Figure 1.

No significant correlation between standard sleep parameters and daytime sleepiness of shift workers

(A) Using activity (black vertical lines) and light exposure (yellow line) measured by the wrist actigraphy, the status of participants over time was categorized as either wake and active (black shade), wake and rest (pink shade), sleep and active (gray shade), or sleep and rest (blue shade) with Actiware-Sleep software, and then the six standard sleep parameters were calculated. TIB: time in bed; SL: sleep latency; TST: total sleep time; WASO: wakefulness after sleep onset; #Awak: number of awakenings; SE: sleep efficiency.

(B and C) Scatterplots of TST (B) and SL (C) versus ESS of shift workers ($n=21$). See Figures S1A–S1D for scatterplots of the other sleep parameters. Shift workers with similar TST (e.g., 6-7 h; B) had dramatically different daytime sleepiness. The line represents the least-square fitting line. $\rho$ and $P$ denote the Spearman's rank correlation coefficient and p value of Spearman's rank correlation test, respectively.

(D) Correlations between the six standard sleep parameters and daytime sleepiness of shift workers were weak and not significant.

See also Figure S1 and Table S1.