcription of the catabolic gene CYP24A1 observed.

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.

Geo-climatic heterogeneity in self-reported asthma, allergic rhinitis and chronic bronchitis in Italy

BACKGROUND

Several studies highlighted a great variability, both between and within countries, in the prevalence of asthma and chronic airways diseases.

AIM

To evaluate if geo-climatic variations can explain the heterogeneity in the prevalence of asthma and respiratory diseases in Italy.

METHODS

Between 2006 and 2010, a postal screening questionnaire on respiratory health was administered to 18,357 randomly selected subjects, aged 20-44, living in 7 centers in northern, central, and southern Italy. A random-effects meta-analysis was fitted to evaluate the between-centers heterogeneity in the prevalence of asthma, asthma-like symptoms, allergic rhinitis, and chronic bronchitis (CB). A principal component analysis (PCA) was performed to synthetize the geo-climatic information (annual mean temperature, range of temperature, annual rainfalls, global solar radiations, altitude, distance from the sea) of all the 110 Italian province capital towns. The associations between these geo-climatic components obtained with PCA and the prevalence of respiratory diseases were analyzed through meta-regression models.

RESULTS

10,464 (57%) subjects responded to the questionnaire. There was a significant between-centers heterogeneity in the prevalence of asthma (I(2)=59.5%, p=0.022) and CB (I(2)=60.5%, p=0.019), but not in that of asthma-like symptoms or allergic rhinitis. Two independent geo-climatic components explaining together about 80% of the overall geo-climatic variability were identified: the first principally summarized the climatic variables; the second the topographic ones. Variations in the prevalence of asthma across centers were significantly associated with differences in the climatic component (p=0.017), but not with differences in the topographic one.

CONCLUSIONS

Our findings suggest that climate play a role in determining the between-center heterogeneity in the prevalence of asthma in Italy, with higher prevalence in dry-hot Mediterranean climates, and lower in rainy-cold northern climates.

Fractional exhaled nitric oxide (FeNO) among office workers in an academic institution, Malaysia--associations with asthma, allergies and office environment

OBJECTIVE

There are few studies on fractional exhaled nitric oxide (FeNO) and respiratory symptoms among adults in tropical areas. The aim was to study associations between FeNO and selected personal factors, respiratory symptoms, allergies, office characteristics and indoor office exposures among office workers (n = 460) from a university in Malaysia.

METHODS

Information on health was collected by a questionnaire, skin prick test and FeNO measurement. Temperature, relative air humidity, carbon monoxide and carbon dioxide were measured in the offices. Settled dust was vacuumed in the offices and analyzed for endotoxin, (1,3)-β-glucan and house dust mites allergens, namely Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1). Two-level linear mixed models and multiple logistic regression were used to analyze the associations.

RESULTS

One-fourth (25.9%) of the office workers had elevated FeNO level (≥ 25 ppb) and 61.5% had HDM, cat, seafood or pollen allergy. Male gender (p < 0.001), current smoking (p = 0.037), height (p < 0.001) and atopy (p < 0.001) were associated with FeNO. The amount of vacuumed dust was associated with FeNO among atopic subjects (p = 0.009). Asthma and rhinitis symptoms were associated with FeNO (p < 0.05), especially among atopic subjects. In particular, a combination of atopy and elevated FeNO were associated with doctor-diagnosed asthma (p < 0.001), rhinitis (p < 0.001) and airway symptoms last 12 months (p < 0.001).

CONCLUSION

Gender, smoking, height and atopy are important risk factors for elevated FeNO levels. A combination of allergy testing and FeNO measurement could be useful in respiratory illness epidemiology studies and patient investigations in tropical areas.

