Ptsd, Dementia, and Sleep Disorder: A Possible Association

To the Editor: A recent article in this journal described three World War II veterans with cognitive impairment who presented with symptoms suggestive of post traumatic stress disorder (PTSD).1 The nature and type of dementia in these patients was not specified. Fluctuating cognition is one of the three major diagnostic criteria for dementia with Lewy bodies (DLB). Fluctuations are described as marked variation in a patient's cognitive or functional abilities or periods of confusion or decreased responsiveness alternating with reasonable lucidity. While identification of fluctuations is difficult, two of the reported patients had episodes of confusion and withdrawal suggestive of fluctuations. Other core features of DLB include recurrent visual hallucinations and spontaneous motor features of parkinsonism.2 The presence of any one criterion is required for a diagnosis of possible DLB, and two or more criteria are required to make a diagnosis of probable DLB. The clinical histories do not mention the presence of visual hallucinations or neuroleptic sensitivity, and the neurological examination was not reported in sufficient detail to ascertain whether these patients might have had features of parkinsonism. All three patients were diagnosed with depression before the onset of their symptoms. All also suffered from paranoid delusions. Delusions and other behavioral disturbances, while seen in the late stages of Alzheimer's disease (AD), are not common presenting symptoms. Delusions are one of the supportive features of DLB. We have recently reported the validity of the proposed clinical criteria for DLB in our clinical-pathological series.3 We found that whereas delusions had high specificity (91%) in cases with mild to moderate dementia, it had low sensitivity in the diagnosis of DLB (38%). A combination of any three major or minor clinical criteria had the best predictive value (75%) in mild to moderate disease. A subjective disturbance of sleep, including the occurrence of repetitive, stereotypical anxiety dreams, is characteristic of PTSD.4-6 The phenomenology of the PTSD anxiety dream has seemed most consistent with an underlying rapid eye movement (REM) sleep dysfunction.4, 5 Whereas near total paralysis is characteristic of the REM phase of sleep, motor activity is common in the sleep disorder seen in PTSD.6 REM sleep behavior disorder (RBD) is a recently described parasomnia characterized by excessive and elaborate motor activities during sleep and is associated with pathological absence of muscle atonia during REM sleep. The relationship between sleep disturbances in PTSD and RBD needs further research. However, the identification of RBD-like signs in PTSD, in previous cases as well as in this series, adds to the evidence for a fundamental disturbance of REM sleep mechanisms in PTSD.4-6 Other reports have described patients with RBD presenting with or subsequently developing cognitive impairment.7, 8 Most of these patients also meet criteria for possible or probable DLB. The pattern of cognitive differences from AD in these patients with RBD and dementia is similar to reported comparisons between DLB and AD. A recent international workshop on criteria for DLB has recommended including depression and RBD as additional supportive features for the diagnosis of DLB.9 The clinical features in these patients suggest a diagnosis of possible or probable DLB. The clinical descriptions do not have features typical of other common types of dementia, such as AD or vascular dementia. It is possible that in some patients PSTD and/or RBD may either herald or present with cognitive impairment, which may subsequently evolve into DLB. Further studies with longitudinal assessments will be required to address this issue. Additional investigations utilizing as polysomnography, sleep questionnaires, and detailed neuropsychological assessments may also help in this regard. The finding of a specific disturbance of sleep unique to PTSD has significant therapeutic implications and also contributes to a better understanding of the nature of the dementia associated with the cases reported. Editors note: This letter was reffered to the author of the original paper, and a reply follows.