Beneficial effects of severe sleep apnea therapy on nocturnal glucose control in persons with type 2 diabetes mellitus

Effects of Positive Airway Pressure Therapy on Glycemic Variability in Patients With Type 2 Diabetes and OSA: A Randomized Controlled Trial

BACKGROUND

Glycemic variability is associated with increased risk for cardiovascular disease in patients with type 2 diabetes independent of glycosylated hemoglobin A1c (HbA1c) levels. Given the conflicting evidence on the effect of positive airway pressure (PAP) therapy for OSA on HbA1c, elucidating its effect on glycemic variability has value.

RESEARCH QUESTION

Does the use of PAP therapy for OSA improve glycemic variability in patients with type 2 diabetes?

STUDY DESIGN AND METHODS

A randomized controlled trial was conducted in 184 patients with type 2 diabetes and moderate-to-severe OSA. Participants received either 3 months of PAP therapy with lifestyle counseling or lifestyle counseling alone. End points included the SD of glucose levels along with other metrics derived from continuous glucose monitoring and self-monitoring of blood glucose.

RESULTS

No differences were noted in either primary or secondary continuous glucose monitoring end points between the two groups. Average use of PAP therapy was 5.4 h/night (SD, 1.6). Exploratory analyses by sex showed significant differences in the primary and secondary outcomes. In female participants, PAP therapy was associated with improvement in the SD of glucose levels, with a mean difference in change between intervention and control groups of 3.5 mg/dL (P = .02). PAP therapy was also associated with lower post-dinner and bedtime glucose levels: 20.1 mg/dL (P < .01) and 34.6 mg/dL (P < .01), respectively.

INTERPRETATION

PAP therapy did not improve glycemic control or variability in patients with moderate-to-severe OSA and type 2 diabetes. Exploratory analyses suggested that PAP therapy may improve glucose variability in female participants. Post-dinner and bedtime glucose levels were higher in those who did not receive PAP therapy.

TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT02454153; URL: www.

CLINICALTRIALS

gov.

Effect of CPAP on blood glucose fluctuation in patients with type 2 diabetes mellitus and obstructive sleep apnea

Purpose

This study aimed to investigate the effect of continuous positive airway pressure (CPAP) on blood glucose fluctuation in patients with type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA).

Methods

Patients with T2DM and OSA were divided into an intervention group and a control group. All patients were treatment naïve. The intervention group was given CPAP therapy. The subjects were monitored using a continuous glucose monitoring system (CGMS) for 2 weeks.

Results

Of 60 patients, 30 were selected to receive CPAP intervention while 30 without CPAP served as controls. The CPAP tolerance of the intervention group was good, with average time on CPAP therapy of 55.2 ± 4.3 days, and average daily time on CPAP therapy of 8.3 ± 2.8 h. The postprandial blood glucose (PBG), fasting blood glucose (FBG), and HbA1c levels in the intervention group decreased significantly (P < 0.05). Significant variations in 24-h mean blood glucose and night-time mean blood glucose were significantly lower with CPAP therapy than without therapy (P < 0.05, respectively). The mean of daily differences and mean ambulatory glucose excursions were both considerably lower with treatment than without (P < 0.05, respectively). There was also a significant difference in time in range and time above range (P < 0.05, respectively).

Conclusion

CPAP treatment may significantly improve the blood glucose level and blood glucose stability in patients with T2DM and OSA. CPAP is an effective treatment method beyond lifestyle intervention and drug therapy.

Circadian Clocks, Sleep, and Metabolism

A molecular circadian clock exists not only in the brain, but also in most cells of the body. Research over the past two decades has demonstrated that it directs daily rhythmicity of nearly every aspect of metabolism. It also consolidates sleep-wake behavior each day into an activity/feeding period and a sleep/fasting period. Otherwise, sleep-wake states are mostly controlled by hypothalamic and thalamic regulatory circuits in the brain that direct overall brain state. Recent evidence suggests that hypothalamic control of appetite and metabolism may be concomitant with sleep-wake regulation, and even share the same control centers. Thus, circadian control of metabolic pathways might be overlaid by sleep-wake control of the same pathways, providing a flexible and redundant system to modify metabolism according to both activity and environment.

Treatment Effects of Short-Term Continuous Positive Airway Pressure on Blood Glucose Control in Type 2 Diabetic Patients with Obstructive Sleep Apnea Syndrome

Purpose

The study aimed at assessing glucose control measured with a continuous glucose monitoring system (CGMS) before and after short-term continuous positive airway pressure (CPAP).

Materials and Methods

Twenty-four type 2 diabetic patients (T2DM) with Obstructive sleep apnea syndrome (OSAS) (mean age 55.0 ± 9.0 years; BMI 29.5 ± 5.2 kg/m²) were admitted and kept under diet control for 2 days, then underwent 2 overnight polysomnographies: a diagnostic study and one with CPAP titration. Then they were treated by CPAP during sleep for the following three nights. Participants were divided into subgroup D (only diet control) and subgroup M (with DM medication). CGMS was utilized over the last five days. Glucose control was also assessed with plasma insulin and a clinical measure of insulin resistance (HOMA-IR) index.

