Evaluation of peripheral and autonomic neuropathy among patients with newly diagnosed impaired glucose tolerance

A Systematic Review and Meta-Analysis of the Prevalence of Small Fibre Impairment in Patients with Fibromyalgia

Converging evidence shows that patients with fibromyalgia syndrome have signs of small fibre impairment, possibly leading to pain and autonomic symptoms, with a frequency that has not yet been systematically evaluated. To fill this gap, our review aims to define the frequency of somatic and autonomic small fibre damage in patients with fibromyalgia syndrome, as assessed by objective small fibre-related testing. We found 360 articles on somatic and autonomic small fibre assessment in patients with fibromyalgia. Out of the 88 articles assessed for eligibility, 20 were included in the meta-analysis, involving 903 patients with fibromyalgia. The estimated prevalence of somatic small fibre impairment, as assessed with skin biopsy, corneal confocal microscopy, and microneurography, was 49% (95% confidence interval (CI): 39–60%, I² = 89%), whereas the estimated prevalence of autonomic small fibre impairment, as assessed with heart rate variability, sympathetic skin response, skin conductance, and tilt testing, was 45% (95% CI: 25–65%, I² = 91%). Our study shows that a considerable proportion of patients with fibromyalgia have somatic and autonomic small fibre impairment, as assessed by extensive small fibre-related testing. Nevertheless, the heterogeneity and inconsistencies across studies challenge the exact role of small fibre impairment in fibromyalgia symptoms.

Frequency of carpal tunnel syndrome and hand dysfunction in prediabetes: A cross-sectional, controlled study

Objectives

This study aims to evaluate the frequency of carpal tunnel syndrome (CTS), to investigate the impairment of hand functions in patients with prediabetes (PD), and to compare laboratory findings of PD patients with and without CTS.

Patients and methods

Between June 2018 and January 2019, a total of 115 patients (29 males, 86 females; mean age: 51.4±11.8 years; range, 24 to 78 years) who were recently diagnosed with PD and a total of 54 healthy participants (17 males, 37 females; mean age: 48.4±13.2 years; range, 21 to 78 years) as the control group were included. Demographic and clinical data of the patients including oral glucose tolerance test (OGTT) and glycated hemoglobin (HbA1c) were recorded, and both groups were examined for the presence of CTS. Clinically suspected CTS was confirmed by electrodiagnostic studies. The hand grip strength (HGS) was measured and hand functions were evaluated using the Duruöz Hand Index (DHI).

Results

There were no significant differences in the age, sex, occupation, body mass index (BMI), or insulin resistance between the groups. A total of 24 (20.9%) patients with PD and eight (14.8%) healthy controls had CTS (p=0.349). Hand functions were worse in the PD patients than the control group (p=0.044). Age, occupation, BMI, insulin resistance, OGTT at 0 and 2 h, and HbA1c values were similar between the PD patients with or without CTS.

Conclusion

Our study, for the first time, reveals that CTS is slightly more common and hand functions are impaired in PD compared to the healthy individuals. Based on these findings, we suggest that hand functions should be evaluated in PD patients.

Analysis of risk factors of diabetes peripheral neuropathy in type 2 diabetes mellitus and nursing intervention

The aim of the present study was to explore the risk factors of diabetes peripheral neuropathy (DPN) in type 2 diabetes mellitus, and to propose corresponding nursing intervention measures to provide the basis for early diagnosis, treatment and prevention of DPN. A retrospective analysis was performed on 130 patients with type 2 diabetes mellitus (T2DM) in the communities surrounding our hospital from January 2017 to June 2018. They were divided into a DPN group (62 cases) and non-DPN group (control group, 68 cases). First, a univariate analysis was performed. DPN or non-DPN were used as dependent variables, and statistically significant parameters in univariate analysis were used as independent variables. Multivariate logistic regression analysis was included to analyze the peripheral nerves in type 2 diabetes mellitus. At the same time, the patients with DPN were given individualized comprehensive nursing intervention. Univariate analysis showed that body mass index (BMI), diabetes duration, smoking history, drinking history, family history of diabetes, fasting blood glucose (FBG), postprandial blood glucose (PBG), glycosylated hemoglobin (HbA1c), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), systolic blood pressure, 24-h urine microalbumin excretion (24hmALB), glomerular filtration rate (GFR), serum creatinine in DPN group were significantly different from those in the control group (P<0.05). Logistic regression analysis showed that the duration of diabetes, PBG, glycosylated hemoglobin (HbA1c), HDL-C, 24hmALB, and GFR were independent risk factors for DPN. The quality of life [Physiological function (PF), Role-physical (RP), Role-emotional (RE), General health (GH), Social function (SF), Mental health (MH), Bodily pain (BP), Vitality (VT)] in the DPN group was significantly improved after six months of individualized nursing intervention compared with that before intervention (P<0.05). In conclusion, the high risk factors of DPN should be identified as early as possible, to prevent and delay the occurrence and development of diabetes peripheral neuropathy, so as to improve the quality of life of these patients.

