Olfaction is a Marker of Severity but Not Diagnosis in Anorexia Nervosa: a Systematic Review and Meta-Analysis

Perceptual Dysfunction in Eating Disorders

Eating disorders (EDs) are characterized by abnormal responses to food and weight-related stimuli and are associated with significant distress, impairment, and poor outcomes. Because many of the cardinal symptoms of EDs involve disturbances in perception of one's body or abnormal affective or cognitive reactions to food intake and how that affects one's size, there has been longstanding interest in characterizing alterations in sensory perception among differing ED diagnostic groups. Within the current review, we aimed to critically assess the existing research on exteroceptive and interoceptive perception and how sensory perception may influence ED behavior. Overall, existing research is most consistent regarding alterations in taste, visual, tactile, and gastric-specific interoceptive processing in EDs, with emerging work indicating elevated respiratory and cardiovascular sensitivity. However, this work is far from conclusive, with most studies unable to speak to the precise etiology of observed perceptual differences in these domains and disentangle these effects from affective and cognitive processes observed within EDs. Further, existing knowledge regarding perceptual disturbances in EDs is limited by heterogeneity in methodology, lack of multimodal assessment protocols, and inconsistent attention to different ED diagnoses. We propose several new avenues for improving neurobiology-informed research on sensory processing to generate actionable knowledge that can inform the development of innovative interventions for these serious disorders.

Olfactory Dysfunction and Glaucoma

BACKGROUND

Olfactory dysfunction is a well-known phenomenon in neurological diseases with anosmia and hyposmia serving as clinical or preclinical indicators of Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders. Since glaucoma is a neurodegenerative disease of the visual system, it may also entail alterations in olfactory function, warranting investigation into potential sensory interconnections.

METHODS

A review of the current literature of the last 15 years (from 1 April 2008 to 1 April 2023) was conducted by two different authors searching for topics related to olfaction and glaucoma.

RESULTS

three papers met the selection criteria. According to these findings, patients with POAG appear to have worse olfaction than healthy subjects. Furthermore, certain predisposing conditions to glaucoma, such as pseudoexfoliation syndrome and primary vascular dysregulation, could possibly induce olfactory changes that can be measured with the Sniffin Stick test.

CONCLUSIONS

the scientific literature on this topic is very limited, and the pathogenesis of olfactory changes in glaucoma is not clear. However, if the results of these studies are confirmed by further research, olfactory testing may be a non-invasive tool to assist clinicians in the early diagnosis of glaucoma.

The Impact of Clinical Factors, Vitamin B12 and Total Cholesterol on Severity of Anorexia Nervosa: A Multicentric Cross-Sectional Study

Severe forms of Anorexia Nervosa (AN) are characterized by medical complications, psychiatric comorbidity, and high mortality. This study investigated potential associations between clinical/biological factors and the severity of AN, measured by the Body Mass Index (BMI). Red and white blood cells, hemoglobin, platelets, iron, vitamins D and B12, folate, and total cholesterol were measured in a mixed sample of 78 inpatients and outpatients. Linear regressions and one-way analyses of variance (ANOVAs) were carried out to evaluate the relationship between BMI and clinical/biochemical variables. BMI was significantly lower in hospitalized patients (F = 4.662; p = 0.034) and in those under pharmacological treatment (F = 5.733; p = 0.019) or poly-therapy (F = 5.635; p = 0.021). Higher vitamin B12 (β = -0.556, p < 0.001), total cholesterol (β = -0.320, p = 0.027), and later age at onset (with a trend towards significance) (β = -0.376, p = 0.058) were associated with a lower BMI. Increased total cholesterol and vitamin B12, later age at onset, current pharmacological treatment, and poly-therapy might be distinctive in patients with a lower BMI. In clinical practice, these findings may contribute to the early identification of AN patients at higher risk of developing complicated or chronic forms of the disorder. Further studies on larger samples are needed to identify potential predictive factors of AN severity in the framework of precision medicine.

Differential alterations of amygdala nuclei volumes in acutely ill patients with anorexia nervosa and their associations with leptin levels

BACKGROUND

The amygdala is a subcortical limbic structure consisting of histologically and functionally distinct subregions. New automated structural magnetic resonance imaging (MRI) segmentation tools facilitate the in vivo study of individual amygdala nuclei in clinical populations such as patients with anorexia nervosa (AN) who show symptoms indicative of limbic dysregulation. This study is the first to investigate amygdala nuclei volumes in AN, their relationships with leptin, a key indicator of AN-related neuroendocrine alterations, and further clinical measures.

METHODS

T1-weighted MRI scans were subsegmented and multi-stage quality controlled using FreeSurfer. Left/right hemispheric amygdala nuclei volumes were cross-sectionally compared between females with AN (n = 168, 12-29 years) and age-matched healthy females (n = 168) applying general linear models. Associations with plasma leptin, body mass index (BMI), illness duration, and psychiatric symptoms were analyzed via robust linear regression.

