Autonomic dysfunction in obstructive sleep apnea is associated with impaired glucose regulation

Cardiac Autonomic Neuropathy in Prediabetes: A Case-Control Study

Introduction

Early detection and diagnosis of diabetic autonomic neuropathy, especially cardiac autonomic neuropathy (CAN), have gained attention recently because of their elevated cardiovascular mortality risk. Although the connection between type 2 diabetes mellitus and autonomic neuropathy is well established, evidence is emerging that the association might predate the stage of prediabetes.

Objective

The present study was undertaken to compare the prevalence of CAN in prediabetes versus that in normoglycemic controls.

Materials and Methods

The study population was selected by purposive sampling from individuals attending a tertiary care hospital from January 2018 to June 2019. Fifty individuals with prediabetes diagnosed by the American Diabetes Association's glycated haemoglobin criteria and 50 age- and gender-matched healthy controls were recruited. CAN was assessed by standard cardiovascular reflex tests, as described by Ewing and Clarke. Changes in R-R with deep breathing, Valsalva manoeuver, and changes in blood pressure (BP) in response to standing and sustained handgrip were evaluated. Three-time domains [standard deviation of normal-to-normal intervals (SDNN), root mean square of successive RR intervals (rMSSD) and percentage of successive normal to normal R-R (NN) intervals that differ by more than 50 ms (pNN50)] and four frequency domain indices [very low-frequency band (VLF), low-frequency band (LF), high-frequency band (HF), LF/HF ratio) of heart rate variability (HRV)] were examined.

Results

The mean heart rate was 71.37 ± 7.94 and 65.59 ± 8.73 beats/min in patients with prediabetes and controls, respectively (P < 0.05). All three-time-domain indices of HRV were significantly lower in persons with prediabetes compared to controls. The peak frequency of LF, peak power of LF, normalised unit of LF, and LF/HF ratio was significantly lower in subjects with prediabetes than in controls. There was no difference in the traditional cardiovascular autonomic reflex testing.

Conclusion

Our study demonstrates the presence of subclinical autonomic dysfunction in persons with prediabetes. Early detection of CAN in prediabetes can have future implications for cardiovascular risk reduction.

Screening of obstructive sleep apnea syndrome by the deep breathing technique

STUDY OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) is associated with alterations in heart rate variability (HRV) in relation to chronic autonomic dysfunction. We tested the ability of the deep breathing technique-a simple way to evaluate HRV-to identify patients with OSAS.

METHODS

Consecutive patients referred for suspected OSAS (without obesity, diabetes, and heart diseases) were included. They underwent a measure of HRV at rest and of heart rate oscillations during expiration vs inspiration (DeltaHRDB) when breathing deeply at the resonant frequency of 6 cycles per minute (deep breathing technique) while sitting awake, followed by a nighttime polysomnography. We measured DeltaHRDB and performed temporal and spectral HRV analysis.

RESULTS

Of 31 included participants (77% male), 14 had mild to moderate OSAS (apnea-hypopnea index median [IQR]: 18 [12]) and 17 had no OSAS. The conventional HRV analysis did not reveal any difference between the groups with vs without OSAS. However, the DeltaHRDB was lower in those with than without OSAS. Lower DeltaHRDB correlated with higher apnea-hypopnea index, arousal index, and desaturation degree. A DeltaHRDB below 11 beats per minute (bpm) predicted OSAS with a sensitivity of 100% and specificity of 86%.

CONCLUSIONS

The deep breathing technique accurately identifies a reduction in cardiac changes in patients with mild to moderate OSAS. It could be used as a simple screening tool to select patients for polysomnography.

CITATION

Onanga M, Joanny S, Rivals I, et al. Screening of obstructive sleep apnea syndrome by the deep breathing technique. J Clin Sleep Med. 2023;19(2):293-302.

Sleep-disordered breathing in cystic fibrosis

Sleep-disordered breathing (SBD) is an under recognized comorbidity in the cystic fibrosis (CF) population across the lifespan. Nocturnal hypoxemia, obstructive sleep apnea, and nocturnal hypoventilation are respiratory abnormalities that occur commonly during sleep in patients with lung disease, and have deleterious consequences to the quality of life in people with CF. Effective screening for these abnormalities is needed to allow for timely initiation of treatment, which has been reported to be efficacious. Lack of treatment leads to worsened pulmonary, cardiovascular, and metabolic outcomes in patients. In this review, we give an overview of SBD for the CF clinician, including prevalence, treatment, and suggestions for future research. We strongly encourage the CF community to incorporate evaluation for SBD in CF clinical care so that outcomes for the subset of the CF patients with comorbid SBD improve.

Circadian Patterns of Patients with Type 2 Diabetes and Obstructive Sleep Apnea

Sleep apnea, a condition that modifies sleep and circadian rhythms, is highly prevalent in patients with diabetes. However, it is not known if there is an association between sleep apnea, circadian alterations and glycemic regulation in this type of patient. Here, a polysomnographic study was carried out on 21 women and 25 men (mean age = 64.3 ± 1.46 years) with diagnoses of type 2 diabetes to detect the presence of sleep apnea. Moreover, patients wore an actigraph and a temperature sensor on the wrist for one week, to study the manifestation of the circadian rhythms. The correlations of circadian and polysomnographic variables with the severity of apnea, measured by the apnea-hypopnea index, and with glycemic dysregulation, measured by the percentage of glycated hemoglobin, were analyzed. The mean apnea-hypoapnea index of all the participants was 39.6 ± 4.3. Apnea-hypoapnea index correlated with % N1, negatively with % N3, and also the stability of the active circadian rhythm. However, no significant correlation was found between the apnea-hypopnea index and wrist temperature rhythm and glycated hemoglobin. Glycated hemoglobin levels were negatively associated with the percentage of variance explained by the wrist temperature circadian rhythm (calculated via 24 and 12 h rhythms). This association was independent of body mass index and was strongest in patients with severe apnea. In conclusion, patients with diabetes showed altered circadian rhythms associated with a poor glycemic control and this association could partially be related to the coexistence of sleep apnea.

