Exercise might help reduce the risk of readmission to hospital of patients with serious lung disease, new research has shown.

The study involved 6,000 US patients with the lung condition chronic obstructive pulmonary disease (COPD). This includes conditions such as emphysema and chronic bronchitis.

Researchers examined the health records of more than 6,000 California patients, aged over 40.

The patients, who had all been in hospital for treatment of COPD during 2011 and 2012, provided information about their physical activity levels.

Compared to non-active patients, those who exercised 150 minutes a week or more were 34 percent less likely to be readmitted to the hospital with a flare-up of their condition within a month.

It was found that those who exercised less than 150 minutes a week still had a 33 percent lower risk of readmission compared to those who took no exercise.

The researchers said their study was unique in that it was able to capture information about patients' usual physical activity well before they were initially admitted to hospital.

The researchers say the findings of their study provides evidence that supports the promotion of physical activity for patient with COPD.

While the study doesn't establish a direct causative relationship between exercise and reduced chances of hospital readmission in COPD cases, it does suggest a link exists between the two, the researchers said.

The research is published in the Annals of the American Thoracic Society.