Selenium status shows poor association with childhood asthma
medwireNews: Selenium status is not associated with risk for asthma or atopy in children, study findings suggest.
In a prospective birth cohort study conducted in New Zealand, levels of the trace mineral were not statistically different between children who did and did not develop allergic disease.
"Historically, New Zealand adults and children have low selenium status, and associations with asthma have been reported," Christine Thomson (University of Otago, Dunedin, New Zealand) and team write in Clinical & Experimental Allergy.
However, "the results of this study do not support a strong association between selenium status and the high incidence of asthma in New Zealand," they add.
The New Zealand Asthma and Allergy Cohort Study was established in 1996 and involves a total of 1105 infants born between 1997 and 2001 in Wellington and Christchurch. The study was initiated to examine early life factors associated with the later development of, or protection from, asthma and allergy.
For the current analysis, Thomson and team examined plasma levels of selenium and whole blood glutathione peroxidase (GPx) in samples taken from 635 children when they were 6 years of age.
Children and their parents completed questionnaires about the occurrence and severity of asthma, wheeze, hayfever, rhinitis, eczema, and rash. Family history of allergic disease, exposure to household tobacco smoke, and skin prick test sensitivity were also assessed.
Compared with children from Wellington, infants from Christchurch were found to have significantly lower mean levels of selenium (95 vs 73 µg/L) and GPx (41 vs 34 U/g Hb).
While selenium and GPx levels were found to be lower if children had been exposed to household tobacco smoke within the past 12 months, the association was not significant once confounding factors, such as family history, were considered.
Selenium and GPx levels were also not linked to any health outcomes once multivariate adjustment was performed. However, there was a trend for lower levels of selenium and GPx in children with versus without persistent wheeze, and for lower GPx levels in those with versus without hayfever.
Thomson and team concede that their study only looked at selenium status once children had reached 6 years of age, and perhaps earlier exposure to the trace mineral is important for the development of allergic disease.
"Unfortunately, we were unable to address this possibility and few other studies have done so," they comment, noting further observational studies in early life are needed.
"It is clear that any descriptive studies need sufficient numbers of patients to control for the many confounding factors. Similarly, intervention studies need careful planning," the team advises.
By Sara Freeman, medwireNews Reporter