Chronic Microvascular Complications in Prediabetic States-An Overview

A prediabetic state is a major risk factor for the development of diabetes, and, because of an identical pathophysiological background of both conditions, their prevalence increases parallelly and equally fast. Long-term hyperglycemia is the main cause inducing chronic complications of diabetes, yet the range of glucose levels at which they start has not been yet unequivocally determined. The current data show that chronic microvascular complications of diabetes can be observed in patients with abnormal glucose metabolism in whom glycaemia is higher than optimal but below diagnostic criteria for diabetes. Prediabetes is a heterogenous nosological unit in which particular types are differently characterized and show different correlations with particular kinds of complications. Analysis of the latest research results shows the need to continue studies in a larger population and can imply the need to verify the currently employed criteria of diagnosing diabetes and chronic complications of diabetes in people with prediabetes.

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.

Reduced corneal nerve fibre length in prediabetes and type 2 diabetes: The Maastricht Study

PURPOSE

In individuals with diabetes, injury to the corneal nerve fibres predisposes to delayed corneal epithelial healing, reduced corneal sensitivity and corneal erosion. We investigated to what extent a reduction in corneal nerve fibre length (CNFL) is present in individuals with prediabetes or type 2 diabetes (DM2) compared with individuals with normal glucose metabolism (NGM).

METHODS

Using composite images acquired by corneal confocal microscopy, we assessed total CNFL per mm² in the subbasal nerve plexus of the cornea in 134 participants (mean age 59 ± 8 years, 49% men, 87 NGM, 20 prediabetes, 27 DM2). Multivariable linear regression was used to assess the association between CNFL and glucose metabolism status, adjusted for age and sex.

RESULTS

In individuals with type 2 diabetes, the mean CNFL was significantly reduced [β = -1.86 mm/mm² (95% CI -3.64 to -0.08), p = 0.04], as compared with individuals with normal glucose metabolism after adjustment for age and sex. Part of the reduction was present in individuals with prediabetes [β = -0.96 mm/mm² (95% CI -2.91 to 0.99), p = 0.34], with a linear trend of corneal nerve fibre reduction with severity of glucose metabolism status (p trend = 0.04).

CONCLUSIONS

A significant reduction in CNFL was found in individuals with DM2 compared with individuals with NGM. A trend of reduction in CNFL was observed between individuals with NGM and prediabetes. The reduction in corneal nerve fibre length could contribute to a delayed corneal healing and an increased risk for corneal complications after surgery.

Cardiac Autonomic Neuropathy in Obesity, the Metabolic Syndrome and Prediabetes: A Narrative Review

Cardiac autonomic neuropathy (CAN) is a major complication of type 1 and type 2 diabetes mellitus (T1DM and T2DM). The increased morbidity, cardiovascular and all-cause mortality associated with CAN is established from numerous epidemiological studies. However, CAN is increasingly recognised in people with prediabetes (pre-DM) and the metabolic syndrome (MetS) with a reported prevalence up to 11% and 24% respectively. CAN is associated with components of MetS including hypertension and obesity, predating hyperglycaemia. The aetiology of CAN is multifactorial and there is a reciprocal relationship with insulin resistance and MetS. Obstructive sleep apnoea (OSA) is also associated with CAN possibly through MetS and an independent mechanism. An estimated global prevalence of the impaired glucose tolerance (IGT) form of pre-DM of 587 million people by 2045 means CAN will become a major clinical problem. CAN is independently associated with silent myocardial ischaemia, major cardiovascular events, myocardial dysfunction and cardiovascular mortality. Screening for CAN in pre-DM using risk scores with analysis of heart rate variability (HRV) or Sudoscan is important to allow earlier treatment at a reversible stage. The link between obesity and CAN highlights the therapeutic potential of lifestyle interventions including diet and physical activity to reverse MetS and prevent CAN. Weight loss achieved using these dietary and exercise lifestyle interventions improves the sympathetic and parasympathetic HRV indices of cardiac autonomic function. Further research is needed to identify high-risk populations of people with pre-DM or obesity that might benefit from targeted pharmacotherapy including metformin, sodium/glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) analogues. Bariatric surgery also improves HRV through weight loss which might also prevent CAN in severe obesity. This article reviews the literature on CAN in obesity, pre-DM and MetS, to help determine a rationale for screening, early intervention treatment and formulate future research questions in this highly prevalent condition.

Update on the Impact, Diagnosis and Management of Cardiovascular Autonomic Neuropathy in Diabetes: What Is Defined, What Is New, and What Is Unmet

The burden of diabetic cardiovascular autonomic neuropathy (CAN) is expected to increase due to the diabetes epidemic and its early and widespread appearance. CAN has a definite prognostic role for mortality and cardiovascular morbidity. Putative mechanisms for this are tachycardia, QT interval prolongation, orthostatic hypotension, reverse dipping, and impaired heart rate variability, while emerging mechanisms like inflammation support the pervasiveness of autonomic dysfunction. Efforts to overcome CAN under-diagnosis are on the table: by promoting screening for symptoms and signs; by simplifying cardiovascular reflex tests; and by selecting the candidates for screening. CAN assessment allows for treatment of its manifestations, cardiovascular risk stratification, and tailoring therapeutic targets. Risk factors for CAN are mainly glycaemic control in type 1 diabetes mellitus (T1DM) and, in addition, hypertension, dyslipidaemia, and obesity in type 2 diabetes mellitus (T2DM), while preliminary data regard glycaemic variability, vitamin B12 and D changes, oxidative stress, inflammation, and genetic biomarkers. Glycaemic control prevents CAN in T1DM, whereas multifactorial intervention might be effective in T2DM. Lifestyle intervention improves autonomic function mostly in pre-diabetes. While there is no conclusive evidence for a disease-modifying therapy, treatment of CAN manifestations is available. The modulation of autonomic function by SGLT2i represents a promising research field with possible clinical relevance.