The Impact of Glycolipid Metabolic Disorders on Severity Stage-Specific Variation of Cardiac Autonomic Function in Obstructive Sleep Apnea: A Data-Driven Clinical Study

BACKGROUND

Cardiac autonomic dysfunction (CAD) is a common pathology in cardiovascular diseases; however, the role of glycolipid metabolic disorders in CAD development in obstructive sleep apnea (OSA) remains poorly understood.

METHODS

In total, 4152 patients with suspected OSA were recruited in our sleep center. Metabolic characteristics including anthropometric and glycolipid data were collected. Heart rate variability (HRV) was measured to assess the risk of CAD; its dose-response relationship with OSA severity was evaluated via restricted cubic spline (RCS) analysis. A segmented multivariate linear regression (SMLR) model was used to evaluate the roles of metabolic variables in different stages of OSA.

RESULTS

The RCS showed that CAD risk increased in a nonlinear relationship pattern with OSA severity, from slow fluctuation at earlier stages to rapid change in later stages. After integrating the clinical definition and RCS selected knots, we obtained the new four OSA severity stages. SMLR model showed that the overall value of glycolipid variables for prediction of HRV abnormalities was greater than the value of OSA variables at earlier stages, while OSA variables were more effective predictors in more severe stages. The discordance in respective relationship of HRV with metabolic and OSA variables sheds the light how metabolic disorders promoted the development of CAD in OSA, the later further in turn deteriorates cardiac function.

CONCLUSION

These results are indicative of stage-specific involvement of glycolipid metabolic factors underlying CAD nonlinear changes in patients with OSA. Early control glycolipid disorders may help the control of CAD development in patients with OSA.

Is there cardiac autonomic neuropathy in prediabetes?

Although there is considerably more data showing an association between type 2 diabetes mellitus (T2DM) and autonomic neuropathy, accumulating evidence indicates that cardiovascular autonomic neuropathy (CAN) is common in persons with impaired glucose tolerance (IGT). Furthermore, CAN may occur early after a metabolic insult and obesity, especially among mean, and seems to play an important role in the early pathogenesis of CAN. Autonomic symptoms are common in subjects with IGT. In addition to defects in CAN, in subjects with IGT, there is impaired sudomotor function and abnormalities of endothelial peripheral vasoreactivity. At the present time, the only interventions that may be effective in preventing or reversing IGT associated autonomic neuropathy are lifestyle improvement. These include a tailored diet and exercise program. Other approaches that may be beneficial include modulation of oxidative stress and improvement of metabolic regulation in subjects with IGT. Interventions are most likely to be effective early in the course of disease and therefore it is extremely important to have early diagnosis of IGT and autonomic neuropathy.

Abnormalities in autonomic function in obese boys at-risk for insulin resistance and obstructive sleep apnea

STUDY OBJECTIVES

Current evidence in adults suggests that, independent of obesity, obstructive sleep apnea (OSA) can lead to autonomic dysfunction and impaired glucose metabolism, but these relationships are less clear in children. The purpose of this study was to investigate the associations among OSA, glucose metabolism, and daytime autonomic function in obese pediatric subjects.

METHODS

Twenty-three obese boys participated in: overnight polysomnography; a frequently sampled intravenous glucose tolerance test; and recordings of spontaneous cardiorespiratory data in both the supine (baseline) and standing (sympathetic stimulus) postures.

RESULTS

Baseline systolic blood pressure and reactivity of low-frequency heart rate variability to postural stress correlated with insulin resistance, increased fasting glucose, and reduced beta-cell function, but not OSA severity. Baroreflex sensitivity reactivity was reduced with sleep fragmentation, but only for subjects with low insulin sensitivity and/or low first-phase insulin response to glucose.

CONCLUSIONS

These findings suggest that vascular sympathetic activity impairment is more strongly affected by metabolic dysfunction than by OSA severity, while blunted vagal autonomic function associated with sleep fragmentation in OSA is enhanced when metabolic dysfunction is also present.

Pulmonary Function and Sleep Breathing: Two New Targets for Type 2 Diabetes Care

Population-based studies showing the negative impact of type 2 diabetes (T2D) on lung function are overviewed. Among the well-recognized pathophysiological mechanisms, the metabolic pathways related to insulin resistance (IR), low-grade chronic inflammation, leptin resistance, microvascular damage, and autonomic neuropathy are emphasized. Histopathological changes are exposed, and findings reported from experimental models are clearly differentiated from those described in humans. The accelerated decline in pulmonary function that appears in patients with cystic fibrosis (CF) with related abnormalities of glucose tolerance and diabetes is considered as an example to further investigate the relationship between T2D and the lung. Furthermore, a possible causal link between antihyperglycemic therapies and pulmonary function is examined. T2D similarly affects breathing during sleep, becoming an independent risk factor for higher rates of sleep apnea, leading to nocturnal hypoxemia and daytime sleepiness. Therefore, the impact of T2D on sleep breathing and its influence on sleep architecture is analyzed. Finally, the effect of improving some pathophysiological mechanisms, primarily IR and inflammation, as well as the optimization of blood glucose control on sleep breathing is evaluated. In summary, the lung should be considered by those providing care for people with diabetes and raise the central issue of whether the normalization of glucose levels can improve pulmonary function and ameliorate sleep-disordered breathing. Therefore, patients with T2D should be considered a vulnerable group for pulmonary dysfunction. However, further research aimed at elucidating how to screen for the lung impairment in the population with diabetes in a cost-effective manner is needed.

