Sleepy, tired, drowsy, and fatigue have different meanings for a university student sample

Study Objectives: This pilot study aimed to investigate differences in the semantic meanings that individuals attribute to the words “sleepy,” “fatigued,” “tired,” and “drowsy.” Methods: Ninety-six undergraduate students ranked the target words on 3 independent dimensions (evaluative, potency, and activity) to assess their meaning using the semantic differential technique. Participants also completed online questionnaires to assess their sleep difficulties and current states of sleepiness and fatigue. Results: There were significant differences between all 4 words in connotative meaning on the evaluative dimension, P < .05 for all post-hoc comparisons, with the differences largest between “sleepy” and “fatigued.” “Drowsy” was significantly closer in meaning to “sleepy” than to “fatigued,” P = .04, and “tired” was not significantly closer in meaning to “sleepy” or “fatigued,” P = .13. No significant association was found between insomnia severity index scores and “sleepy” ratings, r _(s) = 0.08, P = .42, but a small effect was found with “fatigued” ratings, r _(s) = 0.24, P = .02. Conclusions: These preliminary findings indicate that individuals consider these words as distinct concepts, relatively unaffected by the current severity of their insomnia symptoms. This adds to the argument for not using these words interchangeably, which we encourage sleep medicine researchers and clinicians to consider when employing these words in research and clinical practice.