Objectively confirmed prevalence of sleep-related rhythmic movement disorder in pre-school children.

Objective: Childhood sleep-related rhythmic movement disorder (RMD) (ie, sleep-related repetitive movements involving large muscle groups) can impair sleep quality, cause local injury, and disturb household members. Previous parental reports indicate prevalence rates in children under three years of age between 5.5 and 67%. We studied the prevalence of RMD with objective home videosomnography.

Methods: Parents of 707 children having their one-year routine health check (357 male), 740 children having their two-year health check (395 male), and 17 children of unknown age (nine male), were asked if their child showed sleep-related rhythmic movements. If telephone interview confirmed likely RMD, parents completed a standardised clinical questionnaire and three nights of home videosomnography.

Results: At the one-year health check, 31/707 possible cases of RMD were identified [maximal prevalence: 4.38%; 95% CI (2.81, 5.89)] compared to 11/740 at the two-year check [maximal prevalence: 1.49%, 95% CI (0.61, 2.36)]. Of 42 possible cases, nine had resolved; 14 were uncontactable, or did not wish to participate, and four did not complete the study protocol. In four of 10 remaining one-year olds and four of five remaining two-year olds parental report was objectively confirmed by videosomnography. Minimal prevalence based on objective observation was therefore 0.28% [95% CI (0.08, 1.30)] at one-year check and 0.41% [95% CI (0.08, 1.24)] at two-year check.

Conclusions: Prevalence of RMD in a large population of infants and toddlers was lower than previously reported (maximum prevalence 2.87%, minimum prevalence 0.34%). It is important to confirm parental report using objective measures.