A simple cough makes us tired and we feel like taking the day off from school, work or even household chores. For people with asthma, they experience periods of wheezing, chest tightness, shortness of breath and coughing that might be mild or severe and might happen occasionally or even every day in life! The term ‘asthma’ is common and we all know that asthma patients carry a small tube-like device that’s called the inhaler but not many of us know what exactly causes the illness and if it can be prevented too! Asthma is a chronic, long-term condition that intermittently inflames and narrows the airways in the lungs. Its prevalence has increased tremendously in the recent decades affecting more than 300 million people worldwide and the numbers are expected to grow with yet another 100 million people affected by it by 2025. The World Health Organization (WHO) has estimated that 15 million disability-adjusted life-years (DALY) are lost and 2,50,000 deaths happen every year. It not only has social and financial burden on the affected individual but also poses a huge burden on healthcare resources. Symptoms mainly occur during the night or early in the morning disrupting sleep and above all, the quality of life of the individual is severely compromised. Anyone of any age can be a victim of this illness whose risk factors are not evident as it presents differently in both adults and children. Genes, obesity, environmental factors, allergens, infections, outdoor/indoor pollutants and tobacco smoke are some of the risk factors of asthma. The disease cannot be cured but only be managed and controlled. Treatment usually includes using controllers and relievers.
There are increasing evidences showing that vitamin D deficiency plays an integral role in chronic diseases including asthma. Also known as the sunshine vitamin, this nutrient deficiency is increasingly witnessed among the general population in individuals as young as 10-year-old to elderly people. Would you believe if I say that half of the healthy population worldwide are vitamin D-deficient? A fat-soluble vitamin, vitamin D helps in calcium absorption, for improved bone health, is vital for immune regulation and plays an important role in respiratory infections. The increase in this nutrient deficiency is mainly due to inappropriate dietary intake, lifestyle factors, behavioral changes and insufficient exposure to sun. This vitamin is also critical for inborn and adaptive immunity that might be relevant in preventing asthma, protecting against asthma, reducing its morbidity and severity. There are many examples in which vitamin D deficiency has been associated with increased airway hyperresponsiveness (AWH), lower pulmonary function, worse asthma control and steroid resistance.
The present indoor-based lifestyle and our modernized and Westernized practices keep us indoors away from the bright sun’s shining rays leading to severe vitamin D deficiency levels among any population. Though the role of vitamin D in asthma is not crystal clear we do have several cross-sectional studies that show a link between vitamin D and asthma: low levels of 25(OH)D levels in patients with mild to moderate asthma is related to poor asthma control, reduced lung function, reduced glucocorticoid response, frequent exacerbations and increased steroid use. There are also clinical trials showing the protective influence of vitamin D supplementation among asthmatic patients.
Asia is a continent that mostly faces the warmth of sunshine and in South Asia most of the days are sunny. Still, vitamin D deficiency is highly prevalent in the countries here due to various factors such as improper diet, inadequate calcium levels, culture and customs that mostly keep elderly, female population and children confined within the four walls of the house preventing them from enjoying the sun’s rays or enabling them to have sufficient vitamin D levels in their body. Indians are majorly affected with almost 69% to 82% of the Indian population suffering from vitamin D deficiency. Surprisingly, it’s not only those living in the subcontinent suffering from the deficiency but also immigrants in other countries such as Denmark, UK and Norway are highly affected.
Research on Vitamin D’s Relationship with Markers of Asthma Severity
The study was conducted in North India with 120 participants who were aged between 18 and 80 consisting of both males and females. These individuals met the asthma criteria, did not have a history of vitamin D or calcium intake in the past one month and did not have any other respiratory and systemic disorders. All the 120 participants’ sputum eosinophil count, blood eosinophil count, serum IgE level measurements, serum 25-hydroxy vitamin D levels and spirometry tests were performed. Those individuals whose vitamin D levels were on par with requirements were taken as controls in the study. The mean age of the subjects was 30.81 ±8.97, there were 72 males (60%), 48 females (40%), 57.5% were smokers and 42.5% were non-smokers. All the patients were separated into vitamin D-sufficient and vitamin D-insufficient groups and were also grouped depending on asthma severity as intermittent, mild, moderate and severe asthmatics. Vitamin D deficiency was highly witnessed in asthma patients, there was a direct relationship between serum vitamin D levels, severity of asthma, asthma control, serum IgE levels, sputum eosinophils and lung function. The table below shows different asthma severity levels in patients who are vitamin D-sufficient and insufficient.
Serum IgE levels are linked to asthma and in this study, vitamin D-sufficient participants had lower serum IgE levels compared to the other group. IgE is an excellent determinant of allergy and the study showed that severe asthma patients had higher IgE levels compared to mild asthma. Those individuals with insufficient vitamin D had a higher mean for sputum eosinophils than those with sufficient vitamin. Higher vitamin D levels are inversely associated with IgE, sputum eosinophils and peripheral blood eosinophil counts and also decreased use of anti-inflammatory meds, reduced hospital stays and less airway hyper responsiveness. This study clearly shows that vitamin D insufficiency was highly prevalent in asthma patients and the severity of asthma also depended on the insufficiency of the vitamin. Hence, supplements could be considered for those patients with asthma.
