We read with interest the recent study by Provini et al.,1 which showed an increased prevalence of sleep-related eating disorder (SRED) in patients with restless legs syndrome (RLS). The “out-of-control” nocturnal eating behaviors that they observed in RLS patients were strikingly similar to the compulsive and binge eating that we2 and others3 have observed in patients treated with dopamine agonists. In our experience, nocturnal eating is a common clinical feature of dopamine agonist-related compulsive eating in Parkinson's disease.2 Similar impulse control disorders (ICDs) have also been reported in patients treated with dopamine agonists for other conditions, including RLS.4–7
Although the authors reported no differences in dopaminergic medication usage in RLS patients with and without SRED, they showed a trend in this direction (67% versus 52%, P = 0.20) that might have reached statistical significance if they had discriminated between dopamine agonists and levodopa and/or included a quantitative comparison of dopamine agonist use in the two groups. The authors also reported higher Maudsley Obsessive-Compulsive Inventory scores in RLS subjects with SRED, suggesting that these patients may have had other comorbid compulsive tendencies; this is comparable to the frequent occurrence of other ICDs in patients with dopamine agonist-related compulsive eating.2, 8 The authors' observation of SRED in untreated RLS patients, however, raises the possibility of a biological link between RLS and SRED.
We recommend further study to evaluate the extent to which SRED in RLS patients is a side-effect of dopamine agonists versus a direct or indirect consequence of the disease. We congratulate the authors on bringing this important issue to attention.