RESULTS

Globally, most amygdala nuclei volumes in both hemispheres were reduced in AN v. healthy control participants. Importantly, four specific nuclei (accessory basal, cortical, medial nuclei, corticoamygdaloid transition in the rostral-medial amygdala) showed greater volumetric reduction even relative to reductions of whole amygdala and total subcortical gray matter volumes, whereas basal, lateral, and paralaminar nuclei were less reduced. All rostral-medially clustered nuclei were positively associated with leptin in AN independent of BMI. Amygdala nuclei volumes were not associated with illness duration or psychiatric symptom severity in AN.

CONCLUSIONS

In AN, amygdala nuclei are altered to different degrees. Severe volume loss in rostral-medially clustered nuclei, collectively involved in olfactory/food-related reward processing, may represent a structural correlate of AN-related symptoms. Hypoleptinemia might be linked to rostral-medial amygdala alterations.

Encountering patients with anorexia nervosa - An emotional roller coaster. nurses’ lived experiences of encounters in psychiatric inpatient care

Purpose

The aim of this study was to illuminate the meaning of nurses’ lived experiences of encounters with adult patients with anorexia nervosa in psychiatric inpatient care.

Methods

A qualitative phenomenological hermeneutical design was used. Personal interviews with a narrative approach were conducted with 11 nurses with experience of encountering patients with anorexia nervosa in psychiatric inpatient care.

Results

Three key themes were revealed: Being overwhelmed by emotions consisting of three subthemes: Bearing feelings of incomprehension, Navigating emotions, and Being disappointed and frustrated; Seeking strength to cope consisting of three subthemes: Relying on colleagues and routines, Feeling hope and motivation, and Building inner security; and Trying to build relations consisting of two subthemes: Getting closer to the patient and Relating to relatives.

Conclusion

Our findings illuminate the “emotional roller-coaster” which nurses are embedded in during their daily work experiences. Being able to balance one’s professional role, seeing the person behind the patient, and the illness is important in all nurse-patient encounters. An examination of nurses’ lived experiences can contribute new and important knowledge, an in-depth understanding of the nurses’ work situation, and can help identify any need for increased knowledge.

Associations among perceived taste and smell sensitivity, gastrointestinal symptoms, and restrictive eating in a community sample of adults

Restrictive eating is associated with several poor health outcomes. Exteroceptive sensory modalities, including taste and smell, are employed while eating and disturbances in exteroceptive sensitivity may influence eating behavior. Meal-related gastrointestinal disturbances, such as early satiety and postprandial fullness, are well-documented in eating disorders and may influence eating behavior. This study examined the relationships of perceived sensitivity to taste or smell and gastrointestinal symptoms with restrictive eating, and potential interactions between gastrointestinal symptoms and perceived sensitivity to taste or smell. Adults aged 18-65 were recruited via ResearchMatch.org (N = 420) and completed questionnaires assessing restrictive eating, perceived sensitivity to taste and smell, and gastrointestinal symptom severity. There was a weak relationship between restrictive eating and perceived sensitivity to taste (r = -0.115, p = .022) and smell (r = -0.101, p = .039). There was a strong relationship between gastrointestinal symptom severity and restrictive eating (r = 0.583, p < .001). Gastrointestinal symptom severity moderated the relationship between perceived sensitivity to taste and restrictive eating, such that this relationship was strongest at lower levels of gastrointestinal symptom severity (Estimate = -0.136, p = .014). There was no observed interaction between perceived sensitivity to smell and gastrointestinal symptoms (Estimate = 0.001, p = .156). Results indicate that increased perceived sensitivity to taste, smell, and gastrointestinal symptom severity were each associated with greater restrictive eating. The relationship between perceived sensitivity to taste and restrictive eating is strongest at lower gastrointestinal symptom severity. Future research should examine whether tailoring treatments for individuals who present with elevated perceived sensitivity to taste or smell, gastrointestinal symptoms, or both is effective in reducing restrictive eating.

