"I feel sleepy during the day even though I'm getting enough sleep," or "I'm careful about what I eat and exercise, but I can't control my blood sugar levels." Some people over 40 may have these kinds of concerns.
These discomforts may be caused by poor sleep quality. Diabetes and sleep actually have a profound effect on each other. It is not uncommon for people to fall into a negative loop in which lack of sleep worsens blood sugar levels, and conversely, high blood sugar reduces the quality of their sleep.
This article provides a clear explanation of the mechanism behind the vicious cycle between diabetes and sleep, as well as its relationship with obstructive sleep apnea syndrome (OSA), a condition that should be treated with particular caution.
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Why lack of sleep worsens blood sugar levels
Did you know that lack of sleep has a negative effect on blood sugar levels? Recent research has shown that even a slight lack of sleep can cause insulin resistance, a condition in which insulin, the hormone that lowers blood sugar levels, becomes less effective.
It has been reported that even in healthy people, simply reducing sleep time from 8 hours per night to 4 hours can induce insulin resistance. Similar findings have also been reported when sleep time is reduced from 8.5 hours per day to 5.5 hours for two weeks. The same is true for adolescents, and particularly in pre-adolescents aged 10-13, nocturnal lifestyles are correlated with high fasting blood glucose levels, regardless of weight.
There are five main mechanisms thought to be involved in how sleep disorders impair glucose metabolism:
- The body is constantly in "excitement mode" (overactive sympathetic nervous system)
- Increased levels of hormones that increase blood sugar levels (cortisol and growth hormone)
- The body goes into a mild state of inflammation
- The body becomes rusty and cells are not repaired properly even if they are damaged (oxidative stress)
- Disruption of the body clock (clock gene synchronization failure)
Furthermore, lack of sleep also affects appetite. The hormone leptin, which suppresses appetite, decreases, while ghrelin, which stimulates appetite, increases, making it easier to eat more. In fact, people who sleep less and those who sleep more tend to consume fewer vegetables and fruits and more high-fat foods and fast food.
Source: Keio University Health Management Center, Sugar | The importance of sleep in metabolism
Why diabetes reduces sleep quality
On the other hand, diabetes itself can also cause poor sleep quality. In a 2015 study conducted by a research group at Osaka City University on 63 type 2 diabetes patients, blood sugar control status and sleep quality were analyzed. The results confirmed that the worse HbA1c, an indicator of blood sugar control, the less deep sleep (slow-wave sleep that rests the brain) was obtained, and the poorer the sleep quality. In other words, it is easy to fall into a vicious cycle in which diabetes reduces sleep quality, and this lack of sleep further worsens blood sugar levels.
Source: Japan Obesity Prevention Association | Improving blood sugar control improves sleep quality. Sleep disorders can be treated.
Association between poor glycemic control, impaired sleep quality, and increased arterial thickening in type 2 diabetic patients
Sleep apnea syndrome (SAS) is common among diabetics
When discussing diabetes and sleep, attention must be paid to sleep apnea syndrome (SAS), which is a very common condition among diabetic patients.
What is SAS?
Sleep apnea is a condition in which breathing stops for 10 seconds or more during sleep. If apnea or hypopnea occurs five or more times per hour, resulting in insufficient sleep and excessive daytime sleepiness, it is called sleep apnea syndrome (SAS).
There are two main types of SAS. One is "obstructive sleep apnea syndrome (OSAS)," which occurs when the upper airway (throat, etc.), which is the airway, physically collapses. The other is "central sleep apnea syndrome (CSAS)," which occurs when the brain's ability to control breathing stops due to a disease of the brain, nerves, or heart. There is also mixed sleep apnea syndrome, which has both causes.
Obstructive sleep apnea syndrome (OSAS)
It is said that most cases of SAS are obstructive sleep apnea syndrome (OSAS). OSAS is characterized by respiratory efforts, with the chest and abdomen moving as the body desperately tries to breathe even when breathing stops. OSAS is strongly associated with type 2 diabetes, and it has been consistently shown that people with OSAS are more likely to develop insulin resistance and impaired glucose tolerance (a condition in which blood sugar levels are difficult to lower).
The reason why OSAS worsens glucose metabolism is thought to be that, in addition to the mechanism of sleep deprivation mentioned above, the "hypoxia" caused by respiratory arrest and "sleep fragmentation" (fragmented sleep) reduce the function of the pancreatic beta cells, which secrete insulin. OSAS and type 2 diabetes have a bidirectional relationship, with each having a negative effect on the other.
It is extremely important for type 2 diabetes patients to receive diagnosis and treatment for OSAS in order to reduce the risk of future cardiovascular events. If your family points out the following, these are signs that OSAS may be present:
- snore
- Indication of breathing interruptions during sleep
- Choking or gasping during sleep
You should also be careful if you experience excessive daytime sleepiness or insomnia.
Central sleep apnea syndrome (CSAS)
On the other hand, "Central Sleep Apnea Syndrome (CSAS)" is characterized by the absence of chest or abdominal movement (respiratory effort) due to a lack of commands from the respiratory center. CSAS can occur in association with heart or brain diseases such as heart failure and cerebrovascular disease. Subjective symptoms are also different from OSAS, and are characterized by "fatigue" and "shortness of breath at night (dyspnea)."
Source: Department of Respiratory Medicine, Graduate School of Medicine, Chiba University, Department of Respiratory Medicine, Chiba University Hospital | Sleep Apnea Syndrome
Source: The Epidemiology of Sleep and Diabetes
Source: Keio University Health Management Center | The importance of sleep in glucose metabolism
Source: Sleep Apnea Syndrome Treatment Guidelines 2020 | CQ8. OSA Diagnosis and Subjective and Objective Symptoms
Source: Sleep Apnea Syndrome Treatment Guidelines 2020 | CQ9.CSB Diagnosis and Subjective and Objective Symptoms
Measures to improve sleep quality and break the vicious cycle
In diabetes treatment, sleep care is important in addition to blood sugar control. Studies of Japanese people have also investigated the relationship between sleep quality and diabetes risk. A four-year follow-up study of 3,570 local government employees in Hokkaido reported that those who perceived a sense of sleep deprivation, rather than the actual amount of sleep, had a five-fold higher risk of developing diabetes compared to those who did not. First, it is important to review your own sleep quality. If you suspect you have obstructive sleep apnea syndrome (OSAS), be sure to take measures. Obesity is a major cause of OSAS, so lifestyle changes such as weight loss, diet, and exercise are important measures to combat SAS. However, if you experience snoring, apnea, or excessive daytime sleepiness, self-care alone will have its limits. It is important to consult a specialist and undergo testing. If you are diagnosed with SAS, an effective treatment called CPAP (Continuous Positive Airway Pressure) therapy is available, which delivers air through a nasal mask during sleep to prevent airway obstruction.
Source: Short sleep duration and poor sleep quality increase the risk of diabetes in Japanese workers with no family history of diabetes.
summary
Diabetes and sleep disorders are closely related and affect each other. If you dismiss it as "just a lack of sleep," you may end up creating a constitution that makes insulin less effective. Reviewing the "quality of sleep" while controlling blood sugar is an important key to treatment.
If your family members point out that you snore too loudly or stop breathing while you sleep, or if you feel very sleepy during the day, do not ignore the problem and consult a specialist medical institution as soon as possible.