Diabetic autonomic neuropathy

Diabetes mellitus is the commonest cause of an autonomic neuropathy in the developed world. Diabetic autonomic neuropathy causes a constellation of symptoms and signs affecting cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory, and sudomotor systems. Several discrete syndromes associated with diabetes cause autonomic dysfunction. The most prevalent of these are: generalized diabetic autonomic neuropathy, autonomic neuropathy associated with the prediabetic state, treatment-induced painful and autonomic neuropathy, and transient hypoglycemia-associated autonomic neuropathy. These autonomic manifestations of diabetes are responsible for the most troublesome and disabling features of diabetic peripheral neuropathy and result in a significant proportion of the mortality and morbidity associated with the disease.

Syncope: Case Studies

Syncope, or the sudden loss of consciousness, is a common presenting symptom for evaluation by neurologists. It is not a unique diagnosis but rather a common manifestation of disorders with diverse mechanisms. Loss of consciousness is typically preceded by a prodrome of symptoms and sometimes there is a clear trigger. This article discusses several cases that illustrate the various causes of syncope. Reflex syncope is the most common type and includes neurally mediated, vasovagal, situational, carotid sinus hypersensitivity, and atypical forms. Acute and chronic autonomic neuropathies and neurodegenerative disorders can also present with syncope.

Autonomic Neuropathy and Endothelial Dysfunction in Patients With Impaired Glucose Tolerance or Type 2 Diabetes Mellitus

Autonomic neuropathy is one of the most common complications of diabetes mellitus (DM). The etiology of autonomic impairment is not well-understood, yet. There is need for studies to investigate the cause-effect relationships of inflammation and/or endothelial dysfunction and diabetic autonomic neuropathy. Only a few reports have mentioned autonomic neuropathy in individuals with impaired glucose tolerance (IGT), previously. Furthermore, the association between the plasma markers of endothelial dysfunction (von Willebrand factor (vWF), soluble E-selectin) and autonomic neuropathy in patients with IGT or DM has not been studied before. In this study, we aimed to investigate the correlation between plasma markers of endothelial dysfunction and autonomic neuropathy in patients with IGT or type 2 DM (T2DM).In this case-control study, 25 IGT patients, 25 T2DM patients with autonomic symptoms, and 30 controls were included. Demographical data, HbA1c, vWF, and soluble E-selectin (sE-selectin) levels were analyzed. Sympathetic skin response (SSR) and heart rate variability (HRV) were used as the indicator of autonomic activity.Plasma levels of HbA1c, vWF, and sE-selectin were higher in patients with IGT than the controls; patients with T2DM had higher levels than both the controls and the patients with IGT. SSR measures were similar among the groups. However, higher number of T2DM patients had absent plantar SSR than controls. HRV analysis at rest revealed lower standard deviation of R-R interval, coefficient of variation of R-R interval, low-frequency (LF) power and total power in patients with IGT and T2DM than the controls. In addition, HRV analysis at deep breathing showed lower high-frequency (HF) power in IGT group. LF:HF ratio was lower in both patient groups at rest. No strong correlation was found between the levels of HbA1c, vWF, sE-selectin, HRV, and SSR measures.Our results support that endothelial dysfunction is evident in individuals with IGT or T2DM and HRV is impaired in early stages in the course of T2DM. However, increased levels of biomarkers of endothelial damage do not correlate with HRV or SSR. More studies are needed to clarify the disease pathogenesis and its clinical correlates. Impaired HRV in T2DM could be due to mechanisms other than endothelial dysfunction.

Individuals with impaired glucose tolerance demonstrate normal cardiac sympathetic innervation using I-123 mIBG scintigraphy

BACKGROUND

Impaired glucose tolerance (IGT) is associated with an increased risk of type 2 diabetes (T2DM) and cardiovascular disease. Some but not all studies have reported cardiac autonomic dysfunction in subjects with IGT and there is only one direct study of cardiac innervation in subjects with IGT. The purpose of this study was to assess global and regional cardiac sympathetic innervation and cardiac autonomic function in individuals with IGT.

