The world's largest study of its kind has found boys with asthma are more likely to break their bones than girls with the lung disease.

The study of more than 16,000 Victorian primary school students aged from three to 14, the world's largest of its kind, found boys with moderately severe asthma were 30 per cent more likely to fracture a bone than boys without the lung disease.

The same association was not found in girls.

The researchers suggest girls with asthma may have fewer fractures due to faster maturing bodies, as girls enter puberty at a younger age than boys.

Differences in risk-taking behaviours between boys and girls at certain ages could also be a contributing factor, the authors suggested.

The study, published in the Journal of Paediatrics and Child Health, also found the use of inhaled corticosteroids - the medication commonly taken to treat asthma - did not influence the association between asthma and increased risk of fractures in boys.

Lead researcher, Dr Sharon Brennan-Olsen at the University of Melbourne says the findings highlight the importance of promoting good bone health among young asthmatics.

"What we do in early childhood determines what could happen in later life, and whether those children develop musculoskeletal problems," said Dr Brennan-Olsen.

An estimated one-in-seven children have asthma, a long-term respiratory condition caused by hypersensitivity and inflammation of the airways.

Dr Brennan-Olsen, who is also a research fellow at the Australian Institute for Musculoskeletal Science, said the underlying disease process may influence bone development in children.

"Because asthma is an inflammatory disease it can lead to bone loss by interfering with the mechanisms in the bone formation and resorption," she explained.

For parents of boys with asthma specifically, Dr Brennan-Olsen says unfortunately there is not much they can do except be aware of the increased risk of fracture.

"They may be more likely to fracture but there is nothing we can do about it because of the disease process, but rest assured its not to do with the medication, so don't stop taking that medication whether it be preventers or relievers," she said.

Abstaining from physical activity is not recommended for children with asthma, Dr Brenan-Olsen added.

"The recommendations are to remain physically active because it's not only good for the bone health but also good for the asthma," she said.