COPD patients have a significantly increased risk of developing nonamnestic mild cognitive impairment, according to the results of a study carried out by researchers at the Mayo Clinic.
It stands to reason that the 13.5 million Americans who have chronic obstructive pulmonary disease (COPD) also have disease-related comorbidities. The chronic airflow limitation that accompanies COPD increases anxiety and makes each breath a challenge. It also increases the likelihood of a sedentary lifestyle. Some studies have linked COPD and its propensity to cause hypoxemia and hypercapnia with development of mild cognitive impairment (MCI). MCI is the earliest sign of dementia, and identifying modifiable risk factors could help prevent cognitive decline.
Researchers from the Mayo Clinic set out to determine COPD’s relationship with MCI in greater detail. To do so, they looked at previous studies’ limitations and designed their study to fill knowledge gaps. They were particularly interested in determining whether a COPD diagnosis increases risk for incident MCI and MCI subtypes and whether COPD duration makes a difference in this comorbidity. Published online in JAMA Neurology on March 14, 2014, the study results reveal that COPD—especially COPD of longer duration—affects cognition.
MCI occurs in two types—amnestic (A-MCI) and nonamnestic (NA-MCI)—with the former more likely to be associated with future Alzheimer’s disease. A-MCI affects memory, while NA-MCI affects attention and concentration, information processing, and psychomotor speed.
This prospective study enrolled 1425 patients aged 70 to 89 with normal cognition at baseline, of whom 171 had been diagnosed with COPD. The researchers randomly selected patients from Olmsted County, Minnesota, using medical records. Participants were interviewed by a nurse and underwent neurologic exams and neurophysiological testing at baseline and every 15 months thereafter for a mean follow-up period of 5.1 years.
Among the participants, 370 developed MCI. The results indicated that a COPD diagnosis increased the risk for NA-MCI by 83%, and this was a significant finding. Patients with COPD durations longer than 5 years at baseline were at the greatest risk of developing MCI, particularly NA-MCI. One limitation to the study’s findings was that the researchers did not consider smoking duration, having classified patients at baseline as those who had ever smoked and those who had never smoked.
COPD is incurable, but treatable. The increased risk for NA-MCI in COPD patients hints that inflammation and vascular disease may be factors in its pathogenesis. MCI risk may also be associated with hypoxia. COPD appears to be an important risk factor for MCI. This is another reason to promote early, aggressive treatment and lifestyle interventions in patients with COPD.
Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.