Is the brain of migraineurs “different” even in dreams?

Do you remember if you have olfactory dreams? A content analysis of LOFTER and a questionnaire survey conducted in China

OBJECTIVES

Dreams often involve visual and auditory sensations, but olfactory experiences have not received the same amount of attention. This study explores the prevalence and content of olfactory dreams in China and investigates the relationship between olfactory imagery, olfactory significance, and olfactory dreamers.

METHODS

In the first part of the study, 4302 dream records from LOFTER were screened and classified to preliminarily identify the prevalence and content of olfactory dreams. In the second part, 718 participants completed an online questionnaire about olfactory dreams, imagery, and significance.

RESULTS

The prevalence of olfactory dreams in the diary dream entries and questionnaire survey participants were 3.95% and 18.70%, respectively. Instances in which odors appeared in dreams were more positive than negative and were mainly related to food, burning and smoke, body odor, nature, and certain environments and objects. Moreover, individuals with olfactory dreams showed better olfactory imagery, and stronger olfactory significance.

CONCLUSIONS

Olfactory sensations occurred in the dreams of Chinese individuals, but their prevalence was very low. Most of the odors that emerged in these dreams were ones that the dreamers were familiar with in their daily lives.

Olfaction-Related Factors Affecting Chemosensory Dream Content in a Sleep Laboratory

Mental activity in sleep often involves visual and auditory content. Chemosensory (olfactory and gustatory) experiences are less common and underexplored. The aim of the study was to identify olfaction-related factors that may affect the occurrence of chemosensory dream content. Specifically, we investigated the effects of all-night exposure to an ambient odour, participants' appraisal of their current olfactory environment, their general propensity to notice odours and act on them (i.e., odour awareness), and their olfactory acuity. Sixty pre-screened healthy young adults underwent olfactory assessment, completed a measure of odour awareness, and spent three nights in weekly intervals in a sleep laboratory. The purpose of the first visit was to adapt to the experimental setting. On the second visit, half of them were exposed to the smell of vanillin or thioglycolic acid and the other half to an odourless control condition. On the third visit, they received control or stimulation in a balanced order. On each visit, data were collected twice: once from the first rapid eye movement (REM) stage that occurred after 3 a.m., and then shortly before getting up, usually from a non-REM stage. Participants were asked to report the presence of sensory dream content and to assess their current olfactory environment. Neither exposure, nor participants' assessments of the ambient odour, or olfactory acuity affected reports of chemosensory dream content but they were more frequent in individuals with greater odour awareness. This finding may have implications for treatment when such experiences become unwanted or bothersome.

Nightmares in Migraine: A Focused Review

Nightmares usually occur during the sleep phase of rapid eye movement (REM) and are associated with some physical symptoms, including sweating, shortness of breath, and lower limb movements. Emotions of fear, anger, shame, and sadness may also accompany nightmares. These symptoms can occur during dreaming, upon awakening, or later when the dream experience is recollected. Nightmares may sporadically occur for everyone, but nightmare disorders are associated with features of impaired mental and physical health and require professional medical treatment. The occurrence of nightmares with several disorders has been reported in the literature, but in migraines it has only been investigated in a small number of studies. Considering the existing relationship between sleep disorders and migraine, the occurrence of nightmares in migraine can negatively affect this association and elevate the risk of depression and anxiety. This, in turn, further reduces the quality of life of affected individuals. Hence, expanding the knowledge on the link between nightmares and migraine, promoting an acceptable quantity and quality of sleep through pharmacological and nonpharmacological interventions in the management of nightmares in migraine, and further scientific investigation of the biopsychosocial mechanisms underlying the link, will be highly valuable for optimal care. This focused review, therefore, gives a brief overview of the current understanding of nightmares in migraine to highlight the open questions and value of further research. The ultimate goal is to contribute to timely recognition and sufficient action to offer beneficial outcomes for affected patients.

