Daytime sleepiness is highly prevalent in the elderly and has a negative impact on perceived health, quality of life, functional status, risk of falling, and even mortality. In the aging Western society, there is an increasing need to recognize and assess daytime sleepiness in elderly people. However, the evaluation of daytime sleepiness in this population faces several challenges, e.g., decreased perception of sleepiness in the elderly, increased comorbidity and cognitive decline that may complicate assessment, and a lack of normative data for assessment tools in the elderly and of elderly-specific assessment tools for sleepiness. More research is needed in the neglected field of excessive daytime sleepiness in the elderly. In particular, prospective studies are warranted to explore the relationship between daytime sleepiness and various functional endpoints. © Springer-Verlag 2011.