Investigating the Relationship Between Postprandial Sleepiness and Diabetes

1. Introduction to Postprandial Sleepiness and Diabetes
Postprandial sleepiness refers to sleepiness most commonly after eating midday. Blood glucose and sleepiness patterns after meals were reported. It was investigated whether lunch-related periodical sleepiness is also present in diabetic patients and whether it is related to blood glucose changes 1.
In 1973, Chuang presented sleep propensity curves on non-diabetic patients, which showed steep increases in sleepiness after food intake around midday, and these curves appeared after being on a work schedule. He viewed these post-lunch pattern changes as metabolic effects due to the state of awake.
Later, during observations on nursing staff in different work schedules, it was found that good adjusters or rigid night workers on a night duty showed abrupt increases in sleepiness after lunch. This was mainly due to work environment influences, suggesting being under low stress (“lunch dead time”).
A prodomal approach to post-meal/onset sleepiness examined neurohormonal factors, in particular the ingestion of carbohydrates and long chains and free fatty acids, the vagus-mediated input from the stomach, and neurogenic inputs through the nucleus of the solitary tract to the hypothalamus and locus coeruleus 2.
These factors may be added upon food intake and duration of the secretion of neurohormones such as CCK, GLP-1, and other peptide hormones from the gut, which bind to receptors of ARC and induce temporary sleepiness (paradoxical inhibition of normal peptides such as orexins).
2. Understanding the Physiology of Postprandial Sleepiness
Many individuals can relate to feeling sleepy after a heavy meal. Engaging with other activities can help alleviate this sensation temporarily, but sleepiness often returns, leading individuals to choose their mode of transportation based on how likely they are to fall asleep.
However, specific muscle activities or other stimuli can help refocus attention. Often, the presence of an empty plate induces sleepiness, gradually descending into an all-consuming sleep.
This trend is commonly observed in social drinking settings where, under the influence, everything becomes “interesting,” and sleepiness or a blackout eventually sets in. Thus, sleepiness following a meal is a familiar phenomenon, but what exactly are the physiological aspects behind post-meal sleepiness?
After a meal, the animus and food consumed must undergo a significant process, beginning with chewing and moving to the stomach and intestines while being broken down into constituents oxidized for energy production or converted into and stored as lipids or glycogen for future usage.
Initially, the food bolus passes over several sphincters before entering the esophagus. Swallowing initiates a series of peristaltic actions that rapidly progress down the esophagus, connecting the mouth to the volitional upper and lower esophageal sphincters before entering the stomach.
The processed food in the stomach can be subsequently released into the open duodenum in small boluses; this process is referred to as gastric emptying. Following movement into the duodenum, the coordination of sphincters, muscular contractions, and secretions contributes to a synchronized digestion process: retropulsion, segmentation, and peristalsis 3.
3. Overview of Diabetes and its Symptoms