METHODS AND RESULTS

We undertook (123)I-mIBG scintigraphy and cardiac autonomic function in 15 subjects with IGT and 15 age and sex-matched healthy controls. Early heart to mediastinum ratio (HMR) (1.71 ± 0.17 vs 1.67 ± 0.13, P = .49), late HMR (1.73 ± 0.18 vs 1.73 ± 0.16, P = .97) and washout rate (WR) (18.6 ± 4.2 vs 19.1 ± 7.6%, P = .84), did not differ between subjects with IGT and control subjects. More detailed regional analysis revealed reduced tracer uptake at the apex, base and inferior wall in all subjects and the anterior wall in a minority of subjects. There were no differences in total score (56.6 ± 4.0 vs 53.3 ± 8.4, P = .193), modified score (48.5 ± 3.3 vs 46.2 ± 6.0, P = .215), anterior wall score (10.2 ± 1.3 vs 10.1 ± 1.6, P = .898), inferior wall score (8.9 ± 1.9 vs 7.7 ± 2.6, P = .163), basal score (18.7 ± 1.9 vs 18.2 ± 3.3, P = .636) and tests of cardiac autonomic function between the groups.

CONCLUSION

Global and regional measures of MIBG uptake and washout as well as cardiac autonomic function did not differ between subjects with IGT and healthy controls.

Increased prevalence of cardiac autonomic dysfunction at different degrees of glucose intolerance in the general population: the KORA S4 survey

AIMS/HYPOTHESIS

Cardiac autonomic nervous dysfunction (CAND) raises the risk of mortality, but the glycaemic threshold at which it develops is unclear. We aimed to determine the prevalence of, risk factors for and impact of CAND in glucose intolerance and diabetes.

METHODS

Among 1,332 eligible participants aged 55-74 years in the population-based cross-sectional KORA S4 study, 130 had known diabetes mellitus (k-DM), and the remaining 1,202 underwent an OGTT. Heart rate variability (HRV) and QT variability were computed from supine 5 min ECGs.

RESULTS

In all, 565 individuals had normal glucose tolerance (NGT), 336 had isolated impaired fasting glucose (i-IFG), 72 had isolated impaired glucose tolerance (i-IGT), 151 had combined IFG-IGT (IFG-IGT) and 78 had newly detected diabetes mellitus (n-DM). Adjusted normal HRV limits were defined in the NGT population (5th and 95th percentiles). Three HRV measures were more frequently abnormal in those with k-DM, n-DM, IFG-IGT and i-IFG than in those with NGT (p < 0.05). The rates of CAND (≥2 of 4 HRV indices abnormal) were: NGT, 4.5%; i-IFG, 8.1%; i-IGT, 5.9%; IFG-IGT, 11.4%; n-DM, 11.7%; and k-DM, 17.5% (p < 0.05 vs NGT, except for i-IGT). Reduced HRV was associated with cardiovascular risk factors used to construct a simple screening score for CAND. Mortality was higher in participants with reduced HRV (p < 0.05 vs normal HRV).

CONCLUSIONS/INTERPRETATION

In the general population aged 55-74 years, the prevalence of CAND is increased not only in individuals with diabetes, but also in those with IFG-IGT and, to a lesser degree, in those with i-IFG. It is associated with mortality and modifiable cardiovascular risk factors which may be used to screen for diminished HRV in clinical practice.

Prediabetes and associated disorders

Prediabetes represents an elevation of plasma glucose above the normal range but below that of clinical diabetes. Prediabetes includes individuals with IFG, IGT, IFG with IGT and elevated HbA1c levels. Insulin resistance and β-cell dysfunction are characteristic of this disorder. The diagnosis of prediabetesis is vital as both IFG and IGT are indeed well-known risk factors for type 2 diabetes with a greater risk in the presence of combined IFG and IGT. Furthermore, as will be illustrated in this review, prediabetes is associated with associated disorders typically only considered in with established diabetes. These include cardiovascular disease, periodontal disease, cognitive dysfunction, microvascular disease, blood pressure abnormalities, obstructive sleep apnea, low testosterone, metabolic syndrome, various biomarkers, fatty liver disease, and cancer. As the vast majority of individuals with prediabetes are unaware of their diagnosis, it is therefore vital that the associated conditions are identified, particularly in the presence of mild hyperglycemia, so they may benefit from early intervention.

Corneal confocal microscopy detects neuropathy in subjects with impaired glucose tolerance

OBJECTIVE

Impaired glucose tolerance (IGT) represents one of the earliest stages of glucose dysregulation and is associated with macrovascular disease, retinopathy, and microalbuminuria, but whether IGT causes neuropathy is unclear.

RESEARCH DESIGN AND METHODS

Thirty-seven subjects with IGT and 20 age-matched control subjects underwent a comprehensive evaluation of neuropathy by assessing symptoms, neurological deficits, nerve conduction studies, quantitative sensory testing, heart rate variability deep breathing (HRVdb), skin biopsy, and corneal confocal microscopy (CCM).

RESULTS

Subjects with IGT had a significantly increased neuropathy symptom profile (P < 0.001), McGill pain index (P < 0.001), neuropathy disability score (P = 0.001), vibration perception threshold (P = 0.002), warm threshold (P = 0.006), and cool threshold (P = 0.03), with a reduction in intraepidermal nerve fiber density (P = 0.03), corneal nerve fiber density (P < 0.001), corneal nerve branch density (P = 0.002), and corneal nerve fiber length (P = 0.05). No significant difference was found in sensory and motor nerve amplitude and conduction velocity or HRVdb.

