Role of vitamin D in cystic fibrosis and non-cystic fibrosis bronchiectasis

Metabolism and pharmacokinetics of vitamin D in patients with cystic fibrosis

Patients with cystic fibrosis (CF) commonly have lower circulating concentrations of 25-hydroxyvitamin D (25(OH)D) than healthy populations. We comprehensively compared measures of vitamin D metabolism among individuals with CF and healthy control subjects. In a cross-sectional study, serum from participants with CF (N = 83) and frequency-matched healthy control subjects by age and race (N = 82) were analyzed for: 25(OH)D2 and 25(OH)D3, 1α,25-dihydroxyvitamins D2 and D3 (1α,25(OH)2D2 and 1α,25(OH)2D3), 24,25-dihydroxyvitamin D3 (24,25(OH)2D3), 4β,25-dihydroxyvitamin D3 (4β,25(OH)2D3), 25-hydroxyvitamin D3-3-sulfate (25(OH)D3-S), and 25-hydroxyvitamin D3-3-glucuronide (25(OH)D3-G). In a 56-day prospective pharmacokinetic study, ∼25 μg deuterium-labeled 25(OH)D3 (d6-25(OH)D3) was administered intravenously to participants (N = 5 with CF, N = 5 control subjects). Serum was analyzed for d6-25(OH)D3 and d6-24,25(OH)2D3, and pharmacokinetic parameters were estimated. In the cross-sectional study, participants with CF had similar mean (SD) total 25(OH)D concentrations as control subjects (26.7 [12.3] vs. 27.7 [9.9] ng/mL) and had higher vitamin D supplement use (53% vs. 22%). However, participants with CF had lower total 1α,25(OH)2D (43.6 [12.7] vs. 50.7 [13.0] pg/mL), 4β,25(OH)2D3 (52.1 [38.9] vs. 79.9 [60.2] pg/mL), and 25(OH)D3-S (17.7 [11.6] vs. 30.1 [12.3] ng/mL) (p < 0.001 for all). The pharmacokinetics of d6-25(OH)D3 and d6-24,25(OH)D3 did not differ between groups. In summary, although 25(OH)D concentrations were comparable, participants with CF had lower 1α,25(OH)2D, 4β,25(OH)2D3, and 25(OH)D3-S concentrations than healthy controls. Neither 25(OH)D3 clearance, nor formation of 24,25(OH)2D3, appears to account for these differences and alternative mechanisms for low 25(OH)D in CF (i.e., decreased formation, altered enterohepatic recirculation) should be explored.

Prevalence of Anemia and its Relation with Shwachman Score in Children with Cystic Fibrosis

Background

Cystic fibrosis is a chronic and progressive genetic disease with a worldwide prevalence. As the disease progresses, symptoms develop, and make its management more challenging. Accumulating evidence suggests that early diagnosis of CF can significantly contribute to preventing reported nutritional problems including anemia, vitamin deficiencies, and hypoalbuminemia. This cross-sectional study was conducted to assess disease severity in cystic fibrosis patients using the Shwachman-Kulczycki score, as well as to determine its relation with anemia and vitamin D deficiency.

Materials and Methods

Clinical and CF-related laboratory data were collected from the medical records of 57 CF patients with a definitive diagnosis. At the time of diagnosis, physicians performed simultaneous, blood sampling and scoring of patients using the Shwachman scoring system.

Results

The mean age of patients was 16.12±6.48 years. Total scores of 86-100, 71-85, 56-70, 41-55, and <40, were reported in 5.4%, 7.1%, 14.3%, 14.3%, and 58.9% of CF patients, respectively. A significant correlation was found between disease severity and patients' age (P=0.02). The analysis also showed that the disease severity was significantly higher in anemic patients when compared to non-anemics (p =0.006). Based on the results, 33 patients with normochromic, 11 patients with microcytic, and 6 patients with macrocytic anemia were diagnosed in this study. We did not find a significant difference between disease severity and vitamin D levels (P=0.150).

Conclusion

The scoring system used in the current study could reflect properly the clinical status of CF patients. However, simultaneous use of various methods using a larger sample size for comparison of results is suggested to improve the accuracy of findings.

