Sleep Apnoea in Diabetic Patients with Autonomic Neuropathy

Risk of incident obstructive sleep apnoea in patients with type 1 diabetes: a population-based retrospective cohort study

AIMS/HYPOTHESIS

People with type 2 diabetes are at increased risk of developing obstructive sleep apnoea. However, it is not known whether people with type 1 diabetes are also at an increased risk of obstructive sleep apnoea. This study aimed to examine whether people with type 1 diabetes are at increased risk of incident obstructive sleep apnoea compared with a matched cohort without type 1 diabetes.

METHODS

We used a UK primary care database, The Health Improvement Network (THIN), to perform a retrospective cohort study between January 1995 and January 2018 comparing sleep apnoea incidence between patients with type 1 diabetes (exposed) and without type 1 diabetes (unexposed) (matched for age, sex, BMI and general practice). The outcome was incidence of obstructive sleep apnoea. Baseline covariates and characteristics were assessed at the start of the study based on the most recent value recorded prior to the index date. The Cox proportional hazards regression model was used to estimate unadjusted and adjusted hazard ratios, based on a complete-case analysis.

RESULTS

In total, 34,147 exposed and 129,500 matched unexposed patients were included. The median follow-up time was 5.43 years ((IQR 2.19-10.11), and the mean BMI was 25.82 kg/m2 (SD 4.33). The adjusted HR for incident obstructive sleep apnoea in patients with type 1 diabetes vs those without type 1 diabetes was 1.53 (95% CI 1.25, 1.86; p<0.001). Predictors of incident obstructive sleep apnoea in patients with type 1 diabetes were older age, male sex, obesity, being prescribed antihypertensive or lipid-lowering drugs, atrial fibrillation and depression.

CONCLUSIONS/INTERPRETATION

Individuals with type 1 diabetes are at increased risk of obstructive sleep apnoea compared with people without diabetes. Clinicians should suspect obstructive sleep apnoea in patients with type 1 diabetes if they are old, have obesity, are male, have atrial fibrillation or depression, or if they are taking lipid-lowering or antihypertensive drugs.

Sleep apnea and eye diseases: evidence of association and potential pathogenic mechanisms

Eye diseases are an important group of increasingly prevalent disorders that contribute very significantly to disability and represent a considerable health burden. Some data suggest that several of these diseases may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to intermediate mechanisms, such as intermittent hypoxia or sleep fragmentation. The aims of this systematic review were to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and the more relevant eye diseases as well as to evaluate the potential pathogenic mechanisms. There is a body of largely low-level evidence for the association of OSA with glaucoma, nonarteritic ischemic optic neuropathy, central serous chorioretinopathy, and diabetic retinopathy. Meta-analysis of available case-control studies shows that OSA increases the risk of glaucoma (pooled odds ratio: 1.50; 95% confidence interval: 1.25 to 1.80; P < .001), nonarteritic ischemic optic neuropathy (3.62; 1.94 to 6.76; P < .001), and diabetic retinopathy (1.57; 1.09 to 2.27; P = .02). Moreover, several pathogenic pathways have been identified, mainly related to hypoxic damage, mechanical stress, systemic inflammation, oxidative stress, sympathetic tone, and endothelial dysfunction. In contrast, information about the effect of apnea-hypopnea suppression on the development and progression of eye damage is either nonexistent or of a very low level of evidence. In conclusion, OSA has emerged as an additional potential risk factor for many eye diseases, although their link is weak and contradictory, so further examination is required.

CITATION

García-Sánchez A, Villalaín I, Asencio M, García J, García-Rio F. Sleep apnea and eye diseases: evidence of association and potential pathogenic mechanisms. J Clin Sleep Med. 2022;18(1):265-278.

Interactions between and Shared Molecular Mechanisms of Diabetic Peripheral Neuropathy and Obstructive Sleep Apnea in Type 2 Diabetes Patients

Type 2 diabetes (T2D) accounts for about 90% of all diabetes patients and incurs a heavy global public health burden. Up to 50% of T2D patients will eventually develop neuropathy as T2D progresses. Diabetic peripheral neuropathy (DPN) is a common diabetic complication and one of the main causes of increased morbidity and mortality of T2D patients. Obstructive sleep apnea (OSA) affects over 15% of the general population and is associated with a higher prevalence of T2D. Growing evidence also indicates that OSA is highly prevalent in T2D patients probably due to diabetic peripheral neuropathy. However, the interrelations among diabetic peripheral neuropathy, OSA, and T2D hitherto have not been clearly elucidated. Numerous molecular mechanisms have been documented that underlie diabetic peripheral neuropathy and OSA, including oxidative stress, inflammation, endothelin-1, vascular endothelial growth factor (VEGF), accumulation of advanced glycation end products, protein kinase C (PKC) signaling, poly ADP ribose polymerase (PARP), nitrosative stress, plasminogen activator inhibitor-1, and vitamin D deficiency. In this review, we seek to illuminate the relationships among T2D, diabetic peripheral neuropathy, and OSA and how they interact with one another. In addition, we summarize and explain the shared molecular mechanisms involved in diabetic peripheral neuropathy and OSA for further mechanistic investigations and novel therapeutic strategies for attenuating and preventing the development and progression of diabetic peripheral neuropathy and OSA in T2D.