Results

The mean (±SD) apnea-hypopnea index (AHI) at diagnostic polysomnography was 51.2 ± 22.4 (range 10-88) events/h. CPAP treatment in the subjects with OSAS resulted in the index of oxygenation desaturations being reduced from 33.3 ± 20.1 to 1.1 ± 1.6 (P =0.00). CGMS showed mean 24-hours glucose values significantly lower after CPAP treatment than at baseline in both subgroups (7.97±1.31 vs 7.52±0.94, P=0.033 in subgroup D; and 7.72±1.51 vs 7.17±1.21, P=0.05 in subgroup M), as the fasting plasma insulin levels and HOMA-IR were also decreased significantly after CPAP treatment (13.0 ± 7.5μU/mL vs 10.8 ± 5.4μU/mL, P=0.044; and 4.2 ± 2.2 vs 3.1±1.7, P=0.003, respectively). Standard deviation (SD) and mean amplitude of glucose excursions (MAGE) were also decreased in the subgroup D (1.91 ± 1.10 vs 1.61 ± 1.20, P=0.014; 1.26 ± 1.13 vs 1.01 ± 0.98, P=0.008, respectively) only.

Conclusion

Short-term CPAP treatment in OSAS with type 2 diabetic patients is accompanied by a decrease in blood glucose level and improved insulin sensitivity. Glucose variability was reduced but only in the patients with diet control.

Rationale and design of the Hyperglycemic Profiles in Obstructive Sleep Apnea (HYPNOS) trial

The Hyperglycemic Profiles in Obstructive Sleep Apnea (HYPNOS) randomized clinical trial was conducted in adults with type 2 diabetes and moderate-to-severe obstructive sleep apnea (OSA) to determine whether treatment with positive airway pressure (PAP) therapy is associated with improvements in glycemic measures. Participants were randomly assigned to PAP therapy with lifestyle counseling or lifestyle counseling alone. While observational and experimental evidence indicate that intermittent hypoxemia and recurrent arousals in OSA may alter glucose metabolism and worsen glycemic measures, the effect of treating OSA with PAP therapy on these measures in type 2 diabetes is uncertain. Adequately powered randomized clinical trials have yet to be performed to demonstrate whether PAP therapy for OSA in patients with type 2 diabetes can improve glycemic measures. The HYPNOS trial was designed to determine whether PAP therapy for OSA in patients with type 2 diabetes over 3 months leads to improvements in glycemic measures including glycemic variability (standard deviation) based on Dexcom G4 Platinum continuous glucose monitoring. Secondary objectives were to assess the effects of PAP therapy for OSA on measures of: (1) glycemic variability based on Abbott Freestyle Pro Libre continuous glucose monitoring; (2) point-of-care hemoglobin A1c (HbA1c); (3) degree of post-prandial hyperglycemia as determined by 7-point self-monitoring of blood glucose; (4) clinic and ambulatory blood pressure; and (5) endothelial function. The HYPNOS trial was designed to address gaps in our understanding of the effects of PAP therapy on glucose metabolism in adults with type 2 diabetes and moderate-to-severe OSA. Trial Registration: ClinicalTrials.gov Identifier NCT02454153.

Chronotherapeutic efficacy of suvorexant on sleep quality and metabolic parameters in patients with type 2 diabetes and insomnia

AIMS

This study aimed to assess the chronotherapeutic efficacy of suvorexant on subjective sleep parameters and metabolic parameters in patients with type 2 diabetes and insomnia.

METHODS

Thirteen patients with type 2 diabetes who met the Pittsburg Sleep Quality index criteria for primary insomnia took suvorexant 20 mg/day (15 mg/day for ≥65 years) for 14 ± 2 weeks. The following parameters were assessed before and after the treatment: sleep diary for sleep duration and quality (i.e., sleep onset latency, waking after sleep onset, and sleep efficiency [sSE]), Insomnia Severity Index, clinical and biochemical data, continuous glucose monitoring (CGM), and validated self-administered questionnaire on food intake.

RESULTS

Suvorexant significantly improved sSE, abdominal circumference, and sucrose intake (all p < 0.05), but did not change HbA1c, CGM parameters, or body weight. Correlation analysis revealed that changes in sSE were associated with those in HbA1c and body weight (r = -0.61 and r = -0.66, respectively; both p < 0.05).

CONCLUSIONS

Suvorexant significantly improved sleep quality and obesity-associated parameters in patients with type 2 diabetes in 14 weeks. Improvements in sleep quality were associated with improvements in glycemic control. Sleep disorder treatment using suvorexant may provide metabolic benefits for patients with type 2 diabetes.

The Interlinked Rising Epidemic of Insufficient Sleep and Diabetes Mellitus

For healthy existence, humans need to spend one-third of their time sleeping. Any qualitative or quantitative disturbances in sleep would result in an increased prevalence of obesity, metabolic disorders, diabetes, cardiovascular diseases, and hypertension. The paper aims to highlight the growing global problem of insufficient sleep and its significant impact on the rising incidence of diabetes mellitus. An extensive literature search was done in all major databases for "insufficient sleep" and "Diabetes Mellitus" for this review. Shorter (<6 h) and longer (>9 h) durations of sleep have been adversely related to insulin resistance. Though the relation between insufficient sleep and diabetes mellitus is more or less understood, little is known about how oversleeping or hypersomnia (10⁻12 h) increases the risk of diabetes. The relationship between sleep disturbances and diabetes is dual-sided, as chronic sleep disturbances would elevate the risk of developing insulin resistance, while diabetes would worsen the quality of sleep. Both the qualitative and quantitative disturbances in sleep significantly increase the risk of developing diabetes, which is supported by numerous community-based and hospital-based epidemiological studies discussed in this review. Obstructive sleep apnea is one of the most common sleep disorders and is characterized by chronic intermittent hypoxia and increased sympathetic activity, thus leading to a higher prevalence of diabetes. Sleep therapy may serve as a low-cost method for fighting against the rising epidemic of diabetes.