Recent advances in vitamin D implications in chronic respiratory diseases

Chronic airway inflammatory and infectious respiratory diseases are the most common medical respiratory conditions, associated with significant morbidity and mortality. Vitamin D (1,25(OH)₂D₃) deficiency has been shown to be highly prevalent in patients with chronic airway inflammatory and infectious diseases, correlated with increased disease severity. It has been established that vitamin D modulates ongoing abnormal immune responses in chronic respiratory diseases and is shown to restrict bacterial and viral colonization into the lungs. On the contrary, other studies revealed controversy findings regarding vitamin D efficacy in respiratory diseases. This review aims to update the current evidence regarding the role of vitamin D in airway inflammation and in various respiratory diseases. A comprehensive search of the last five years of literature was conducted using MEDLINE and non-MEDLINE PubMed databases, Ovid MEDLINE, SCOPUS-Elsevier, and data from in vitro and in vivo experiments, including clinical studies. This review highlights the importance of understanding the full range of implications that vitamin D may have on lung inflammation, infection, and disease severity in the context of chronic respiratory diseases.

Sputum neutrophil elastase and its relation to pediatric bronchiectasis severity: A cross‐sectional study

Background and Aims

Sputum neutrophil elastase (NE) is a marker of neutrophilic airway inflammation in bronchiectasis. Yet, not much is known about its role in pediatric bronchiectasis severity. This study aimed to assess the sputum NE value as a biomarker of clinical and radiological severity in pediatric bronchiectasis.

Methods

This was a cross‐sectional study assessing sputum NE in a total of 50 bronchiectasis patients under the age of 18 years—30 patients with cystic fibrosis (CF) and 20 patients with non‐CF bronchiectasis were included. Bronchiectasis severity was assessed using Shwachman–Kulczycki (SK) score, CF‐ABLE score, and CF risk of disease progression score, among CF patients, and bronchiectasis severity index (BSI) and FACED criteria among non‐CF bronchiectasis patients, associations between sputum NE and bronchiectasis severity were assessed in both patient groups.

Results

Sputum NE was directly correlated with C‐reactive protein (r = 0.914, p < 0.001), (r = 0.786, p < 0.001), frequency of exacerbations (r = 0.852, p < 0.001) (r = 0.858, p < 0.001), exacerbations severity (r = 0.735, p = 0.002), (r = 0.907, p < 0.001), and the number of hospital admissions (r = 0.813, p < 0.001), (r = 0.612, p  =0.004) in the last year among CF, and non‐CF bronchiectasis patients, respectively. Additional linear correlations were found between sputum NE, CF risk of disease progression score (p < 0.001), CF‐ABLE score (p < 0.001), and lower forced expiratory volume 1% of predicted (p = 0.017; ρ = −0.8) among CF patients. Moreover, sputum NE was positively correlated with the neutrophil count (p = 0.018), and BSI severity score (p = 0.039; ρ = 0.465) among non‐CF bronchiectasis patients.

Conclusions

Sputum NE may be considered a good biomarker of bronchiectasis severity in both CF and non‐CF bronchiectasis patients, as confirmed by the exacerbations rate, CF risk of disease progression, and BSI scores.

Vitamins A, D, E status as related to supplementation and lung disease markers in young children with cystic fibrosis

BACKGROUND

The variable response to fat-soluble vitamin supplementation in young children with cystic fibrosis (CF), and factors contributing to this variability, remain under-investigated.

OBJECTIVE

To determine if recommended supplement doses normalize serum vitamins A (retinol), D (25-hydroxy-vitamin D, 25OHD), and E (α-tocopherol), and identify factors predictive of achieving sufficiency, in children with CF in the first 3 years of life.

DESIGN

We studied 144 infants born during 2012-2017 and diagnosed with CF through newborn screening. Serum retinol, 25OHD, α-tocopherol and plasma cytokines interleukin (IL)-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α were measured in early infancy and yearly thereafter. Vitamin supplement intakes and respiratory microbiology were assessed every 1-2 months in infancy and quarterly thereafter.

RESULTS

The prevalence of vitamin D insufficiency (<30 ng/ml) at all ages combined was significantly higher (22%) compared to vitamin A (<200 ng/ml, 3%) and vitamin E (<5 µg/ml, 5%). All children were vitamin A sufficient by age 2 years. Vitamin E insufficiency was rare. Only 42% were early responders of vitamin D and 17% remain insufficient despite high supplement intakes. IL-6 was positively correlated, while IL-8, IL-10, and TNF-α were negatively correlated, with retinol and 25OHD. Multiple regression analysis revealed that supplement dose, season, α-tocopherol, pancreatic insufficiency, respiratory infections and IL-10 were significant predictors of 25OHD.

