In older adults, severe chronic obstructive pulmonary disease (COPD) is associated with lower cognitive function, according to research from Mount Sinai School of Medicine.

After comparing the cognitive performance of more than 4,150 adults with and without COPD, the Mount Sinai researchers found that individuals with severe COPD had significantly lower cognitive function than those without, even after controlling for confounding factors.

"Our findings should raise awareness that adults with severe COPD are at greater risk for developing cognitive impairment, which may make managing their COPD more challenging, and will likely further worsen their general health and quality of life," wrote lead author William W. Hung, MD, MPH, in an announcement about the study.

The researchers hypothesize that periods of hypoxia in patients with COPD might lead to brain abnormalities that could reduce cognitive capacity. Alternatively, the researchers theorize that hypoxia may cause or exacerbate diseases that are characterized by cognitive impairment, such as Alzheimer’s disease.

The study is the first to formally test the relationship between cognitive impairment among adults with COPD longitudinally in large populations.

"We wanted to determine whether the observed relationship between COPD and cognitive impairment was, in fact, something we could document over time, and if so, we wanted to determine whether the degree to which it occurred was significant," said Hung.

To conduct the study, Hung and colleagues reviewed data from the Health and Retirement Study, a national prospective biennial survey of Americans 50 years of age and older. They included data from survey takers who had undergone cognitive testing in 1996 and again in 1998, 2000, or 2002. Of the individuals included, 492 had COPD, with one third (153) of them having severe disease. Using a 35-point cognition scale, the researchers found that scores among all patients with COPD declined on average by one point over the 6-year period between 1996 and 2002.

After dividing those with COPD into two categories of disease—severe or nonsevere—the researchers found that severity and cognitive decline were linked. Even after controlling for sociodemographic characteristics and other confounding factors, the mean cognition scores for those with severe COPD were significantly lower (0.9 points; p=0.01) than those without COPD.

According to Hung, executive functions that require greater cognitive ability, such as handling money and medications, are more poorly performed at greater levels of cognitive impairment.

The results of the study appear in the July 15 issue of the American Journal of Respiratory and Critical Care Medicine.