Vitamin D Deficiency and Cardiometabolic Risks: A Juxtaposition of Arab Adolescents and Adults

The recent exponential surge in vitamin D research reflects the global epidemic of vitamin D deficiency and its potential impact on several chronic diseases in both children and adults. Several subpopulations, including Arab adolescent boys and girls, remain understudied. This study aims to fill this gap. A total of 2225 apparently healthy Saudi adolescents (1187 boys and 1038 girls, aged 13-17 years old) and 830 adults (368 men and 462 women, aged 18-50 years old) were respectively recruited from different public schools and medical practices within Riyadh, Saudi Arabia. Anthropometrics were taken and fasting blood samples withdrawn to examine serum glucose and lipid profile by routine analysis and 25-hydroxyvitamin D by ELISA. Almost half of the girls (47.0%) had vitamin D deficiency as compared to only 19.4% of the boys (p<0.001), 36.8% of the adult women and 17.7% of the adult men (p<0.001). Furthermore, in boys there were more significant inverse associations between serum 25(OH)vitamin D levels and cardiometabolic indices than girls, while in contrast women had more significant associations than men. Vitamin D deficiency was significantly associated with diabetes mellitus type 2 (DMT2) [OR 3.47 (CI1.26-5.55); p<0.05] and pre-DM [OR 2.47 (CI 1.48-4.12); p<0.01] in boys. Furthermore, vitamin D insufficiency was significantly associated with abdominal obesity in boys [OR 2.75 (CI 1.1-7.1); p<0.05]. These associations for DMT2 and abdominal obesity were not observed in adult males, girls and adult women. Vitamin D deficiency/insufficiency and hyperglycemia is high among Arab adolescents. Vitamin D deficiency is mostly associated with cardiometabolic risk factors in adolescent Arab boys. This indicates a sex- and age-related disadvantage for boys with low vitamin D status and challenges the extra-skeletal protection of vitamin D correction in adolescent females.

Coastal climate is associated with elevated solar irradiance and higher 25(OH)D level

INTRODUCTION

There is evidence that populations living close to the coast have improved health and wellbeing. Coastal environments are linked to promotion of physical activity through provision of safe, opportune, aesthetic and accessible spaces for recreation. Exposure to coastal environments may also reduce stress and induce positive mood. We hypothesised that coastal climate may influence the vitamin D status of residents and thus partly explain benefits to health.

MATERIALS AND METHODS

Ecological and cross-sectional analyses were designed to elucidate the connection between coastal residence and vitamin D status. We divided residential data, from developed land use areas and the Lower Super Output Areas or Data Zones (Scotland) of the 1958 Birth Cohort participants, into the following coastal bands: <1 km, 1-5 km, 5-20 km, 20-50 km and over 50 km. In the ecological analysis we used a multiple regression model to describe the relationship between UV vitd and coastal proximity adjusted for latitude. Subsequently, using the residential information of the participants of the 1958 Birth Cohort we developed a multiple regression model to understand the relationship between serum 25(OH)D (a marker of vitamin D status) and coastal proximity adjusted for several factors related to vitamin D status (e.g. diet, outdoor activity).

RESULTS

We found that coastal proximity was associated with solar irradiance; on average a 99.6 (96.1-103.3)J/m(2)/day regression coefficient was recorded for settlements <1 km from the coast compared with those at >50 km. This relationship was modified by latitude with settlements at a lower latitude exhibiting a greater effect. Individuals living closer to the coast in England had higher vitamin D levels than those inland, particularly in autumn.

CONCLUSION

Geographic location may influence biochemistry and health outcomes due to environmental factors. This can provide benefits in terms of vitamin D status but may also pose a risk due to higher skin cancer risk. We provide further evidence in support of the claim that coastal environments can provide opportunities for health and wellbeing.

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 consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.

Vitamin D, allergies and asthma: focus on pediatric patients

In recent years, the interest of the scientific world towards vitamin D gradually increased, and several studies have been conducted to dissect its possible role in modulating the development/course of allergic diseases. Also, Vitamin D supplementation has been assessed as a beneficial approach for treating allergies in some, but not all studies. We reviewed herein the available and relevant literature concerning the possible links between Vitamin D, its supplementation and allergic diseases. A literature search was made independently by the Authors, identifying articles for a narrative review. As per literature, Vitamin D plays a key role in calcium and phosphate metabolism, and it is essential for bone health in infants, children and adolescents. However, there is presently insufficient evidence to support vitamin D supplementation for prevention or treatment of allergic diseases in infants, children and adolescents, concerning allergic rhinitis, asthma, food allergy and atopic dermatitis.