CONCLUSION

Diagnosis through newborn screening coupled with supplementation normalized serum retinol and α-tocopherol in almost all infants with CF by age 3 years. However, response to vitamin D supplements in young children with CF occurred later and variably despite early and sustained supplementation.

Impact of vitamin D status on CF and non-CF bronchiectasis outcomes

Background

Vitamin D deficiency occurs frequently in cystic fibrosis (CF) and non-CF bronchiectasis patients. Yet, few studies have assessed the impact of vitamin D status on the clinical outcomes in pediatric bronchiectasis. This study is designed to assess vitamin D level and determine its effect on exacerbations, bacterial colonization, and lung function in pediatric patients with CF and non-CF bronchiectasis.

Results

This cross-sectional case-control study assessing vitamin D level was performed in a total of sixty cases under the age of 18 years—forty cases with CF and non-CF bronchiectasis and twenty age- and sex-matched healthy controls. Associations between serum vitamin D and clinical and laboratory parameters were assessed in the patient groups. Vitamin D deficiency was more prevalent among CF and non-CF bronchiectasis patients (75%, 45%) compared to controls (10%) (P < 0.001). In addition, vitamin D deficiency was associated with more frequent and severe pulmonary exacerbations (66.7%, 46.7%) (P=0.033, < 0.001), chronic Pseudomonas infection (80%) (P=0.060) among CF patients, and with lower FEV1 (66%) (P= 0.071) among non-CF bronchiectasis. Moreover, a cutoff value of vitamin D level equal or less than 22.5 ng/ml was accurate in differentiating moderate from mild pulmonary exacerbations in both patients’ groups (AUC=0.809) (p=0.004).

Conclusions

Vitamin D deficiency is not uncommon in both CF and non-CF bronchiectasis. In this population, vitamin D deficiency is associated with more frequent pulmonary exacerbations, chronic Pseudomonas infection, and worse lung function.

Medical nutritional therapy in infected bronchiectasis with impending respiratory failure: A case report

OBJECTIVE

Bronchiectasis is a chronic infective and inflammatory respiratory disease that causes significant morbidity and mortality. Repeated respiratory infections may lead to infected bronchiectasis (IB) and acute exacerbations which often require hospital admission, increase risk of malnutrition and impact quality of life and eventually leads to death. Nutritional therapy is needed to modulate inflammation and enhance immunity to reduce severity of exacerbation, overcome malnutrition, as well as to decrease morbidity and mortality.

METHODS

A 59-year-old female patient, diagnosed with IB. The patient had low oral intake due to productive cough and anorexia since 2 weeks before admission. Moreover, she had gradual shortness of breath that caused an impending respiratory failure during hospitalization, supported by continuous positive airway pressure (CPAP). Nutritional assessment was made based on Subjective Global Assessment (SGA) score C. Abnormal laboratory findings seen were increased in neutrophil-to-lymphocyte ratio (NLR) 9.3, moderate depletion of immune system with total lymphocyte count (TLC) 808.4/μl, hypoalbuminemia (3.2g/dl) and increased in liver enzymes: aspartate aminotransferase (AST) 206U/l, Alanine aminotransferase (ALT) 224U/l. Nutritional therapy was given gradually with target calorie 1400-1900kcal, protein 0.8-1.5g/kg IBW/day, carbohydrates 45-50%, and fat 33.3-43% through oral and parenteral nutrition. The patient was given supplementations such as vitamins (A, B complex, C, D), zinc, curcumin and snakehead fish extract high albumin content.

RESULT

After 14 days of treatment, significant clinical and metabolic improvement in NLR, TLC, plasma albumin, liver enzymes (AST/ALT), blood gas analysis, and functional capacity (handgrip strength) were found.

CONCLUSION

An adequate nutritional therapy with macro and micro-nutrients in IB patient can improve clinical outcome, nutritional status and quality of life.

25-Hydroxy vitamin D and body composition are associated with pulmonary function in non-cystic fibrosis bronchiectasis: A cross-sectional study

BACKGROUND

Previous studies have emphasized the effects of vitamin D on the lung function of cystic fibrosis (CF) adult patients. The main aim of the present study sought to determine the association between circulating 25-hydroxyvitamin D (25-OH D) concentration and clinical outcomes in non-cystic fibrosis (non-CF) bronchiectasis subjects. Secondary, we assessed the possible relationship between body composition and respiratory dysfunction in these patients.

