Verbal memory impairment in COPD: its mechanisms and clinical relevance

Abstract

Study objectives: Identification of mechanisms accounting for verbal memory impairment in patients with severe COPD; assessing the relationship between verbal memory and the overall cognitive performance; verifying if verbal memory impairment affects medication adherence.

Design: Case-comparison study.

Setting: Outpatient Departments of Pneumology and Neurology, Day Hospital of General Surgery.

Patients: Forty-two COPD ambulatory patients, age 70+/-9.7 years, with hypoxemia and hypercarbia (group A); 27 normal subjects of comparable age and educational level (group B); 31 patients with Alzheimer's disease (group C); and 26 older normal subjects (group D).

Measurements and results: The overall cognitive function and verbal memory were evaluated by the Mental Deterioration Battery and 14 indexes of verbal memory. Defective retrieval and recognition mechanisms distinguished group A from group B. According to discriminant analysis, verbal memory profile of COPD patients was group specific in 38.1% of cases and conformed to that of group B, C, and D in 19%, 16.7%, and 26.2% of cases, respectively. In COPD patients, both immediate and delayed recall, the strongest determinants of the discriminant function, were significantly correlated with the overall cognitive performance (rho=0.64, p=0.001; rho=0.61, p=0.001, respectively). Poor adherence to medication regimen was significantly associated with abnormal delayed recall score (82.3% vs 36% in subjects with normal delayed recall, p<0.008).

Conclusions: Decline of verbal memory parallels that of the overall cognitive function in COPD patients and is due to the impairment of both active recall and passive recognition of learned material. It could be an important determinant of the level of medication adherence.