Associations of cognition with physical functioning and health-related quality of life among COPD patients

Background Neurocognitive impairment has been described in COPD patients, but little is known about its relationship with physical functioning and health-related quality of life (HRQL) in this chronically ill patient group. Methods 301 stable COPD patients completed the Trail Making Test (TMT-A: Psychomotor speed and TMT-B: Executive control); 198 patients completed the Memory Impairment Screen (MIS). Standardization of TMT-A and TMT-B scores to a normative population yielded classifications of normal, borderline, or impaired cognitive status. Using multivariable regression, we examined the relationship between the TMT-A, TMT-B, and MIS with physical functioning (physical activity, 6-min walk test, and grip strength) and health-related quality of life (HRQL) measured with the Chronic Respiratory Questionnaire and the SF-36. Results Nearly 30% of patients had either borderline or impaired cognition on the TMT-A or TMT-B. Adjusted models indicated that those with either borderline or impaired cognitive functioning had weaker grip strength (TMT-A borderline: β = -2.9, P < 0.05; TMT-B borderline: β = -3.0, P < 0.05; TMT-B impaired: β = -2.5, P < 0.05) and lower scores on the mental health component summary score (MCS-SF-36 HRQOL) measure (TMT-A impaired: β = -4.7, P < 0.01). No adjusted significant associations were found for other physical functioning measures or the other HRQL measures. Impaired memory showed a significant association only with the MCS scale. Conclusions Cognitive function was not associated with most standard indicators of physical function or most measures of HRQL in COPD patients. Both TMT-A and TMT-B were associated with weaker grip strength, and the TMT-A and MIS with poorer mental health.