MATERIALS AND METHODS

Sixty-two non-CF bronchiectasis patients (24 male/38 female), aged 18-72, were recruited in this cross-sectional study. Anthropometric indices, lung function tests, and bronchiectasis severity valuations were determined. Body composition, including Mid-arm muscle circumference (MAMC, cm) was calculated using triceps skinfold (TSF,mm) and mid-arm circumference (MAC,cm) under the reference formula. Then serum 25-hydroxyvitamin D concentration and C-reactive protein level were measured. The correlation between vitamin D level and pulmonary function and disease exacerbation tests was primarily assessed. Additionally, we evaluated the correlation between body composition and lung function tests.

RESULTS

Circulating 25-hydroxyvitamin D status positively was correlated with lung function tests, including FEV₁ (r = 0.30, p value = 0.035) and FVC (r = 0.36, p value = 0.011), and also be associated with the extent of pulmonary involvement (r = -0.34, p value = 0.03). There was a significant negative correlation between percentage body fat and respiratory function, FEV₁/FVC ratio (r = -0.43, p value < 0.001). In contrast, there was a strong correlation between skeletal muscle mass and pulmonary function tests (r = 0.26, p value = 0.04).

CONCLUSION

There is a positive association between low 25-hydroxyvitamin D status and lung dysfunction in participants with non-CF bronchiectasis. The pulmonary dysfunction also correlated with more percentage body fat and low skeletal muscle mass in these patients. Therefore, the evaluation of body composition and serum vitamin D are suggested in the disease management of the patients with non-CF bronchiectasis. However, these associations should be interpreted with caution due to the likelihood of reverse causation. More high-quality prospective studies are warranted to confirm our observations and determine the mechanisms underlying these findings.

Bronchiectasis-Could Immunonutrition Have a Role to Play in Future Management?

Bronchiectasis is a chronic condition in which areas of the bronchial tubes become permanently widened predisposing the lungs to infection. Bronchiectasis is an age-associated disease with the highest prevalence in people older than 75 years. While the prevalence of bronchiectasis is higher in males, disease is more severe in females who have a poorer prognosis. The overall prevalence of the disease is thought to be rising. Its aetiology is multi-faceted, but a compromised immune system is now thought to play a central role in the pathology of this disease. Research has begun to study the role of malnutrition and certain nutrients-vitamin D and zinc-along with the role of the lung microbiome in relation to the management of bronchiectasis. Given this, the present mini review sets out to provide an overview of the state-of-the-art within the field, identify research gaps and pave the way for future developments and research investment within this field.

Association of vitamin D status with lung function measurements in children and adolescents with cystic fibrosis

BACKGROUND

Vitamin D status is considered a potential determinant of lung function in cystic fibrosis (CF). The aim of this retrospective longitudinal study was to investigate the decline of spirometric values in association with vitamin D status.

METHODS

The data regarding 25-hydroxy vitamin D (25OHD) serum levels, spirometric measurements (FEV1, FVC, FEF25-75%), and factors known to be associated with the decline of lung function in CF were retrospectively collected over a 5-year period. The spirometric indices were recorded as the best and the average value of each year, as well as the value, recorded concurrently or closely with 25OHD level measurement.

RESULTS

A significantly positive relationship was observed between 25OHD serum levels and the best annual value of FEV1 (P = .034), and the values of FEV1 (P = .010) and FVC (P = .018) measured concurrently or closely with serum 25OHD levels. The evolution of the best annual value of FEV1 was worse in patients with a mean 5-year value of 25OHD levels less than 20 ng/mL compared with patients with a mean 5-year value of ≥30 ng/mL (P < .001), or ≥20 to <30 (P < .001). There was no significant difference between patients with mean 5-year 25OHD levels ≥30 ng/mL and ≥20 to <30 ng/mL (P = .76).

CONCLUSIONS

Vitamin D status is associated with lung function in patients with CF. Levels of 25OHD above 20 ng/mL were associated with higher best annual FEV1.

The Immunomodulatory Role of Vitamin D in Respiratory Diseases

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The growing interest in the new role of vitamin D, particularly as an immunomodulatory factor, has spurred basic research and the development of clinical trials to better understand the influence of supplementation on various diseases. Vitamin D is an important nutrient factor in human health due to its role in calcium metabolism regulation, cellular growth, differentiation and its fundamental discovered activity in immune functions. It has influenced different diseases, particularly inflammatory and autoimmune diseases, through immune response regulation, modulating innate and adaptive immunity.