Association between climate factors, pollen counts, and childhood hay fever prevalence in the United States

BACKGROUND

Climate factors and pollen counts may play a role in hay fever.

OBJECTIVE

We sought to determine the impact of specific climate factors and pollen counts on the US prevalence of hay fever and statewide variation in prevalence.

METHODS

We used a merged analysis of the 2007 National Survey of Children's Health from a representative sample of 91,642 children aged 0 to 17 years and the 2006-2007 National Climate Data Center and Weather Service measurements of relative humidity (%), indoor heating degree days, precipitation, Palmer Hydrological Drought Index, clear sky and issued ultraviolet indices, stratospheric ozone levels, and outdoor air temperature and National Allergy Bureau total pollen counts. Multivariate survey logistic regression models controlled for sex, race/ethnicity, age, household income, and birthplace.

RESULTS

The US prevalence of hay fever in childhood was 18.0% (95% CI, 17.7% to 18.2%), with the highest prevalence in southeastern and southern states. Hay fever prevalence was significantly lower with second and third quartile mean annual relative humidity (logistic regression, P ≤ .01 for both), fourth quartile mean annual Palmer Hydrological Drought Index (P = .02), third and fourth quartile mean annual heating degree days (P < .0001 for both), and third and fourth quartile mean annual stratospheric ozone levels but increased with second, third, and fourth quartile mean annual temperature (P ≤ .02 for both), fourth quartile mean annual precipitation (P = .0007), mean total pollen counts (P = .01), and second, third, and fourth quartile issued ultraviolet index (P ≤ .0001 for all). Principal-component analysis was also used to determine the combined effects of correlated climate variables and pollen counts.

CONCLUSIONS

This study provides evidence of the influence of climate on the US prevalence of childhood hay fever.

Don't it make your brown eyes blue? A comparison of iris colour across latitude in Australian twins

BACKGROUND

The aim was to determine whether latitudinal (Queensland versus Tasmania) variation in reported disease frequency in Australia may be biased by differences in population.

METHODS

A retrospective analysis was conducted from data of two large Australian twin studies (n = 1,835) having undertaken ophthalmic examination, namely, Twins Eye Study in Tasmania (TEST) and the Brisbane Adolescent Twins Study (BATS). Ordinal logistic regression was used to compute odds ratios and predicted probabilities for each category of eye colour by state.

RESULTS

Tasmanian residence was associated with lower odds of darker iris colour (odds ratio 0.77, 95% CI [0.63-0.95]) signifying that participants living in Tasmania (TAS) are less likely to have darker-coloured irides than those residing in Queensland (QLD). For individuals living in Tasmania the predicted probability (TAS versus QLD) of having light blue eyes was greater (16.7 versus 13.3 per cent), approximately the same for green eyes and less for brown/dark brown-coloured eyes (6.2 versus 7.9 per cent).

CONCLUSIONS

We found a general trend of individuals living in the southern states (TAS/VIC) of Australia having lighter-coloured irides compared to those living in the north (QLD). This finding has potential implications for all epidemiological research conducted to explore differences in UV-associated disease frequency in Australia, as population heterogeneity may confound the estimates obtained.

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.

The impact of Vitamin D deficiency on asthma, allergic rhinitis and wheezing in children: An emerging public health problem

BACKGROUND

Vitamin D deficiency has been declared a public health problem for both adults and children worldwide. Asthma and related allergic diseases are the leading causes of morbidity in children. The objective of this study was to investigate the potential role of Vitamin D deficiency in childhood asthma and other allergic diseases such as allergic rhinitis and wheezing.

