Measurement of itch using actigraphy in pediatric and adult populations.

We have studied nocturnal movements using wrist-worn accelerometers in 33 adults with a range of pruritic dermatoses, 30 adult control subjects, 25 children with atopic dermatitis, and 17 pediatric control subjects. In all, 26 adults and 20 children were studied on more than one occasion, up to a maximum of 6 occasions. Participants were examined and a range of subjective measures about the extent of skin disease, itch, and quality of sleep were recorded. We show clear differences between patients and control subjects for both age groups studied, with activity medians approximately twice as high in the patients as in the control subjects ( P < .001). Studies on the same person show a considerable night-to-night variation that is unlikely to relate to measurement error, but instead, we believe, reflect genuine differences in nocturnal activity (and perhaps disease severity). Movement through the night did not seem to follow any obvious pattern. The relation between subjective measures, Severity sCORing of Atopic Dermatitis (SCORAD) index scores, and objective recorded activity was imperfect, with much unaccounted for variation. In particular, in adults, but not in children, we found a negative correlation (-0.44, P < .02) between objective movement activity and self-reported quality of sleep. Our results support the use of objective measures of scratch in the assessment of disease activity, and suggest that the relation between subjective and objective measures of disease severity may not be straightforward.