Alexithymia associated with nightmare distress in idiopathic REM sleep behavior disorder

Idiopathic REM sleep behavior disorder (iRBD) is characterized by atypical REM sleep motor activity, vivid dreams and nightmares, and dream-enacting behaviors that can result in injuries to the patient and bed partner. It is also a known predictor of Parkinson disease (PD). Alexithymia has been associated with disturbances in sleep and dreaming (e.g., nightmares) and is a non-motor symptom of PD. We assessed alexithymia and disturbed dreaming in iRBD patients with the aim of determining if these two factors are elevated and interrelated among this population.

Questionnaire study of clinically diagnosed patients.

Clinical sleep disorders center.

Thirty-two iRBD patients and 30 healthy age- and sex-matched control participants.

Participants completed the 20-item Toronto Alexithymia Scale (TAS-20), the Dream Questionnaire, and the Beck Depression Inventory. iRBD patients obtained higher TAS-20 total scores (62.16 ± 13.90) than did controls (52.84 ± 7.62; F 1,59 = 10.44, P < 0.01), even when controlling for depressive symptoms, and more frequently attained the suggested cutoff for alexithymia than did controls (P < 0.01). iRBD patients obtained higher scores on the Difficulty Identifying Feelings alexithymia subscale. For both iRBD and control groups, the Difficulty Indentifying Feelings subscale correlated positively with the Nightmare Distress scale of the Dream Questionnaire.

Elevated alexithymia scores among idiopathic rapid eye movement sleep behavior disorder patients, and especially a difficulty in identifying feelings, parallels evidence of dysautonomia in this population. The higher incidence of distressing nightmares and the association of nightmares with alexithymia further extend similar findings for both clinical and non-clinical samples and suggest that an affect regulation disturbance may be common to the two sets of symptoms.