Increased Short-Term Beat-to-Beat QT Interval Variability in Patients with Impaired Glucose Tolerance

Prediabetic states and diabetes are important risk factors for cardiovascular morbidity and mortality. Determination of short-term QT interval variability (STVQT) is a non-invasive method for assessment of proarrhythmic risk. The aim of the study was to evaluate the STVQT in patients with impaired glucose tolerance (IGT). 18 IGT patients [age: 63 ± 11 years, body mass index (BMI): 31 ± 6 kg/m2, fasting glucose: 6.0 ± 0.4 mmol/l, 120 min postload glucose: 9.0 ± 1.0 mmol/l, hemoglobin A1c (HbA1c): 5.9 ± 0.4%; mean ± SD] and 18 healthy controls (age: 56 ± 9 years, BMI: 27 ± 5 kg/m2, fasting glucose: 5.2 ± 0.4 mmol/l, 120 min postload glucose: 5.5 ± 1.3 mmol/l, HbA1c: 5.4 ± 0.3%) were enrolled into the study. ECGs were recorded, processed, and analyzed off-line. The RR and QT intervals were expressed as the average of 30 consecutive beats, the temporal instability of beat-to-beat repolarization was characterized by calculating STVQT as follows: STVQT = Σ|QTn + 1 - QTn| (30x√2)-1. Autonomic function was assessed by means of standard cardiovascular reflex tests. There were no differences between IGT and control groups in QT (411 ± 43 vs 402 ± 39 ms) and QTc (431 ± 25 vs 424 ± 19 ms) intervals or QT dispersion (44 ± 13 vs 42 ± 17 ms). However, STVQT was significantly higher in IGT patients (5.0 ± 0.7 vs 3.7 ± 0.7, P < 0.0001). The elevated temporal STVQT in patients with IGT may be an early indicator of increased instability of cardiac repolarization during prediabetic conditions.

Sensory and autonomic function and structure in footpads of a diabetic mouse model

Sensory and autonomic neuropathy affects the majority of type II diabetic patients. Clinically, autonomic evaluation often focuses on sudomotor function yet this is rarely assessed in animal models. We undertook morphological and functional studies to assess large myelinated and small unmyelinated axons in the db/db type II diabetes mouse model. We observed that autonomic innervation of sweat glands in the footpads was significantly reduced in db/db mice compared to control db/+ mice and this deficit was greater compared to reductions in intraepidermal sensory innervation of adjacent epidermis. Additionally, db/db mice formed significantly fewer sweat droplets compared to controls as early as 6 weeks of age, a time when no statistical differences were observed electrophysiologically between db/db and db/+ mice studies of large myelinated sensory and motor nerves. The rate of sweat droplet formation was significantly slower and the sweat droplet size larger and more variable in db/db mice compared to controls. Whereas pilocarpine and glycopyrrolate increased and decreased sweating, respectively, in 6 month-old controls, db/db mice did not respond to pharmacologic manipulations. Our findings indicate autonomic neuropathy is an early and prominent deficit in the db/db model and have implications for the development of therapies for peripheral diabetic neuropathy.

Characterization of sleep breathing pattern in patients with type 2 diabetes: sweet sleep study

BACKGROUND

Although sleep apnea-hypopnea syndrome (SAHS) is highly prevalent in patients with type 2 diabetes (T2D), it is unknown whether or not subjects with and without T2D share the same sleep breathing pattern.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional study in patients with SAHS according to the presence (n = 132) or not (n = 264) of T2D. Both groups were matched by age, gender, BMI, and waist and neck circumferences. A subgroup of 125 subjects was also matched by AHI. The exclusion criteria included chronic respiratory disease, alcohol abuse, use of sedatives, and heart failure. A higher apnea hypopnea index (AHI) was observed in T2D patients [32.2 (10.2-114.0) vs. 25.6 (10.2-123.4) events/hours; p = 0.002). When sleep events were evaluated separately, patients with T2D showed a significant increase in apnea events [8.4 (0.1-87.7) vs. 6.3 (0.0-105.6) e/h; p = 0.044), as well as a two-fold increase in the percentage of time spent with oxygen saturation <90% [15.7 (0.0-97.0) vs. 7.9 (0.0-95.6) %; <0.001)], higher rates of oxygen desaturation events, and also higher daily sleepiness [7.0 (0.0-21.0) vs. 5.0 (0.0-21.0); p = 0.006)] than subjects without T2D. Significant positive correlations between fasting plasma glucose and AHI, the apnea events, and CT90 were observed. Finally, multiple linear regression analyses showed that T2D was independently associated with AHI (R2 = 0.217), the apnea index (R2 = 0.194), CT90 (R2 = 0.222), and desaturation events.

CONCLUSIONS/SIGNIFICANCE

T2D patients present a different pattern of sleep breathing than subject without diabetes. The most important differences are the severity of hypoxemia and the number of apneas whereas the incidence of hypopnea episodes is similar.