Distinct impacts of sleep-disordered breathing on glycemic variability in patients with and without diabetes mellitus

BACKGROUND

Sleep-disordered breathing (SDB) is highly prevalent in patients with diabetes mellitus (DM) and heart failure (HF) and contributes to poor cardiovascular outcomes. Enlarged glycemic variability (GV) is a risk factor of cardiac events independently of average blood glucose level, but the influence of SDB on GV is uncertain. In this study, we examined whether the impact of SDB on GV is modified by the presence of DM with or without HF.

METHODS AND RESULTS

Two hundred three patients (67.5±14.1 [SD] years old, 132 males) who were admitted to our institute for examination or treatment of DM and/or HF underwent continuous glucose monitoring and polysomnography. Both HbA1c (8.0±2.0 vs. 5.7±0.4%) and mean amplitude of glycemic excursion (MAGE, median: 95.5 vs. 63.5 mg/dl) were significantly higher in a DM group (n = 100) than in a non-DM group (n = 103), but apnea-hypopnea index (AHI: 29.0±22.7 vs. 29.3±21.5) was similar in the two groups. AHI was correlated with log MAGE in the non-DM group but not in the DM group, and multivariate regression analysis revealed that AHI was an independent variable for log MAGE in the non-DM group but not in the DM group. We then divided the non-DM patients into two subgroups according to BNP level (100 pg/ml). AHI was positively correlated with log MAGE (r = 0.74, p<0.001) in the non-DM low-BNP subgroup, but such a correlation was not found in the non-DM high-BNP subgroup. Continuous positive airway pressure (CPAP) reduced MAGE from 75.3 to 53.0 mg/dl in the non-DM group but did not reduce MAGE in the DM group.

CONCLUSION

Severity of SDB was associated with higher GV, but DM as well as HF diminished the contribution of SDB to GV. Treatment with CPAP was effective for reduction of GV only in patients without DM.

Obstructive Sleep Apnea and Diabetes: A State of the Art Review

OSA is a chronic treatable sleep disorder and a frequent comorbidity in patients with type 2 diabetes. Cardinal features of OSA, including intermittent hypoxemia and sleep fragmentation, have been linked to abnormal glucose metabolism in laboratory-based experiments. OSA has also been linked to the development of incident type 2 diabetes. The relationship between OSA and type 2 diabetes may be bidirectional in nature given that diabetic neuropathy can affect central control of respiration and upper airway neural reflexes, promoting sleep-disordered breathing. Despite the strong association between OSA and type 2 diabetes, the effect of treatment with CPAP on markers of glucose metabolism has been conflicting. Variability with CPAP adherence may be one of the key factors behind these conflicting results. Finally, accumulating data suggest an association between OSA and type 1 diabetes as well as gestational diabetes. This review explores the role of OSA in the pathogenesis of type 2 diabetes, glucose metabolism dysregulation, and the impact of OSA treatment on glucose metabolism. The association between OSA and diabetic complications as well as gestational diabetes is also reviewed.

PERK/eIF2α contributes to changes of insulin signaling in HepG2 cell induced by intermittent hypoxia

AIMS

Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with abnormal glucose metabolism. Nowadays, endoplasmic reticulum (ER) stress emerges as an important mechanism underlying the development of type 2 diabetes mellitus (T2DM). However, it remains unclear that intermittent hypoxia (IH) could induce ER stress, resulting in abnormality of glucose metabolism. Thus, in the current study we explore the changes of insulin signaling under IH and the role of ER stress underlying these changes.

MAIN METHODS

HepG2 cells were exposed to room air (RA) or IH for 8h, 16h and 24h respectively. Oxygen concentration in IH groups was in a dynamic cycle from 21% to 1% every 5min, while it remained at 21% in RA groups. Insulin was added into cell culture medium for AKT and p-AKT measurement. In another experiment set, HepG2 cells were pre-cultured with 4-PBA prior to IH or RA exposure. Expression of AKT, p-AKT, p-JNK, p-IRE1, p-PERK and p-eIF2α was examined by Western Blot.

KEY FINDINGS

Compared with RA, p-AKT expression in HepG2 cells under IH for 24h was significantly lower even with insulin treatment. Expression of p-JNK, p-IRE1, ATF6, p-PERK and p-eIF2α were upregulated. p-AKT level in HepG2 with 4-PBA preculture under IH was restored. p-PERK and p-eIF2α expression in HepG2 cells in IH groups with 4-PBA preculture were inhibited while levels of p-JNK and p-IRE1 remained unchanged.

SIGNIFICANCE

IH, the hallmarker of OSAHS, could disturb insulin signaling via activating PERK/eIF2α.

Nocturnal Hypoxemia Causes Hyperglycemia in Patients With Obstructive Sleep Apnea and Type 2 Diabetes Mellitus

BACKGROUND

Our purpose was to investigate the relationship between oxygen saturation (SpO2) and dynamic interstitial glucose level (IGL) in patients with obstructive sleep apnea (OSA) along with type 2 diabetes mellitus (T2DM), and to investigate the potential mechanisms thereof.

