Insulin Sensitivity and Sleep, or Lack Thereof
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Study after worldwide study (and there were many this year) correlate the ramifications of sleep deprivation on insulin sensitivity. The jury was clear – sleep loss affects the body’s ability to match up the glucose-insulin response.Sleep isn’t always made a priority, especially in the young population. Loss of slow wave sleep (SWS), the deepest and most restorative sleep, and loss of sleep hours in general, is connected with insulin resistance without insulin secretion. Both types of sleep loss have been shown to increase brain activity in areas associated with food stimulus. This makes sense since evidence shows hunger, appetite and ghrelin levels increase while leptin levels decrease.
The relative risk (RR) of developing diabetes from less than or equal to 5 or 6 hours of sleep ranges from 1.57 to 1.84, as reported by meta-analyses of several population-based studies. Meanwhile, RR of developing type 2 diabetes with a family history ranges from 1.7 to 2.3. Five hours a night for just one week causes significant reduction in insulin sensitivity. A Penn State Cohort followed 1,000 men for 14 years and 741 women for 10 years, and found the risk of mortality was 21 percent for men and 5 percent for women. Insomniacs’ risk of type 2 diabetes, with polysomnogram verified sleep of less than 5 hours, was “nearly threefold highe.”
The connection between partial sleep restriction and alterations in glucose metabolism has been established for quite some time. The definition of partial sleep restriction, however, may need to be redefined. Sleep with less than 5 hours, not less than 6 hours like some studies use, is the parameter that is most strongly associated with negative outcomes, yet this represents only a small fraction of the population.
If you think this means that missing one night or one hour of sleep is okay, then think again. A 2010 study published in Diabetes Care shows how 7 type 1 diabetics suffered peripheral insulin resistance after just one night of four hours sleep. Also, 19 healthy, normal-weight young men lost an hour and half sleep daily for 3 weeks and saw changes in insulin sensitivity, leptin level variation and body weight.A cross-section of 771 Danish participants showed just one-hour increase in sleep correlated with 25 percent risk reduction of impaired glucose regulation. It also showed 0.3 mmol/mol reduction in HbA(1c).
There are misconceptions regarding burning more calories for time awake. The difference per hour compared to sleep averaged about 17 kcal. Risk of increased hunger and food intake, as well as reduction in overall physical activity from fatigue, needs to be considered.
The question is how much of this propensity for insomnia, or desire to stay up late, perhaps even work night shifts, is genetic?
In 2013, a study in Finland involving over 4,000 participants found that those who considered themselves “evening types” had a 2.5-fold odds ratio for type 2 diabetes, as compared to those who are morning people. Neither sleep duration or sleep sufficiency are apparently of any influence. Specific circadian gene variants with evening preference have also shown weight loss resistance and susceptibility to metabolic syndrome and type 2 diabetes. Not only that, but it has been found that “the heritability of body mass index is increased in short sleepers.”
This doesn’t mean you should sleep more. Apparently “long sleep,” or more than 9 hours of sleep, can bring along “higher fasting and 120-min. insulin, 120-min. glucose, and HOMA and lower Insulin Sensitivity Index.” Of course sleep in most of these studies is self-reported, but the idea here seems to be that long sleepers are actually poor sleepers who stay in bed longer in an attempt to compensate for poor sleep quality. Fatigue from another undiagnosed condition has also been surmised, but it is also noted that long sleepers are usually less physically active. In addition, there is evidence that long sleep predicts the incidence of diabetes. This should be of consideration. After all, just “a 1-point increment in sleep quality was associated with a 2% increase in both the insulin sensitivity index (0,120) and homeostasis model assessment of insulin sensitivity, as well as a 1% decrease in homeostasis model assessment of B-cell function.9
So, when changing sleep habits, consider quality. Refreshingly, some of the damage done with sleep deprivation (such as decreased insulin sensitivity and other metabolic issues) can be reversed with recovery sleep. If sleep habits need to be improved, start by going to bed a half-hour earlier every day, or just jump in, and tuck in by a reasonable hour every night.
For information on a related topic, please listen to our Clinical Rounds from May 30, 2012 on Sleep Anea with Roschelle Banks, DDS.
