Extent and prevalence of cognitive dysfunction in chronic obstructive pulmonary disease, chronic non-obstructive bronchitis, and in asymptomatic smokers, compared to normal reference values

BACKGROUND Chronic obstructive pulmonary disease (COPD) can affect cognition. The effects of other less severe chronic airway disorders on cognition remain to be clarified. This study aimed to measure and compare cognitive deterioration in subjects with COPD, subjects with chronic non-obstructive bronchitis (CNOB), and asymptomatic smokers (AS), and to relate the corresponding prevalence to several demographic and clinical variables and to normal reference values. METHODS Four hundred and two subjects (COPD n=229, CNOB n=127, and AS n=46) of comparable age were included in the study. Cognitive impairment was assessed using the Mini Mental Status test, the Clock Drawing test, and the Trail Making test A and B. RESULTS The extent and prevalence of cognitive deterioration was greater in COPD subjects, followed by CNOB subjects and AS (P<0.001). The Medical Research Council and COPD Assessment test scores, forced expiratory volume in the first second predicted, and arterial partial pressure of O2 and of CO2 were related to the extent and the prevalence of cognitive deterioration. COPD subjects, CNOB subjects, and AS aged 40-69 years showed the greatest cognitive impairment (P<0.01 compared to normal values). This was particularly clear in COPD subjects. CONCLUSION Cognitive impairment may start at the early stages of chronic airway damage and progress with a worsening of the respiratory condition. Indeed, the greatest cognitive deterioration was seen in COPD subjects. Cognition impairment may contribute to explaining the insufficient adherence to therapeutic plans and strategies, and the increasing social costs in respiratory subjects.