Comorbidity of diabetes and obstructive sleep apnea in hospitalized patients

Obstructive sleep apnea (OSA) and type 2 diabetes are two morbidities commonly encountered in the hospitalized setting. Both diseases will present with an array of complications if not managed in a timely, competent manner. However, a growing body of evidence suggests a link between these two pathologies. It is our hope that through careful review of the literature, we may generate heightened awareness of the OSA/diabetes comorbidity. Through better understanding of these conditions and their interactions, we may insure efficient management in the clinical setting and prevent exacerbation of common complications.

Effect of glycemic control on nocturnal arterial oxygen saturation: a case-control study in type 2 diabetic patients

BACKGROUND

There is growing evidence suggesting a deleterious effect of type 2 diabetes on lung function and sleep breathing. The aim of this case-control study was to evaluate whether or not an improvement in glycemic control could arrest or ameliorate nocturnal hypoxemia in type 2 diabetes.

METHODS

Thirty patients with type 2 diabetes with HbA1c ≥8% (cases) and 10 non-diabetic subjects were analyzed. Controls were closely matched to cases by age, gender, body mass index, and neck circumference. The nocturnal oxygen desaturation index (ODI) was calculated at baseline and 5 days after blood glucose improvement with pharmacological intervention. Four different oxygen desaturation thresholds (reductions in SaO2  ≥ 3%, 4%, 6%, and 8%) as indicators of hypoxemia severity (ODI-3%, ODI-4%, ODI-6%, ODI-8%) were used.

RESULTS

At baseline, patients with diabetes showed a higher number of ODI-3%, ODI-4%, and ODI-6% in comparison with controls. A significant reduction in ODI-3% (29.7 [4.8-107.9] events per hour at baseline versus 24.6 [3.1-97.7] e/h at discharge, P < 0.001), ODI-4% (21.7 [1.6-79.3] versus 14.7 [0.3- 79.4], P = 0.003), ODI-6% (9.3 [0.3-71.8] versus 4.0 [0.0-73.7], P = 0.001), and ODI-8% (4.1 [0.0-64.3] versus 1.1 [0.0-69.8], P = 0.033) was observed in patients with diabetes after 5 days of follow-up. However, no changes in ODI events were observed in non-diabetic patients after the same period. No significant changes in weight were observed in either group.

CONCLUSIONS

Glycemic control improvement significantly reduces the increased number of nocturnal oxygen desaturations that exist in type 2 diabetes. Although the mechanisms are not yet fully understood, the rapid effect without changes in body weight suggests a central mechanism involving respiratory center output.

Insular cortex metabolite changes in obstructive sleep apnea

STUDY OBJECTIVE

Adults with obstructive sleep apnea (OSA) show significant autonomic and neuropsychologic deficits, which may derive from damage to insular regions that serve those functions. The aim was to assess glial and neuronal status from anterior insular metabolites in OSA versus controls, using proton magnetic resonance spectroscopy (PMRS), and thus to provide insights for neuroprotection against tissue changes, and to reduce injury consequences.

DESIGN

Cross-sectional study.

SETTING

University-based medical center.

PARTICIPANTS

Thirty-six patients with OSA, 53 controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We performed PMRS in bilateral anterior insulae using a 3.0-Tesla magnetic resonance imaging scanner, calculated N-acetylaspartate/creatine (NAA/Cr), choline/creatine (Cho/Cr), myo-inositol/creatine (MI/Cr), and MI/NAA metabolite ratios, and examined daytime sleepiness (Epworth Sleepiness Scale, ESS), sleep quality (Pittsburgh Sleep Quality Index, PSQI), and neuropsychologic status (Beck Depression Inventory II [BDI-II] and Beck Anxiety Inventory [BAI]). Body mass index, BAI, BDI-II, PSQI, and ESS significantly differed between groups. NAA/ Cr ratios were significantly reduced bilaterally, and left-sided MI/Cr and MI/NAA ratios were increased in OSA over controls. Significant positive correlations emerged between left insular MI/Cr ratios and apnea-hypopnea index values, right insular Cho/Cr ratios and BDI-II and BAI scores, and negative correlations appeared between left insular NAA/Cr ratios and PSQI scores and between right-side MI/Cr ratios and baseline and nadir change in O2 saturation.

CONCLUSIONS

Adults with obstructive sleep apnea showed bilaterally reduced N-acetylaspartate and left-side increased myo-inositol anterior insular metabolites, indicating neuronal damage and increased glial activation, respectively, which may contribute to abnormal autonomic and neuropsychologic functions in the condition. The activated glial status likely indicates increased inflammatory action that may induce more neuronal injury, and suggests separate approaches for glial and neuronal protection.

Interaction of sleep quality and sleep duration on impaired fasting glucose: a population-based cross-sectional survey in China

OBJECTIVES

To explore the interactions of sleep quality and sleep duration and their effects on impaired fasting glucose (IFG) in Chinese adults.

DESIGN

Cross-sectional survey.

SETTING

Community-based investigation in Xuzhou, China.

PARTICIPANTS

15 145 Chinese men and women aged 18-75 years old who fulfilled the inclusion criteria.

PRIMARY AND SECONDARY OUTCOME MEASURES

The Pittsburgh Sleep Quality Index was used to produce sleep quality categories of good, common and poor. Fasting blood glucose levels were assessed for IFG. Sleep duration was measured by average hours of sleep per night, with categories of <6, 6-8 and >8 h. The products of sleep and family history of diabetes, obesity and age were added to the logistic regression model to evaluate the addictive interaction and relative excess risk of interaction (RERI) on IFG. The attributable proportion (AP) of the interaction and the synergy index (S) were applied to evaluate the additive interaction of two factors. Bootstrap measures were used to calculate 95% CI of RERI, AP and S.