MATERIALS AND METHODS

This cross-sectional study was conducted in Primary Health Care Centers (PHCs), from March 2012 to October 2013. A total of 2350 Qatari children below the age of 16 were selected from PHCs, and 1833 agreed to participate in this study giving a response rate of (78%). Face-to-face interviews with parents of all the children were based on a questionnaire that included variables such as socio-demographic information, assessment of nondietary covariates, Vitamin D intake, type of feeding, and laboratory investigations. Their health status was assessed by serum Vitamin D (25-hydoxyvitamin D), family history and body mass index.

RESULTS

Most of the children who had asthma (38.5%), allergic rhinitis (34.8%) and wheezing (35.7%) were below 5 years. Consanguinity was significantly higher in parents of children with allergic rhinitis (48.6%), followed by those with asthma (46.4%) and wheezing (40.8%) than in healthy children (35.9%) (P < 0.001). The proportion of severe Vitamin D deficiency was significantly higher in children with wheezing (23.4%), allergic rhinitis (18.5%), and asthma (17%) than in healthy children (10.5%). Exposure to the sun was significantly less in Vitamin D deficient children with asthma (60.3%), allergic rhinitis (62.5%) and wheezing (64.4%) than in controls (47.1%) (P = 0.008). It was found that Vitamin D deficiency was a significant correlate for asthma (odds ratio [OR] =2.31; P < 0.001), allergic rhinitis (OR = 1.59; P < 0.001) and wheezing (relative risk = 1.29; P = 0.05).

CONCLUSION

The study findings revealed a high prevalence of Vitamin D deficiency in children with asthma and allergic diseases. Vitamin D deficiency was a strong correlate for asthma, allergic rhinitis and wheezing.

Systemic lupus erythematosus patients in the low-latitude plateau of China: altitudinal influences

The current study was to investigate the features of hospitalized patients with systemic lupus erythematosus (SLE) at different altitudes. The correlation between SLE activity and altitudinal variations was also explored. Medical records of 1029 patients were retrospectively reviewed. Activity of SLE in each organ system was recorded using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). There was no significant correlation between SLE activity and altitudes (r = 0.003, p = 0.159). Age at onset for SLE patients at high altitudes was significantly younger than that at low and moderate altitudes (p = 0.022 and p = 0.004, respectively). Age at SLE admission at low altitudes was significant older than those at moderate and high altitudes (p = 0.011 and p < 0.001, respectively). Patients at high altitudes had shorter duration from disease onset to admission than those at moderate altitudes (p = 0.009). Incidence of Sm antibodies-positive for resident patients at high altitudes was 36.4%, which were higher than that at moderate altitudes (p = 0.003). We found increasing trends of CNS activity in active patients; immunological and renal activities in inactive patients were correlated with elevated altitudes (p = 0.024, p = 0.004, p = 0.005), while arthritis scores in active patients showed the tendency of decreasing with the rise of elevation (p = 0.002). Hemoglobin level, red blood cell and platelet counts at high altitudes were significantly lower than those at low altitudes (p < 0.05, respectively). There was no significant difference in hemoglobin level between moderate- and low-altitude groups (p > 0.05). No significant difference in platelet counts between moderate- and high-altitude groups was observed (p > 0.05). Our findings suggest that some clinical features, laboratory tests and activity of main organs in SLE are influenced by altitudes. Furthermore, organ activities of active and inactive SLE patients have different patterns of altitudinal variations. These distinctive variations likely reveal that peculiar environmental factors at high altitudes can affect the development of SLE.

The association between serum vitamin D level and immunoglobulin E in Korean adolescents

OBJECTIVE

Vitamin D has immune modulatory functions, and thus its relationship with allergic disease has been evaluated in a number of studies. However, no concrete link between serum IgE level and vitamin D has been established. Thus, the purpose of study was to confirm the association of serum vitamin D level with the serum IgE (total and Dematophagoides farinae specific IgE) in Korean adolescents.