MATERIALS AND METHODS

A total of 130 patients with OSA and T2DM underwent polysomnography and oral glucose tolerance tests at the Sleep Medicine Center. Using the lowest (L) SpO2% tested, patients were divided into mild, moderate and severe LSpO2 groups. Polysomnography and continuous glucose monitoring systems were used to analyze the altered pattern of SpO2 and dynamic IGL in the 3 groups.

RESULTS

LSpO2 during sleep in patients with OSA and T2DM stimulated an increase in IGL. The moderate and severe levels were represented by IGL45 and IGL30, respectively. The average nocturnal and peak IGL after LSpO2 in the severe group were significantly higher than in the mild and moderate groups. Stepwise multiple regression analysis showed that the body mass index (β = 0.301, P < 0.001), homeostatic model assessment of insulin resistance (β = 0.260, P < 0.001), apnea-hypopnea index (β = 0.309, P < 0.001), average SpO2 (β = -0.423, P = 0.008), LSpO2 (β = -0.369, P < 0.001) and microarousal index (β = 0.335, P = 0.044) were probably related to nocturnal IGL in patients with OSA along with T2DM.

CONCLUSIONS

Severe and moderate OSA with T2DM is marked by a delayed IGL peak following LSpO2. Nocturnal hypoxemia causes hyperglycemia in patients with OSA along with T2DM.

An update on cardiovascular effects of obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome is an important health problem which may cause or worsen systemic diseases. Chronic intermittent hypoxia during repetitive airflow cessations may cause endothelial dysfunction. Sleep apnoea is also shown to be associated with hypercoagulability which may be due to decreased nitric oxide levels and impaired vasodilatation. Endothelial dysfunction, increased systemic inflammation, sympathetic nervous system activation, increased oxidative stress and dysglycaemia may all contribute to cardiovascular processes such as hypertension, arrhythmia, stroke, heart failure and coronary artery disease in patients with obstructive sleep apnoea. Treatment approaches in patients with obstructive sleep apnoea mainly focus on maintaining upper airway patency either with positive airway pressure devices or upper airway appliances. Strategies involving positive airway pressure therapy are associated with decreased morbidity and mortality. Obstructive sleep apnoea should be suspected as an underlying mechanism in patients with cardiovascular disease and warrants appropriate treatment.

Intermittent hypoxia is an independent marker of poorer glycaemic control in patients with uncontrolled type 2 diabetes

AIM

This study investigated the association between intermittent hypoxia and glycaemic control in patients with uncontrolled type 2 diabetes (T2D) not treated for sleep apnoea.

METHODS

This was a single-centre cross-sectional study of stable patients with T2D and HbA1c ≥7% (53 mmol/mol). Patients underwent overnight pulse oximetry and, if intermittent hypoxia-defined by a 4% oxyhaemoglobin desaturation index ≥15-was observed, respiratory polygraphy was performed. All participants completed the Pittsburgh Sleep Questionnaire and Hospital Anxiety and Depression Scale. The association between intermittent hypoxia and poorer glycaemic control (defined by an HbA1c level above the median of 8.5%) was estimated by multivariate logistic regression analysis.

RESULTS

Out of 145 patients studied, 54 (37.2%) had intermittent hypoxia (with sleep apnoea confirmed in 53). Patients with intermittent hypoxia had 0.7% (7.7 mmol/mol) higher median HbA1c levels than patients without intermittent hypoxia (P=0.001). Intermittent hypoxia was associated with poorer glycaemic control after adjusting for obesity, age at onset and duration of diabetes, insulin requirement, sleep quality and depressive mood (OR: 2.31, 95% CI: 1.06-5.04, model adjusted for body mass index; OR: 2.46, 95% CI: 1.13-5.34, model adjusted for waist-to-height ratio).

CONCLUSION

Intermittent hypoxia, a consequence of sleep apnoea, is frequent and has a strong independent association with poorer glycaemic control in patients with uncontrolled T2D.

Intermittent hypoxia-induced glucose intolerance is abolished by α-adrenergic blockade or adrenal medullectomy

Obstructive sleep apnea causes intermittent hypoxia (IH) during sleep and is associated with dysregulation of glucose metabolism. We developed a novel model of clinically realistic IH in mice to test the hypothesis that IH causes hyperglycemia, glucose intolerance, and insulin resistance via activation of the sympathetic nervous system. Mice were exposed to acute hypoxia of graded severity (21, 14, 10, and 7% O2) or to IH of graded frequency [oxygen desaturation index (ODI) of 0, 15, 30, or 60, SpO2 nadir 80%] for 30 min to measure levels of glucose fatty acids, glycerol, insulin, and lactate. Glucose tolerance tests and insulin tolerance tests were then performed under each hypoxia condition. Next, we examined these outcomes in mice that were administered phentolamine (α-adrenergic blockade) or propranolol (β-adrenergic blockade) or that underwent adrenal medullectomy before IH exposure. In all experiments, mice were maintained in a thermoneutral environment. Sustained and IH induced hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent fashion. Only severe hypoxia (7% O2) increased lactate, and only frequent IH (ODI 60) increased plasma fatty acids. Phentolamine or adrenal medullectomy both prevented IH-induced hyperglycemia and glucose intolerance. IH inhibited glucose-stimulated insulin secretion, and phentolamine prevented the inhibition. Propranolol had no effect on glucose metabolism but abolished IH-induced lipolysis. IH-induced insulin resistance was not affected by any intervention. Acutely hypoxia causes hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent manner. During IH, circulating catecholamines act upon α-adrenoreceptors to cause hyperglycemia and glucose intolerance.