RESULTS

The prevalence of IFG was greatest in those with poor sleep quality and short sleep duration (OR 6.37, 95% CI 4.66 to 8.67; p<0.001) compared with those who had good sleep quality and 6-8 h sleep duration, after adjusting for confounders. After adjusting for potential confounders RERI, AP and S values (and their 95% CI) were 1.69 (0.31 to 3.76), 0.42 (0.15 to 0.61) and 2.85 (2.14 to 3.92), respectively, for the interaction between poor sleep quality and short sleep duration, and 0.78 (0.12 to 1.43), 0.61 (0.26 to 0.87) and -65 (-0.94 to -0.27) for the interaction between good sleep quality and long sleep duration.

CONCLUSIONS

The results suggest that there are additive interactions between poor sleep quality and short sleep duration.

Autonomic markers of impaired glucose metabolism: effects of sleep-disordered breathing

BACKGROUND

The association between diabetes and abnormalities in autonomic function is well-known, but it is not clear if this association can be extended to subjects with prediabetic impaired glucose metabolism (IGM). Sleep-disordered breathing (SDB), which commonly occurs in this population, is often overlooked. We sought to determine how autonomic function, monitored in an overnight sleep study setting, may be impaired in subjects with IGM and/or SDB.

METHODS

Polysomnograms (PSGs) selected from the Cleveland Family Study database were categorized into four groups: normal, SDB (respiratory disturbance index > 5/h), IGM, and both SDB and IGM. Impaired glucose metabolism was defined as an oral glucose tolerance test (OGTT) level > 140 mg/dl. Time-domain and frequency-domain indices of heart rate variability were used to quantify autonomic impairment. Baroreflex sensitivity determined using pulse transit time (BRS(PTT)), an indirect measure of baroreflex sensitivity based on spontaneous pulse transit time fluctuations, was used as a surrogate measure of baroreflex sensitivity.

RESULTS

Based on 31 PSGs from subjects (16 males, 15 females) ages 20.8-61.2 years, both SDNN and BRS(PTT) were found to be 20-25% lower in SDB and ~40% lower in IGM and SDB + IGM as compared to subjects without either condition. In analyses of continuous measures, mean standard deviation of 5 min R-R intervals (SDNN) and BRS(PTT) were found to be negatively correlated with OGTT following adjustment for age and body mass index. Oral glucose tolerance test and age were the two most significant factors for predicting SDNN and BRS(PTT).

CONCLUSIONS

Our analyses suggest that cardiac autonomic control is impaired in IGM, regardless of whether SDB is present. The abnormal autonomic function involves degradation of baroreflex regulation.

Effect of mild hyperglycemia on autonomic function in obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) has been hypothesized to cause a hypersympathetic state, which may be the mechanism for the increased incidence of cardiovascular disease in OSA. However, there is a high prevalence of hyperglycemia in OSA patients, which may also contribute to autonomic dysfunction.

METHODS

Thirty-five patients with OSA and 11 controls with average body mass index (BMI) of 32.0 ± 4.6 underwent polysomnography, glucose tolerance testing, autonomic function tests, lying and standing catecholamines, overnight urine collection, and baseline ECG and continuous blood pressure measurements for spectral analysis. A linear regression model adjusting for age and BMI was used to analyze spectral data, other outcome measures were analyzed with Kruskal-Wallis test.

RESULTS

Twenty-three OSA patients and two control patients had hyperglycemia (based on 2001 American Diabetes Association criteria). Apnea-hypopnea index (AHI) correlated with total power and low frequency (LF) power (r = 0.138, 0.177, p = 0.031; and r = 0.013) but not with the LF/high frequency (HF) ratio (p = 0.589). Glucose negatively correlated with LF systolic power (r = -0.171, p = 0.038) but not AHI (p = 0.586) and was marginally associated with pnn50, total power, LF, and HF power (p ranged from 0.07 to 0.08).

CONCLUSION

These data suggest that patients with OSA and mild hyperglycemia have a trend towards lower heart rate variability and sympathetic tone. Hyperglycemia is an important confounder and should be evaluated in studies of OSA and autonomic function.

Normal and elevated HbA1C levels correlate with severity of hypoxemia in patients with obstructive sleep apnea and decrease following CPAP treatment

PURPOSE

Sleep apnea is associated with higher HbA1C levels in patients with and without diabetes but whether its severity correlates with HbA1C levels ranging from normal to abnormal is less clear. Also, the effect of continuous positive airway pressure (CPAP) treatment on HbA1C levels in patients with sleep apnea is controversial.

METHODS

Thirty consecutive patients with obstructive sleep apnea were studied. None of the patients was previously diagnosed with diabetes. All patients underwent overnight polysomnography and HbA1C levels were determined. Patients were subdivided into three groups according to their HbA1C levels: <6% (n = 10), 6-6.5% (n = 10), and ≥6.5% (n = 10). Polysomnography and determination of HbA1C level were repeated in patients with severe sleep apnea (n = 12) following 3-5 months of CPAP treatment.

RESULTS

HbA1C levels across the spectrum from normal to abnormal correlated with severity of hypoxemia (average SpO(2), r = -0.43, p = 0.019 and percent time with SpO(2) < 90%, r = 0.48, p = 0.007). HbA1C levels decreased from a mean of 6.47 ± 0.67% to a mean of 6.28 ± 0.51%, p = 0.038 in 12 patients with severe sleep apnea following 3-5 months of CPAP treatment.