CONCLUSIONS

Subjects with IGT have evidence of neuropathy, particularly small-fiber damage, which can be detected using skin biopsy and CCM.

Impaired baroreflex sensitivity in subjects with impaired glucose tolerance, but not isolated impaired fasting glucose

Impaired baroreflex sensitivity (BRS) is associated with adverse cardiovascular outcomes. There are currently no studies on BRS changes in subjects with different glycemic statuses, including normal glucose tolerance (NGT), isolated impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and newly diagnosed diabetes (NDD). The aim of this study was to investigate the effects of NDD, IGT and isolated IFG on BRS, based on a community-based data. A total of 768 subjects were classified as NGT (n = 498), isolated IFG (n = 61), IGT (n = 126) and NDD (n = 83). Spontaneous BRS was determined by the spectral α coefficient method, i.e., the square root of the ratio between the power of the RR interval and the power of systolic blood pressure in the LF frequency region (0.04-0.15 Hz) after the subjects had rested in a supine position for 5 min. Valsalva ratio was calculated as the longest RR interval after release of the Valsalva maneuver, divided by the shortest RR interval during the maneuver. As compared with NGT subjects, NDD (p = 0.039) and IGT (p = 0.041) subjects had a reduced spontaneous BRS in multivariate analysis based on analysis of covariance. NDD subjects exhibited a lower Valsalva ratio than NGT subjects (p = 0.043). However, there were no significant differences in spontaneous BRS and Valsalva ratio between subjects with isolated IFG and NGT. In conclusion, NDD and IGT subjects had an impaired BRS as compared to NGT subjects. However, reduced BRS was not apparent in subjects with isolated IFG.

Determination of peripheral neuropathy prevalence and associated factors in Chinese subjects with diabetes and pre-diabetes - ShangHai Diabetic neuRopathy Epidemiology and Molecular Genetics Study (SH-DREAMS)

OBJECTIVE

This study determined the prevalence and factors associated with peripheral neuropathy (PN) in subjects with diabetes mellitus, impaired glucose regulation (IGR), and normal glucose tolerance (NGT) in a community-based Chinese population.

RESEARCH DESIGN AND METHODS

A total of 2035 subjects in Shanghai were classified as having NGT, IGR, or diabetes. All subjects underwent complete foot examination. PN was assessed according to the neuropathy symptom and neuropathy disability scores. Binary logistic regression was performed to analyze the contributions of factors to PN.

RESULTS

The prevalence of PN was 8.4%, 2.8%, and 1.5% in diabetes mellitus, IGR, and NGT subjects, respectively (P<0.05 for diabetes vs. NGT, and IGR). The subjects with known diabetes had the highest frequency of PN (13.1%). Among the subjects without diabetes, those with PN were older, had a higher waist circumference and 2-h postprandial plasma glucose levels, and were more likely to be hypertensive. Among the IGR subjects, other than age, the 2-h postprandial plasma glucose level was an independent factor significantly associated with PN. Meanwhile, among the subjects with diabetes, PN was associated with fasting plasma glucose, duration of diabetes, and decreased estimated glomerular filtration rate.

CONCLUSIONS

The prevalence of PN is slightly higher in individuals with IGR than that in individuals with NGT, but small fibre damage in IGR as the earliest nerve fibre deficit may be underestimated in our study. As an independent risk factor, postprandial plasma glucose level may be an important target for strategies to prevent or improve PN in IGR subjects.

Autonomic dysfunction and circadian blood pressure variations in people with impaired glucose tolerance

AIMS

To assess circadian blood pressure variability in people with impaired glucose tolerance and a healthy control population.

METHODS

Seventy-five people with impaired glucose tolerance and 40 healthy volunteers (frequency matched on 10-year age bands and sex) underwent a detailed neurological assessment. Autonomic neuropathy was detected by the five standard cardiovascular autonomic tests and heart rate variability was characterized by the triangle index. Diurnal indices were assessed by 24-h ambulatory blood pressure monitoring. Systolic and diastolic diurnal indices were defined as: (mean daytime blood pressure - mean night-time blood pressure) × 100/mean daytime blood pressure.

RESULTS

Mean 24-h systolic and diastolic blood pressure was significantly higher in the group with impaired glucose tolerance compared with the control group [126 ± 12 (mean ± SD) vs. 117 ± 10, 75 ± 7 vs. 71 ± 6 mmHg, both P < 0.05). Systolic and diastolic diurnal indices and heart rate variability triangular index were significantly lower in people with impaired glucose tolerance compared with control subjects (9.1 ± 7.8 vs. 13.2 ± 5.4, 14.5 ± 9.7 vs. 18.4 ± 7.1 mmHg, 28.0 ± 8.4 vs. 39.5 ± 9.3, all P < 0.05). Differences in mean diastolic blood pressure, heart rate variability triangular index and the frequency of non-dippers between those with impaired glucose tolerance and control subjects seemed to be independent of BMI and the presence of cardiovascular autonomic neuropathy, as simultaneous adjustment for BMI and cardiovascular autonomic neuropathy had no major effect on the results.

