Phantom boarder symptom in elderly Japanese

Phantom boarder symptom (PBS) is classified as a delusional misidentification syndrome, and is often encountered in elderly individuals who have mild or major neurocognitive disorders. With the ageing of society, patients presenting with PBS are increasing in Japan. This retrospective study was conducted to examine the aetiology and identify significant predictors of PBS.

The records of 511 consecutive patients who visited our hospital with suspicion of dementia between September 2013 and September 2019 were retrospectively examined. From those, 16 patients who presented with PBS (1 male, 15 females; mean age 79.9 ± 4 years) were selected and case features were investigated in detail. Clinical symptoms, background factors, and final diagnoses were noted. PBS was most common in patients affected by dementia with Lewy bodies (DLB). Predictive factors were evaluated using multiple logistic regression analysis.

The final diagnosis of the 16 subjects was DLB in 7, Alzheimer's disease in 3, delusional disorder in 3, unspecified dementia in 2, and vascular dementia in 1. Analysis limited to DLB cases showed that a low Mini-Mental State Examination (MMSE) score and living alone were related to higher risk for PBS.

Various types of dementia, especially DLB, as well as cognitive impairment and living alone were found to be strong predictors of PBS.