CONCLUSIONS

The severity of hypoxemia in patients with sleep apnea correlates with HbA1C levels ranging from normal to pre-diabetes and diabetes. CPAP treatment for 3-5 months decreases HbA1C levels in patients with severe sleep apnea.

Obstructive sleep apnea symptoms beyond sleepiness and snoring: effects of nasal APAP therapy

OBJECTIVE

The purpose of this study was to evaluate the prevalence and assess the response to nasal automatic positive airway pressure (APAP) therapy of less typical symptoms in patients diagnosed with obstructive sleep apnea (OSA), like fatigue, gasping, nocturia, nocturnal sweating, morning headaches, heartburn, and erectile dysfunction.

METHODS

Ninety-eight male patients with moderate to severe OSA were included in the study (n = 98). In the beginning of the study, an overnight sleep study was performed to all subjects using a five-channel recording device. Patients started APAP therapy with pre-determined minimum and maximum pressures of 4 and 15 cmH(2)0, respectively. The total Sleep Disorders Questionnaire was answered by all subjects before and 6 months after APAP therapy. Questions 4, 18, 23, 25, 58, 88, and 148 were used in this study. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) 17.0 software.

RESULTS

Subjects had a mean (SD) age of 55.1 (10.8) years and an average of 52.2 (21.4) apnea-hypopnea events per hour of sleep. At baseline, nocturia was the most prevalent symptom (38%), followed by nocturnal sweating (34%), gasping (30%), erectile dysfunction (25%), fatigue (23%), heartburn (15%), and morning headaches (10%). After 6 months of APAP therapy, a statistically significant reduction on the prevalence of all symptoms was observed, except for erectile dysfunction and morning headaches.

CONCLUSION

The findings suggest that APAP therapy is effective in controlling the majority of OSA symptoms beyond sleepiness and snoring.

Obstructive sleep apnea syndrome: natural history, diagnosis, and emerging treatment options

Sleep apnea is an entity characterized by repetitive upper airway obstruction resulting in nocturnal hypoxia and sleep fragmentation. It is estimated that 2%-4% of the middle-aged population has sleep apnea with a predilection in men relative to women. Risk factors of sleep apnea include obesity, gender, age, menopause, familial factors, craniofacial abnormalities, and alcohol. Sleep apnea has been increasingly recognized as a major health burden associated with hypertension and increased risk of cardiovascular disease and death. Increased airway collapsibility and derangement in ventilatory control responses are the major pathological features of this disorder. Polysomnography (PSG) is the gold-standard method for diagnosis of sleep apnea and assessment of sleep apnea severity; however, portable sleep monitoring has a diagnostic role in the setting of high pretest probability sleep apnea in the absence of significant comorbidity. Positive pressure therapy is the mainstay therapy of sleep apnea. Other treatment modalities, such as upper airway surgery or oral appliances, may be used for the treatment of sleep apnea in select cases. In this review, we focus on describing the sleep apnea definition, risk factor profile, underlying pathophysiologic mechanisms, associated adverse consequences, diagnostic modalities, and treatment strategies.

Sleep-disordered breathing and obesity: pathophysiology, complications, and treatment

Sleep-disordered breathing (SDB) is a medical condition that has increasingly recognized adverse health effects. Obesity is the primary risk factor for the development of SDB and contributes to cardiovascular and metabolic abnormalities in this population. However, accumulating evidence suggests that SDB may be related to the development of these abnormalities independent of obesity. Periodic apneas and hypopneas during sleep result in intermittent hypoxemia, arousals, and sleep disturbances. These pathophysiologic characteristics of SDB are likely mechanisms underlying cardiovascular and metabolic abnormalities including hypertension and other cardiovascular diseases, altered adipokines, inflammatory cytokines, insulin resistance, and glucose intolerance. Treatment of SDB with continuous positive airway pressure reverses some but not all of these abnormalities; however, studies to date have demonstrated inconsistent findings. Weight loss strategies, including diet, exercise, medications, and bariatric surgery, have been evaluated as a treatment strategy for SDB. In preliminary studies, dietary intervention and exercise reduced severity of SDB. One study demonstrated improvements in SDB severity using the weight-reducing medication sibutramine. In morbidly obese subjects, bariatric surgery effectively induces weight loss and improvement in SDB severity and symptoms, but long-term benefits remain uncertain. Large randomized trials are required to determine the utility of these strategies as long-term approaches to improving SDB and reducing associated complications.

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.

[Links between diabetes mellitus and sleep disorders: focusing on obstructive sleep apnea]

During the past decades obesity and diabetes have become increasingly common in modern, industrialized societies. At the same time sleep disorders, chronic sleep loss and sleep deprivation have also become more and more prevalent. There may be a positive feed back circle between the two disorders: sleep problems may affect endocrine function and metabolic conditions, while metabolic abnormalities potentially interfere with sleep regulation. Sleep-disordered breathing, obstructive sleep apnea in particular, has the strongest association with glucose metabolism. Prevalence and severity of obstructive sleep apnea are higher among diabetic individuals compared to non-diabetic subjects. Central obesity is an important risk factor both in diabetes and sleep apnea, and recent evidence supports the direct association between them. Diabetic neuropathy and metabolic syndrome parameters correlate with the presence and severity of obstructive sleep apnea. Intermittent hypoxia may cause insulin resistance, consequently increasing the risk of diabetes and further impairing glycemic control. Specialists in both diabetology and sleep medicine need to work together to prevent the negative interactions between these two groups of disorders and to also preserve patients' quality of life and to improve outcomes.

