On World Diabetes Day, we look at the links between sleep and diabetes, and why focusing on good sleep could also have benefits for managing your blood sugar.
What is diabetes?
Diabetes is a condition where we have too much sugar, or glucose, in the bloodstream.
We all need some glucose to give us energy, but with diabetes, excess glucose over time can cause serious health problems.
The glucose in our blood comes from the food we eat, especially from carbohydrates. For people without diabetes, if levels of glucose go too high after a meal, the pancreas produces a hormone called insulin, which triggers the body’s cells to take in glucose.
There are two main types of diabetes. In type 1 diabetes, the pancreas doesn’t produce any insulin at all. People living with type 1 have to carefully monitor their blood sugar themselves and inject themselves with insulin if they become too high or eat extra sugar if they become too low.
About 90% of people with diabetes have type 2 diabetes. In type 2 diabetes, there can be a shortage of insulin, or the body doesn’t use insulin as effectively; this is called ‘insulin resistance’. People living with type 2 diabetes may be able to manage their condition by making lower sugar food choices, or a combination of lifestyle choices and medication.
There are several rarer types of diabetes, including gestational diabetes, which some women develop during pregnancy. There is also a condition called prediabetes which means your blood glucose levels are slightly higher than normal, and you are at increased risk of developing type 2 diabetes in the future.
Is lack of sleep linked to the risk of developing diabetes?
Some of the risk factors for type 2 diabetes we can’t change, such as ageing, having a family history, or being of South Asian, African-Caribbean or Black African descent. However, there are many lifestyle-related risk factors that we can try to avoid, such as being overweight, lack of physical activity, smoking, excess alcohol and having high blood pressure.
There is strong evidence that people who sleep for fewer than 6 hours per day are at increased risk of type 2 diabetes: the risks are 48% higher for those sleeping fewer than 5 hours, and 18% higher for those sleeping fewer than 6 hours, compared to those sleeping 7 to 8 hours (Anothaisintawee 2015). In one study, researchers found that adults sleeping 5 hours or less were twice as likely to develop prediabetes as those sleeping for 7 hours (Engeda 2013).
There is also some evidence that sleeping for too long, more than 9 hours, is linked to increased risks of future diabetes, but it is not clear why; it may be that longer sleep is a sign of an existing, undiagnosed illness.
Sleep quality may be just as important as sleep quantity. One study in 240 pregnant women, women reporting poor quality sleep had a threefold increased risk of developing gestational diabetes (Peivadi 2021).
Sleep quality can also be disturbed by sleep disorders, such as sleep apnoea. A review of several different studies found that sleep apnoea patients were at twice the risk of developing type 2 diabetes vs. normal sleepers (Anothaisintawee 2015).
Could good sleep habits help patients to manage their diabetes?
For those living with diabetes, maintaining healthy sleep patterns is likely to support good blood sugar management.
The A1C test—also known as the hemoglobin A1C or HbA1c test—is a simple blood test that measures your average blood sugar levels over the past 3 months . Adults with type 1 diabetes who slept <6.5 hours per night had higher A1C levels than those who slept >6.5 hours per night ( Borel 2013).
How does poor sleep affect blood sugar control?
So, why do these links between sleep and diabetes occur? Sleep has powerful restorative effects on our mental, emotional and physical health. A shortage of sleep, or disrupted sleep, could influence diabetes risks in a number of different ways.
Researchers are still investigating the exact mechanisms, but they are likely to include:
Sleep and insulin sensitivity
Studies in the laboratory have shown that if you deliberately deprive a healthy person of sleep - for example, just 4 hours in bed - and then give them a large amount of glucose, their bodies will respond with greater insulin resistance than for healthy people who have slept for a normal amount of time (Spiegel 2005). It seems that fat cells, called adipocytes, are particularly vulnerable to a reduction in insulin sensitivity after sleep loss. Similar effects were seen for adults with type 1 diabetes, where a single night of 4 hours of sleep led to decreased insulin sensitivity in comparison to 8.5 hours sleep (Donga 2010).
Sleep and appetite hormones: leptin and grehlin
Acute sleep deprivation causes a reduction in the release of the hormone, leptin, which makes us feel full. Lack of sleep can also cause higher levels of grehlin, which makes us hungry. We are therefore more likely to consume more calories after a poor night’s sleep. We consume on average an extra 385 calories after a sleepless night ( Khatib 2016). Over time, this increase in appetite and reduction in satiety could not only to more glucose in the blood, but also to weight gain, obesity, and sleep-disordered breathing.
Sleep and inflammation
Our immune system protects the body from foreign invaders and helps us to recover from infection. inflammation can occur as part of the healing process, but left unchecked, chronic inflammation is known to add to the risks of diabetes, heart disease and obesity. Deep sleep has anti-inflammatory effects, so if you’re not getting enough good quality sleep, the body is less able to control levels of inflammation.
Sleep and self-care
A shortage of sleep, or poor quality sleep, can negatively influence our ability to regulate our emotions. We tend to be less motivated, find it harder to focus and have lower self-control after a poor night’s sleep. For example, poor sleepers are less likely to engage in regular physical activity, to smoke, and to drink excessively, which can further worsen blood sugar control. Persistent poor sleep could therefore make it harder to make healthier lifestyle decisions, or to take the correct diabetes medication.
Why does diabetes make you tired? Is it because of poor sleep?
Diabetes patients often report feeling tired, despite adequate amounts of sleep. There seems to be a reciprocal relationship between diabetes and disrupted sleep, where both increase the risk of the other. Both excessively high and low sugar levels have been linked to poor sleep quality. For example, in patients with type 1 diabetes, higher A1C (indicating poorer blood sugar control over the last 2-3 months) was associated with less time in deep, slow-wave sleep ( Feupe 2013).
Obstructive sleep apnoea is also more common in type 2 diabetes patients, and could lead to daytime sleepiness.
However, feelings of excessive fatigue in diabetes may in fact not be linked to sleep. Remember that if you do not have enough insulin, or if the insulin is not working properly, the cells cannot take in enough glucose for energy. This can leave you feeling very lethargic. If blood sugar levels are too low, you will also feel fatigued. If you routinely wake up feeling tired in the morning, despite having had a full night’s sleep, it’s worth testing your blood sugar to see if your tiredness is related to your blood glucose.
What can you do to improve both blood sugar control and sleep?
Many of the well known steps that you can take to improve sleep will also have benefits for preventing or managing diabetes.
● Consider a time restricted eating window, and regular eating times
Several small studies in overweight volunteers have found that by shortening their daily eating window to 8-12 hours, they are better able to lose weight. Perhaps more importantly, such time restricted eating patterns have been linked to better sleep, more energy during the day, and better control of blood sugar. A recent trial found that weight loss was most effective when people were encouraged to adopt consistent timing of their first and last meals, a shorter eating window, and to consume most of their calories earlier in the day (Fleischer et al 2022).
● Maintain a regular sleep-wake cycle
Aim to get out of bed at the same time, to within an hour, as often as possible. If you work shifts, simply get into a routine on rest days as often as you can. This will help sync your body clocks and prepare for sleep at the same time each night.
● Move regularly
Avoiding too much sitting can help to reduce your risks of diabetes. Regular physical activity improves mood and helps people to fall asleep and enjoy better sleep quality.
● Spend time developing relationships with friends
An often overlooked factor for improving health and wellbeing - and sleep - is to reduce loneliness. A recent study found that lonely people were twice as likely to develop diabetes over 20 years (Henriksen 2022). When you are tired, you may not feel like socialising, but spending time with good friends will help to reduce stress levels, improve your mood, and may improve your sleep quality.