METHODS

A total of 365 subjects between 10 and 18 years of age were enrolled through the Korea National Health and Nutrition Examination Survey (KNHANES). Serum levels of vitamin D, total IgE, and Dermatophagoides farinae (Df) specific IgE were measured, and data for potential confounding variables were collected. Multivariate regression analyses were used to determine the independent effects of these variables.

RESULTS

Levels of both total and Df specific IgE were positively correlated with serum concentration of vitamin D (Spearman's rho (R)=0.126, p=0.016; R=0.152, p=0.004, respectively). These results were confirmed by multivariate linear regression analysis after adjusting for sex, age, and body mass index (coefficient (B): 10.45 95% confidence interval (CI): 0.59-20.31; B: 1.06, 95% CI: 0.31-1.80, respectively). And, the association between serum vitamin D and IgE showed the different results depending on the presence or absence of Df sensitization.

CONCLUSIONS

Serum concentration of vitamin D was positively associated with levels of both total IgE and Df-specific IgE in Korean adolescents.

Immunoregulatory mechanisms of vitamin D relevant to respiratory health and asthma

Vitamin D deficiency is prevalent among people with various immune-mediated conditions, including autoimmune diseases and asthma. Serum 25(OH)D levels inversely correlate with asthma severity, glucocorticoid responsiveness/dosage, and markers of pathogenesis, such as airway remodeling, IgE, and eosinophilia. Trials involving supplementation with active vitamin D or a precursor are beginning to emerge with variable results that, in part, reflect differences in study design. This review looks at the mechanisms by which vitamin D may protect against asthma, including increasing glucocorticoid responsiveness, skewing immune cells towards a regulatory phenotype, reducing the incidence of infections, airway remodeling, eosinophilia, and lowering the levels of IgE. Also discussed is the therapeutic potential for vitamin D, which is likely to be applicable to immune-mediated conditions beyond simply asthma.

Link between vitamin D and airway remodeling

In the last decade, many epidemiologic studies have investigated the link between vitamin D deficiency and asthma. Most studies have shown that vitamin D deficiency increases the risk of asthma and allergies. Low levels of vitamin D have been associated with asthma severity and loss of control, together with recurrent exacerbations. Remodeling is an early event in asthma described as a consequence of production of mediators and growth factors by inflammatory and resident bronchial cells. Consequently, lung function is altered, with a decrease in forced expiratory volume in one second and exacerbated airway hyperresponsiveness. Subepithelial fibrosis and airway smooth muscle cell hypertrophy are typical features of structural changes in the airways. In animal models, vitamin D deficiency enhances inflammation and bronchial anomalies. In severe asthma of childhood, major remodeling is observed in patients with low vitamin D levels. Conversely, the antifibrotic and antiproliferative effects of vitamin D in smooth muscle cells have been described in several experiments. In this review, we briefly summarize the current knowledge regarding the relationship between vitamin D and asthma, and focus on its effect on airway remodeling and its potential therapeutic impact for asthma.

Vitamin D and maternal and child health: overview and implications for dietary requirements

The essentiality of vitamin D for normal growth and development has been recognized for over 80 years, and vitamin D fortification programs have been in place in the United States for more than 70 years. Despite the above, vitamin D deficiency continues to be a common finding in certain population groups. Vitamin D deficiency has been suggested as a potential risk factor for the development of preeclampsia, and vitamin D deficiency during infancy and early childhood is associated with an increased risk for numerous skeletal disorders, as well as immunological and vascular abnormalities. Vitamin D deficiency can occur through multiple mechanisms including the consumption of diets low in this vitamin and inadequate exposure to environmental ultraviolet B rays. The potential value of vitamin D supplementation in high-risk pregnancies and during infancy and early childhood is discussed. Currently, there is vigorous debate concerning what constitutes appropriate vitamin D intakes during early development as exemplified by differing recommendations from the Institute of Medicine Dietary Reference Intake report and recent recommendations by the Endocrine Society. As is discussed, a major issue that needs to be resolved is what key biological endpoint should be used when making vitamin D recommendations for the pregnant woman and her offspring.