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The aim of this review was to explore the role of vitamin D in the main respiratory diseases in children such as asthma, chronic rhinosinusitis, cystic fibrosis and recurrent respiratory infections.

Bronchiectasis and cough: An old relationship in need of renewed attention

Bronchiectasis is an increasingly recognised respiratory condition with limited therapeutic options and a complex spectrum of clinical manifestations that invariably includes chronic cough. As the primary presentation of bronchiectasis in most cases, chronic cough and its mechanistic underpinnings are of central importance but remain poorly understood in this setting. Bronchiectasis is also increasingly identified as an underlying cause of chronic cough highlighting the interrelationship between the two conditions that share overlapping clinical features. Several therapeutic approaches have illustrated positive effects on bronchiectasis-associated cough, however, more focused treatment of heterogeneous cough subtypes may yield better outcomes for patients. A current challenge is the identification of bronchiectasis and cough endophenotypes that may allow improved patient stratification and more targeted therapeutic matching of the right treatment to the right patient. Here we discuss the complex disease phenotypes of bronchiectasis and their interrelationship with cough while considering current and emerging treatment options. We discuss some key cough promoters in bronchiectasis including infection, allergy and immune dysfunction.

Vitamin D inhibits pro-inflammatory cytokines in the airways of cystic fibrosis patients infected by Pseudomonas aeruginosa- pilot study

Background

Vitamin D plays an important role in inflammatory responses after antigen exposure. Interleukin-23 (Il-23) promotes Il-17-dependent inflammation during Pseudomonas aeruginosa (P. aeruginosa) pulmonary infection. We aimed to compare the ability of calcitriol and cholecalciferol to modulate the inflammatory response of the CF airways infected with P. aeruginosa.

Methods

This was a randomized, placebo-controlled, double-blind, cross-over trial. Twenty-three patients with CF (aged 6–19), chronically infected by P. aeruginosa were randomly assigned to: calcitriol group receiving 1,25(OH)₂D 0,5 mcg daily or cholecalciferol group receiving cholecalciferol 1000 IU daily for three months. The levels of Il-23 and Il-17A in the exhaled breath concentrate (EBC) were measured. Calcium-phosphorus balance was also evaluated (serum concentration of calcium, phosphorus, 25OHD, parathormone (PTH) and calcium/creatinine ratio in urine). Data were analyzed using means of Stata/Special Edition, release 14.2. A level of P < 0.05 was considered statistically significant.

Results

The level of Il-17A in EBC significantly decreased in calcitriol group from 0,475 pg/mL (± SD 0,515 pg/mL) to 0,384 pg/mL (± SD 0,429 pg/mL) (p = 0,008); there was no change in cholecalciferol group (p = 0,074). The level of Il-23 in EBC did not significantly change in calcitriol group (p = 0,086); there was significant decrease in cholecalciferol group from 8,90 pg/mL (± SD 4,07 pg/mL) to 7,33 pg/mL (± SD 3,88 pg/mL) (p = 0,001). In calcitriol group serum phosphorus and PTH significantly decreased (p = 0,021 and p = 0,019 respectively), the concentration of calcium significantly increased (p = 0,001); there were no changes in cholecalciferol group.

Conclusions

Both analogs of vitamin D revealed their anti-inflammatory effect and reduced the level of Il-17A and Il-23 in the airway of CF patients with chronic P. aeruginosa infection. We observed improvement in calcium-phosphorus metabolism after supplementation with calcitriol, without adverse effects. It is recommended to use vitamin D in CF patients.

Vitamin D and disease severity in bronchiectasis

BACKGROUND

Bronchiectasis is a complex respiratory disease characterised by permanent dilatation of bronchi. Vitamin D plays a role in infective disease by modulating the inflammation. Patients affected by bronchiectasis are frequently Vitamin D deficient and it correlates with lung function decline. We want to understand if there is a correlation between Vitamin D and clinical and radiological severity of bronchiectasis.

METHODS

We included 57 patients (17 males/40 female with mean age 60 ± 12 years) between October 2017 and March 2018. We excluded patients with cystic fibrosis, traction bronchiectasis and reporting Vitamin D supplementation. Bronchiectasis severity index (BSI) and Bhalla score were calculated, blood inflammatory markers and Vit. D were measured and lung function tests were performed.