New frontiers in obstructive sleep apnoea

OSA (obstructive sleep apnoea), the most common respiratory disorder of sleep, is caused by the loss of upper airway dilating muscle activity during sleep superimposed on a narrow upper airway. This results in recurrent nocturnal asphyxia. Termination of these events usually requires arousal from sleep and results in sleep fragmentation and hypoxaemia, which leads to poor quality sleep, excessive daytime sleepiness, reduced quality of life and numerous other serious health consequences. Furthermore, patients with untreated sleep apnoea are at an increased risk of hypertension, stroke, heart failure and atrial fibrillation. Although there are many predisposing risk factors for OSA, including male gender, endocrine disorders, use of muscle relaxants, smoking, fluid retention and increased age, the strongest risk factor is obesity. The aim of the present review is to focus on three cutting-edge topics with respect to OSA. The section on animal models covers various strategies used to simulate the physiology or the effects of OSA in animals, and how these have helped to understand some of the underlying mechanisms of OSA. The section on diabetes discusses current evidence in both humans and animal models demonstrating that intermittent hypoxia and sleep fragmentation has a negative impact on glucose tolerance. Finally, the section on cardiovascular biomarkers reviews the evidence supporting the use of these biomarkers to both measure some of the negative consequences of OSA, as well as the potential benefits of OSA therapies.

Obstructive sleep apnoea and diabetes: an update

PURPOSE OF REVIEW

The relationship between obstructive sleep apnoea (OSA) and dysglycaemia is well established. However, uncertainty remains as to the extent that obesity mediates this relationship. The impact of OSA treatment on glucose metabolism and the consequences of having OSA in patients with diabetes is unclear. This review aims to summarize the latest evidence regarding the links between OSA and dysglycaemia.

RECENT FINDINGS

OSA is associated with insulin resistance in lean individuals and predicts insulin resistance worsening longitudinally. Continuous positive airway pressure (CPAP) lowers insulin resistance in CPAP-compliant patients. OSA is associated with impaired β-cell function. In patients with type 2 diabetes (T2D), the association between OSA and glycosylated haemoglobin (HbA1c) is related to nocturnal hypoxaemia. Apnoea hypopnoea index (AHI) during rapid eye movement (REM) (not non-REM) sleep is associated with HbA1c. In-laboratory, supervised CPAP improves glycaemia. OSA is associated with and predicts the progression of some diabetic vascular complications. Intensive lifestyle intervention in patients with T2D improves OSA independent of weight loss.

SUMMARY

OSA is associated with insulin resistance and β-cell dysfunction independent of obesity. OSA is associated with HbA1c and vascular complications in patients with T2D. CPAP might improve insulin resistance and glycaemic measures. Lifestyle intervention has a significant impact on AHI in patients with T2D.

Novel insights into metabolic sequelae of obstructive sleep apnoea: a link between hypoxic stress and chronic diabetes complications

An increasing body of evidence suggests that obstructive sleep apnoea (OSA) is independently associated with an increased risk of cardiovascular disease, glucose intolerance, and deteriorations in glycaemic control. Despite the knowledge of a multifactorial pathogenesis of long-term diabetes complications, there is a paucity of information on impact of comorbidities associated with chronic intermittent hypoxemia on development and progression of chronic diabetes complications. This review explores the clinical and scientific overlap of OSA and type 2 diabetes mellitus (T2DM) and its possible impact on the development and progression of diabetes macrovascular and microvascular complications. Multiple prospective observational cohort studies have demonstrated that OSA significantly increases the risk of cardiovascular disease independent of potential confounding risk factors. The current evidence further suggests that OSA with concurrent T2DM is associated with an increased risk of oxidative stress-induced damage of vulnerable endothelial and mesangial cells and peripheral nerves. Further studies are needed to validate the impact of OSA treatment on diabetes micro- and macrovascular complications. Since it is presently still unknown whether OSA treatment may provide a diabetes-modifying intervention that could delay or halt the progression of chronic diabetes complications, the emphasis is on early diagnosis and satisfactory treatment of both OSA and T2DM.

Effect of continuous positive airway pressure on type 2 diabetes mellitus and glucose metabolism

BACKGROUND

Obstructive sleep apnea (OSA) is a prevalent condition that is associated with significant comorbidities, including obesity, hypertension, cardiovascular disease, and insulin resistance. Continuous positive airway pressure (CPAP) is an effective treatment for OSA. The effect of CPAP on glucose metabolism in patients with OSA has been controversial. This study evaluates the impact of CPAP on patients with OSA and type 2 diabetes mellitus (T2DM) or prediabetes.

MATERIALS AND METHODS

PubMed, Ovid Medline, and EMBASE were searched for original English language studies performed on or after 2003. Subjects were aged > 18 years, were diagnosed with OSA via polysomnography, and had either T2DM or prediabetes according to laboratory evaluation.