Vitamin D in asthma and future perspectives

Humans have the ability to synthesize vitamin D during the action of ultraviolet (UV) radiation upon the skin. Apart from the regulation of calcium and phosphate metabolism, another critical role for vitamin D in immunity and respiratory health has been revealed, since vitamin D receptors have also been found in other body cells. The term "vitamin D insufficiency" has been used to describe low levels of serum 25-hydroxyvitamin D that may be associated with a wide range of pulmonary diseases, including viral and bacterial respiratory infection, asthma, chronic obstructive pulmonary disease, and cancer. This review focuses on the controversial relationship between vitamin D and asthma. Also, it has been found that different gene polymorphisms of the vitamin D receptor have variable associations with asthma. Other studies investigated the vitamin D receptor signaling pathway in vitro or in experimental animal models and showed either a beneficial or a negative effect of vitamin D in asthma. Furthermore, a range of epidemiological studies has also suggested that vitamin D insufficiency is associated with low lung function. In the future, clinical trials in different asthmatic groups, such as infants, children of school age, and ethnic minorities are needed to establish the role of vitamin D supplementation to prevent and/or treat asthma.

Prevalence of asthma symptoms in schoolchildren, and climate in west European countries: an ecologic study

The aim of the present study was to estimate the associations between the prevalence of asthma symptoms in schoolchildren and meteorological variables in west European countries that participated in the International Study of Asthma and Allergies in Children (ISAAC), Phase III 1997-2003. An ecologic study was carried out. The prevalence of asthma was obtained from this study from 48 centers in 14 countries, and meteorological variables from those stations closest to ISAAC centers, together with other socioeconomic and health care variables. Multilevel mixed-effects linear regression models were used. For schoolchildren aged 6-7 years, the prevalence rate of asthma decreased with an increase in mean annual sunshine hours, showed a positive association with rainy weather, and warm temperature, and a negative one with relative humidity and physician density (PD). Current wheeze prevalence was stronger in autumn/winter seasons and decreased with increasing PD. Severe current wheeze decreased with PD. For schoolchildren aged 13-14 years, the prevalence rates of asthma and current wheeze increased with rainy weather, and these rates decreased with increased PD. Current wheeze, as measured by a video questionnaire, was inversely associated with sunny weather, and nurse density. Severe current wheeze prevalence was stronger during autumn/winter seasons, decreased with PD, and indoor chlorinated public swimming pool density, and increased with rainy weather. Meteorological factors, including sunny and rainy weather, and PD may have some effect on the prevalence rates of asthma symptoms in children from west European countries.

The influence of sun exposure in childhood and adolescence on atopic disease at adolescence

BACKGROUND

It has been postulated that ultraviolet ray exposure in childhood might influence the development of allergic disease. We examined whether reported sun exposure during childhood or in adolescence is related to the occurrence of atopy or allergic disease.

METHODS

Population-based longitudinal cohort study with sixteen-year follow-up (N = 415). Subjects were recruited at birth as part of an infant health study. The reported daily duration of sun exposure in the summer months was recorded at 8 and 16 yrs of age. Allergen sensitization and the presence of eczema, asthma, and rye grass positive rhinitis were recorded at age 16.

RESULTS

Reported sun exposures of more than 4 h per day during summer holidays in adolescence were associated with reduced eczema and rhinitis but not inhalant allergen sensitization or asthma risk. Thus, higher sun exposure during summer holidays and summer weekends in adolescence was associated with significantly reduced eczema (test of trend p-value = 0.001 summer holidays; test of trend p-value = 0.003 summer weekends) and rye grass positive rhinitis (test of trend p-value = 0.03 summer holidays; test of trend p-value = 0.02 summer weekends). Sun exposure at adolescence or age 8 was not related to inhalant allergen sensitization. There was no association between serum 25(OH)D levels at adolescence with either inhalant allergen sensitization or allergic disease and adjustment for serum 25(OH)D levels did not alter these findings.

