Results from a small Australian trial have challenged the belief that melatonin is effective against REM‐sleep behaviour disorder (RBD) symptoms in people with Parkinson’s disease.
The findings will come as a setback for management of the condition that causes a loss of muscle atonia during REM sleep, leading to dream enactment behaviours that are frequently injurious to patients and their partners.
Reported to affect 20% to 50% of people with Parkinson’s disease, there are currently few effective treatments available other than clonazepam, which has significant adverse effects.
In a randomised, double‐blind trial (RCT), researchers at the Woolcock Institute of Medical Research, Sydney, recruited 30 patients with Parkinson’s disease and RBD symptoms.
Patients were randomised to either 4mg prolonged‐release melatonin (Circadin) or placebo at bedtime for eight weeks.
The primary outcome was the aggregate of self-reported REM sleep behaviour disorder incidents recorded over weeks 5 to 8 of treatment. When compared to placebo, no differences were seen with melatonin for RBD symptoms (3.4 vs. 3.6 events/week for melatonin and placebo, respectively). Similarly, patients reported no differences in the number of nights per week affected by RBD.
The melatonin treatment appeared to be safe and well tolerated, with adverse events of mild headaches, fatigue, and morning sleepiness seen in similar levels in both active and control groups.
Writing in Movement Disorders, the study investigators said melatonin had previously been reported to have efficacy in observational studies and case reports of people with Parkinsons and RBD. However the results were varied, with some patients showing no response to melatonin even at higher doses (25mg) than used in the current prospective trial.
They said the negative findings from the small study did not rule out an effect for melatonin, and some effects on BPD symptoms might have been missed by subjects due to the reliance on self reporting.
“Larger, multicentred RCT’s are still warranted to assess the efficacy of both drugs for reducing RBD. Such trials should plan for observing strong placebo effects when using patient‐reported outcomes,” they concluded.