The link between poor sleep and diabetes

Sleep is essential to the healthy functioning of our bodies. No one knows exactly what it's main purpose is but it is certainly involved in general body repair and restoration. After a hard day's activity, sleep seems crucial for rejuvenating our bodies for the next day. Without adequate amounts of sleep, we tend to feel irritable, tired and listless. Thus sleep is very good for our health, especially if we can manage eight hours, on average.

In fact, what many people do not often realise is that a lack of sleep—especially on a regular basis—is associated with long-term health consequences, not just diabetes, especially high blood pressure, and heart disease. These conditions, in turn, may lead to a shortened life expectancy.

Scientists have recently discovered that people who sleep less than six hours each night appear to have a higher risk of developing' impaired fasting glucose' — a condition that can precede type 2 diabetes (when the body makes in too much insulin but isn't able to use it efficiently, thus becoming insulin resistant). Population studies have shown that diabetes rates rise as sleep declines. While the available data provide compelling reasons to get eight hours of quality sleep every night, they couldn't explain how diabetes might be influenced by sleep. Yet, tests repeatedly proved that people who slept less than six hours, on average were more prone to having type 2 diabetes.

So how are the two factors connected?

Human bodies have a clock, an internal rhythm that dictates when we fall asleep and when we get up. They are the 'molecular timekeepers, made and degraded every 24 hours', that set this daily cycle. When any part of this ticking clock is faulty, sleep schedules gradually change. Not only that, it seems our bodily rhythms, including the clock that sets human sleep cycles, is 'squarely in the blood sugar business'. Sleep-deprived subjects, seem to crave starchy, sweet foods, they exhibit insulin resistance and do not regulate their blood sugar well. These tend to lead to obesity which also predisposes diabetes in a vicious circle.

Investigations by three international teams of researchers have suggested that rising diabetes and falling sleep are linked by a protein that senses the 'sleep-inducing hormone melatonin'. Melatonin, the regulator of the body's sleep clock, is closely linked to increased glucose levels and diabetes. Best known for its sleep-inducing properties, melatonin levels in the body are tied to daylight: when the lights go down, melatonin levels rise and drowsiness soon follows. When daylight occurs, the level drops and we no longer feel sleepy.

The scientific experiments also revealed how the melatonin directly interact with insulin-producing cells. The melatonin 'receptor' was thought to be expressed in the brain — where the body's master clock resides. When scientists added melatonin to human beta-cells in the lab, insulin production went down. It seems that the presence of the melatonin 'receptor' on the insulin-secreting cells makes it more likely that it is directly controlling the output of insulin. The connection between the melatonin and insulin makes perfect sense, because in the middle of the night, when melatonin levels are high, the need for insulin should be much lower.

Though the researchers are not yet sure how melatonin levels are different in sleep-deprived people, compared to those with good levels of sleep, another study in 2008 found that people who get less than five hours of sleep a night were significantly more likely to have type 2 diabetes. "Healthy young adults who were prevented from entering deep sleep for just three nights couldn't properly regulate blood sugar levels." What was even more surprising, "the subjects became more resistant to insulin during the study, eventually reaching the levels of insulin sensitivity that resemble the insulin resistance of diabetic people."

Other studies have also confirmed that people who slept for five hours or less on average are more likely to become overweight or obese than those who got more sleep because the less sleep one gets is the more one tends to eat foods that are higher in carbohydrates and sugar - which means consuming even more calories!

Sources:
http://www.americandiabetes.com/the-link-between-sleep-and-diabetes
http://www.sciencenews.org/view/generic/id/39146/title/Lack_of_sleep_has_genetic_link_with_type_2_diabetes
http://americanheart.mediaroom.com/index.php?s=43&item=693