Studies on Bronchial Asthma among Sudanese Patients
The study included 86 asthmatic patients aged 18 and above diagnosed with clinical asthma. Those >70 years of age, suffering from renal, lung and liver disease and on vitamin D, calcium and anticonvulsant drugs were excluded from the study. Their asthma levels were classified from mild to severe based on the different symptoms and blood samples were taken to measure vitamin D levels. Almost 70% patients were females and all the participants had suffered from this illness for around 10 years or so. Two-thirds of the study group had normal body mass index and only one-third were overweight/obese. Those who had well-controlled asthma were 24.4%, their mean age was 40 years, had normal BMI and 12 were males, participants with partially controlled asthma were 37.2%, mean age was 37.46 years and 26 of them were females. Those with uncontrolled asthma were 38.4%, their mean age was 45.36 years and 24 of them were females. Normal Vitamin D levels were present only in 2.3% patients while the rest had insufficient or deficient vitamin D levels. 25 (OH) level in the controlled asthma group was 25.82±17.27 ng/ml, in the partially controlled group it was 17.85±7.06ng/ml and in the uncontrolled asthma group it was 16.48±7.14ng/ml.
This study showed that only 47.7% individuals had vitamin D deficiency in comparison to few other studies which showed that almost 90% patients suffered from the deficiency. This might be because of the geographic location of Sudan that’s sunnier and hence, the people there are exposed to much more sunlight. This study also showed that vitamin D level had no role in asthma severity contradicting with previous study results. The Sudan study clearly shows that vitamin D level played a significant role in asthma control and aggravation of asthma but did not affect the severity of the illness in any way.
Vitamin D Deficiency in Asthmatic Children
The case-controlled study included 53 asthma patients and 53 controls. Children with asthma and hyperreactive airway disease were included as asthma patients. Vitamin D levels in both the groups were measured by radioimmunoassay (RIA) and was categorized as sufficient (>30 ng/ml), insufficient (20-30) and deficient (<20 ng/ml). The severity of asthma was also classified as mild, moderate and severe persistent. Both the groups had similar male gender distribution (56% vs 59%) and mean age. In the asthmatic group the mean duration of the disease was 13.1±24.6 months, 11.3% had mild asthma, 45.3% had moderate asthma and 43.4% had severe asthma. 5 of 31 kids aged below 5 years (16.1%) had high risk and 7 of 22 kids older than 5 years (31.8%) had high risk. While 73.6% asthma patients had vitamin D deficiency only 49.1% people in the control group had vitamin D deficiency, vitamin D insufficiency was 18.9% in both groups and normal vitamin D levels were 7.5% and 32.1% respectively.
A study on 616 asthmatic kids showed that vitamin D deficiency/insufficiency was present in 28% kids and increased vitamin D levels led to decrease in asthma aggravations and also decreased the need for visits to the emergency department in hospitals. A cross-sectional study on 560 kids aged 6-14 years showed that kids with vitamin D insufficiency were 2.6 times at an increased risk of developing asthma exacerbations. Cohort studies show that lower dietary maternal intake of vitamin D result in increased asthma morbidity and wheezing rates in children. Studies in Finland and Japan on more than 750 mother-kid pairs show that dietary vitamin D intake during pregnancy was inversely linked to incidence of wheezing in kids.
Clinical trials show that vitamin D offers protection against serious asthma attacks. A 6-month clinical trial showed that kids who received 500 IU/d supplementation of vitamin D had lower risk of asthma exacerbation; another trial on 100 asthmatic kids too showed the same results. But there were some other trials which did not show any association between vitamin D intake and reduction in asthma levels.
Vitamin D can definitely be a supplement therapy for managing asthma. While most studies do support the use of vitamin D for keeping asthma under control there are few studies that show that vitamin D supplements either have no effect or are responsible for increased asthma attacks.
Correlation between Asthma Severity & Serum Vitamin D Levels: Experience from a Tertiary Care Centre in North India: http://www.jbiomeds.com/biomedical-sciences/correlation-between-asthma-severity-and-serum-vitamin-d-levels-experience-from-a-tertiary-care-centre-in-north-india.php?aid=23236
The Relationship between Vitamin D Level & Severity & Control of Bronchial Asthma among Adult Sudanese Patients: https://www.msjonline.org/index.php/ijrms/article/view/4784/3904
Vitamin D Deficiency and its Impact on Asthma Severity in Asthmatic Children: https://ijponline.biomedcentral.com/articles/10.1186/s13052-016-0300-5
A Review on the Role of Vitamin D in Asthma: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5491340/
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