A NEW study focussing on the analysis of genetic data was recently conducted to determine whether previous observational studies correlating low levels of vitamin D with increased risk of asthma and atopic dermatitis, along with increased immunoglobulin E (IgE) levels, were supported by genetic variation.
The term ‘atopy’ is used to define a person’s predisposition to allergic diseases such as asthma. Atopy is usually accompanied by increased levels of IgE, which has a role against parasitic infection. The study, led by Dr Brent Richards, McGill University, Montreal, Canada, was important as vitamin D deficiency is a growing problem within the USA, affecting >40% of the population. Single nucleotide polymorphisms (SNPs) were analysed in existing data from >100,000 patients who had previously taken part in large-scale studies. SNPs are amongst the most common mutations found within a person’s DNA. The research team specifically focussed on four genetic variations (mutations) that are known to be linked to low levels of 25-hydroxyvitamin D, a vitamin D deficiency marker.
Adult-onset asthma and childhood asthma were analysed separately to determine whether there were distinct correlations. In conclusion, no significant differences in the incidence of asthma were observed comparing patients with the four genetic variations and those without. Dr Richards explained: “Our previous findings suggest that low vitamin D levels increase risk for some inflammatory diseases like multiple sclerosis, but these effects do not translate to other inflammatory diseases like asthma and atopic dermatitis.”
The researchers highlighted that, at this stage, correlation between the four genetic variations and levels of the active form of vitamin D cannot be ruled out. The analysis was conducted in a white population with European ancestry, which was one of the study’s limitations. Further research may need to be conducted to broaden analysis to non-European populations.
“Our findings suggest that previous associations between low vitamin D and atopic disease could be due to spurious associations with other factors. Efforts to increase vitamin D levels will probably not result in decreased risk of adult and paediatric asthma, atopic dermatitis, or elevated IgE levels.” added first author, Dr Despoina Manousaki, Lady Davis Institute, Jewish General Hospital, Montreal, Canada.