Impulse-control disorders and restless leg syndrome in Parkinson's Disease: Association or coexistence

Background: Both Impulse-control disorders and related behaviours (ICD-RB) and restless leg syndrome (RLS) are relatively common in patients with Parkinson's disease, but little is known are they related or independent complications of dopaminergic therapy. The aim of this study was to determine the correlation between ICD-RBs and RLS and also, to determine the associated significant psycho-behavioural profile of RLS patients in presence of ICD-RBs. Methods: PD who visited neurology OPD were screened for the presence of addictive behaviors, alcohol and substance abuse, ICDs including Impulse control disorders not elsewhere classified with the help of a QUIP questionnaire. RLS was evaluated by diagnostic criteria set by the International RLS study group. To evaluate the association of RLS and ICDs, cohort was divided into groups of patients who had both ICD and RLS, ICD with no RLS, RLS with no ICD and no ICD or RLS. Results: Among 122 PD patients who visited OPD, 95 eligible were included in the study. Out of these 95 patients, 51 (53.6%) had at least one ICD-RB and 18 (18.9%) had RLS. ICD-RB in decreasing order of frequency were compulsive medication (47.4%), compulsive eating (29.4%), compulsive buying (17.6%), gambling (11.7%), hypersexuality (3.9%), and others (29.8%). Among 18 patients with RLS, 12 (66.7%) were associated with at least one ICD-RB. The compulsive behaviours significantly associated with PD-RLS group were gambling (27.8%), followed by compulsive eating (44.2%). While comparing disease characteristics, PD-ICD/RLS patients had statistically significant disease duration (p 0.007) and higher LEDD (p 0.004). Other demographic and socioeconomic features did not reveal any differences between the groups. Conclusion: 11% of PwPD can have co-occurrence of RLS and ICD-RBs. Circadian fluctuation in levels of dopamine release on the background of hyper-dopaminergic state produces waves of crest and trough, which may be possible for this behavioral profile. Long-term dopaminergic treatment or degenerative process itself may be the cause leading to emergence of both RLS and ICD-RBs in PD patients.