Cognitive dysfunction in patients with chronic obstructive pulmonary disease--a systematic review

Background: Substantial healthcare resources are spent on chronic obstructive pulmonary disease (COPD). In addition, the involvement of patients in monitoring and treatment of their condition has been suggested. However, it is important to maintain a view of self-care that takes differences in cognitive ability into account. The aim of this study was to determine the occurrence and severity of cognitive dysfunction in COPD patients, and to assess the association between severity of COPD and the level of cognitive function.

Methods: We conducted a systematic review, and a search in the following databases: Medline, PsychINFO, Cochrane Library, EMBASE, CINAHL, and SweMed up to July 2010. The articles were included if participants were patients with COPD, relevant outcome was cognitive function investigated by a neuropsychological test battery, and the severity of COPD had been assessed.

Results: Fifteen studies were included, involving 655 COPD patients and 394 controls. Cognitive function was impaired in COPD patients as compared to healthy controls, but the level of functioning was better than in patients with Alzheimer's disease. There was a significant association between severity of COPD, as measured by lung function and blood gases, and cognitive dysfunction, but only in patients with severe COPD.

Conclusions: Cognitive impairment can be detected in severe COPD patients, but the clinical relevance of the cognitive dysfunction is not yet known. Future studies should concentrate on the consequences of cognitive dysfunction for daily living in these patients, and solutions involving a high degree of self-care might require special support.