The Time of Day Sleepiness Scale to assess differential levels of sleepiness across the day

Objective: The study evaluated the Time of Day Sleepiness Scale (ToDSS) to determine subjective estimates of sleepiness in the morning, afternoon, and evening. Scores on the ToDSS were compared to the Epworth Sleepiness Scale (ESS). The ToDSS was evaluated on three cohorts of patients at a sleep medicine clinic. Method: The items of the ToDSS are modified from the ESS to enable subjective assessment in the morning (before noon), afternoon (noon to 1800 h), and evening (after 1800 h). The scale takes about 5 min to complete. For each item, patients provide an estimate of their level of sleepiness in three separate columns, each indicating the time of day (morning, afternoon, and evening). Results: Each ToDSS score evidenced a one factor structure. The ToDSS enabled the assessment of differential levels of sleepiness across the day among several cohorts, with scores increasing in the afternoon and evening. The ESS and each score of the ToDSS demonstrated high correlations. Lower subjective estimates of sleepiness were documented after treatment with continuous positive airway pressure. Conclusions: The ToDSS was shown to have comparable psychometric features to the ESS and provided perceived sleepiness levels across the day in an efficient and cost-effective manner. It also enabled characterization of treatment response among a cohort of patients with obstructive sleep apnea.