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Author's response to letter to the editor [Refers to: Tomoyuki Kawada, Hiroko Suzuki, Takako Shimizu, Masao Katsumata Polygraphic sleep latency and subjective sleepiness by visual analog scale (VAS): The limitation of VAS Applied Ergonomics, Volume 43, Issue 1, January 2012, Pages 266]
journal contributionposted on 2017-12-06, 00:00 authored by L Lack, Michelle ShortMichelle Short, J Dorrian, Gregory RoachGregory Roach, X Xhou, N Lovato, Sally FergusonSally Ferguson, R Tremaine
Kawada et al. (2011) report a significant but moderately low correlation (r= -0.44) between subjective and objective sleepiness, measured by responses on a visual analogue scale (VAS) and sleep onset latency (SOL), respectively. Their correlation was calculated using single measures of VAS and SOL associated with a (daytime?) nap collected with 50 participants. The low correlation in this study was used to emphasize the point that VAS determined subjective sleepiness cannot be used as a substitute for objective sleepiness measured by SOL. Indeed, acceptable correlations for good measures of validity would normally have to be >0.70. Therefore, it could be dangerous to predict objective sleepiness at some specific time in a given individual from a single measure of subjective sleepiness.
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External Author AffiliationsUniversity of South Australia