Self-reports are not related to objective assessments of cognitive function and sedation in patients with cancer pain admitted to a palliative care unit

Cancer patients often report complaints of cognitive impairment and sedation. It is not well known if subjective complaints reflect objective assessments of cognitive function (CF) and sedation. We obtained self-reports of sedation and CF from 29 patients admitted to a palliative care unit and receiving morphine treatment. Sedation was reported on a verbal rating scale (VRS) and CF was reported using the EORTC QLQ-C30 health-related quality-of-life questionnaire CF scale. The self-reports were compared with objective assessments of sedation and CF by applying the Observer's Assessment of Alertness/Sedation (OAA/S) scale and Mini Mental State Examination (MMS), respectively. The assessments were repeated for seven patients who were readmitted to the palliative care unit. The patient self-reports of memory, concentration and sedation were dichotomized into noncomplainers and complainers. The percentages of complainers were 54%, 46% and 37% for memory, concentration and sedation, respectively. Patients who complained from difficulties with concentration or memory did not score differently from noncomplainers on objective assessments of CF (MMS score), but had a significantly higher level of fatigue. Patients complaining from sedation did not score differently from noncomplainers on objective assessments of sedation (OAA/S score). We observed no significant correlations between EORTC QLQ-C30 CF scale scores and MMS scores, or between VRS sedation scores and OAA/S scores. The study demonstrates a lack of relationship between patient self-reports and objective methods for assessing sedation and cognitive failure. This finding illustrates the importance of differentiating between observations and patient self-reports. The results also question the validity of patient self-reports for measurements of cognitive failure and sedation.