Increase in Body Mass Index ups the risk of asthma in mid-childhood, new research shows.

Researchers analyzed the data of 4,835 children who were a part of the Avon Longitudinal Study of Parents and Children that started in 1991. All the children were 7.5-years-old. The researchers assessed the effects of genetic variants linked to BMI on asthma risk. They calculated a weighted genetic score using 32 independent BMI-related DNA sequence variations.

The findings revealed that the genetic scores of the children could help predict their risk of developing asthma in mid-childhood. Children who had higher levels of body mass and lean mass had a higher risk of asthma.

According to the analysis, the researchers stated that for every extra unit of BMI, there was a relative increase in asthma risk by 55 percent. The team said that in order to reduce the risk of childhood asthma risk, children should maintain normal BMI levels.

"Environmental influences on the development of asthma in childhood have been extensively investigated in epidemiological studies, but few of these provide strong evidence for causality... [higher BMI in mid-childhood] could help explain some of the increase in asthma risk toward the end of the 20th century, although the continued rise in obesity but with a slowing in the rise in asthma prevalence in some countries implies that other non-BMI-related factors are also likely to be important," the authors said, according to the press release.

The study, 'Effects of BMI, Fat Mass, and Lean Mass on Asthma in Childhood: A Mendelian Randomization Study,' was published in PLOS Medicine.