Not Only COVID-19: Involvement of Multiple Chemosensory Systems in Human Diseases

Chemosensory systems are deemed marginal in human pathology. In appraising their role, we aim at suggesting a paradigm shift based on the available clinical and experimental data that will be discussed. Taste and olfaction are polymodal sensory systems, providing inputs to many brain structures that regulate crucial visceral functions, including metabolism but also endocrine, cardiovascular, respiratory, and immune systems. Moreover, other visceral chemosensory systems monitor different essential chemical parameters of “milieu intérieur,” transmitting their data to the brain areas receiving taste and olfactory inputs; hence, they participate in regulating the same vital functions. These chemosensory cells share many molecular features with olfactory or taste receptor cells, thus they may be affected by the same pathological events. In most COVID-19 patients, taste and olfaction are disturbed. This may represent only a small portion of a broadly diffuse chemosensory incapacitation. Indeed, many COVID-19 peculiar symptoms may be explained by the impairment of visceral chemosensory systems, for example, silent hypoxia, diarrhea, and the “cytokine storm”. Dysregulation of chemosensory systems may underlie the much higher mortality rate of COVID-19 Acute Respiratory Distress Syndrome (ARDS) compared to ARDSs of different origins. In chronic non-infectious diseases like hypertension, diabetes, or cancer, the impairment of taste and/or olfaction has been consistently reported. This may signal diffuse chemosensory failure, possibly worsening the prognosis of these patients. Incapacitation of one or few chemosensory systems has negligible effects on survival under ordinary life conditions but, under stress, like metabolic imbalance or COVID-19 pneumonia, the impairment of multiple chemosensory systems may lead to dire consequences during the course of the disease.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Olfactory capacity in anorexia nervosa: correlations with set-shifting ability

PURPOSE

The purpose of this study is to examine olfactory capacity in adults with anorexia nervosa (AN), in terms of odor identification and odor threshold and search for possible correlations between odor identification and cognitive flexibility in this population.

METHODS

Thirty-nine patients diagnosed with AN and 60 healthy participants, participated. Odor identification was assessed using the University Pennsylvania Smell Identification Test and a two alternative forced choice, ascending method with n-butanol was used to assess odor threshold. Cognitive flexibility was determined using the Intra/Extra-Dimensional Set-Shift test (IED), a subtest of the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

Patients with AN presented a poorer performance in odor identification compared with controls (p = 0.001). No differences were found in odor threshold, between the two groups. Patients with AN exhibited poor cognitive flexibility compared with controls (p = 0.003). A significant correlation between odor identification and cognitive flexibility was documented in AN (p = 0.01), but not in controls.

CONCLUSION

Our findings suggest that olfactory capacity is altered in AN: Qualitative characteristics of olfaction were affected in patients with AN (lower odor identification), while there was no difference in quantitative characteristics (odor threshold) compared with controls. Furthermore, odor identification in AN was correlated to cognitive flexibility.

LEVEL OF EVIDENCE

Level III: case-control analytic study.

Nurses' perceptions on and experiences in conflict situations when caring for adolescents with anorexia nervosa: A qualitative study

Anorexia nervosa (AN), which primarily affects adolescent girls and young women, is characterized by excessive dieting, leading to severe weight loss and a pathological fear of becoming overweight, or unhealthy behaviours that hinder weight gain. Caring for patients who have AN is particularly challenging for nursing staff, who are on the front line and have the closest contact with patients. However, little is known about how nursing staff care for adolescent patients with AN in Taiwan. This study aimed to explore nurses' perceptions on and experiences in conflict situations in caring for adolescents with AN. A qualitative study approach was conducted. Through semi-structured interviews, ten nursing staff from the paediatric ward at a university-affiliated medical centre in central Taiwan shared their experiences. Recorded interviews were transcribed and analysed by content analysis. This analysis identified three themes with eight subthemes: (i) struggling to develop therapeutic relationships, (ii) selective focusing, and (iii) difficulty changing minds. The findings of this study indicated a need for ongoing support for nursing staff, the development of therapeutic relationships with adolescent patients with AN, extensive nursing staff preparation, and the development of in-service training programs to enable nursing staff to care for these patients with greater understanding.

Current directions in biomarkers and endophenotypes for anorexia nervosa: A scoping review

There are currently no validated biomarkers for anorexia nervosa (AN), though recent literature suggests an increased research interest in this area. Biomarkers are objective, measurable indicators of illness that can be used to assist with diagnosis, risk assessment, and tracking of illness state. Related to biomarkers are endophenotypes, which are quantifiable phenomena that are distinct from symptoms and which link genes to manifest illness. In this scoping review, we sought to provide a summary of recent research conducted in the pursuit of biomarkers and endophenotypes for AN. The findings indicate that a number of possible biomarkers which can assess the presence or severity of AN independently of weight status, including psychophysical (e.g., eye-tracking) and biological (e.g., immune, endocrine, metabolomic, neurobiological) markers, are currently under investigation. However, this research is still in early phases and lacking in replication studies. Endophenotype research has largely been confined to the study of several neurocognitive features, with mixed evidence to support their classification as possible endophenotypes for the disorder. The study of biomarkers and endophenotypes in AN involves significant challenges due to confounding factors of illness-related sequalae, such as starvation. Future research in these areas must prioritise direct evaluation of the sensitivity, specificity and test-retest reliability of proposed biomarkers and enhanced control of confounding physical consequences of AN in the study of biomarkers and endophenotypes.