Sleep parameters assessed by actigraphy in Fabry's disease patients: a proof-of-concept.

BACKGROUND: In a previous study developed by our group, we identified a phase inversion in 6-sulfatoxymelatonin - melatonin metabolite in urine - daily profile in Fabry's disease patients. Since melatonin is an endogenous marker, it could also be accompanied by behavioral changes in sleep-wake cycle, which impairs the overall patient's life quality. OBJECTIVE: In this study, we evaluated sleep-wake cycle in Fabry disease patients. We hypothesized that patients would have increased daytime naps, given our previous results for urinary 6-sulfatoxymelatonin. PATIENTS/METHODS: This was a cross-sectional and case-control study, performed between October 2016 and May 2017. Volunteers recorded activity and rest rhythm by actigraphy and answered Pittsburgh Sleep Quality Index (PSQI). From actigraphy data, we calculated sleep parameters: sleep latency, wake after sleep onset, sleep (WASO) efficiency, awakenings index (PSQI), and the amount and duration of daytime naps. We included 16 Fabry disease patients with biochemical and molecular diagnosis and 10 control individuals matched by age and gender. RESULTS: We did not observe significant differences for any of the parameters analyzed (p > 0.05). However, evaluating the magnitude of the effect, we found that patients dozed, on average, about 42 min longer (d = 0.9 - large effect size) than control group. CONCLUSIONS: This is a preliminary study, a proof-of-concept, and our results indicate that changes in melatonin secretion phase may have behavioral consequences in sleep-wake cycle, with longer duration of daytime naps.