Depression diagnosed by the mini international neuropsychiatric interview plus (MINI) in patients with chronic obstructive pulmonary disease: relationship with functional capacity and quality of life

BACKGROUND: The prevalence of depression in patients with chronic obstructive pulmonary disease (COPD) is associated with a worsening of prognosis. Most studies classify COPD patients as depressive or non-depressive based on symptoms, rather than on a diagnosis using specific tools. Thus, the aim of this study was to determine the impact of depression, as diagnosed by the Mini International Neuropsychiatric Interview Plus (MINI), on functional capacity estimated by the 6-minute walk test (6MWT) and unsupported upper-limb exercise test, and quality of life estimated by Saint George’s Respiratory Questionnaire (SGRQ), among patients with COPD. RESULTS: Using the MINI as a diagnostic tool, 22.2 % of all patients (6.6 % of all men and 41.6 % of all women) were diagnosed with depression. No significant differences were found between depressive and non-depressive patients with regard to anthropometric measurements, lung function, functional capacity, or quality of life variables. The best models for the dependent variables representing functional capacity and quality of life revealed that the covariates SGRQ(TOTAL) and gender (R(2) = 16.7 %) were significant in explaining the response variable for functional capacity of the upper limbs. Results also showed that age, monthly income, insomnia, and the results of a 6MWT were significant in explaining overall quality of life (R(2) = 46 %), and that the percentage of the predicted forced expiratory volume in the first second post-bronchodilator and gender were significant in explaining walking distance (R(2) = 22 %). Depression, as diagnosed by the MINI, was not significant in explaining any of the dependent variables. CONCLUSIONS: Despite a high prevalence of depression in COPD patients, especially in women, depression, as diagnosed by the MINI, was not correlated with functional capacity tests or quality of life in patients with moderate to very severe COPD in the present study. This suggests that depression identified by this diagnostic test may be more accurate than depression diagnosed by tests that evaluate symptoms, as they may be influenced by the perceptions of the patient in relation to their health.