July 9 (HealthDay News) -- Severe chronic obstructive pulmonary disease appears linked to lower cognitive function in older adults, making it more difficult for them to remember and perform daily tasks, a new study finds.

Researchers at Mount Sinai School of Medicine in New York City analyzed national data on 4,150 Americans aged 50 and older, including 492 with COPD. Of those, 153 had severe COPD. On a 35-point cognition scale, scores among all COPD patients declined an average of one-point between 1996 and 2002. Further analysis showed that patients with severe COPD had significantly lower scores than those without COPD.

"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," study author Dr. William W. Hung said in a news release.

The results suggest that patients with severe COPD have a 22 percent increase in the difficulty they experience with daily tasks.

"While this number may not appear to be of major concern on the individual level, on a population level it is roughly equivalent to nearly a quarter of severe COPD patients experiencing difficulty with basic life skills," Hung said.

"In this regard, these findings have serious implications. Often patients with cognitive difficulties, if undetected and untreated, have lower adherence to their treatment and follow-up regimens, and as a consequence may deteriorate more rapidly and have worse health outcomes," he explained.

The researchers suggested that periods of low oxygen levels -- hypoxia -- may reduce cognitive ability or exacerbate illnesses like Alzheimer's disease that have an impact on memory and attention.

Health-care professionals need to be aware that patients with severe COPD are at increased risk for cognitive decline and have greater challenges and needs, Hung concluded.

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

SOURCE: American Thoracic Society, news release, July 2009