Obstructive sleep apnea and type 2 diabetes in older adults

Both obstructive sleep apnea (OSA) and type 2 diabetes mellitus are commonly seen in older adults. Over the last decade, there has been increasing recognition that OSA is highly prevalent in persons with type 2 diabetes and related metabolic conditions such as insulin resistance and glucose intolerance. Intermittent hypoxemia and recurrent arousals in OSA trigger a repertoire of pathophysiological events, which can in turn alter glucose homeostasis and possibly increase the risk for type 2 diabetes. Conversely, there is evidence that type 2 diabetes may alter the progression and expression of sleep-disordered breathing.

Sleep apnea-hypopnea syndrome and type 2 diabetes. A reciprocal relationship?

Epidemiological data suggest that sleep apnea-hypopnea syndrome (SAHS) is independently associated with the development of insulin resistance and glucose intolerance. Moreover, despite significant methodological limitations, some studies report a high prevalence of SAHS in patients with type 2 diabetes mellitus (DM2). A recent meta-analysis shows that moderate-severe SAHS is associated with an increased risk of DM2 (relative risk=1.63 [1.09 to 2.45]), compared to the absence of apneas and hypopneas. Common alterations in various pathogenic pathways add biological plausibility to this relationship. Intermittent hypoxia and sleep fragmentation, caused by successive apnea-hypopnea episodes, induce several intermediate disorders, such as activation of the sympathetic nervous system, oxidative stress, systemic inflammation, alterations in appetite-regulating hormones and activation of the hypothalamic-pituitary-adrenal axis which, in turn, favor the development of insulin resistance, its progression to glucose intolerance and, ultimately, to DM2. Concomitant SAHS seems to increase DM2 severity, since it worsens glycemic control and enhances the effects of atherosclerosis on the development of macrovascular complications. Furthermore, SAHS may be associated with the development of microvascular complications: retinopathy, nephropathy or diabetic neuropathy in particular. Data are still scant, but it seems that DM2 may also worsen SAHS progression, by increasing the collapsibility of the upper airway and the development of central apneas and hypopneas.

Cardiovascular autonomic neuropathy contributes to sleep apnea in young and lean type 1 diabetes mellitus patients

Knowledge about association between sleep apnea and cardiovascular autonomic neuropathy (CAN) in type 1 diabetes mellitus (T1DM) might give some insight into the pathogenesis of this condition in these patients. In obese patients, excessive central adiposity, including a large neck circumference, can contribute to obstructive sleep apnea (OSA). Its presence in non-obese patients, however, indicates that it could be correlated with autonomic neuropathy. The aim of this study was to compare the prevalence of OSA in young and lean T1DM patients with and without CAN. We studied 20 adult, non-obese, T1DM patients who were divided into two groups according to the results of the cardiovascular autonomic reflex tests (CARTs). These two groups (9 with CAN and 11 without CAN) were compared to a control group of 22 healthy individuals, who were matched by age and BMI. A polysomnography was performed and sleep was analyzed. The CAN+ group had a significantly higher prevalence of sleep apnea compared to the other groups (67% CAN+; 23% CAN-; 4.5% controls: CAN+ vs. Control; p = 0.006 and CAN+ vs. CAN-; p = 0.02). The CAN- group had higher sleep efficiency compared to the CAN+ group, demonstrating impaired sleep architecture in diabetics with this chronic complication. In conclusion, OSA may be related to the presence of CAN in young and lean T1DM patients. It could contribute to worse the prognosis and reducing the quality of life of these patients without specific treatment of these conditions.

The Relationship between Diabetic Neuropathy and Sleep Apnea Syndrome: A Meta-Analysis

Aims. High prevalence of sleep apnea syndrome (SAS) has been reported in patients with diabetes. However, whether diabetic neuropathy (DN) contributes to this high prevalence is controversial. Our aim of this study is to compare the prevalence of SAS between patients with and without DN. Methods. Systematic literature searches were conducted for cross-sectional studies that reported the number of patients with DN and SAS using MEDLINE (from 1966 to Nov 5, 2012) and EMBASE (from 1974 to Nov 5, 2012). Odds ratios (ORs) of SAS related to DN were pooled with the Mantel-Haenszel method. Results. Data were obtained from 5 eligible studies (including 6 data sets, 880 participants, and 429 cases). Overall, the pooled OR of SAS in patients with DN compared with that in non-DN patients was significant (OR (95% CI), −1.95 (1.03–3.70)). The pooled OR of SAS was 1.90 (0.97–3.71) in patients with type 2 diabetes. Excluding data on patients with type 1 diabetes, a higher OR was observed in younger patients (mean age <60 years) than in those ≥60 years among whom the OR remained significant (3.82; 95% CI, 2.24–6.51 and 1.17; 95% CI, 0.81–1.68). Conclusions. Current meta-analysis suggested the association of some elements of neuropathy with SAS in type 2 diabetes. Further investigations are needed to clarify whether the association is also true for patients with type 1 diabetes.

