Anorexia Nervosa Associated with Being an Early Riser

Hannah Wilcox, BS

Credit: LinkedIn

Anorexia nervosa is associated with being an early riser—and thus the morning chronotype—according to a new study.¹

Many disorders tend to be evening-based like depression, binge eating disorder, and schizophrenia. With anorexia nervosa being morning-based, it stands apart from other disorders.

A new study, led by Hannah Wilcox, BS, from Massachusetts General Hospital and Harvard Medical School, sought to evaluate the association between anorexia nervosa and circadian and sleep traits—including daytime napping, daytime sleepiness, sleep duration, and insomnia—through mendelian randomization. The investigators also evaluated the associations between a polygenic risk score for anorexia nervosa and sleep disorders in a clinical biobank.

“The clinical implications of our new findings are currently unclear; however, our results could direct future investigations into circadian-based therapies for anorexia nervosa prevention and treatment,” Wilcox said in a press release.²

The genetic association study used bidirectional 2-sample mendelian randomization with associations between anorexia nervosa and chronotype and sleep traits.¹ The investigators pulled data from the clinical Mass General Brigham biobank (n = 47,082) to receive polygenic risk scores for anorexia nervosa, as well as electronic health records to find prevalent sleep disorders. Analyses took place between February – August 2023.

The study included 16,992 cases, with majority female (87.7 - 97.4%), and 55,525 controls (49.6 - 63.4% female). The investigators found genetic liability for anorexia nervosa was linked to a more morning chronotype (β = 0.039; 95% CI, 0.006 – 0.072). Similarly, a genetic liability for morning chronotype was linked to an increased risk of anorexia nervosa (β = 0.178; 95% CI, 0.042 – 0.315).

Moreover, sensitivity and secondary analyses provided robust data. The team found genetic liability for insomnia was linked to an increased risk of anorexia nervosa (β = 0.369; 95% CI, 0.073 – 0.666).

The biobank analysis, with 47,082 participants with a mean age of 60.4 years old and over half female (53.8%, n = 25,318), showed the polygenic risk scores for anorexia nervosa was linked to 10% higher odds for organic or persistent insomnia (odds ratio: 1.10; 95% CI, 1.03 – 1.17). When using the biobank analysis to evaluate the anorexia nervosa polygenic risk scores with anorexia nervosa diagnosis, the investigators noted each standard deviation increase in the polygenic risk scores was linked to a 36% higher odds of anorexia nervosa (odds ratio: 1.36; 95% CI, 1.14 – 1.63).

The biobank analysis also did not find significant associations with other sleep disorders like sleep apnea and restless sleep syndrome. There were also no associations between anorexia nervosa polygenic risk scores and time in bed, sleep debt, or social jetlag.

Meanwhile in the mendelian randomization analysis, the investigators found an association between insomnia and the increased risk of anorexia nervosa (β = 0.339; 95% CI, 0.052 – 0.627) but no associations between anorexia nervosa and the sleep traits, daytime napping, daytime sleepiness, or sleep duration.

“Our findings suggest the role of morningness as an underrecognized risk factor for anorexia nervosa whose importance should be further investigated in the context of other established risk factors,” the investigators wrote. “If deemed a relevant risk factor, interventions promoting later sleep schedules may be considered to ameliorate risk conferred by a morning chronotype.”

The team also noted anorexia nervosa is an eating disorder most likely with a circadian feature, as observational studies demonstrated the disorder was associated with skipping breakfast and lunch, as well as morning bright light therapy being not as effective than for night-based binge eating disorders. Also, participants with anorexia nervosa had “enhanced and advanced cortisol awakening response” which is seen with people who have a morning chronotype.

“Our findings also direct research into circadian-based mechanisms for future anorexia nervosa treatment,” the investigators wrote. “Unlike morning bright light therapy, which has resulted in mixed findings in preliminary studies, bright light therapy in the evening, as is recommended for patients with early morning awakening insomnia, may be efficacious in the prevention and treatment of anorexia nervosa.”

References

1. ^{Wilcox H, Paz V, Saxena R, Winkelman JW, Garfield V, Dashti HS. The Role of Circadian Rhythms and Sleep in Anorexia Nervosa. JAMA Netw Open. 2024;7(1):e2350358. Published 2024 Jan 2. doi:10.1001/jamanetworkopen.2023.50358}
2. ^{Study Reveals New Genetic Link Between Anorexia Nervosa and Being An Early Riser. EurekAlert. January 4, 2024. https://www.eurekalert.org/news-releases/1030123. Accessed January 4, 2024.}