Visual hallucinations: a prevalence study among hospice inpatients.

The aim of the study was to determine the prevalence of visual hallucinations among hospice inpatients, and the prevalence of a number of possible associated risk factors. One hundred consecutive admissions to St. John's Hospice in Wirral were screened for visual hallucinations in a semi-structured interview. The prevalence of opioid administration, other drugs known to cause hallucinations, brain tumours, liver metastases, bone metastases, lung metastases, known renal failure, eye disease, Alzheimer's disease, Parkinson's disease, other neurodegenerative disorder, psychiatric disorder and epilepsy were also recorded. Subjects were screened for cognitive function using the Folstein mini-mental state examination (MMSE). Survival times from assessment to death were calculated. The results were analysed using arithmetical means with 95% confidence intervals (CI) and odds ratios with 95% confidence intervals. Almost half (47%) the patients had experienced visual hallucinations within the previous month. Hypnagogic or hypnopompic hallucinations of a person standing by the bedside were the commonest type. Median survival time for hallucinators was 15 days (range 0-50 days) and for non-hallucinators was 11 days (range 0-89 days). There was no significant difference in cognitive scores between hallucinators and non-hallucinators. Hallucinations were associated with multiple possible risk factors in every case. Hallucinators were more likely to be taking opioids, although the association was not strong (odds ratio 4.48, 95% CI = 1.6-12.19), and were taking larger numbers of potentially hallucinogenic drugs. It is not clear why some patients on opioids hallucinate and others do not. Data on the prevalence of various possible risk factors yielded ample material for the planning of future studies.