Cognitive Functioning in Patients with Chronic Obstructive Pulmonary Disease and Mild Hypoxemia Compared with Patients with Mild Alzheimer Disease and Normal Controls

Objective: To examine neuropsychologic functions in patients with chronic obstructive pulmonary disease (COPD) and mild hypoxemia compared with patients with mild Alzheimer disease and normal controls.

Background: Cognitive deficits have been documented in patients with COPD, but few studies have compared the neuropsychologic status of these patients with that of other neurologic groups.

Method: Cognitive test results from 32 patients with COPD and mild hypoxemia (mean age, 70.3 years; mean education, 13.2 years; mean partial arterial oxygen pressure, 68.8 mm Hg) who had no neurologic symptoms were compared with 31 subjects with mild Alzheimer disease (AD) and 31 normal controls similar in age, education, and sex. Seventy-three percent of the patients with COPD were receiving supplementary oxygen.

Results: Significant group differences across 11 cognitive scores were found using analysis of variance, and post hoc analyses indicated that patients with mild AD performed significantly worse than normal controls and patients with COPD on most tests. The group with COPD and the group with AD demonstrated lower letter fluency compared with controls. Although the patients with COPD performed significantly worse than controls on verbal fluency tasks, they were not in the clinically impaired range, and, overall, the group with COPD was similar to the controls on most cognitive tests.

Conclusions: These findings suggest that many patients with COPD and mild hypoxemia who don't have neuropsychiatric histories may perform normally on cognitive measures. Oxygen therapy may partially account for preservation of cognitive function in these patients. Results also suggest that patients with COPD and normal controls can be readily distinguished from patients with mild AD based on levels and patterns of neuropsychologic test results. Any significant cognitive deficits in patients with mildly hypoxemic COPD may warrant continued neurologic evaluation.