More recently, some
reviews have highlighted the negative impact of psychological
comorbidity on HRQoL in COPD patients
[8,9]. Specifically, previous studies of large samples of
COPD patients have found an association between psychological
impairment (i.e., anxiety and/or depressive
symptoms) and worse respiratory-specific HRQoL,
independent of COPD severity [10-12]. An aspect
poorly explored in previous research is the identification
of effect modifiers of the relationship between psychological
status and HRQoL. Only one earlier study
has examined the differences in the association
between anxiety and depression and HRQoL by severity
groups [13]. It is currently not known whether
socio-demographic factors or comorbidities modify the
association between anxiety and depression and the
HRQoL of COPD patients.