Diabetes is a chronic medical condition in which the body cannot no longer keep blood sugar (glucose) levels to normal. The pancreas either does not produce enough insulin, or the body cannot respond effectively to the insulin produced, leading to elevated levels of glucose within the blood.
An excess of glucose in the blood can cause damage to blood vessels and nerves and will have an effect on other organs too. Insulin resists the rise in blood glucose levels and is required for the metabolism of various other sugars, starch, lipids, amino acids, etc. 1.
There are three major types of diabetes: Type 1 diabetes, Type 2 diabetes, and Gestational diabetes.
1. Type 1 diabetes: a chronic disease that occurs when the pancreas does not produce enough insulin due to autoimmune destruction of pancreatic beta cells. It is usually diagnosed in children and young adults but can occur at any age. 2.
Type 2 diabetes: a chronic disease that occurs when the body is unable to use insulin effectively or produce adequate insulin to maintain normal glucose levels. It is most commonly diagnosed in middle-aged or older adults but is increasingly thought to also occur in children and adolescents.
Type 2 diabetes accounts for approximately 90–95% of all diabetes 2. 3. Gestational diabetes: a form of glucose intolerance that is first recognized during pregnancy. It typically resolves after the pregnancy.
Some of the main symptoms of diabetes are excessive thirst, frequent urination, extreme hunger, fatigue, blurred vision, and unexplained weight loss. Other symptoms that may develop are slow healing sores, dry itchy skin, frequent infections, and tingling or numbness in the hands or feet.
4. Research Studies on the Link Between Postprandial Sleepiness and Diabetes
The Interlinked Rising Epidemic of Insufficient Sleep and Diabetes Mellitus Sleep quality and quantity can, in turn, affect the secretion of insulin, rising blood sugar, and glucose intolerance. Chronic exposure to impaired sleep architecture (insufficient sleep or sleep-disordered breathing) can therefore increase the risk factors for development of the metabolic syndrome components and T2DM in otherwise healthy individuals.
A prospective cohort study done in Japan concluded that medium and high frequencies of difficulty initiating sleep are associated with higher risks of diabetes mellitus in relatively healthy Asian workers 1.
Excessive long and short duration of sleep is associated with type 2 diabetes. A recent study from Japan investigated the link between sleep quality and diabetes among 3249 diabetic patients using the Pittsburgh Sleep Quality Index (PSQI); these patients were found to have poor subjective sleep quality due to increased sleep latency and a shorter duration of sleep.
The short duration of sleep is associated with increased incidence of T2DM as well as poor metabolic control in both type 1 and type 2 DM. It has been proposed that improving sleep quality, treating sleep disorders, and optimizing sleep duration could be used as a regimen to indirectly promote glycemic control.
A recently published review emphasized that sleep quality assessments can be important early risk indicators thereby reducing the incidence of a wide spectrum of morbidities. Another review critically analyzed various common treatments for insomnia and OSA on both sleep and glucose metabolism in patients with type 2 diabetes 4.
Association of Sleep Quality and Waking Time with Prediabetes: The Qazvin Metabolic Diseases Study, IranSevere postprandial sleepiness is commonly noted after lunch. This is noted often with large or carbohydrate-rich meals and is accompanied by drowsiness, reduced alertness, incapacitating fatigue, or in severe cases, even sleep onset.
The physiological basis for sleepiness after meals is a matter of scientific interest as well as of practical implication in health, work, and road/air safety. In terms of meal and sleep, several experiments have shown a direct relationship between sleep and feeding variables.
However, the interplay between circadian and food entrainable circadian timing signals in regulating postprandial function remains unclear. A review of the existing literature encompassing animal models and human epidemiological studies suggests a link between sleep and metabolism, particularly obesity and diabetes.
However, more scientific studies with rigorous methodology are warranted before drawing firm conclusions about the causative direction of the relationship. Ultimately, it may become possible not only to identify who is at elevated risk of diabetes due to these lifestyle adjustments, but to use this information for better health outcome predictions and the development of individualised lifestyle interventions.
Also Read: Best Diet for Diabetic Heart Patients
5. Conclusion: Investigating the Relationship Between Postprandial Sleepiness and Diabetes

In conclusion, the exploration of the relationship between postprandial sleepiness and diabetes has highlighted the need for further research in this area. Understanding the factors that underlie postprandial sleepiness and its association with metabolic responses is especially crucial given the anticipated increase in diabetes prevalence.
By investigating individual differences in postprandial sleepiness through the experimental manipulation of factors like circadian phase, sleep opportunity, habitual sleep duration, and meal characteristics, researchers can provide a clearer picture of the mechanistic link between postprandial sleepiness and aspects of glucose metabolism relating to diabetes pathology and progression.
In turn, findings from this research can help to dictate the field of health and nutrition more widely, initially informing medical interventions to limit sleepiness for those predisposed to impaired glucose metabolism, and eventually driving greater awareness of postprandial sleepiness among the wider public.
Although this review has provided an overview of ongoing work in the field, further questions remain, addressing both methodological aspects of current studies and gaps in existing literature. First, the extent to which glucose tolerance is impaired in relation to the magnitude of postprandial sleepiness remains unclear; studies would thus benefit from examining both variables within the same experimental framework.
The majority of studies investigating either postprandial sleepiness or glucose metabolism characteristics have employed a small number of fixed experimental conditions (e.g., single or two meal types, gradual increases in food portion size); this limits attempts to draw generalizable conclusions regarding the robustness of their findings.
In further studies targeting factors underlying postprandial sleepiness, consideration should be given to the interaction of multiple simultaneous influences, such as diet composition and macronutrient balance in addition to amount and timing of food intake 3.
Finally, the role of environmental context and lifestyle choices in determining individual patterns of food intake warrants deeper investigation, particularly within non-laboratory settings.
References:
1. Kumar Chattu V, Kumary Chattu S, Burman D, Warren Spence D et al. The Interlinked Rising Epidemic of Insufficient Sleep and Diabetes Mellitus. 2019. ncbi.nlm.nih.gov
2. Plantinga L, N. Rao M, Schillinger D. Prevalence of Self-Reported Sleep Problems Among People With Diabetes in the United States, 2005-2008. 2012. ncbi.nlm.nih.gov
3. Tsereteli N, Vallat R, Fernandez-Tajes J, M. Delahanty L et al. Impact of insufficient sleep on dysregulated blood glucose control under standardised meal conditions. 2022. ncbi.nlm.nih.gov
4. Ghorbani A, Esmailzadehha N, Mohammadpoorasl A, Ziaee A. Association of Sleep Quality and Waking Time with Prediabetes: The Qazvin Metabolic Diseases Study, Iran. 2015. ncbi.nlm.nih.gov