Progressive neuropsychologic impairment and hypoxemia. Relationship in chronic obstructive pulmonary disease.

In previous work we showed that patients with chronic obstructive pulmonary disease (COPD) suffered decrements in neuropsychologic functioning suggestive of organic mental disturbance. This study combined data from two multicenter clinical trials to explore the nature and possible determinants of such neuropsychologic change. Three groups of patients with COPD whose hypoxemia was mild (N = 86), moderate (N = 155), or severe (N = 61) were compared with age- and education-matched nonpatients (N = 99). The rate of neuropsychologic deficit rose from 27% in mild hypoxemia to 61% in severe hypoxemia. Various neuropsychologic abilities declined at different rates, suggesting differential vulnerability of neuropsychologic functions to progress of COPD. Multivariate analyses revealed a consistent significant relationship between degree of hypoxemia and neuropsychologic impairment, but the amount of shared variance was small (7%). Increasing age and lower education were also associated with impairment.