Obstructive sleep apnoea and type 2 diabetes mellitus: a bidirectional association

Obstructive sleep apnoea and type 2 diabetes are common medical disorders that have important clinical, epidemiological, and public health implications. Research done in the past two decades indicates that obstructive sleep apnoea, through the effects of intermittent hypoxaemia and sleep fragmentation, could contribute independently to the development of insulin resistance, glucose intolerance, and type 2 diabetes. Conversely, type 2 diabetes might increase predisposition to, or accelerate progression of, obstructive and central sleep apnoea, possibly through the development of peripheral neuropathy and abnormalities of ventilatory and upper airway neural control. Although more research is needed to clarify the mechanisms underlying the bidirectional association between the two disorders, their frequent coexistence should prompt all health-care professionals to embrace clinical practices that include screening of a patient presenting with one disorder for the other. Early identification of obstructive sleep apnoea in patients with metabolic dysfunction, including type 2 diabetes, and assessment for metabolic abnormalities in those with obstructive sleep apnoea could reduce cardiovascular disease risk and improve the quality of life of patients with these chronic diseases.

Autonomic neuropathy increases the risk of obstructive sleep apnea in obese diabetics

BACKGROUND

Nonobese diabetics with diabetic autonomic neuropathy (DAN) show an elevated prevalence of obstructive sleep apnea-hypopnea (OSAH).

OBJECTIVE

It was the aim of this study to assess if the presence of DAN could further increase the risk of developing OSAH in obese diabetics.

METHODS

Eighteen obese diabetic patients, 8 with DAN [age 57 +/- 5 years, body mass index (BMI) 35 +/- 4] and 10 without DAN (age 56 +/- 8 years, BMI 37 +/- 5), were recruited. Ten age-matched obese subjects were studied as controls (age 53 +/- 12 years, BMI 34 +/- 3). All subjects underwent a cardiorespiratory sleep study in the in-hospital sleep laboratory to obtain the apnea-hypopnea index (AHI) and oxygen desaturation indices.

RESULTS

Diabetics with DAN (Ob-DAN+) had a higher AHI than diabetics without DAN (Ob-DAN-) and controls, amounting to 39.5 +/- 13 versus 15.8 +/- 12 (p < 0.01) and 19.3 +/- 21 (p < 0.05), respectively. A moderate-to-severe OSAH (AHI > or = 15) occurred in all Ob-DAN+ and only in 4 Ob-DAN- and 4 control patients. Moreover, the indices reflecting the impairment of oxygen saturation (SaO(2)) during sleep such as the mean lowest SaO(2) and sleep time with a SaO(2) <90% were more severely affected in Ob-DAN+ patients compared with the other groups and were associated with longer obstructive respiratory events.

CONCLUSIONS

Apneas-hypopneas are more frequent and last longer in Ob-DAN+ than in other obese subjects, with or without diabetes.

Association of sleep apnea and type II diabetes: a population-based study

RATIONALE

Cross-sectional association has been reported between sleep-disordered breathing (SDB) and insulin resistance, but no prospective studies have been performed to determine whether SDB is causal in the development of diabetes.

OBJECTIVES

The purpose of our study was to investigate the prevalence and incidence of type II diabetes in subjects with SDB and whether an independent relationship exists between them.

METHODS

A cross-sectional and longitudinal analysis was performed in 1,387 participants of the Wisconsin Sleep Cohort. Full polysomnography was used to characterize SDB. Diabetes was defined in two ways: (1) physician-diagnosis alone or (2) for those with glucose measurements, either fasting glucose > or = 126 mg/dl or physician diagnosis.

MEASUREMENTS AND MAIN RESULTS

There was a greater prevalence of diabetes in subjects with increasing levels of SDB. A total of 14.7% of subjects with an apnea-hypopnea index (AHI) of 15 or more had a diagnosis of diabetes compared with 2.8% of subjects with an AHI of less than 5. The odds ratio for having a physician diagnoses of diabetes mellitus with an AHI of 15 or greater versus an AHI of less than 5 was 2.30 (95% confidence interval, 1.28-4.11; p = 0.005) after adjustment for age, sex, and body habitus. The odds ratio for developing diabetes mellitus within 4 yr with an AHI of 15 or more compared with an AHI of less than 5 was 1.62 (95% confidence interval, 0.67-3.65; p = 0.24) when adjusting for age, sex, and body habitus.