Peripheral neuropathy in survivors of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common form of cancer in children. Recent advances in treatment have led to dramatically improved survival rates. Standard ALL treatment includes multiple administrations of the chemotherapeutic drug vincristine, which is a known neurotoxic agent. Although peripheral neuropathy is a well-known toxicity among children receiving vincristine acutely, the long-term effects on the peripheral nervous system in these children are not clear. The objective of this study was to determine the prevalence of neuropathy and its impact on motor function and quality of life (QOL) among children who survived ALL. Thirty-seven survivors of childhood ALL aged 8-18 underwent evaluation for neuropathy through self-reported symptoms, standardized examinations, and nerve conduction studies (NCS). Functional impact of neuropathy was assessed using the Bruininks-Oseretsky test of Motor Proficiency (BOT-2). QOL was assessed using the PedsQL. Nerve conduction study abnormalities were seen in 29.7% of children who were longer than 2 years off therapy for ALL. Most children with an abnormal examination or NCS did not have subjective symptoms. Although overall motor function was below population norms on the BOT-2, presence of neuropathy did not significantly correlate with motor functional status or QOL.

Fatigue and autonomic dysfunction in non-alcoholic fatty liver disease

BACKGROUND

Fatigue is a significant symptom in nonalcoholic fatty liver disease (NAFLD) that impacts upon quality of life and is unrelated to liver disease severity. We examined the relationship between parameters of blood pressure regulation with perception of fatigue in NAFLD.

METHODS

Thirty-four non-diabetic subjects with histologically proven, non-cirrhotic NAFLD (26 [77%] males and 8 [23%] females) (mean +/- SD age 54 +/- 11) and 34 age, sex and BMI matched non-diabetic controls underwent subjective and objective evaluation of cardiovascular autonomic function (24 h blood pressure and head up tilt testing). All subjects completed the fatigue impact scale.

RESULTS

The NAFLD group had significantly higher autonomic symptom burden assessed using the orthostatic grading scale (OGS) compared to controls (4 +/- 4 vs. 1 +/- 2; p = 0.0003). Increasing orthostatic symptoms correlated with increasing fatigue (p = 0.006; r(2) = 0.3). Fatigue in NAFLD correlated inversely with 24 h measurement of systolic, diastolic and mean blood pressures (all p < 0.03; r(2) = 0.2). This relationship was predominantly related to lower blood pressure at night (p < 0.003; r(2) = 0.3). On head up tilt testing 57% of the NAFLD group had neurally-mediated hypotension (vasovagal syncope and/or orthostatic hypotension) (p = 0.006 compared to controls). The degree of blood pressure drop in response to standing correlated with fatigue severity (p = 0.008; r(2) = 0.3) and the autonomic symptom burden (OGS) (p = 0.03; r(2) = 0.2).

CONCLUSION

Autonomic symptoms are prevalent in NAFLD and associate with objective measures of autonomic dysfunction. Fatigue in NAFLD is associated with lower blood pressure and autonomic dysfunction. Studies are needed to determine whether this is a potential therapeutic target for fatigue in NAFLD.

The insulin gene variable number of tandemrepeats (INS VNTR) genotype and sleep disordered breathing in childhood obesity

Aim of our study is to verify the association between the genetic predisposition to hyperinsulinism due to the presence of the insulin gene (INS) I/I genotype and the development of sleep-related breathing disorders (SRBD) in obese children and adolescents. Two hundred and fifty-six obese children and adolescents (125 girls) have been investigated. As initial screening all subjects' mothers filled out the Sleep Disturbances Scale for Children (SDSC). The Sleep-Disordered Breathing (SDB) scale has been taken into account. Successively, a subgroup of 34 patients belonging to the first (14 children) and the last (20 children) SDB score quintiles underwent an overnight polysomnography and the apnea-hypopnea index (AHI) was evaluated. All subjects were genotyped for the INS VNTR and fasting insulin levels were evaluated. The population was divided into two groups according to the genotype: the first group was comprehensive of patients homozygotes for class I allele and the second group was composed by class III allele heterozygotes and homozygotes patients. Subjects I/I showed statistically signifIcant higher insulin levels (p<0.001) and SDB scores (p<0.001). Moreover, in the subgroup of patients investigated with polysomnography, class I homozygous subjects showed higher AHI compared to those patients carrying class III allele (p<0.001). Our data support the hypothesis that INS VNTR is associated with the development of SDB among obese children and adolescents.

Diabetes is an independent risk factor for severe nocturnal hypoxemia in obese patients. A case-control study

BACKGROUND

Type 2 diabetes mellitus (T2DM) and obesity have become two of the main threats to public health in the Western world. In addition, obesity is the most important determinant of the sleep apnea-hypopnea syndrome (SAHS), a condition that adversely affects glucose metabolism. However, it is unknown whether patients with diabetes have more severe SAHS than non-diabetic subjects. The aim of this cross-sectional case-control study was to evaluate whether obese patients with T2DM are more prone to severe SAHS than obese non-diabetic subjects.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty obese T2DM and 60 non-diabetic women closely matched by age, body mass index, waist circumference, and smoking status were recruited from the outpatient Obesity Unit of a university hospital. The exclusion criteria included chronic respiratory disease, smoking habit, neuromuscular and cerebrovascular disease, alcohol abuse, use of sedatives, and pregnancy. Examinations included a non-attended respiratory polygraphy, pulmonary function testing, and an awake arterial gasometry. Oxygen saturation measures included the percentage of time spent at saturations below 90% (CT90). A high prevalence of SAHS was found in both groups (T2DM:80%, nondiabetic:78.3%). No differences in the number of sleep apnea-hypopnea events between diabetic and non-diabetic patients were observed. However, in diabetic patients, a significantly increase in the CT90 was detected (20.2+/-30.2% vs. 6.8+/-13,5%; p = 0.027). In addition, residual volume (RV) was significantly higher in T2DM (percentage of predicted: 79.7+/-18.1 vs. 100.1+/-22.8; p<0.001). Multiple linear regression analyses showed that T2DM but not RV was independently associated with CT90.

