Abstract
In addition to a large variety of somatic symptoms, fever also affects cognition, sleep, and mood. In an online survey with 164 participants, 100 fever dream reports were submitted. Fever dreams were more bizarre and more negatively toned and included more references to health and temperature perception compared to “normal” most recent dreams – findings that are in line with the continuity hypothesis of dreaming. Future studies should follow up this line of research by conducting diary studies during naturally occurring febrile illnesses and sleep laboratory studies with experimentally induced fever. It would also be very interesting to study the effect of thermal stimulation applied during sleep on dream content. This research helps to understand subjective experiences while sleeping in an extreme condition (elevated body temperature).
Highlights
Fever is an elevation of body temperature that exceeds the normal daily variation and is based on an increased hypothalamic set point (Dinarello and Porat, 2015)
The present study indicates that fever affects dreaming; fever dreams are more bizarre – confirming the previous finding of our pilot study (Schredl et al, 2016b) in an independent sample – and included more negative dream emotions, less dream characters and interactions, and more health-related topics and heat perceptions than the matched normal non-fever dreams
As fever dreams have not yet been studied systematically, it is reassuring that we were able to replicate the pilot findings with a new independent sample indicating that the present findings are substantial
Summary
Fever is an elevation of body temperature that exceeds the normal daily variation and is based on an increased hypothalamic set point (Dinarello and Porat, 2015). An actigraphy study (Smith, 2012b), monitoring 15 participants suffering from a common cold, found only small or no significant sleep disturbances; only those persons who reported nasal obstruction as a major symptom had reduced sleep efficiency. Higher temperatures of about 39◦C during sleep (experimentally induced via pyrogens) significantly increased wake time and reduced slow wave and rapid eye movement (REM) sleep (Karacan et al, 1968). In addition to the somatic symptoms associated with fever, negative moods and cognitive impairments like psychomotor slowing and lower working memory performance can accompany common colds with fever (Hall and Smith, 1996; Smith, 2012a). Even small increases in body temperature induced by experimentally administered endotoxin can impair cognitive performance and increase depressive mood (Reichenberg et al, 2001)
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