Asthmatics are twice as likely to suffer from nightmares, snoring and other disturbed sleep problems than other people despite major improvements in medications in the past decade, a major study has revealed.

Australian respiratory specialists have called for GPs to take a closer look at the sleep quality of their asthmatic patients after a large Swedish population study showed sleep problems were widespread and significantly more severe.

"Many people have assumed that because these new drugs are effective against night time asthma then people with the condition are sleeping well but that doesn't seem to be the case," said Professor Guy Marks, an asthma epidemiologist at the Woolcock Institute of Medical Research in Sydney.

A team from Uppsala University compared the sleep patterns of asthmatics in the 1997 with their sleep in 2008 to see if the popular class of drugs called long-acting beta agonists introduced in the meantime had improved sufferers' sleep.

"What we found was that despite these improvements in asthma management and therapy, sleep is still a major problem for asthmatics," lead researcher Professor Christer (Christer) Janson told journalists at the European Respiratory Society congress in Berlin.

"They had double the prevalence of problems falling asleep, and also more problems staying asleep, waking up too early and other sleep disruptions that left them with excessive daytime sleepiness.

"That is the dangerous one because it can lead to car accidents and accidents at work."

The findings are based on a survey of almost 26,000 people, including 1,600 with asthma.

Prof Christer said he believed the problem was persisting because many asthmatics do not strictly adhere to their medication routine.

Prof Marks said it was also possible that other problems like obesity, smoking, lack of exercise or the snoring condition obstructive sleep apnoea could be partly responsible.

"It would pay to have a closer look at the sleeping patterns of asthmatics and see what factors can be changed to improve it," Prof Marks said.

Meanwhile, a Norwegian study presented to the conference suggested female asthmatics suffer more coughing and chest tightness in the night.

Researchers said female sex hormones appeared to be playing a mysterious role in asthma, making females more prone to the condition around puberty and around the time of their menstrual cycle. A woman's asthma also often changes, for better or for worse, during pregnancy.