RESULTS

Of the 22 articles that met the selection criteria, 17 studies (77%) showed that a prolonged use of CPAP produced significant changes in glucose metabolism of patients who had T2DM and prediabetes. These changes were observed in studies measuring glycosylated hemoglobin (HbA1c), postprandial or nocturnal glucose, and insulin sensitivity or resistance. Of the 17 studies, 4 showed improvement in HbA1c levels or increased insulin sensitivity only after long-term use of CPAP for ≥ 3 months.

CONCLUSION

This literature review shows that CPAP improves not only hypoxia while restoring normal breathing during sleep, but also glucose metabolism in patients with OSA and T2DM or prediabetes. A few studies have shown that patients can experience even better results with long-term CPAP treatment (≥ 3 months of daily use) for > 4 hours a night. Therefore, this improvement in glucose metabolism with the use of CPAP may contribute to T2DM prevention and decrease further progression of the disease. However, additional studies are needed to confirm these findings.

Obstructive Sleep Apnoea and Type 2 Diabetes

With the growing prevalence of obesity, the burden of type 2 diabetes is increasing. Obstructive sleep apnoea (OSA) is a very common medical condition that is associated with increased risk of cardiovascular disease and mortality. Obesity is a common risk factor for OSA and type 2 diabetes and hence it is not surprising that OSA and type 2 diabetes are interlinked. OSA has been shown to be an independent risk factor for the development of incident pre-diabetes/type 2 diabetes. OSA is also associated with worse glycaemic control and vascular disease in patients with type 2 diabetes. However, evidence for the benefits of OSA treatment in patients with type 2 diabetes is still lacking. The aim of this article is to provide an overview of OSA, the relationships between OSA and dysglycaemia and the impact of OSA in patients with type 2 diabetes, highlighting recent advances in the field.

Relationship between sleep disorders and the risk for developing type 2 diabetes mellitus

Sleep is increasingly being recognized as an important factor in the homeostasis of multiple body functions, including blood glucose metabolism. One of the most common sleep disorders, obstructive sleep apnea, is not only highly prevalent in patients with type 2 diabetes mellitus, but may contribute to the development of abnormalities in blood glucose metabolism. Evidence suggests that effectively treating sleep apnea, specifically with continuous positive airway pressure, improves glycemic and nonglycemic outcomes. Other common sleep disorders, such as insufficient sleep, shift work disorder, and restless legs syndrome, may also have a significant influence on the development and management of diabetes and its complications. The purpose of this article is to review the recent literature on the relationship between sleep disorders and blood glucose metabolism.

Obstructive sleep apnea and type 2 diabetes: is there a link?

Type 2 diabetes is a chronic illness that is increasing in epidemic proportions worldwide. Major factors contributing to the development of type 2 diabetes include obesity and poor lifestyle habits (e.g., excess dietary intake and limited physical activity). Despite the proven efficacy of lifestyle interventions and the use of multiple pharmacological agents, the economic and public health burden of type 2 diabetes remains substantial. Obstructive sleep apnea (OSA) is a treatable sleep disorder that is pervasive among overweight and obese adults, who represent about two thirds of the U.S. population today. An ever-growing number of studies have shown that OSA is associated with insulin resistance, glucose intolerance and type 2 diabetes, independent of obesity. Evidence from animal and human models that mimic OSA provides potential mechanisms for how OSA may alter glucose metabolism. Up to 83% of patients with type 2 diabetes suffer from unrecognized OSA and increasing severity of OSA is associated with worsening glucose control. However, it is still unclear whether OSA may lead to the development of diabetes over time. More data from large-scale longitudinal studies with rigorous assessments of diabetes and OSA are needed. In addition, there is still controversy whether continuous positive airway pressure (CPAP) treatment of OSA improves glucose metabolism. Large-scale randomized-controlled trials of CPAP treatment of OSA with well-validated assessments of insulin sensitivity and glucose tolerance are needed. These studies may reveal that OSA represents a novel, modifiable risk factor for the development of prediabetes and type 2 diabetes.

Obstructive sleep apnea and stroke

Obstructive sleep apnea (OSA) is a common disorder that has been associated with many cardiovascular disease processes, including hypertension and arrhythmias. OSA has also been identified as an independent risk factor for stroke and all-cause mortality. OSA is highly prevalent in patients with transient ischemic attacks and stroke. Routinely screening patients with transient ischemic attacks or stroke for sleep apnea is becoming more common. In stroke patients with OSA, treatment with continuous positive airway pressure may prevent subsequent cardiovascular events and improve neurologic outcomes. This review explores the pathophysiology of the association between OSA and stroke, and the clinical implications of identification and treatment of OSA in patients with stroke.

Continuous positive airway pressure and type 2 diabetes mellitus

Obstructive sleep apnea (OSA) is a sleep disorder, increasingly recognized. It is commonly present in obese persons, treated with continuous positive airway pressure (CPAP), being the gold standard. The disorder has been associated with diabetes mellitus and possibly related to hypoxia per se, increased sympathetic activity, disturbed hypothalamic-pituitary-adrenal axis and increased inflammatory cytokines and leptin, all of which can adversely affect both glucose metabolism and insulin sensitivity. Given this association and the presence of common risk factors, this review assessed the impact of CPAP on diabetes mellitus through various metabolic parameters including HbA1c, nocturnal glucose and insulin resistance, in addition to the effect of CPAP on the prevention of diabetes mellitus. Results have been conflicting; Randomized controlled trials are recommended to allow objective and definite conclusions.