CONCLUSIONS/SIGNIFICANCE

T2DM adversely affects breathing during sleep, becoming an independent risk factor for severe nocturnal hypoxemia in obese patients. Given that SAHS is a risk factor of cardiovascular disease, the screening for SAHS in T2DM patients seems mandatory.

Dysautonomia, a heuristic approach to a revised model for etiology of disease

Dysautonomia refers to a disease where the autonomic nervous system is dysfunctional. This may be a central control mechanism, as in genetically determined familial dysautonomia (Riley-Day Syndrome), or peripherally in the distribution of the sympathetic and parasympathetic systems. There are multiple reports of a number of different diseases associated with dysautonomia. The etiology of this association has never been explained. There are also multiple publications on dysautonomia associated with specific non-caloric nutritional deficiencies. Beriberi is the prototype of autonomic dysfunction. It is the best known nutritional deficiency disease caused by an imbalance between ingested calories and the vitamins required for their oxidation, particularly thiamin. Long thought to be abolished in modern medical thinking, there are occasional isolated reports of the full-blown disease in developed Western cultures. Apart from genetically and epigenetically determined disease, evidence is presented that marginal high calorie malnutrition, particularly with reference to simple carbohydrates, is responsible for widespread dysautonomia. The brain and heart are the organs that have a fast rate of oxidative metabolism and are affected early by any mechanism that reduces oxidative efficiency. It is hypothesized that this results in a chaotic state of the hypothalamic/autonomic/endocrine axis. Due to the lack of adequate automatic controls, this may be responsible in some cases for breakdown of organ systems through long-standing energy deficiency, thus leading eventually to organic disease.

Standing balance and trunk position sense in impaired glucose tolerance (IGT)-related peripheral neuropathy

Type 2 diabetes mellitus (T2DM) and pre-diabetes or impaired glucose tolerance (IGT) affect a large segment of the population. Peripheral neuropathy (PN) is a common complication of T2DM, leading to sensory and motor deficits. While T2DM-related PN often results in balance- and mobility-related dysfunction which manifests as gait instability and falls, little is known about balance capabilities in patients who have evidence of PN related to IGT (IGT-PN). We evaluated patients with IGT-PN on commonly-used clinical balance and mobility tests as well as a new test of trunk position sense and balance impairment, trunk repositioning errors (TREs). Eight participants aged 50-72 years with IGT-PN, and eight age- and gender-matched controls underwent balance, mobility and trunk repositioning accuracy tests at a university neurology clinic and mobility research laboratory. Compared to controls, IGT-PN participants had as much as twice the magnitude of TREs and stood approximately half as long on the single leg balance test. People with IGT-PN exhibit deficits in standing balance and trunk position sense. Furthermore, there was a significant association between performance on commonly-used clinical balance and mobility tests, and electrophysiological and clinical measures of neuropathy in IGT-PN participants. Because IGT-related neuropathy represents the earliest stage of diabetic neuropathy, deficits in IGT-PN participants highlight the importance of early screening in the dysglycemic process for neuropathy and associated balance deficits.

Obstructive sleep apnea and type 2 diabetes: interacting epidemics

Type 2 diabetes is a major public health concern with high morbidity, mortality, and health-care costs. Recent reports have indicated that the majority of patients with type 2 diabetes also have obstructive sleep apnea (OSA). There is compelling evidence that OSA is a significant risk factor for cardiovascular disease and mortality. Rapidly accumulating data from both epidemiologic and clinical studies suggest that OSA is also independently associated with alterations in glucose metabolism and places patients at an increased risk of the development of type 2 diabetes. Experimental studies in humans and animals have demonstrated that intermittent hypoxia and reduced sleep duration due to sleep fragmentation, as occur in OSA, exert adverse effects on glucose metabolism. Based on the current evidence, clinicians need to address the risk of OSA in patients with type 2 diabetes and, conversely, evaluate the presence of type 2 diabetes in patients with OSA. Clearly, there is a need for further research, using well-designed studies and long-term follow-up, to fully demonstrate a causal role for OSA in the development and severity of type 2 diabetes. In particular, future studies must carefully consider the confounding effects of central obesity in examining the link between OSA and alterations in glucose metabolism. The interactions among the rising epidemics of obesity, OSA, and type 2 diabetes are likely to be complex and involve multiple pathways. A better understanding of the relationship between OSA and type 2 diabetes may have important public health implications.

Obstructive sleep apnea in older adults

The "typical" presentation of obstructive sleep apnea (OSA) is chronic loud snoring and excessive daytime sleepiness in middle-aged obese men. OSA can result in increased risk for cardiovascular morbidity and mortality. The diagnostic features of OSA in older adults are similar to those in younger adults; however, the older adult may be less likely to seek medical attention or have the sleep disorder recognized because symptoms of snoring, sleepiness, fatigue, nocturia, unintentional napping, and cognitive dysfunction may be ascribed to the aging process itself or to other disorders. This article reviews the basic terminology and pathophysiology of sleep-disordered breathing, discusses why OSA may be even more prevalent in older adults than in the middle-aged group, and reviews similarities and differences between the two groups in the manifestations, consequences, and treatments of OSA.