Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation/mental retardation syndrome caused by a defect in cholesterol metabolism. Abnormal sleep patterns have been described in SLOS, but previous investigations have relied on parental surveys (Ryan et al, 1998). Children with other mental retardation syndromes are known to have high rates of sleep problems causing disruptive behavior during the day and significant parental stress (Quine, 1992; Didden et al, 2001). The aim of this study is to objectively measure sleep quality in children with SLOS. Actigraphy was obtained on nine children with SLOS ranging in age from 1.1 to 11.3 years at the start of data collection using the AW6 Actiwatch® and associated software (Mini-Mitter/Respironics, Inc). Three to four weeks of continuous data were collected at 1-minute intervals. A sleep diary was supplied to the responsible caregiver, capturing estimates of bedtime, sleep onset, sleep offset, and get-up time, in addition to notable wake after sleep onset (WASO) and times when the watch was removed. A research associate, experienced with actigraphy scored sleep, matched diary and event marker data with actigraphic evidence of bedtime and sleep intervals. All data collection began in the General Clinical Research Center at OHSU after parental instruction on use and proceeded to subject's residence. Data for subjects who live outside the Pacific Time zone were adjusted to account for jet-lag or other zeitgeibers. Time in bed ranged from 9.5 to 12.5 hours (= 10.33 hrs) with total sleep time (TST) ranging from 6.1 to 9.4 hrs (= 8.0 hrs), offering a mean sleep efficiency (SE) of 76.2%. SE ranged from 71% to 83%. Standard deviations (SD) for SE ranged from 6.36% (n = 19 nights for the subject with lowest variability) to 13.54% (n = 23 nights for subject with highest variability). Sleep efficiency in typically developing children generally ranges from 87% to 97% (Sadeh, 2000; Tikotzky, 2001). Sleep onset latency (SOL) ranged from 0.1 to 1.2 hours (= 40 min). Sleep onset ranged from 20:37 to 24:58 (SD 1.0 hrs) and sleep offset 5:57 to 9:11 (SD 1.4 hrs) with onset at 22:35 and offset at 7:49. Our study demonstrates that actigraphy can successfully measure sleep in children with SLOS. Sleep diary reports and event markers correlated well with actigraphic data. Children with SLOS have low sleep efficiency and prolonged sleep onset latency. These sleep abnormalities could impact daytime functioning. There do not appear to be abnormalities in sleep/wake schedules (circadian rhythms).
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