Rapid eye movement sleep behaviour disorder, depression and cognitive impairment - Case study

Rapid eye movement (REM) sleep behaviour disorder is a relatively new diagnostic category. It has never before been associated with a treatable depressive condition. Aims To report on a 74-year-old man with a history of depression and REM sleep behaviour disorder, associated with mild cognitive impairment. Method Assessment using brain CT, MRI, PET, electroencephalography, neuropsychological testing and nocturnal polysomnography. Results Depression was treated with sertraline. Sleep laboratory studies supported a diagnosis of REM sleep behaviour disorder, which was treated with clonazepam. Sleep apnoea, revealed later, was treated with nasal continuous positive airways pressure. Brain MRI showed mild atrophy, but neuropsychological testing indicated no progressive cognitive deterioration. Conclusions This case draws attention to REM sleep behaviour disorder and its potential interaction with depression and cognitive impairment, producing symptoms which can be mistaken for early dementia. The diagnosis of REM sleep behaviour disorder is easily missed, and it requires careful history-taking and sleep investigation in all suspected sufferers. Associated neurological, sleep and psychiatric conditions (including depression and cognitive impairment) may confound the diagnosis. Declaration of interest None.