CONCLUSIONS

Increased sun exposure during summer holidays in adolescence was associated with reduced eczema and rhinitis risk, independently of measured vitamin D levels but no difference in inhalant allergen sensitization or asthma. The beneficial effects of sun exposure on allergic disease may operate independently from vitamin D or an effect on allergen sensitization.

Vitamin D in allergic disease: shedding light on a complex problem

Vitamin D is unique among nutritional factors because the intake of this special vitamin represents the sum of vitamin D obtained from diet, nutritional supplements, and endogenous production after exposure to sunlight. The current recommended nutritional intake requirements reflect needs based on its established role in calcium absorption and bone health. However, recent studies have revealed that vitamin D has important functions in the immune system and might influence the course of immune-mediated disorders, including atopic dermatitis and asthma. This review discusses the scientific rationale for a role for vitamin D in immune function, gives an update on allergic disease associations with lower vitamin D serum levels, and discusses recent observations relating to vitamin D in immune function.

Reversible control by vitamin D of granulocytes and bacteria in the lungs of mice: an ovalbumin-induced model of allergic airway disease

Vitamin D may be essential for restricting the development and severity of allergic diseases and asthma, but a direct causal link between vitamin D deficiency and asthma has yet to be established. We have developed a 'low dose' model of allergic airway disease induced by intraperitoneal injection with ovalbumin (1 µg) and aluminium hydroxide (0.2 mg) in which characteristics of atopic asthma are recapitulated, including airway hyperresponsiveness, antigen-specific immunoglobulin type-E and lung inflammation. We assessed the effects of vitamin D deficiency throughout life (from conception until adulthood) on the severity of ovalbumin-induced allergic airway disease in vitamin D-replete and -deficient BALB/c mice using this model. Vitamin D had protective effects such that deficiency significantly enhanced eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male but not female mice. Vitamin D also suppressed the proliferation and T helper cell type-2 cytokine-secreting capacity of airway-draining lymph node cells from both male and female mice. Supplementation of initially vitamin D-deficient mice with vitamin D for four weeks returned serum 25-hydroxyvitamin D to levels observed in initially vitamin D-replete mice, and also suppressed eosinophil and neutrophil numbers in the bronchoalveolar lavage fluid of male mice. Using generic 16 S rRNA primers, increased bacterial levels were detected in the lungs of initially vitamin D-deficient male mice, which were also reduced by vitamin D supplementation. These results indicate that vitamin D controls granulocyte levels in the bronchoalveolar lavage fluid in an allergen-sensitive manner, and may contribute towards the severity of asthma in a gender-specific fashion through regulation of respiratory bacteria.

Influence of Mediterranean diet on asthma in children: a systematic review and meta-analysis

BACKGROUND

There is epidemiological evidence that Mediterranean diet exposure is associated with lower asthma prevalence in children. We aimed to summarize the available data and to know whether the Mediterranean setting modifies this association.

METHODS

The literature search, up to May 2012, was on epidemiological studies in the general population of children assessing whether adherence to Mediterranean diet (measured as a score) was associated with the prevalence of 'current wheeze'; 'current severe wheeze'; or 'asthma ever'. Odds ratios (OR) of the eight included studies compared the highest tertile of the score with the lowest. Random-effects meta-analyses for the whole group of studies and stratified by Mediterranean setting (centers <100 Km from the Mediterranean coast) were performed. Differences between strata were assessed using the Q test.

RESULTS

For 'current wheeze', there was a negative significant association with the highest tertile of Mediterranean diet score (OR 0.85, 95% CI 0.75-0.98; p = 0.02), driven by Mediterranean centers (0.79, 0.66-0.94, p = 0.009), although the difference with the non-Mediterranean centers (0.91, 0.78-1.05, p = 0.18) was not significant. The results for 'current severe wheeze' were as follows: 0.82, 0.55-1.22, p = 0.330 (all); 0.66, 0.48-0.90, p = 0.008 (Mediterranean); and 0.99, 0.79-1.25, p = 0.95 (non-Mediterranean); with the difference between regions being significant. For 'asthma ever', the associations were as follows: 0.86, 0.78-0.95, p = 0.004 (all); 0.86, 0.74-1.01, p = 0.06 (Mediterranean); 0.86, 0.75-0.98; p = 0.027 (non-Mediterranean); with the difference between regions being negligible.