Effect of continuous positive airway pressure therapy on glucose control

Obstructive sleep apnea (OSA) and diabetes mellitus are both highly prevalent disorders. There has been a recent recognition of an association between insulin resistance and sleep apnea. Continuous positive airway pressure (CPAP) has emerged as an effective therapy for treatment of OSA and has been shown to positively influence numerous pathophysiological factors that contribute to cardiovascular risk. There is emerging data that explores the influence of CPAP therapy, insulin sensitivity and glycemic control. In the current review, we examine this literature critically and formulate a synopsis that summarizes the current knowledge in this field.

Hypoxic damage to pancreatic beta cells--the hidden link between sleep apnea and diabetes

Despite a large body of epidemiologic and clinical evidence suggesting that sleep disordered breathing is an independent risk factor for development of type 2 diabetes (T2DM), the underlying pathogenesis of altered glucose metabolism in sleep apnea remains to be unraveled. While previous studies have proposed some causal pathways linking sleep apnea with T2DM through increased insulin resistance and deterioration in insulin sensitivity, there has been a particular lack of research into sleep apnea-related alterations in pancreatic beta-cell function. Drawing upon our previous observation that sleep apnea is independently associated with an increased basal pancreatic beta-cell function in adults with normal glucose metabolism, the idea presented here suggests that sleep apnea imposes an excessive demand for insulin secretion, which may lead to progressive pancreatic beta-cell failure in high-risk individuals. Specifically, we hypothesize that in addition to diabetogenic effects of acute hypoxic activation of the sympathetic nervous system, the chronic intermittent hypoxemia represses the expression of key genes regulating biosynthesis of pancreatic proinsulin convertases with a resultant progressive decrease in their catalytic activity. The long-term hypoxic damage to pancreatic beta-cells may thus contribute to progression of glucose dysregulation in persons with untreated sleep apnea over time. Strategies to prevent and decrease the high prevalence and associated morbidity of T2DM are critically needed. The ideas and hypotheses presented here address the unexplored pathophysiological mechanisms underlying the potential causal link between sleep apnea and T2DM. Future hypotheses-testing will seek to delineate the role of sleep apnea in the development of T2DM, probe the underlying molecular mechanisms for pancreatic beta-cell dysfunction in sleep apnea, and obtain information on clinical, epidemiologic, and other factors responsible for protecting individuals from alterations in insulin-glucose homeostasis. These results could further be utilized in testing genetic susceptibilities and various therapy modalities to prevent pancreatic beta-cell dysfunction and maintain normal glucose status in persons with sleep apnea in the long term.

Effects of CPAP-respiration on markers of glucose metabolism in patients with obstructive sleep apnoea syndrome: a systematic review and meta-analysis

Background: Obstructive Sleep Apnoea Syndrome (OSAS) is a condition of obstruction, apneas and arousals while sleeping. It has been suggested that OSAS independently influences glucose metabolism. The main treatment for OSAS is continuous positive airways pressure (CPAP).

Objectives: To assess the effects of CPAP on insulin resistance and glucose metabolism.

Search strategy: We searched Medline, Embase and the Cochrane Controlled Trial Register (January 2010).

Selection criteria: We included randomised and non-randomised trials comparing CPAP with inactive control or placebo CPAP in adults with OSAS.

Data collection and analysis: Two authors independently assessed trial quality and extracted data. Parallel and crossover group trials were analysed separately. A meta-analysis was carried out.

Results: Three parallel group and two cross-over randomised trials and one controlled trial were included investigating 296 participants. Sample sizes ranged from n=13 to n=102 participants, age was 18 to 75 years, mean body mass index (BMI) 27.2 kg/m² to 37.1 kg/m², mean apnoe hypopnoe index (AHI) 29.7 to 39.7 events per hour, mean dips >4% in arterial oxygen saturation per hour of sleep 1 to 42.7 events. The studies’ methodological quality varied. Follow-up ranged from 4 to 12 weeks. Various endpoints were investigated. CPAP did neither influence plasma insulin levels nor HOMA-index, adiponectin levels or HbA1c value. One study reported a significant positive effect on the insulin sensitivity index (1.68%/min, 95% CI 0.3 to 3.06).

Conclusion: This systematic review does not support the hypothesis that OSAS independently influences glucose metabolism. Sufficiently powered, long-term randomised controlled trials defining changes of insulin resistance as primary endpoint are needed.

Weight and metabolic effects of CPAP in obstructive sleep apnea patients with obesity

Background

Obstructive sleep apnea (OSA) is associated with obesity, insulin resistance (IR) and diabetes. Continuous positive airway pressure (CPAP) rapidly mitigates OSA in obese subjects but its metabolic effects are not well-characterized. We postulated that CPAP will decrease IR, ghrelin and resistin and increase adiponectin levels in this setting.

Methods

In a pre- and post-treatment, within-subject design, insulin and appetite-regulating hormones were assayed in 20 obese subjects with OSA before and after 6 months of CPAP use. Primary outcome measures included glucose, insulin, and IR levels. Other measures included ghrelin, leptin, adiponectin and resistin levels. Body weight change were recorded and used to examine the relationship between glucose regulation and appetite-regulating hormones.

