Cognitive function in COPD.

In order to characterise the overall clinical picture of chronic obstructive pulmonary disease (COPD) a better understanding of all relevant comorbidities is required. It is increasingly recognised that COPD is a multi-component disease, but little attention has been paid to its effects on cognitive function. Cognitive dysfunction is associated with increased mortality and disability; however, it remains poorly understood in COPD. This review examines mechanisms of injury and dysfunction to the brain and considers the methods used to evaluate cognition, and assembles evidence concerning the nature and level of cognitive impairment in COPD. Our main findings are: 1) there may be a pattern of cognitive dysfunction specific to COPD; 2) cognitive function is only mildly impaired in patients without hypoxaemia; 3) the incidence of cognitive dysfunction is higher in hypoxaemia; 4) hypoxaemia, hypercapnia, smoking and comorbidities (such as vascular disease) are unlikely to account for all of the cognitive dysfunction seen in COPD; 5) there is weak or no association between cognitive function and mood, fatigue or health status; 6) cognitive dysfunction may be associated with increased mortality and disability; and 7) there is limited evidence for a significant effect of treatment on cognitive function.