Study objectives: To retrospectively examine the characteristics of a population of patients <50 years of age with clinical and polysomnographic features diagnostic for RBD.
Methods: Review of our sleep centre's database for patients with RBD diagnosed over the last 7 years. Ninety-one patients were separated into two groups according to their age at the time of diagnosis (<50 y and 50 y). Clinical and polysomnographic data were reviewed.
Results: Sixty-two were male; mean age was 52+/-19 y. Thirty-nine were <50 y. In the group <50 y there was a male predominance but in a smaller proportion (M:F=1.4:1) compared with the group 50 (M:F=3:1). Seventy-six patients complained of abnormal behaviour (AB) during sleep, 12 with narcolepsy complained of excessive daytime sleepiness (EDS) with the AB being elicited only during consultation, and three complained of both EDS and AB. All patients, except one in the group 50, described AB related to vivid dreams with violent content. The majority of the patients had the idiopathic form of RBD in both groups (51.2% group <50, 63.4% group 50). The secondary form was associated with narcolepsy in 38.4% of patients in the group <50 y and with a synucleinopathy in 28.8% of patients in the group 50. A strong association was noted between RBD and non-REM parasomnias.
Conclusions: In a population of patients with RBD presenting to a regional sleep laboratory, more than one-third of patients were <50 y at time of diagnosis. The commonest associated disorder was narcolepsy in patients <50 y, and synucleinopathy in those 50 y. The coexistence of RBD with a NREM parasomnia was not uncommon in cases of idiopathic RBD affecting patients <50 y.