CONCLUSIONS

Adherence to the Mediterranean diet tended to be associated with lower occurrence of the three respiratory outcomes. For current and current severe wheeze, the association was mainly driven by the results in Mediterranean populations.

Effects of vitamin D on immune disorders with special regard to asthma, COPD and autoimmune diseases: a short review

This paper reviews the recent data on the role of vitamin D (VD) in the genesis of various immunological disorders. It inhibits immune reactions in general, but it enhances the transcription of 'endogenous antibiotics' such as cathelicidin and defensins. VD inhibits the genesis of both Th1- and Th2-cell mediated diseases. The pleiotropic character VD-induced effects are due to the altered transcription of hundreds of genes. VD supplementation in most related studies reduced the prevalence of asthma. Th1-dependent autoimmune diseases (e.g., multiple sclerosis, Type 1 diabetes, Crohn's disease, rheumatoid arthritis and so on) are also inhibited by VD due to inhibition of antigen presentation, reduced polarization of Th0 cells to Th1 cells and reduced production of cytokines from the latter cells. VD seems to also be a useful adjunct in the prevention of allograft rejection. Last but not least, VD supplementation may be useful in the prevention or adjunct treatment of chronic obstructive pulmonary disease.

Association between latitude and allergic diseases: a longitudinal study from childhood to middle-age

BACKGROUND

Worldwide variations in allergy prevalence suggest that geographic factors may contribute to asthma. Ecologic studies have suggested that latitude, a marker of UV-B exposure and allergen exposures, may be related to clinical allergies.

OBJECTIVE

To examine the relationship between latitude or UV-B based on self-reported geolocation and allergic sensitization and disease prevalence in Australia.

METHODS

The Tasmanian Longitudinal Health Study is a population-based study of respiratory disease spanning childhood to adulthood. The most recent follow-up included a postal survey of 5,729 participants and a clinical substudy of 1,396 participants. Participants' residential addresses were coded for latitude and linked with the UV-B data from satellite-based observations of atmospheric ozone. Multivariable logistic regression analyses were performed to estimate the associations between latitude or UV-B and allergic diseases.

RESULTS

Most northerly latitude, that is, latitude closest to the Equator, and high current UV-B exposure were associated with increased odds of hay fever, food allergy, and skin sensitization to house dust mites and molds. More northerly latitude and higher UV-B exposure were associated with increased odds of current asthma among atopic individuals contrasting with a reduced odds of current asthma among nonatopic individuals.

CONCLUSION

This is the first study, to our knowledge, to demonstrate a differential effect of atopic status on the relationship between latitude and current asthma. Our study demonstrates in a genetically and culturally similar group of individuals that geographic factors may a play role in the development of allergic disease.

Recent advances in the epidemiologic investigation of risk factors for asthma: a review of the 2011 literature

The present review aims to identify and summarize epidemiologic investigations published during 2011 on the environmental risk factors for asthma. Potentially eligible papers were identified by a MEDLINE search. In total, 1,130 items were retrieved. Based on a broad definition of environment, the following topics were included: obesity, diet, vitamin D, air pollution, farming environment, and social factors. Some of the more relevant contributions included evidence that 1) obesity precedes asthma, 2) fruit consumption is longitudinally associated with a lower risk of asthma and atopy, 3) a comprehensive statewide smoking ban was followed by a reduction in hospital admissions for asthma, 4) asthma is one of the diseases showing the largest burdens due to environmental tobacco smoke, 5) traffic-related urban air pollution is associated with bronchial inflammation as measured by fractional exhaled nitric oxide and uncontrolled asthma, 6) aeroallergens and desert dust may contribute to the short-term effects of air pollution and asthma, and 7) maternal exposure to air pollution before and during pregnancy may alter the immune competence in offspring.