Clinical complaints of daytime sleepiness and fatigue: how to distinguish and treat them, especially when they become 'excessive' or 'chronic'?

Chronic daytime fatigue and excessive daytime sleepiness (EDS) are potentially invalidating and also common complaints in primary care and general neurological practice. The lack of distinction in the clinical use of terms like fatigue and sleepiness is an important issue. Although these semiological concepts present fundamental differences from physiological and pathological points of view, general medical literature still often confuses both symptoms. The objective of the present review is to contribute to the clinical distinction between fatigue and sleepiness and describe available measurement tools and respective treatment options. We found that sleepiness and fatigue both present with semiological multidimensionality and clinical complexity. Although relating to different underlying concepts, they can show overlapping features and several clinical conditions can present with both complaints simultaneously. Existing specific assessment tools are sometimes underutilised, causing EDS and fatigue to continue to be confounded. The blurring contributions of several studies are mainly due to the fact that typically only one of these two clinical dimensions is investigated. Despite consensus on objective sleepiness measures, simple and validated objective fatigue assessments are generally lacking and seem elusive. Causal and symptomatic treatment options exist predominantly for sleepiness-associated conditions. Although comprehension of sleepiness and its underlying physiology has seemed to improve over time, descriptions of common pathways of fatigue remain relatively incomplete. Clinical research and practice should systematically investigate both conditions with adequate measurement tools. Behavioural medicine is certainly underestimated, especially in the management of chronic daytime fatigue.