The evaluation of cognitive impairment and relevant factors in patients with chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is understood to be a complex multicomponent disorder. The impairment of cognition is lasting and profound. However, the pattern of the cognitive decline and potentially adverse factors are poorly understood.
OBJECTIVES: To evaluate the cognitive performances and the relevant factors in COPD patients and to investigate the relationship between cognition deficits and the classification of severity of the disease.
METHODS: Twenty-seven mild-to-moderate COPD patients, 35 severe COPD patients and 27 control subjects were recruited. Cognitive states were investigated by the Mini-Mental State Examination (MMSE). Pulmonary function, arterial blood gas and serum clusterin level were evaluated in each subject.
RESULTS: Lower MMSE score and higher serum clusterin concentration were observed in mild-to-moderate COPD patients, while the lowest MMSE score and the highest serum clusterin level were found in severe COPD patients when compared with control subjects. MMSE score is positively correlated with arterial oxygen tension and is inversely associated with serum clusterin level in both mild-to-moderate and severe COPD patients. Furthermore, MMSE scores and serum clusterin concentrations were correlated with forced expiratory volume in 1 s in severe COPD patients.
CONCLUSION: Cognitive impairment was found in COPD patients. It is associated with the classification of disease severity, hypoxemia and serum clusterin level. An increased serum clusterin level may be a relevant peripheral biomarker of cognitive dysfunction in COPD patients.