A Swedish population study from researchers at Karolinska Institutet has revealed that younger siblings, single children, and older siblings are at different risks of developing asthma and other common childhood diseases.

For the study, principal investigator Catarina Almqvist Malmros and her colleagues extracted sibship data from the Swedish Multigenerational Registry linked to the Medical Birth Registry on over 300,000 children born between 1996 and 2002. A total of 43% were first-born, 44% had an older sibling, and just over 13% of the children had no siblings.

The researchers measured the prevalence of disease in the children in 2008 when they were between 6 and 12 years old. Information on specialist care and medication for type 1 diabetes, asthma, ADHD, and respiratory infection was collected from the Swedish Prescribed Drug Register and the National Patient Register. The results of the study showed that younger siblings had a lower risk of asthma and respiratory infections than first-borns with siblings.

“Our study confirms a link between sibship and childhood disease,” says Almqvist Malmros. “We found that single children had a higher risk of asthma, diabetes and ADHD than first-borns who had younger siblings, but showed no difference in the risk of developing respiratory infections.”

A Medical Xpress news report notes that the study provides no answers as to the cause of the correlation between sibship and childhood disease, but the researchers attribute it either to differences in exposure to bacteria and viruses, to the uterine environment during gestation, or to reduced health seeking behavior in parents who are used to viral infections in their second borns, more comfortable with the disease and less likely to seek evaluation or treatment.

Source: Medical Xpress