RESULTS

Vitamin D is deficient in 64% of patients, sufficient in 36% and normal in 7%. Mean BSI is 7.5 ± 5 and mean Bhalla score is 16 ± 4. Vitamin D levels correlate with Bhalla score (R² = 0.68, p < 0.001) and BSI (R² = 0.58, p < 0.0001). The correlation appears to be stronger than other markers of inflammation such as ESR and CRP [R² = 0.33, p = 0.001 and R² = 0.39, p = 0.001 respectively].

CONCLUSIONS

We consider Vitamin D as a good predictor of clinical and radiological severity of bronchiectasis.

Supervised physical exercise improves clinical, anthropometric and biochemical parameters in adult cystic fibrosis patients: A 2-year evaluation

OBJECTIVE

Cystic fibrosis (CF) is the most common inherited, life limiting condition among Caucasians. No healing therapy is currently available for patients with CF. The aim of the study was to define clinical, anthropometric and biochemical effects of regular, supervised physical exercise in a large cohort of patients with CF.

MATERIALS AND METHODS

Fifty-nine adult patients with CF that performed regularly supervised physical exercise in the last 3 years in comparison to 59 sex and age matched sedentary patients with CF were included in the study.

RESULTS

Physical exercise had significantly beneficial effects on: (a) FEV1% decline; (b) anthropometric parameters (lower number of cases with altered BMI, waist and arm circumferences); (c) lipid and glucose metabolism; (d) vitamin D serum levels. Of course, some of this improvement may be because of the better adherence to therapy typical of patients with CF that perform physical activity.

CONCLUSIONS

Such clinical and metabolic effects make supervised physical activity one of the hubs in managing patients with CF.

Vitamin D treatment abrogates the inflammatory response in paraquat-induced lung fibrosis

A high incidence of intentional or accidental paraquat (PQ) ingestion is related to irreversible lung fibrosis and no effective therapy is currently available. Vitamin D has emerged with promising results as an immunomodulatory molecule when abrogating the inflammatory responses of lung diseases. Therefore, we have investigated the role of vitamin D treatments on PQ-induced lung fibrosis in male C57/BL6 mice. Lung fibrosis was induced by a single injection of PQ (10 mg/kg; i.p.). The control group received PQ vehicle. Seven days later, after the PQ injection or the vehicle injection, the mice received vitamin D (5 μg/kg, i.p., once a day) or vehicle, for a further 7 days. Twenty-four hours after the last dose of vitamin D or the vehicle, the analysis were performed. The vitamin D treatments reduced the number of leukocytes in their BALF and they decreased the IL-6, IL-17, TGF-beta and MMP-9 levels and the abrogated collagenase deposits in their lung tissues. Conversely, the vitamin D treatments increased the resolvin D levels in their BALF. Moreover, their tracheal contractility was also significantly reduced by the vitamin D treatments. Altogether, the data that was obtained showed a promising use of vitamin D, in treating the lung fibrosis that had been induced by the PQ intoxications. This may improve its prognostic use for a non-invasive and low cost therapy.

Association between hypovitaminosis D and frequency of pulmonary exacerbations in children and adolescents with cystic fibrosis

Objective

We evaluated the association between vitamin D levels and nutritional status, pulmonary function and pulmonary exacerbations in children and adolescents with cystic fibrosis.

Methods

25-hydroxyvitamin D (25(OH)D) levels of 37 children and adolescents were retrospectively evaluated. Pulmonary function, body mass index, height for age, and pulmonary exacerbations episodes were associated with vitamin D levels divided into two groups: sufficient (≥30ng/mL) and hypovitaminosis (<30ng/mL).

Results

Hypovitaminosis D (25(OH)D <30ng/mL) was observed in 54% of subjects. The mean level of 25(OH)D was 30.53±12.14ng/mL. Pulmonary function and nutritional status were not associated with vitamin D levels. Pulmonary exacerbations over a 2-year period (p=0.007) and the period from measurement up to the end of the follow-up period (p=0.002) were significantly associated with vitamin D levels.

Conclusion

Hypovitaminosis D was associated with higher rates of pulmonary exacerbations in this sample of children and adolescents with cystic fibrosis. Hypovitaminosis D should be further studied as a marker of disease severity in cystic fibrosis. Further prospective and randomized studies are necessary to investigate causality of this association.