Executive function, survival, and hospitalization in chronic obstructive pulmonary disease: A longitudinal analysis of the national emphysema treatment trial (NETT)

Rationale: Cognitive dysfunction has been demonstrated in chronic obstructive pulmonary disease (COPD), but studies are limited to cross-sectional analyses or incompletely characterized populations. Objectives: We examined longitudinal changes in sensitive measures of executive function in a well-characterized population of patients with severe COPD. Methods: This study was performed on patients enrolled in the National Emphysema Treatment Trial. To assess executive function, we analyzed trail making (TM) A and B times at enrollment in the trial (2,128 patients), and at 12 (731 patients) and 24 months (593 patients) after enrollment, adjusted for surgery, marriage status, age, education, income, depression, PaO₂, PaCO2, and smoking. Associations with survival and hospitalizations were examined using Cox regression and linear regression models. Measurements and Main Results: The average age of the patients was 66.4 years, and the averageFEV1 was 23.9% predicted. At the time of enrolment, 38% had executive dysfunction. Compared with those who did not, these patients were older, less educated, had higher oxygen use, higher PaCO2, worse quality of life as measured by the St. George's Respiratory Quotient, reduced well-being, and lower social function. There was no significant change over 2 years in TM A or B times after adjustment for covariables. Changes in TM B times were modestly associated with survival, but changes in TM B2A times were not. Changes in TM scores were not associated with frequency of hospitalization. Lung function, PaO₂, smoking, survival, and hospitalizations were not significantly different in those with executive dysfunction. Conclusions: In this large population of patients with severe emphysema and heavy cigarette smoking exposure, there was no significant decline over 2 years in cognitive executive function as measured by TM tests. There was no association between executive function impairment and frequency of hospitalization, and there was a possible modest association with survival. It is plausible that cerebrovascular comorbidities explain previously described cognitive pathology in COPD.