Asthma-obesity link

New Zealand researchers have confirmed links between asthma and the obesity epidemic.

A long-term Dunedin-based study of about 1000 people has produced strong evidence of the association in females aged over 9.

The researchers estimate that 28 per cent of new asthma cases in girls and women over 9 are due to being overweight.

However, the association is weak for males and non-existent for younger children, says a paper on the study in the American Journal of Respiratory and Critical Care Medicine.

New Zealand's rates of obesity and asthma are rising rapidly.

Asthma costs the health sector and the economy an estimated $825 million a year.

The leader of the asthma research, respiratory physician Dr Bob Hancox, said yesterday that by linking asthma with being overweight, the study confirmed earlier findings. Its new finding was that only adolescent - or adult - onset asthma was associated with being overweight.

"The ones that have had asthma since childhood don't become overweight. Therefore it's not the asthma that causes the overweight; it's something about becoming overweight during adolescence or later that seems to bring on the asthma."

The study did not investigate reasons for the link, but Dr Hancox said increasing amounts of fat might affect a person's breathing.

He said other reasons for the different findings for males and younger children could be that women tended to have more fat than men, adults had more fat than children, and female hormones might play a role.

"We just don't know."