A potential new way to treat one of the world's most common lung diseases is to be investigated after a study found a link between sufferers' iron levels and worse health outcomes.

Researchers are to give iron to people with chronic obstructive pulmonary disease (COPD) - commonly caused by smoking - to see if it can improve the debilitating condition.

It comes after doctors and researchers found that one in five people with COPD who took part in a University of Oxford study based at the Churchill Hospital funded by the NIHR Oxford Biomedical Research Centre had iron deficiency.

Those with iron deficiency had much lower levels of oxygen in their blood, more difficulty exercising, and more frequent flare-ups, which include symptoms such as worsening shortness of breath, cough and wheezing. The results have been published in the scientific journal BMJ Open.

Recruitment is now taking place for a two-year clinical trial involving 48 patients at the Churchill to give iron intravenously to those with COPD.

It will look at whether boosting iron levels is helpful over a period of several months and, if successful, would lead to further studies of iron therapy in more patients over a longer period.

COPD is the name for a collection of lung diseases including chronic bronchitis and emphysema.

Smoking irritates and inflames the lung and this results in scarring and damage to the elasticity of the lungs. Sufferers have difficulties breathing, primarily due to the narrowing of their airways which can leave them breathless when active, a persistent cough with phlegm and frequent chest infections.

Professor Peter Robbins from the University of Oxford, who led the work, said: "We were really quite surprised how big the differences in oxygen levels were between patients with low iron and those with normal iron levels. "We checked to see if it was simply a case of patients with lower oxygen levels having more severe lung disease, but we found that iron deficiency in fact had an effect in its own right.

"The amount of oxygen in the blood is a strong predictor of life expectancy in COPD, so these findings are potentially very significant for patients."

He said: "When people hear about iron deficiency they tend to think only about anaemia, but in fact iron is essential for many other processes in the human body apart from making red blood cells. "We've known for some time that iron was likely to be very important for people living with lung disease. Work done by several groups in Oxford over the past two decades had shown that iron was needed for proper functioning of the blood vessels in the lungs, but we didn't know until now what this meant for patients."

About three million people in the UK have COPD and one dies every 20 minutes from the condition in England. However, only about one in three sufferers have been formally diagnosed and it is estimated the condition costs the NHS more than £800m a year.

About one in four people with COPD cannot work due to the disease and the cost of lost productivity is about £4bn a year.

Dr Annabel Nickol, a Consultant in Chest Medicine at the Churchill Hospital, said: "COPD is a very difficult condition to treat.

"We know giving-up smoking is the most important thing that patients can do to help, but even though most of our patients have done this they are left with very troubling symptoms that interfere with their daily lives and can lead to repeated admissions to hospital.

"Most of the treatments we have at present target the air passages in the lungs, and though they can improve symptoms, they don't have as great an effect on patients' exercise ability and quality of life as we would like. "We think iron deficiency acts in a variety of different ways to worsen the impact of COPD. We now need to establish if treatment with iron can help improve things for people living with the condition, including whether it could reduce admissions to hospital with exacerbations."

The COPD study measured the iron levels of over a hundred patients and assessed their lung health, exercise ability and overall level of well-being.

Prof Robbins said: "Work by other researchers has looked at the importance of iron in heart disease, but lung health tends to get neglected, despite the shocking statistics about the burden of COPD in the UK and worldwide.

"We're very excited about starting this new trial and are hopeful that iron will turn out to be a useful new treatment for patients with COPD that really makes a difference to them.

"The study results that we have just published show that the interactions between iron levels, inflammation and lung function in COPD are very complex indeed.

"It's important to stress that a good deal of further research will be needed to untangle exactly how all these things affect one another. However, based on our results, we thought it was very important to begin a trial of iron as a potential new therapy as soon as possible."

The study is a collaboration between the University of Oxford's Department of Physiology, Anatomy and Genetics and the Oxford Centre for Respiratory Medicine and Oxford Respiratory Trials Unit at Oxford University Hospitals NHS Trust's Churchill Hospital.

Among those who took part in the study was Richard Hayes, 66, of Rose Hill, Oxford, who was diagnosed with COPD four years ago after smoking since the age of 15.

He said: "I have taken part in quite a few bits of research. It helps me keep on top of it, of my knowledge of what's going on. I know if I am getting worse or better."

Both studies have been funded by the NIHR Oxford Biomedical Research Centre, which aims to translate scientific research into new therapies that will quickly be of benefit to patients.