CONCLUSIONS

Diabetes is more prevalent in SDB and this relationship is independent of other risk factors. However, it is not clear that SDB is causal in the development of diabetes.

Hypertension in patients with cushing’s disease: Pathophysiology, diagnosis, and management

Hypertension is a very common comorbidity in patients with Cushing's disease/syndrome, resulting from the interplay of several pathophysiologic mechanisms, including stimulation of mineralocorticoid and glucocorticoid receptors as well as the associated insulin resistance, sleep apnea, and overexpression of renin-angiotensin system. Although treatment of Cushing's disease results in resolution or amelioration of hypertension in these patients, a significant proportion of patients do not achieve complete cure or require a prolonged period of time for complete response to therapy. Therefore, therapeutic strategies for Cushing's-specific hypertension are necessary to decrease morbidity and mortality associated with this disease. In this review, we discuss the pathophysiology of hypertension in patients with Cushing's disease, highlighting the therapeutic options, including the exciting new developments in the role of peroxisome proliferator-activated receptor (PPAR)-g agonists in the management of this patient population.

Upper airway EMG responses to acute hypoxia and asphyxia are impaired in streptozotocin-induced diabetic rats

Obstructive sleep apnoea (OSA) is a major clinical disorder that is characterised by multiple episodes of upper airway obstruction due to failure of the upper airway dilator muscles to maintain upper airway patency. The incidence of OSA is high in many endocrine disorders including both insulin-dependent and non-insulin-dependent diabetes but the reasons for this are not known. We wished to test the hypothesis that central respiratory motor output to the upper airway muscles is preferentially impaired in a rat model of diabetes mellitus. Sternohyoid (SH) and diaphragm (DIA) EMG activities were recorded in control and streptozotocin (STZ)-induced diabetic rats during normoxia, hypoxia (7.5% O2 in N2) and asphyxia (7.5% O2 and 3% CO2) under pentobarbitone anaesthesia. SH EMG responses to acute hypoxia and asphyxia were significantly impaired in STZ-induced diabetic rats compared to control animals (+47.1 +/- 5.7 vs. +11.7 +/- 1.9% during hypoxia in control and diabetic animals respectively and +56.5 +/- 7.9 vs. +15.7 +/- 5.0% during asphyxia). However, DIA EMG responses to hypoxia and asphyxia were not different for the two groups. We propose that the higher prevalence of OSA in diabetic patients is related to preferential impairment of cranial motor output to the dilator muscles of the upper airway in response to physiological stimuli.

Diabetes and sleep disturbances: findings from the Sleep Heart Health Study

OBJECTIVE

To test the hypothesis that diabetes is independently associated with sleep-disordered breathing (SDB), and in particular that diabetes is associated with sleep abnormalities of a central, rather than obstructive, nature.

RESEARCH DESIGN AND METHODS

Using baseline data from the Sleep Heart Health Study (SHHS), we related diabetes to 1). the respiratory disturbance index (RDI; number of apneas plus hypopneas per h of sleep); 2). obstructive apnea index (OAI; >or=3 apneas/h of sleep associated with obstruction of the upper airway); 3). percent of sleep time < 90% O(2) saturation; 4). central apnea index (CAI; >or=3 apneas [without respiratory effort]/h sleep); 5). occurrence of a periodic breathing (Cheyne Stokes) pattern; and 6) sleep stages. Initial analyses excluding persons with prevalent cardiovascular disease (CVD) were repeated including these participants.

RESULTS

Of the 5874 participants included in this report, 692 (11.8%) reported diabetes or were taking oral hypoglycemic medications or insulin and 1002 had prevalent CVD. Among the 4872 persons without CVD, 470 (9.6%) had diabetes. Diabetic participants had worse CVD risk factor profiles than their nondiabetic counterparts, including higher BMI, waist and neck circumferences, triglycerides, higher prevalence of hypertension, and lower HDL cholesterol (P < 0.001, all). Descriptive analyses indicated differences between diabetic and nondiabetic participants in RDI, sleep stages, sleep time <90% O(2) saturation, CAI, and periodic breathing (P < 0.05, all). However, multivariable regression analyses that adjusted for age, sex, BMI, race, and neck circumference eliminated these differences for all sleep measures except percent time in rapid eye movement (REM) sleep (19.0% among diabetic vs. 20.1% among nondiabetic subjects, P < 0.001) and prevalence of periodic breathing (odds ratio [OR] for diabetic subjects versus nondiabetic subjects 1.80, 95% CI 1.02-3.15). Additionally, adjusted analyses showed diabetes was associated with nonstatistically significant elevations in the odds of an increased central breathing index (OR 1.42, 95% CI 0.80-2.55). Addition to the analysis of the 1002 persons with prevalent CVD (including 222 people with diabetes) did not materially change these results.