CONCLUSION

Our data suggest that people with impaired glucose tolerance have increased diastolic blood pressure and abnormal circadian blood pressure regulation, independent of obesity and the presence of cardiovascular autonomic neuropathy.

Autonomic test by EZSCAN in the screening for prediabetes and diabetes

BACKGROUND

Autonomic neuropathy is common in diabetics and may occur in prediabetes. A new and noninvasive autonomic test-EZSCAN evaluates sudomotor function precisely. No generally accepted EZSCAN thresholds to screen for prediabetes and diabetes have been defined.

METHODOLOGY AND PRINCIPAL FINDINGS

Cross-sectional study of 5, 824 Chinese adults aged 40 and older was conducted in Shanghai, China. We used EZSCAN to evaluate autonomic function in different glucose status and screen for prediabetes and diabetes. The prevalence of prediabetes and diabetes were 21.9% and 17.5% respectively. Compared with the lowest quintile, the highest quintile of EZSCAN value had odds ratios for having dysglycemia (prediabetes or diabetes) of 2.08 (95% CI 1.67-2.58) in total population, 2.89 (95% CI 2.06-4.05) in men and 1.70 (95% CI 1.28-2.25) in women after adjustment for confounding factors. EZSCAN value improved the areas under ROC curve for detection of dysglycemia or diabetes beyond the contribution of conventional risk factors by 0.8% and 12.9%. The cut-off point of EZSCAN value higher than 30% provided reasonable sensitivities (70.3-83.7%) to detect dysglycemia not only in total population regardless of sex but also in individuals with high risk of developing diabetes.

CONCLUSIONS AND SIGNIFICANCE

EZSCAN value higher than 30% indicate an increased risk of prevalent prediabetes and diabetes, suggesting that subjects with EZSCAN ≥30% should be further evaluated by oral glucose tolerance test. The improvement of EZSCAN for diabetes detection was still of limited clinical relevance. Thus the clinical application value of EZSCAN is needed to be explored in future studies.

Pain-autonomic interaction after work-induced sleep restriction

BACKGROUND AND PURPOSE

Poor sleep is commonly associated with alterations in pain perception. However, there is a lack of studies that address work-associated sleep restriction (SR) and changes in non-nociceptive perception and autonomic responses after work-induced SR.

METHODS

This study was performed with 19 medical students after a normal-sleep night (NS phase) and after a night shift at the local emergency room (SR phase). We performed clinical assessment, quantitative sensory testing for electrical and temperature sensation, RR interval analysis, and recorded sudomotor skin responses (SSRs).

RESULTS

The total mean duration of sleep was 436 ± 18 min in the NS group and 120 ± 28 min in the SR group (P<0.001). The anxiety scores were higher following the SR phase compared with those after the NS phase (P<0.01). After SR, there was a decrease in heat-pain threshold, but neither warm nor electrical thresholds were affected. Following SR, subjects showed higher SSR amplitudes and an increased number of double responses at an interstimulus interval of 2 s. We also observed a moderate inverse correlation between heat-pain thresholds and SSR amplitude (r= -0.46; P<0.01). However, there was no correlation between anxiety scores and SSR parameters.

CONCLUSIONS

The effects of SR in the context of work stress on pain are specific and appear unrelated to general changes in sensory perception. Hyperalgesia was associated with abnormal autonomic responses, but not with increased anxiety, which suggests an association between the nociceptive and autonomic nervous systems that is independent of the emotional state.

Impaired glucose tolerance and metabolic syndrome in idiopathic neuropathy

Idiopathic neuropathy is one of the most common clinical problems encountered in general medical and neurological practices, accounting for up to 40% of all neuropathies in referral series. Several groups have reported an elevated prevalence of impaired glucose tolerance (IGT) in idiopathic neuropathy subjects, although the only carefully conducted case-control study suggested hypertriglyceridemia was a more important risk factor. The nature of the relationship between IGT and neuropathy is a subject of active debate. An evolving literature suggests metabolic syndrome, particularly dyslipidemia and obesity, are potent neuropathy risk factors for both idiopathic and diabetic neuropathy patients. Once established, diabetic neuropathy is likely to be very difficult to reverse. IGT-associated neuropathy, however, may be more amenable to therapy and could represent an ideal population in which to examine potential therapies for diabetes and obesity related neuropathies. Further research is needed to better define the epidemiological relation between IGT, metabolic syndrome, and neuropathy, its underlying pathophysiology, and to develop appropriate surrogate measures and clinical trials strategies.

Prediabetic neuropathy: does it exist?

