Night eating and night eating syndrome: associations with dysfunctional eating behaviors, mental health and quality-of-life measures in Australian adults.

Purpose: The association of night eating (NE) and NE syndrome (NES) with dysfunctional eating behaviors, mental health and quality-of-life outcomes has been little explored in the general population. The objective of this study was to explore this for dysfunctional eating behaviors: binge-eating, use of purging, dietary restriction, use of medication to control weight; mental health: anxiety/depression; and quality-of-life outcomes: mental and physical health-related quality of life (M/PHRQoL). NE captured whether in the past 3 months, the respondents had any episodes of waking from sleep and eating, or episodes of eating a very large amount of food after evening meal excluding any such events at social gatherings or travelling overseas on a night flight or because of work shifts. NES was defined by at least weekly episodes of NE with 'a lot' of distress.

Methods: In 2017, 2977 adults from randomly selected households in South Australia were interviewed. Analyses for bivariate association were conducted using weighted tetrachoric and weighted polychoric correlations, and ordinal and binary logistic models, to determine the association between current (3 months) NE or NES as an outcome, and binge-eating, use of purging, dietary restriction, use of medication to control weight, anxiety/depression, mental and physical health-related quality of life (M/PHRQoL) as predictors after controlling for age, sex, and body weight. All analyses adjusted for design effect by stratified cluster sampling.

Results: Ordinal logistic regression found significantly higher odds of episodes of NE with binge-eating (OR = 1.756, 95% CI 1.527-2.020, p < 0.001), and significantly lower odds with increased MHRQoL (OR = 0.948, 95% 0.921-0.975, p < 0.001) and increased PHRQoL (OR = 0.976, 95% CI 0.966-0.986, p < 0.001). Binary logistic regression found significantly higher odds of NES with binge-eating (OR = 2.62, p < 0.001), and restrictive dieting (OR = 2.491, 95% CI 1.647-3.769, p < 0.01), and significantly lower odds with MHRQoL (OR = 0.913, 95% CI 0.879-0.948, p < 0.001).

Conclusions: Those with a history of binge-eating have higher likelihood of having both NE and NES which are also increased for the former in those with poorer MHRQoL and PHRQoL, and for the latter in only those with poorer MHRQoL. Revisions of diagnostic schemes may consider these findings in the context of delineation of boundaries between eating disorder syndromes.

Levels of evidence: Multivariate binary logistic regression analyses found there were significantly higher odds of having night eating syndrome in association with binge eating and restrictive dieting and significantly lower odds of night eating syndrome in association with increases in MHRQoL. These results support the Muscatello et al. (Aust N Z J Psychiatry 56:120-1362022, 2022) review noting associations and overlap between night eating syndrome and other eating disorders characterized by recurrent binge-eating, and the reported associations with disorders of restrictive eating. As both night eating and binge-eating are symptoms of over or excessive eating this was not unexpected. However, the findings at a diagnostic level in this study did also support research that has found overlap between night eating syndrome and disorders characterized by restrictive eating and/or purging behaviors. By "at a diagnostic level" what we meant was when at a level associated with marked distress, as the DSM requires either functional impairment or psychological distress to be present as a defining feature of any mental health disorder and distress is a defining feature of NES (American Psychiatric Association 2013). Diagnostic and Statistical Manual of Mental Disorders: DSM-5. Arlington, American Psychiatric Publishing Inc.). MHRQoL rather than PHRQoL was associated with night eating syndrome. More research is required to confirm this result and it does not negate the clinical importance of consideration of physical health status of people with night eating syndrome (Muscatello et al. Aust N Z J Psychiatry 56:120-136, 2022; Sakthivel et al. Eat Weight Disorders-Stud Anorexia Bulimia Obes 28:77, 2023). This study did not find that those who have perceived subjective anxiety/depression have significantly higher odds of NE as well as NES. This may have been because the present study did not have an assessment of depression or anxiety using a validated instrument, but rather a broad self-reported experience of current perceived anxiety and/or depression. Other studies have been also more often conduced in clinical populations which may be expected to have higher rates of mental health comorbidities (Muscatello et al. Aust N Z J Psychiatry 56:120-136, 2022) than this general population sample.

Public significance statement: To our knowledge this is the first study in a representative adult general population examining the relationships between night eating (NE), NE syndrome (NES) and binge eating, purging, strict dieting and general anxiety or general depression. Those with a history of binge eating and having poorer MHRQoL and PHRQoL have higher likelihoods of experiencing NE. The same associations of these factors except for that of PHRQoL were found with NES. Revisions of diagnostic schemes may consider these findings in the context of delineation of boundaries between eating disorder syndromes. As the nature of overeating is defined more broadly in NES than in other eating disorders it is important to explore all forms of overeating when undertaking estimates of the population prevalence and burden of eating disorder.