CONCLUSIONS

These data suggest that diabetes is associated with periodic breathing, a respiratory abnormality associated with abnormalities in the central control of ventilation. Some sleep disturbances may result from diabetes through the deleterious effects of diabetes on central control of respiration. The high prevalence of SDB in diabetes, although largely explained by obesity and other confounders, suggests the presence of a potentially treatable risk factor for CVD in the diabetic population.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Diabetes and cardiovascular disease

This review focuses on several topics related to the epidemiology of diabetes and cardiovascular disease (CVD). These include the CVD risk factors common in the metabolic syndrome, behavioral risk factors and diabetes, gender differences in the association between diabetes and CVD risk, and how the clinical definition of diabetes influences the association of diabetes and CVD. Nontraditional risk factors potentially linking diabetes and CVD are also discussed, including chronic inflammation, advanced glycation endpoints, autonomic neuropathy, sleep-disordered breathing, and genetic susceptibility to diabetes-associated CVD risk.

Influence of autonomic neuropathy of different severities on the hypercapnic drive to breathing in diabetic patients

To investigate the effects of the autonomic nervous system on control of breathing, the neuromuscular (mouth occlusion pressure at 0.1 s after onset of inspiration [P0.1]) and ventilatory (minute ventilation [VE]) response to progressive hyperoxic hypercapnia was assessed in diabetic patients with autonomic dysfunction of different severity. Eighteen diabetics with autonomic neuropathy, nine with parasympathetic damage (DANp), and nine with parasympathetic and sympathetic damage (DANp+s), as indicated by marked postural hypotension, low increment of diastolic BP during sustained handgrip, and lowest resting catecholamine plasma levels, were studied together with a group of 10 diabetic patients without autonomic neuropathy (D) and a group of 10 normal subjects (C). All subjects had pulmonary function tests, including maximal voluntary ventilation and diffusion of carbon monoxide, measurements of respiratory muscle strength as maximal inspiratory mouth pressure (MIP) and maximal expiratory mouth pressure (MEP), and a CO2 rebreathing test (Read's method). Although in the normal range, lung volumes and FEV1 and forced expiratory flows were lower in the DANp and DANp+s groups than in the D and C groups, MIP and MEP were similar among C and diabetic groups, as well as resting P0.1, VE, tidal volume (VT), and respiratory rate (RR). The slope of the linear relationship between P0.1 and end-tidal PCO2 (PETCO2) was higher in DANp+s (0.63+/-0.07 cm H2O/mm Hg) than in C (0.45+/-0.06 cm H2O/mm Hg; p<0.05) and three times greater in DANp+s than in D (0.26+/-0.03 cm H2O/mm Hg; p<0.001) and DANp (0.24+/-0.03 cm H2O/mm Hg; p<0.001), who in turn showed a lower deltaP0.1/deltaPETCO2 than C. The VE increase with increasing PETCO2 was greater in DANp+s (3.70+/-0.85 L/min/mm Hg) than in DANp (2.13+/-0.20 L/min/mm Hg; p<0.05) and D (2.37+/-0.40 L/min/mm Hg; p=0.07), but not significantly higher from that of C (3.17+/-0.36 L/min/mm Hg). No differences were found for deltaVT/deltaPETCO2 among the groups, whereas the deltaRR/deltaPETCO2 relationship was steeper in DANp+s than in DANp (p<0.05) and D (p=0.055). These data reflect a depressed CO2 response both in D and DANp. The presumable decrease of the sympathetic nerve traffic in DANp+s appears to reverse this abnormality. DANp+s, however, exhibit an enhanced CO2 neuromuscular response even in respect to C, suggesting that the sympathetic nervous system might modulate the output of the respiratory centers to hypercapnic stimulus.

Chronobiology and chronotherapy in medicine

There is a fascinating and exceedingly important area of medicine that most of us have not been exposed to at any level of our medical training. This relatively new area is termed chronobiology; that is, how time-related events shape our daily biologic responses and apply to any aspect of medicine with regard to altering pathophysiology and treatment response. For example, normally occurring circadian (daily cycles, approximately 24 hours) events, such as nadirs in epinephrine and cortisol levels that occur in the body around 10 PM to 4 AM and elevated histamine and other mediator levels that occur between midnight and 4 AM, play a major role in the worsening of asthma during the night. In fact, this nocturnal exacerbation occurs in the majority of asthmatic patients. Because all biologic functions, including those of cells, organs, and the entire body, have circadian, ultradian (less than 22 hours), or infradian (greater than 26 hours) rhythms, understanding the pathophysiology and treatment of disease needs to be viewed with these changes in mind. Biologic rhythms are ingrained, and although they can be changed over time by changing the wake-sleep cycle, these alterations occur over days. However, sleep itself can adversely affect the pathophysiology of disease. The non-light/dark influence of biologic rhythms was first described in 1729 by the French astronomer Jean-Jacques de Mairan. Previously, it was presumed that the small red flowers of the plant Kalanchoe bloss feldiuna opened in the day because of the sunlight and closed at night because of the darkness. When de Mairan placed the plant in total darkness, the opening and closing of the flowers still occurred on its intrinsic circadian basis. It is intriguing to think about how the time of day governs the pathophysiology of disease. On awakening in the morning, heart rate and blood pressure briskly increase, as do platelet aggregability and other clotting factors. This can be linked to the acrophase (peak event) of heart attacks. During the afternoon we hit our best mental and physical performance, which explains why most of us state that "I am not a morning person." Even the tolerance for alcohol varies over the 24-hour cycle, with best tolerance around 5 pm (i.e. "Doctor, I only have a couple of highballs before dinner"). Thus, all biologic functions, from those of the cell, the tissue, the organs, and the entire body, run on a cycle of altering activity and function.(ABSTRACT TRUNCATED AT 400 WORDS)