It is now increasingly being appreciated that a substantial proportion of subjects with prediabetes may exhibit peripheral neuropathy and/or neuropathic pain. The reverse is also true, inasmuch as examining patients with idiopathic peripheral neuropathy will frequently reveal prediabetes. In the general population, the prevalence of neuropathy in prediabetes is intermediate between overt diabetes and subjects with normoglycemia. This prediabetic neuropathy is, generally, milder in comparison to diabetic neuropathy and mainly affects small fibers mediating sensory function. Hyperglycemia, microangiopathy, dyslipidemia and the metabolic syndrome have been implicated as pathogenic mechanisms. In practice, therapy of prediabetic neuropathy should be addressed towards normoglycemia and correction of cardiovascular risk factors. However, additional work is needed to establish the long-term results of this approach.

Impaired glycemia and diabetic polyneuropathy: the OC IG Survey

OBJECTIVE

To test whether diabetic polyneuropathies (DPNs), retinopathy, or nephropathy is more prevalent in subjects with impaired glycemia (IG) (abnormality of impaired fasting glucose [IFG], impaired glucose tolerance [IGT], or impaired HbA(1c) [IA1C]) than in healthy subjects (non-IG).

RESEARCH DESIGN AND METHODS

Matched IG and non-IG volunteers were randomly identified from population-based diagnostic and laboratory registries, restudied, and reclassified as non-IG (n = 150), IG (n = 174), or new diabetes (n = 218).

RESULTS

Frequency (%) of DPN in non-IG, IG, and new diabetes was 3 (2.0%), 3 (1.7%), and 17 (7.8%) narrowly defined (no other cause for polyneuropathy) and 19 (12.7%), 22 (12.6%), and 38 (17.4%) broadly defined. Mean and frequency distribution of composite scores of nerve conduction and quantitative sensation tests were not significantly different between IG and non-IG but were worse in new diabetes. Frequency of retinopathy and nephropathy was significantly increased only in new diabetes. In secondary analysis, small but significant increases in retinopathy and nephropathy were found in IGT, IFG, and IGT combined groups.

CONCLUSIONS

In population studies of Olmsted County, Minnesota, inhabitants, prevalence of typical DPN, retinopathy, and nephropathy was significantly increased only in subjects with new diabetes-not in subjects with IG as defined by American Diabetes Association (ADA) criteria of abnormality of IFG, IGT, or IA1C. For atypical DPN, such an increase was not observed even in subjects with new diabetes. In medical practice, explanations other than IG should be sought for patients with atypical DPN (chronic idiopathic axonal polyneuropathy) who have IG.

Neuropathy in prediabetes: does the clock start ticking early?

Between 25% and 62% of patients with idiopathic peripheral neuropathy are reported to have prediabetes, and among individuals with prediabetes 11-25% are thought to have peripheral neuropathy, and 13-21% have neuropathic pain. Population-based studies suggest a gradient for the prevalence of neuropathy, being highest in patients with manifest diabetes mellitus, followed by individuals with impaired glucose tolerance then impaired fasting glucose and least in those with normoglycemia. The most sensitive test to assess glucose metabolism status is the oral glucose tolerance test. Pathogenesis involves hyperglycemia, microvascular abnormalities, dyslipidemia and the metabolic syndrome. Individuals with prediabetes have less severe neuropathy than those with manifest diabetes mellitus. Sensory modalities are more frequently affected than motor modalities, but impairment of small nerve fibers could be the earliest detectable sign. Diagnosis should rely on careful clinical examination, with emphasis on the evaluation of small fibers. An oral glucose tolerance test should be performed in patients with idiopathic neuropathy. The only treatment with any efficacy is lifestyle modification to improve control of hyperglycemia and cardiovascular risk factors, but long-term efficacy of this approach has not been established. This Review summarizes the current evidence on the association between prediabetes and neuropathy.

Neuropathy and impaired glucose tolerance: an updated review of the evidence

There has been considerable interest in the possible association between impaired glucose tolerance (IGT) and neuropathy. A systematic literature search (Medline) and review was here performed. Twenty-three studies were evaluated. Fourteen investigated for the presence of neuropathy in patients with IGT. Nine studied patients with chronic idiopathic axonal polyneuropathy (CIAP), for the prevalence of IGT. The findings suggest that a significant proportion of patients with IGT may have neuropathy, particularly of the small-fibre and painful type. Similarly, a significant percentage of patients without another identifiable cause for painful axonal neuropathy may have IGT. This may however not be applicable to all populations. There are issues relating to the reproducibility, reliability and timing of a single glucose tolerance test (GTT) in establishing a diagnosis of IGT. Furthermore, it is possible neuropathic damage may occur at lower glucose levels than those defining IGT. In conclusion, further prospective long-term study of large IGT cohorts with known prestudy IGT duration is required to confirm and answer the many remaining questions about this presumed association. However, at present time, consideration of IGT as potential cause of painful small-fibre neuropathy appears justified, especially as patients may benefit from dietary and physical exercise interventions.

Assessing autonomic dysfunction in early diabetic neuropathy: the Survey of Autonomic Symptoms

OBJECTIVE

Autonomic symptoms may occur frequently in diabetic and other neuropathies. There is a need to develop a simple instrument to measure autonomic symptoms in subjects with neuropathy and to test the validity of the instrument.

