A new study showed that a high BMI, greater than or equal to the 85th percentile, at the age of seven was linked to an increased risk of asthma and allergy sensitivity at the age of eight.
Children who had a high BMI early on in childhood but had a normal BMI at the age of seven did not have an increased risk of developing asthma or an allergy sensitivity.
"If your child has a high BMI, ask your pediatrician about safe ways to lose weight."
The study was led by Jessica Öhman Magnusson, M.Sc., Institute of Environmental Medicine, Karolinska Institute in Sweden. The link between high BMI and asthma was found in children whose parents who had no allergic history but not in parents who did have an allergic history.
The reason for this could be because the parent's allergic history had already increased the risk of their child developing asthma that a high BMI did not significantly increase the already present risk.
The study also found an increased risk of developing an allergy to inhaled irritants. These irritants included pet dander, tree pollen, dust mites and mold.
There was no link between high BMI and an increased risk of developing a food allergy.
BMI is a measurement of body fat using a person's height and weight. A person multiplies their weight by 703. That number is then divided by height, in inches, squared. A normal BMI falls between the 18.5 to 24.9 range. BMI does not factor in muscle mass which may affect the BMI score.
A high BMI at the age of one, four and seven was linked to a significant increase in developing asthma at the age of eight. There was no link between high BMI during infancy, 12 months or 18 months, and an increased risk of developing asthma.
Children who had a high BMI at four years old but had a normal BMI by the age of seven were not linked to an increased asthma risk.
Researchers analyzed the health records of 2,075 children using school records. Parents answered questions about allergy symptoms and irritant exposure when their child was one year old, two years old, four years old and eight years old. Blood samples were collected when the child turned eight.
Future research can lead to a better understanding of how being overweight affects asthma risk. Asthma is an inflammatory disease and researchers believe leptin, a hormone, may cause an increased inflammation response. Future studies can examine the affect of leptin on asthma.
The study was funded by the Stockholm County Council, the Heart and Lung Foundation, the Swedish Asthma and Allergy Association, the Swedish Foundation for Health Care Science and Allergy Research, and the Swedish Research Council. The authors reported no conflicts.
This study was published in the January edition of Pediatrics.