Nocturnal oxygen desaturation in diabetic patients with severe autonomic neuropathy

The aim of the study was to assess whether diabetic patients with autonomic neuropathy suffer from arterial oxygen desaturation during sleep. Two groups of subjects were evaluated: group I consisted of 12 patients with cardiovascular autonomic neuropathy (five with insulin-dependent diabetes mellitus (IDDM) and seven with non-insulin-dependent diabetes mellitus (NIDDM)). Group II consisted of 8 healthy subjects. Age, percentage male and body mass index (BMI) were similar in both groups. Exclusion criteria were abnormalities in arterial gas measurements, chest X-ray, spirometry or the presence of cardiac arrhythmias, obesity, uremia, alcohol abuse and use of drugs other than insulin and oral hypoglicemic agents. The results of arterial oximetry when the subjects were awake showed no differences between the two groups. However, during sleep, diabetics with autonomic neuropathy had an increased number of desaturation episodes under 85% and those episodes were more prolonged. The results suggest that diabetics with autonomic neuropathy might have abnormal control of respiration that is apparent only during sleep.

Nasal continuous positive airway pressure in the perioperative management of patients with obstructive sleep apnea submitted to surgery

Anesthetic, sedative, and analgesic drugs have been shown in animals and humans to selectively impair upper airway muscle activity. In patients with an already compromised upper airway, these drugs may further jeopardize upper airway patency, especially during sleep. Thus, patients with obstructive sleep apnea syndrome (OSAS) are at high risk for surgery because of the use of the aforementioned drugs in the perioperative period. It has been recommended that such drugs should be avoided or used with extreme caution in patients with OSAS submitted to surgery. We report herein on 16 adult patients with documented OSAS undergoing various types of surgical procedures, including coronary artery bypass surgery. Anesthesia was carried on with the usual type of drugs for each type of surgery. Postoperative opioid analgesia and sedation were not restricted. The first patient, whose OSAS was diagnosed but not treated, died after various complications, including a respiratory arrest in the ward. The second patient experienced serious postoperative complications until a treatment for OSAS with nasal continuous positive airway pressure (N-CPAP) was instituted, and thereafter he made an uneventful recovery. The 14 following patients were started on N-CPAP before surgery, were put on N-CPAP as soon as extubated, on a near-continuous basis, for 24 to 48 h and thereafter for all sleep periods. None of them had major complications. The intensive care unit and hospital stays were the normal ones for each type of surgery in our institution. We conclude that N-CPAP started before surgery and resumed immediately after extubation allowed us to safely manage a variety of surgical procedures in patients with OSAS, and to freely use sedative, analgesic, and anesthetic drugs without major complications. Every effort should be made to identify patients with OSAS and institute N-CPAP therapy before surgery.

Diabetes, sleep disorders, and male sexual function

The prevalence and role of sleep disorders in the sexual problems of diabetic patients remain unexplored. This study was conducted on 40 diabetic men carefully screened to exclude the confounding effects of other medical illnesses or drugs likely to impair sexual function and 40 age-matched healthy volunteers. They underwent an extensive psychosexual interview, medical and psychiatric evaluations, and three recorded nights in a sleep laboratory. Electroencephalogram, eye movements, muscle tone, and nocturnal penile tumescence were monitored continuously. Respiratory airflow and bilateral anterior tibialis recordings were obtained during the first sleep session. Diabetic men had significantly higher prevalences of respiratory and periodic leg movement disturbances during sleep. There was clinical, although not nocturnal penile tumescence, evidence suggesting that respiratory abnormalities during sleep are associated with erectile difficulties in diabetic men. Future studies should include blood oxygenation and respiratory effort measures to clarify the significance of sleep-related airflow disturbances in diabetic patients.

