Serum vitamin D and asthma control still a controversial link: A cross-sectional study and literature review

Background Vitamin D is an important modulator of the innate and adaptive immune system, plays an important role in the airway hyperresponsiveness and the improved asthma control. Several studies suggest that low serum vitamin D may adversely influence asthma outcomes. However, other studies showed inconsistent relationship which increased the controversy of the link between low vitamin D and asthma control. Aims The aim of this study was to investigate the potential relationship between low serum vitamin D with asthma control. Methods A cross-sectional study of consecutive patients with the diagnosis of asthma from the outpatient clinic at King Abdulaziz University hospital was analysed between January and December 2011. They were classified according to their asthma control level. Measurement of serum vitamin D was performed. SPSS was used to examine any statistical correlation. Results Sixty-four asthmatic patients were included in this study; 31.25 per cent (n=20) males and 68.75 per cent (n=44) were females. Serum vitamin D (25-hydroxyvitamin D) deficiency (Less than 50 nmol per litre) was found in 84.3 per cent (n= 54), insufficiency (50 to 74.9 nmol per litre) in 14.1 per cent (n=9), and sufficient serum level (75 nmol per litre or greater) in 1.6 per cent (n=1) patients. Level of asthma control assessment based on GINA guideline revealed 25 (39 per cent) uncontrolled, 27 (42.2 per cent) partially controlled and 12 (18.8 per cent) controlled patients. Low vitamin D was found in 12 (19 per cent) controlled versus 51 (81 per cent) non-controlled asthmatics. There was no significant statistical correlation found between low serum vitamin D level and asthma control (p value 0.85). Conclusion Low vitamin D was prevalent in more than three-quarters of patients with asthma. The relationship between low serum vitamin D level and poor asthma control was not statistically significant. Further studies are needed to explore the association of low vitamin D with asthma control.