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Reeve, Sarah 
ORCID: https://orcid.org/0000-0002-9374-0950, Sheaves, Bryony, Loe, Bao Sheng and Freeman, Daniel
(2026)
Development and validation of the Tiredness Identification Index (TIDI): a combined scale for the assessment of fatigue and sleepiness.
SLEEP Advances, 7 (3).
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Abstract
Study Objectives: Tiredness is a common presentation composed of sleepiness (propensity towards sleeping) and fatigue (feelings of physiological exhaustion). Differentiating between these presentations is important for diagnosis and management. The current study reports on the development and validation of an integrated measure of tiredness (Tiredness Identification Index—TIDI) incorporating assessment of sleepiness and fatigue, and the relationship of the measure with sleep and mental health outcomes. Methods: A sample of 6706 adult participants responded to a pool of sleepiness and fatigue items. Regularized structural equation modelling and confirmatory factor analysis were used to refine the items and factor structure based on convergence against validation measures of fatigue and sleepiness. Regression analyses were then applied to test relationships of the sleepiness and fatigue factors with sleep, mental health, and wellbeing variables. Results: An 8-item scale was developed, composed of a sleepiness (TIDI-sleepiness) and fatigue (TIDI-fatigue) factor with divergent and convergent validity, alongside a general tiredness factor. Higher TIDI-sleepiness was associated with increased apnoea risk and shorter sleep duration, whereas TIDI-fatigue was associated with increased insomnia and reduced sleep efficiency. Controlling for TIDI-sleepiness, TIDI-fatigue was associated with increased depression, anxiety, reduced well-being, and lower physical activity. Increased TIDI-sleepiness and TIDI-fatigue were both associated with paranoia and hallucinations. Conclusions: The results indicate that the TIDI can be used as a brief scale to measure and differentiate fatigue and sleepiness, particularly in non-clinical populations and for research purposes. Assessment of its validity in discriminating fatigue and sleepiness in relevant clinical sleep, mental, and physical health populations should be a focus of future research. Tiredness is a common concern that is linked to a wide range of sleep-related, physical health, and mental health issues. Tiredness is understood to reflect sleepiness (i.e. wanting to go to sleep) or fatigue (i.e. physical exhaustion) or both, but assessment has been limited by difficulty in discriminating sleepiness and fatigue. This paper reports a new measure that enables discrimination between sleepiness and fatigue, and its application to testing relationships between fatigue, sleepiness, sleep, and mental health in a large non-clinical population. The measure requires further testing and validation in the broad range of clinical populations for which fatigue and sleepiness are concerns, but holds the potential to improve the assessment and understanding of fatigue, sleepiness, and tiredness.
| Item Type: | Article |
|---|---|
| Additional Information: | Data availability statement: Data are available from the corresponding author upon request. |
| Uncontrolled Keywords: | sleepiness,fatigue,tiredness,measurement,sdg 3 - good health and well-being ,/dk/atira/pure/sustainabledevelopmentgoals/good_health_and_well_being |
| Faculty \ School: | Faculty of Medicine and Health Sciences > Norwich Medical School |
| UEA Research Groups: | Faculty of Medicine and Health Sciences > Research Centres > Mental Health and Social Care (fka Lifespan Health) |
| Related URLs: | |
| Depositing User: | LivePure Connector |
| Date Deposited: | 07 Aug 2026 13:41 |
| Last Modified: | 17 Aug 2026 07:48 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/104046 |
| DOI: | 10.1093/sleepadvances/zpag072 |
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