The severity of obstructive sleep apnoea is associated with insulin resistance

Oral glucose tolerance tests (OGTT) were performed on eighteen patients with suspected obstructive sleep apnoea who also completed a whole-night polygraphic recording with oximetry. Insulin resistance indices (IRI) were calculated as the product of areas under glucose and insulin curves. In the resulting multiple regression analysis the dependent variable was IRI and the independent variables were age, body mass index (BMI) and the number of nocturnal hypoxic episodes with over 4% desaturation per hour (ODI4). ODI4 was between 4.6 and 70 (median 22.3); IRI ranged from 2.20 to 33.55 (median 7.50). In the regression model the coefficient of determination (R2) for IRI was 0.441 (F-ratio = 3.681, P = 0.038). The strongest determinant of IRI was ODI4 and the regression coefficient of BMI was not significantly different from zero even when possible outliers were excluded. It was found that insulin resistance is related to the severity of sleep anoea. This may be due to a hypoxia-induced hormonal stress reaction which decreases tissue insulin sensitivity. Since upper body obesity is associated with both insulin resistance and sleep apnoea, the distribution of fat should be taken into account in future studies.

Sleep patterns and blood pressure variability in patients with pure autonomic failure

Sleep patterns and 24-h blood pressure variability were studied in four female patients (age range: 56-82 years) with pure autonomic failure. All patients had severe symptomatic postural hypotension, without neurological deficits. In these patients the following patterns were observed: (i) a reversed diurnal blood pressure pattern, with the highest values observed at sleep onset; (ii) a prolonged sleep latency and increased amount of stage 3 sleep; (iii) difficulty with getting up after awakening in the morning, due to severe postural hypotension; (iv) an absence of prominent respiratory abnormalities during sleep; and (v) a dissociation between respiratory and haemodynamic findings. It is concluded that isolated deficiency of presumed postganglionic autonomic function influences sleep architecture, probably through absence of buffering of diurnal haemodynamic alterations, such as by postural hypotension and its consequences for body fluid volume regulation. This may be of relevance when sleep patterns are studied in other types of autonomic failure with postural hypotension involving central or preganglionic lesions, as in patients with the Shy-Drager syndrome or multiple system atrophy.

Pulmonary complications in diabetes mellitus

Diabetes mellitus produces serious complications in several major organ systems. The pulmonary complications, although uncommon and not well recognized, may be life-threatening. We describe a 20-year-old patient with diabetic ketoacidosis in whom pulmonary zygomycosis developed. This condition was complicated by stenosis of the left upper lobe bronchus despite successful treatment of the zygomycosis. Bronchial obstruction has become a well-recognized complication of pulmonary zygomycosis. In addition to infections caused by Zygomycetes, mycobacteria, viruses, and bacteria, the pulmonary complications described in patients with diabetes include pulmonary edema, disordered breathing during sleep, and reductions in elastic recoil of the lungs, diffusing capacity of the lungs for carbon monoxide, and bronchomotor tone. Other reported complications are respiratory alkalosis, cardiorespiratory arrest, pneumothorax, pneumomediastinum, plugging of the airways with mucus, and aspiration pneumonia attributable to diabetic gastroparesis.

Ventilatory and heart rate responses to hypoxia and hypercapnia in patients with diabetes mellitus

The ventilatory response to isocapnic progressive hypoxia and hyperoxic progressive hypercapnia in 24 diabetic patients were compared with those of sex and age matched normal control subjects. The heart rate response to hypoxia was also measured in both groups. In diabetic patients the ventilatory and heart rate responses to hypoxia were significantly lower than those in the control group (0.10 v 0.24 l/min/% fall/m2 and 0.5 l v 1.27 beats/min/% fall respectively). The ventilatory response to hypercapnia was significantly higher (1.09 v 0.76 l/min/mm Hg/m2) in the diabetic patients. There was a significant correlation between the hypoxic ventilatory response and the heart rate response in diabetic patients (r = 0.56), but not in the control group (r = 0.28). In addition, both the ventilatory and the heart rate responses to hypoxia in diabetic patients had weak but significant correlations with the heart rate variation during deep breathing. It is concluded that the ventilatory and heart rate responses to hypoxia in diabetic patients are impaired, whereas the ventilatory response to hypercapnia is well preserved.

Prolonged QT period in diabetic autonomic neuropathy: a possible role in sudden cardiac death?

Twenty four men with insulin dependent diabetes and different degrees of autonomic neuropathy were studied to establish the response of the QT interval to various heart rates. Nine men with autonomic neuropathy had a longer QT interval than 13 healthy individuals and 15 patients who had diabetes without, or with only mild, autonomic neuropathy. Those with autonomic neuropathy also had a proportionally greater lengthening of the QT interval for a given increase in RR interval. The results of this study suggest a basis for the finding that sudden death is more common in patients with diabetic autonomic neuropathy.