Results

CPAP effectively improved hypoxia. However, subjects had increased insulin and IR. Fasting ghrelin decreased significantly while leptin, adiponectin and resistin remained unchanged. Forty percent of patients gained weight significantly. Changes in body weight directly correlated with changes in insulin and IR. Ghrelin changes inversely correlated with changes in IR but did not change as a function of weight.

Conclusions

Weight change rather than elimination of hypoxia modulated alterations in IR in obese patients with OSA during the first six months of CPAP therapy.

Diabetes and sleep: a complex cause-and-effect relationship

Strong associations of diabetes with sleep impairment have been frequently reported. In the present review, we discuss current evidence and hypotheses for how type 1 and type 2 diabetes mellitus are associated with sleep impairment. This association may be described as a vicious circle, where sleep disorders favor the development of type 2 diabetes or exacerbate the metabolic control of both types of diabetes, whereas diabetes itself, especially when associated with poor metabolic control, is often followed by sleep disorders. In this review, novel findings concerning the neuro-endocrine-metabolic mediation of the mentioned circle are highlighted. Understanding how this association occurs, the impact of sleep impairment on diabetes, and the impact of diabetes on the development or exacerbation of sleep disorders should lead to potential new therapeutic strategies for treating both conditions.

Nocturnal hyperglycaemia in type 2 diabetes with sleep apnoea syndrome

We assessed glycaemic status in 26 overweight or obese people with type 2 diabetes suspected of having sleep apnoea syndrome (SAS). In people with SAS (n=13), nocturnal glycaemia was 38% higher, independent of body mass index (particularly during rapid eye movement sleep) compared with non-SAS subjects (p<0.008).

Obstructive sleep apnea: role in the risk and severity of diabetes

Obstructive sleep apnea (OSA) is a treatable sleep disorder that is pervasive among overweight and obese individuals. Current evidence supports a robust association between OSA and insulin resistance, glucose intolerance and the risk of type 2 diabetes, independent of obesity. Up to 83% of patients with type 2 diabetes suffer from unrecognized OSA and increasing severity of OSA is independently associated with poorer glucose control. Evidence from animal and human models that mimic OSA supports a potential causal role for OSA in altered glucose metabolism. Robust prospective and randomized clinical trials are still needed to test the hypothesis that effective treatment of OSA may prevent the development of type 2 diabetes and its complications, or reduce its severity. Type 2 diabetes is occurring at alarming rates worldwide and despite available treatment options, the economic and public health burden of this epidemic remains enormous. OSA might represent a novel, modifiable risk factor for the development of prediabetes and type 2 diabetes.

Disorders of glucose metabolism in sleep-disordered breathing

Despite proliferating literature, the exact relationship between obstructive sleep apnea (OSA) and alterations in glucose metabolism is still controversial. There is growing evidence to suggest that OSA imposes adverse effects on glucose metabolism, but the translation into clinical effect is not well delineated. Many potential mechanisms are being explored, mostly relating to peripheral tissue response to insulin and more recently regarding pancreatic beta cell function of insulin secretion. The effect of OSA on glucose metabolism is likely to be influenced by many personal characteristics. Age, degree of adiposity, lifestyle, comorbidities, and even the stage of glucose disorder itself may modify the relationship between OSA and glucose metabolism. In the biologic system of the human body, all these interact to culminate in clinically relevant outcomes.

Do sleep disorders and associated treatments impact glucose metabolism?

Over the past decade substantial evidence has accumulated implicating disorders of sleep in the pathogenesis of various metabolic abnormalities. This review, which is based on workshop discussions that took place at the 6th annual meeting of the International Sleep Disorders Forum: The Art of Good Sleep 2008 and a systematic literature search, provides a critical analysis of the available evidence implicating sleep disorders such as obstructive sleep apnoea (OSA), insomnia, short or long-term sleep duration and restless legs syndrome as potential risk factors for insulin resistance, glucose intolerance, type 2 diabetes mellitus and the metabolic syndrome. The review also highlights the evidence on whether treatment of specific sleep disorders can decrease metabolic risk. In total, 83 published reports were selected for inclusion. Although several studies show clear associations between sleep disorders and altered glucose metabolism, causal effects and the underlying pathophysiological mechanisms involved have not been fully elucidated. OSA appears to have the strongest association with insulin resistance, glucose intolerance, type 2 diabetes and the metabolic syndrome. There are, however, limited data supporting the hypothesis that effective treatment of sleep disorders, including OSA, has a favourable effect on glucose metabolism. Large randomized trials are thus required to address whether improvement of sleep quality and quantity can curtail excess metabolic risk. Research is also required to elucidate the mechanisms involved and to determine whether the effects of treatment for sleep disorders on glucose metabolism are dependent on the specific patient factors, the type of disorder and the duration of metabolic dysfunction. In conclusion, there is limited evidence on whether sleep disorders alter glucose metabolism and whether treatment can reduce the excess metabolic risk.

Sleep and diabetes

Sleep apnea is clinically recognized as a heterogeneous group of disorders characterized by recurrent apnea and/or hypopnea. Its prevalence ranges from 4% to 24%. It has been implicated as an independent risk factor for several conditions such as hypertension, stroke, arrhythmia, and myocardial infarction. Recently data has been emerging which suggests an independent association of obstructive sleep apnea with several components of the metabolic syndrome, particularly insulin resistance and abnormalities in lipid metabolism. We hereby review the salient features of the association between sleep and diabetes.