The authors of the study, which is published in the European Respiratory Journal, believe it is the first to detail the negative effects of poor air quality in nursing homes across several countries.

The researchers collected data on five indoor air pollutants – PM10, PM0.1, formaldehyde, NO2 and O3.

The pollutants come from a range of sources including heaters, building materials, furniture, cleaning products, disinfectants and cooling systems.

They assessed levels of the pollutants in 50 different nursing homes in seven countries – Belgium, Denmark, France, Greece, Italy, Poland and Sweden. A total of 600 residents took part in the study.

The results showed that exposure to high levels of PM10 and NO2 was significantly associated with breathlessness and cough.

In addition, high levels of PM0.1 were associated with wheeze during the last year and high concentrations of formaldehyde were linked with chronic obstructive pulmonary disease.

The associations were even seen with “moderate” concentrations of indoor air pollutants, the researchers said, adding that they were enhanced in homes with poor ventilation.

Dr Isabella Annesi-Maesano, lead author of the study, said: “Our findings have shown an independent effect of several indoor air pollutants on the lung health of the elderly living in nursing homes.

“This is a worrying problem since the body’s ability to cope with harmful air pollutants decreases as we age,” said Dr Annesi-Maesano.

“Nursing homes should do more to prevent indoor air pollution by limiting its sources and by improving ventilation in their buildings,” she said. “The respiratory health of residents should also be checked on a regular basis.”

Dan Smyth, chair of the European Lung Foundation, added that the findings added to a body of evidence “confirming” that indoor air pollution was a risk factor for respiratory disease.