Autonomic neuropathy: its diagnosis and prognosis

Autonomic neuropathy is now well established as a relatively common and significant complication of diabetes mellitus. Its importance has been clarified in recent years during which the extent of autonomic control over all areas of body function has been defined. Using simple cardiovascular reflex tests, autonomic abnormalities can be demonstrated without any corresponding symptoms. The often stated concept of 'patchy' involvement in diabetic autonomic neuropathy should now be rejected as too should the view that autonomic neuropathy is either 'present' or 'absent' based on a single test result. When generalized and predominantly metabolic disturbances, as in diabetes, give rise to impaired nerve function, autonomic as well as somatic components of the nerve are affected. Where damage is severe this leads to the characteristic florid picture of symptomatic autonomic neuropathy with its particularly poor prognosis. For the physician in a busy clinic, much of the theoretical and experimental basis for autonomic neuropathy may not appear of direct relevance. However, he has now to be aware of the clinical implications of autonomic damage in the diabetic. This may have particular relevance in the care of the diabetic foot (see Chapter 10), the recognition of many of the vague symptoms associated with autonomic damage, the treatment of disabling features such as postural dizziness and nocturnal diarrhoea, and an awareness of the poor prognosis associated with symptomatic autonomic neuropathy. He will also need to be alert to the dangers of general anaesthesia in such patients, and the possibility of sudden unexpected deaths. Diabetic autonomic neuropathy causes widespread abnormalities, some of which are clinically apparent, some of which can be detected by sensitive tests, and others which have yet to be discovered. Inclusion of the neuropeptides and other hormones within the compass of autonomic control has opened up a whole new area of investigative interest, with many complex interrelationships which still need to be unravelled. This should lead to better understanding of the pathophysiological processes that cause damage to diabetic nerves. With so much research effort directed towards better glycaemic control and aldose reductase inhibitors (see Chapter 8), it may eventually be possible to reverse or prevent this potentially disabling and lethal complication of diabetes.

Diabetic autonomic dysfunction, blood pressure, and sleep

We measured serially the blood pressure of 7 normal controls and 11 Type I insulin-dependent and 6 Type II non-insulin-dependent diabetic patients during sleep. All subjects underwent 2 or 3 nights of monitoring during which blood pressure was measured with an arteriosonde, a Doppler-type system with a cuff that automatically inflates every 15 minutes. All 7 normal controls, 3 of 11 Type I, and all 6 Type II diabetic patients had normal results from bedside tests of autonomic function. The Type I patients had abnormal systolic blood pressure measurements throughout the night. Unlike normal controls and Type II diabetics, their blood pressure did not rise progressively in the early morning hours. During rapid eye movement (REM) sleep, their blood pressure measurements were significantly higher and lower than values measured during non-REM sleep, in sharp contrast to those in the other two groups, whose REM sleep-related blood pressure values were slightly above the preceding non-REM sleep measurements.

Anaesthesia in dysautonomia: further complications

A case is described of a patient, known to be suffering from idiopathic autonomic neuropathy, who underwent general anaesthesia for repair of a fractured neck of femur. In addition to profound hypotension, unexpected respiratory depression occurred which has not previously been described in this condition. Other unusual features of this patient's condition are also discussed.

Abnormal breathing patterns during sleep in diabetes

Nineteen diabetic patients, 12 type I (insulin-dependent) and 7 type II (late-onset, non-insulin-dependent), underwent nocturnal polygraphic monitoring after a daytime medical evaluation that included tests of vagal responses and, in 6 patients, pulmonary function and hypercapnic and hypoxic responses. Five lean type I patients had abnormal sleep-related breathing patterns with central or obstructive sleep apnea and brief breathing irregularities during stages 3 to 4 non-rapid-eye-movement sleep, compared with only 1 overweight type II diabetic with moderate obstructive sleep apnea. There was no correlation between daytime ventilatory study findings and abnormal breathing patterns during sleep, but there was a clear relationship between neuropathy and sleep-related breathing abnormalities in type I insulin-dependent diabetics.

Sleep apnoea following cervical cord surgery

Two patients who developed sleep apnoea following upper cervical cord surgery are described. The underlying mechanisms and management of the sleep apnoea syndrome are discussed.

Sleep structure and nocturnal disordered breathing in familial dysautonomia

In 13 patients with familial dysautonomia sleep recordings were obtained to investigate the possibility that autonomic nervous system dysfunction plays a role in disordered breathing during sleep. Sleep structure in some of our patients was abnormal, showing decreased amount of REM sleep and increased REM latencies. All patients showed breathing disorders in sleep. The average number of apneic spells was 73.4 per night; 77% of the patients had more than 50 apneic spells per night. Abnormal breathing patterns were not uniform and were independent of patient's primary complaints. Typically, even severe respiratory irregularities were not associated with the usual cardiac response, indicating that our patients had "cardiac dysautonomia".

Sleep apnoea syndrome and anaesthesia

The sleep apnoea syndrome is reviewed, defined, and classified. Particular emphasis is placed on the identification of a patient population that is prone to sleep apnoea and the diseases and syndromes that are associated with it. For anaesthetists, direct enquiry into daytime and nighttime sleep abnormalities and careful examination of the upper airway are important for preoperative detection of these patients and especially patients with obstructive sleep apnoea who might present for anaesthesia and operation. A typical case is reported and details of the preoperative, peroperative and postoperative management are discussed.