Researchers have found that a commonly used biomarker of kidney disease may also indicate lung problems, particularly chronic obstructive pulmonary disease (COPD).

The study, published in the American Journal of Respiratory and Critical Care Medicine, reported a link between albuminuria -- a condition that indicates the presence of the protein albumin in urine -- and COPD. According to researchers, albuminuria indicates damage to the single layer of cells lining blood vessels, known as the endothelium, in the kidney. 

The findings suggested that for each standard deviation increase in albuminuria, there was a 15 per cent increase in those who developed moderate-to-severe COPD. It also found 26 per cent increase in COPD hospitalisations and deaths. "The pulmonary microvasculature is critical to gas exchange and known to be impaired in patients with COPD, especially those with emphysema," said co-author Elizabeth C. Oelsner from the Columbia University, US. 

"We wanted to test whether albuminuria, a non-invasive and commonly used clinical test, could serve as a marker for increased risk of developing chronic lower respiratory diseases, such as COPD and asthma," Oelsner added. For the study, the research team pooled information from 31,877 participants with an average age of 60 years from six cohort studies. They excluded participants who had been diagnosed with COPD or asthma upon enrolment in the studies. 

The participants were followed for changes in lung function over a median of six years and for respiratory hospitalisations and mortality over a median of 15 years. The team found a three per cent greater decline in FEV1 (the amount of air that can be forcibly exhaled in one second) and an 11 per cent greater decline in the ratio between FEV1 and FVC (the total amount of air that can be forcibly exhaled after taking the deepest breath possible). 

Both FEV1 and FEV1/FVC are important measures of lung function, the researcher said. The researchers noted that these associations remained significant even after taking into account smoking history, diabetes, hypertension and cardiovascular disease.