METHODS

The Survey of Autonomic Symptoms (SAS) consists of 11 items in women and 12 in men. Each item is rated by an impact score ranging from 1 (least severe) to 5 (most severe). The SAS was tested in observational studies and compared to a previously validated autonomic scale, the Autonomic Symptom Profile (ASP), and to a series of autonomic tests.

RESULTS

The SAS was tested in 30 healthy controls and 62 subjects with neuropathy and impaired glucose tolerance or newly diagnosed diabetes. An increased SAS score was associated with the previously validated ASP (rank order correlation=0.68; p<0.0001) and with quantitative measures of autonomic function: a reduced quantitative sudomotor axon reflex test sweat volume (0.31; p<0.05) and an abnormal 30:15 ratio (0.53; p<0.01). The SAS shows a high sensitivity and specificity (area under the receiver operating characteristic curve 0.828) that compares favorably with the ASP. The SAS scale domains had a good internal consistency and reliability (Cronbach α=0.76). The SAS symptom score was increased in neuropathy (95% confidence interval [CI] 2.99-4.14) compared to control (95% CI 0.58-1.69; p<0.0001) subjects.

CONCLUSIONS

The SAS is a new, valid, easily administered instrument to measure autonomic symptoms in early diabetic neuropathy and would be of value in assessing neuropathic autonomic symptoms in clinical trials and epidemiologic studies.

Cardiovascular autonomic dysfunction is associated with central obesity in persons with impaired glucose tolerance

AIMS

The aim of this study was to investigate the prevalence of cardiovascular autonomic neuropathy in persons with previously diagnosed impaired glucose tolerance and to characterize associations between components of metabolic syndrome and cardiovascular autonomic neuropathy in the Finnish Diabetes Prevention Study cohort.

METHODS

Two hundred and sixty-eight individuals with impaired glucose tolerance at baseline in the Finnish Diabetes Prevention Study, but not diagnosed with diabetes during follow-up, were studied for cardiovascular autonomic neuropathy. At the second annual follow-up visit after the end of lifestyle intervention, we performed deep-breathing and active orthostatic tests to detect possible parasympathetic and sympathetic dysfunction. To describe metabolic characteristics, anthropometric measurements, an oral glucose tolerance test and assessments for HbA(1c,) serum lipids and blood pressure were carried out.

RESULTS

Prevalence of parasympathetic dysfunction was 25% and prevalence of sympathetic dysfunction was 6%, with no difference between the former intervention and control group participants or between men and women. Subjects with parasympathetic dysfunction were older, more obese (weight, waist circumference, body mass index) and had higher triglyceride concentration compared with those with normal parasympathetic function (P<0.01 for all). Parasympathetic dysfunction was not significantly associated with other characteristics of metabolic syndrome; for example, high cholesterol, glucose and insulin levels or HbA(1c) . Correlations between the Expiration/Inspiration (E/I) ratio (the longest heart beat duration in expiration divided by the shortest heart beat duration in inspiration) and measures reflecting obesity were statistically significant in the pooled population and in men but not in women.

CONCLUSIONS

Cardiovascular autonomic neuropathy is common in persons with impaired glucose tolerance. Obesity, especially among men, seems to play an important role in the early pathogenesis of cardiovascular autonomic neuropathy.

Assessment of symptomatic diabetic patients with normal nerve conduction studies: utility of cutaneous silent periods and autonomic tests

Established electrophysiological methods have limited clinical utility in the diagnosis of small-fiber neuropathy (SFN). In this study, diabetic patients with clinically diagnosed SFN were evaluated with autonomic tests and cutaneous silent periods (CSPs). Thirty-one diabetic patients with clinically suspected SFN and normal nerve conduction studies were compared with 30 controls. In the upper extremities (UE), the CSP parameters did not differ statistically between the patient and control groups, whereas, in the lower extremities (LE), patients had prolonged CSP latencies (P = 0.018) and shortened CSP durations (P < 0.001). The sensitivity of the CSP duration was 32.6%, and the specificity was 96.7%. The expiration-to-inspiration ratios and amplitudes of the sympathetic skin responses in the lower extremities were also reduced. Our findings indicate that the diagnostic utility of CSPs was higher than that of the autonomic tests to support the clinically suspected diagnosis of SFN.

Where is the core of the volcano? The undetermined origin of primary restless legs syndrome

An association between small fiber neuropathy and primary Restless Legs Syndrome (RLS) is suggested since both of them share common characteristics. Our aim was to investigate the existence of autonomic neuropathy on the basis of autonomic tests. The patients and the age-matched controls were evaluated with Neuropathy Symptom Profile and Autonomic Symptom Profile, nerve conduction studies (NCS), and autonomic tests. Patients suffered from neuropathic and autonomic complaints obviously. There was no significant difference for NCS, heart rate variability tests, and sympathetic skin responses (SSRs) among patients and controls. Since both the NCSs and the autonomic tests were within normal, the complaints were considered to be the consequences of the problem in sensory integration due to the dysfunction of the caudal diencephalic A11 group, rather than a neuropathic process. The cardiac autonomic imbalance possibly emerges as a consequence of arousal periods prior to or during the Periodic Leg Movements (PLM) episodes during sleep, but not due to autonomic neuropathy.