For some patients who are particularly resistant to treatment for type 2 diabetes (T2D), work and environmental factors may be contributing to their poor disease control. The causes and potential treatments for circadian dysrhythmia that may affect metabolic processes were evaluated by a team of researchers at the University of Leeds, UK, published in Endocrinology Review.1
Sleep disruption from rotating shifts, overnight work, artificial light, and erratic eating patterns, all appear to interact with the 24-hour light and dark cycles and clock genes, which may alter glucose metabolism and insulin resistance in some patients.1
In particular, friction between workday and weekend sleep schedules, and concomitant disease states may disturb the circadian rhythm.
In their conclusions, Gregory Potter and his team cited the link between a person’s chronotype or natural sleep rhythm, and shift work as well as clock genes as factors that determine the circadian period and influence individual sleep phenotypes.1
They also pointed to heightened aggravation from artificial light, eating late at night (just before bed), and inconsistent bedtimes can compound the negative metabolic consequences of these behaviors in their paper. It should be noted that the authors did not respond to email requests for comment.
Shift work also exhibits dose-response effects
While the link between shift work and poor sleep has been well documented, newer data reflects a likely effect on increased rates of cancer2 and metabolic disease.3,4 When workers must adjust their sleep patterns in either direction for an hour or more on work days, the resulting circadian disruption may be enough to contribute to obesity, increased insulin resistance, a reduction in lean muscle mass, and more body fat.3,4 The adverse effects of a disrupted sleep rhythm appear associated with negative coping habits such as being sedentary, smoking and increased alcohol consumption both of which add to the existing risks for chronic diseases.5
“This article is very timely and it ties in very well to the growing volume of literature on the epidemic of obesity”, J. Michael Gonzalez-Campoy, MD, PhD, FACE, Medical Director and CEO of the Minnesota Center for Obesity, Metabolism, and Endocrinology, told EndocrineWeb. Dr. Gonzalez-Campoy was the lead author of the American Association of Endocrinologists/American College of Endocrinology Task Force on Healthy Eating Clinical Practice Guidelines.6 He explained that “…one component of diabetes management is adequate sleep time; time for relaxation and enjoyment of life is also very important for optimum health”.
Calorie control, particularly careful monitoring of simple carbohydrates, is the major goal of healthy eating for people with diabetes; yet, food choices and set meals seem to be the hardest goals to meet and appears negatively impacted by erratic work hours and disrupted sleep patterns, according to Dr. J. Gonzalez-Campoy who is a member of the EndocrineWeb editorial board.
Changes in work shifts and sleep patterns that don’t fit a person’s chronotype likely intensify the risk for and poor management of diabetes.
“As such, disturbances of the sleep-wake cycles mostly work by extending wake time, and allowing more time for access to calories,” said Dr. J. Gonzalez-Campoy.
Katano, Nakamura, Nakamura, et al,7 studied sleep duration and found an association between shortened sleep intervals and the number of metabolic syndrome diagnostic components. Metabolic syndrome components included: hypertension, dyslipidemia, impaired fasting glucose, and overweight. A significant positive association was found between sleep duration of fewer than 6 hours, compared to 6-7 hours’ duration, and the number of metabolic syndrome components in each patient, despite BMI cutoff points of either ≥25 kg/m2 or ≥30 kg/m2. The authors wrote, “the most likely reason for the association…may come from the short sleep duration and obesity”.
Though some shift workers seem to adjust to unusual sleep patterns more easily than others, according to Potter, changes in the levels of thyroid stimulating hormone, cortisol, and prolactin, as well as decreased insulin sensitivity, persist even after two years.8 These metabolic changes resulting from circadian misalignments appear common among shift workers.
Practically speaking, optimizing the frequency, duration and timing of shift work for each individual worker could have an important, favorable impact on metabolic consequences. When the sleep schedule varied as little as an hour between work days and weekends, the impact on individuals proved highly variable.8
It’s imperative to identify those at greatest risk for metabolic disruption from disturbed sleep, according to Dr. J. Gonzalez-Campoy. Determining the individual’s chronotype may be the key.
In a study in Current Biology,9 in which shift workers’ chronotypes were identified, those whose schedules were poorly matched to chronotype received new, adjusted schedules, eliminating the most serious circadian friction. Self-reported sleep duration and quality increased, and overall social jetlag (a habitual form of circadian misalignment) was reduced by 1 hour.
When individual chronotypes were adjusted for their work schedules, the negative circadian effects were reduced, but the study did not specifically show a change in any metabolic parameters.
To date, few clinical trials have studied the impact of chronobiology in T2D or interventional nutritional studies.
Dr. Gonzalez-Campoy said the current research, “highlights the importance of including all aspects of health into the counseling of patients with overweight and obesity. Certainly, good sleep hygiene contributes significantly to health”. Studies of chronotype, work schedules, sleep patterns and eating patterns for individual patients may yield practical and powerful ways to reinforce treatment of T2D and other metabolic diseases.
1. Potter, GDM, Skene DJ, Arendt J, Cade, JE, Grant, PJ, Hardie LJ. Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences and Countermeasures. Endocr Rev 2016 Dec;37(6):584-608.
2. Travis RC, Balkwill A, Fensom GK, et al. Night Shift Work and Breast Cancer Incidence: Three Prospective Studies and Meta-analysis of Published Studies. J Natl Cancer Inst. 201;108(12).
6. Gonzalez-Campoy JM, St Jeor ST, Castorino K, Ebrahim A, Hurley D, et al. Clinical practice guidelines for healthy eating for the prevention and treatment of metabolic and endocrine diseases in adults: cosponsored by the American Association of Clinical Endocrinologists/the American College of Endocrinology and the Obesity Society. Endocr Pract. 2013;19 Suppl 3:1-82.
7. Katano S, Nakamura Y, Nakamura A, Murakami Y, Tanaka T, et al. Relationship between sleep duration and clustering of metabolic syndrome diagnostic components. Diabetes Metab Syndr Obes. 2011;4:119-25.
8. Morris CJ, Yang JN, Scheer FA. The impact of the circadian timing system on cardiovascular and metabolic function. Prog Brain Res. 2012;199:337-58.
9. Vetter C, Fischer D, Matera JL, Roenneberg T. Aligning work and circadian time in shift workers improves sleep and reduces circadian disruption. Curr Biol. 2015;25(7):907-11.