Exploring the Connection Between Sleep and Cluster Headache: A Narrative Review

Cluster headache is a rare form of headache associated with sleep and even speculated to be a manifestation of a sleep disorder rather than a primary headache. Cluster headache exhibits both circadian and circannual rhythmicity. While attacks often occur during sleep, the implication that cluster headaches might be involved with rapid eye movement (REM) sleep phases has neither been fully established nor refuted. The regulatory mechanisms governing sleep including hypothalamic activity and the autonomic nervous system response may play a role. Hypothalamic activation has been observed in cluster headache patients during positron emission tomography testing, but only during attacks. While sleep apnea is associated with morning headaches in general, the link between sleep-disordered respiration and cluster headache remains elusive. Hypoarousal during sleep and periods of hypoxia are associated with cluster headache, the latter likely involving inflammatory processes rather than apnea. Further study is needed, as cluster headaches represent a serious primary cephalgia that is incompletely understood.

Oliver Sacks and migraine

Background

Oliver Sacks (1933–2015) published a large number of books on a variety of neurological topics. Of these, numerous copies have been sold and they probably serve as the only or main source of information on neurological diseases for many persons without a medical background. His first book was on migraine and in his subsequent books many descriptions of migraine can be found, mainly those of auras.

Methods

We explored the descriptions of migraine in Sacks’ work in order to evaluate the image of migraine offered to the readers.

Conclusion

Oliver Sacks gave wonderful descriptions of migraine auras, but hardly any of migraine headache. Furthermore, he described rare auras such as ‘amusia’ and olfactory auras. Overall, this makes his descriptions of migraine not very useful to serve as medical information for laypersons. Oliver Sacks, however, wrote great literature.

Sleep, headaches and cerebral energy control: a synoptic view

INTRODUCTION

The amount of cerebral functions is particularly elevated. This intense activity requires a great expenditure of energy: the restoration of energy is the fundamental function of sleep whilst the slowdown in energy consumption may be considered the physiological effect of primary headaches. The continuous interaction of sleep and primary headaches is possible as they share many anatomical and functional cerebral systems. Areas covered: This review describes how sleep and headaches are reciprocally involved in preservation and restoration of brain energy. Data were obtained from the most relevant and recent works available in PubMed about this topic. Expert commentary: The energetic view of sleep, primary headaches and their relationship may have relevant clinical consequences: the investigation and the modification of the multiple aspects, primarily environmental, that may influence sleep and headache, become mandatory to facilitate the cerebral energy preservation by reducing its consumption and by ensuring its recovery.

Dreams of the Rarebit Fiend: food and diet as instigators of bizarre and disturbing dreams

In the early 1900s, the Dream of the Rarebit Fiend comic strip conveyed how the spicy cheese dish Welsh rarebit leads to bizarre and disturbing dreams. Today, the perception that foods disturb dreaming persists. But apart from case studies, some exploratory surveys, and a few lab studies on how hunger affects dreaming, there is little empirical evidence addressing this topic. The present study examines three aspects of the food/dreaming relationship; it attempts to: (1) assess the prevalence of the perception of food-dependent dreaming and the types of foods most commonly blamed; (2) determine if perceived food-dependent dreaming is associated with dietary, sleep or motivational factors; and (3) explore whether these factors, independent of food/dreaming perceptions, are associated with reports of vivid and disturbing dreams. Three hundred and ninety six students completed questionnaires evaluating sleep, dreams, and dietary habits and motivations. Items queried whether they had noticed if foods produced bizarre or disturbing dreams and if eating late at night influenced their dreams. The perception of food-dependent dreaming had a prevalence of 17.8%; with dairy products being the most frequently blamed food category (39-44%). Those who perceived food-dependent dreaming differed from others by reporting more frequent and disturbing dreams, poorer sleep, higher coffee intake, and lower Intuitive Eating Scale scores. Reports of disturbing dreams were associated with a pathological constellation of measures that includes poorer sleep, binge-eating, and eating for emotional reasons. Reports of vivid dreams were associated with measures indicative of wellness: better sleep, a healthier diet, and longer times between meals (fasting). Results clarify the relationship between food and dreaming and suggest four explanations for the perception of food-dependent dreaming: (1) food specific effects; (2) food-induced distress; (3) folklore influences, and (4) causal misattributions. Research and clinical implications are discussed.