Additional Sleep Duration Associates with Improved Blood Sugar Regulation
Year: 2015
Type: article
Abstract: Dr. Spaeth has indicated no financial conflicts of interest. According to recent reports from the Centers for Disease Control and Prevention, nearly 30 million individuals in the United States are currently diagnosed with diabetes and it is estimated that ∼8 million additional individuals exhibit symptoms of the disease but are undiagnosed.1 The hallmark symptom of diabetes is high blood glucose levels over a prolonged period of time due to inadequate insulin production (type 1 diabetes) and/or insulin resistance (type 2 diabetes). The vast majority (∼90%) of diabetics are diagnosed with type 2 diabetes.1 A healthy individual's blood glucose level is regulated by insulin. Insulin, a peptide hormone produced in the pancreas, promotes the absorption of glucose from the blood into muscle and fat tissue, and inhibits the production of glucose by the liver.2 When there is excess glucose in the blood due to the ingestion of food or in response to a stressful event, insulin is released. However, individuals vary in terms of how sensitive their cells are to insulin. Someone with high insulin sensitivity requires smaller amounts of insulin to lower blood glucose levels than someone with lower insulin sensitivity. When individuals have low insulin sensitivity, the body attempts to compensate by producing more insulin. Over time, cells can become unresponsive to insulin (insulin resistance). Therefore, even though individuals with type 2 diabetes produce insulin, muscle and fat tissues do not absorb glucose properly and this leads to an increase in circulating blood glucose levels.2 The prevalence of diabetes has increased dramatically in recent decades among children, adolescents and adults.1,3 Diabetes is associated with exorbitant financial costs, reaching $245 billion in 2012 (direct medical costs: $176 billion), and health consequences, including an increased risk for heart disease, stroke, blindness, kidney failure, lower-limb amputation, and death.1,4 Importantly, these financial costs and health risks are primarily incurred by older patients with longstanding diabetes.5 Therefore, it is critical to intervene early when patients are pre-diabetic or recently diagnosed. Lifestyle interventions, including increased exercise/physical activity, improved diet, and weight loss have been effective in improving insulin sensitivity.6–8 Sleep duration has also been identified as a modifiable behavior that is associated with diabetes risk and can influence insulin sensitivity. Population studies have observed a U-shaped relationship between sleep duration and type 2 diabetes risk; individuals who self-report habitually sleeping less than 7 h or more than 8 h are at increased risk.9 Short sleep duration is associated with decreased insulin sensitivity,10–13 and laboratory studies have shown that sleep restriction leads to decreased insulin sensitivity.14–19 However, it was unknown whether increasing sleep duration could increase insulin sensitivity. In the current issue of SLEEP, Leproult and colleagues20 demonstrate, for the first time, that sleep extension can improve insulin sensitivity. Leproult and colleagues20 used wrist actigraphy and polysomnography to measure sleep-wake in 16 healthy, non-obese young adults who were instructed to maintain their typical sleep schedule for 2 weeks and then increase time in bed by 1 h at night for the next 6 weeks. Measures of glucose and insulin were taken after each condition. Sleep extension was individualized based on each participant's lifestyle. All participants had daytime work/class obligations, and the sample exhibited a shift to an earlier bedtime. Although participants increased time in bed by ∼50 min on average, there were marked individual differences with some actually decreasing time in bed during certain weeks and others increasing time in bed by nearly 2 h. Leproult and colleagues found significant correlations between changes in insulin sensitivity and changes in sleep duration, such that participants who increased their time in bed during the intervention exhibited increased insulin sensitivity. Remarkably, Leproult and colleagues observed changes in insulin sensitivity in healthy, non-obese adults who do not have as much room for improvement as pre-diabetics or type 2 diabetics. One limitation to their study was the small sample size; this finding now needs to be replicated in a large-scale randomized controlled trial in a diverse sample of healthy adults with a wide range of baseline insulin sensitivity and in diabetics. In addition, their study20 did not assess caloric intake or physical activity. Population and laboratory studies consistently report associations between sleep duration and weight, the timing, content and amount of daily food/drink consumption, and physical activity levels.21–25 Therefore, studies are needed to assess how improved sleep duration interacts with other lifestyle changes to influence insulin sensitivity. Given recent increases in the prevalence of type 2 diabetes among children and adolescents,3 it is imperative to assess if sleep extension can improve insulin sensitivity in these younger populations. Finally, if sleep extension is consistently shown to improve insulin sensitivity, basic science studies are needed to identify mechanisms underlying this effect. In addition to providing a critical initial study for research examining the efficacy of sleep extension in improving symptoms of diabetes, Leproult and colleagues20 have also provided insight into the use of sleep extension as an intervention. In their study, the intervention was long in duration (6 weeks), modest in the magnitude of change (+0.8 h/night), and was individualized based on each participant's schedule. Furthermore, the authors carefully assessed sleep-wake using objective measures (actigraphy and polysomnography) and met with subjects every 2 weeks to discuss and improve compliance. This method proved to be successful in terms of compliance and by not having deleterious effects on sleep quality or maintenance. As the authors note, the magnitude of sleep extension is important. Given the U-shaped relationship between sleep duration and diabetes risk, it may be unwise to increase sleep time beyond 9 h per night when attempting to improve insulin sensitivity. Unfortunately the sample in this study was too small to assess differences between participants who were or were not able to increase sleep time. As more laboratories assess the efficacy of sleep extension26–29 on various neurological, behavioral and physiological outcomes, it will be important to track characteristics of compliant and noncom-pliant participants. In summary, Leproult et al.20 provide a valuable initial study in examining how sleep extension can be used as a lifestyle intervention for symptoms of diabetes. Combined with a healthy diet and exercise, sleep extension may be able to enhance the quality of life for millions of individuals by preventing the financial and health burdens of diabetes.
Source: SLEEP
DOI: 10.5665/sleep.4648
Author: Andrea M. Spaeth
Institution: University of Pennsylvania
Language: English
Topic: Sleep and related disorders
Subfield: Experimental and Cognitive Psychology
Field: Psychology
Domain: Social Sciences
Open Access status: green
OpenAlex ID: W2012221440