Autonomic nerve testing predicts the development of complications: a 12-year follow-up study

Cardiovascular autonomic neuropathy and the risk of diabetic kidney disease

Background

Cardiovascular autonomic neuropathy (CAN) is known to affect patients with diabetes mellitus (DM) and cause adverse renal outcomes. We aimed to analyze the association between CAN and diabetic kidney disease (DKD).

Method

We enrolled 254 DM patients (mean age, 56.7 ± 15.2 years; male: female ratio, 1.17:1) with 19 (7.5%) type 1 DM patients and 235 (92.5%) type 2 DM patients. All patients had undergone cardiovascular autonomic function tests between January 2019 and December 2021 in a tertiary hospital in Korea. Cardiovascular autonomic neuropathy was categorized as normal, early, or definite after measuring three heart rate variability parameters. Diabetic kidney disease refers to a persistently elevated urinary albumin-creatinine ratio (uACR ≥30 mg/g) or reduced estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m2). Logistic and Cox regression analyses were performed.

Results

Patients with elevated uACR (n=107) and reduced eGFR (n=32) had a higher rate of definite CAN. After adjusting for covariates, definite CAN was associated with elevated uACR (OR=2.4, 95% CI 1.07-5.36) but not with reduced eGFR (OR=3.43, 95% CI 0.62-18.90). A total of 94 patients repeated uACR measurements within 2 years (mean follow-up, 586.3 ± 116.8 days). Both definite and early CAN were independent risk factors for elevated uACR (HR=8.61 and 8.35, respectively; both p<0.05). In addition, high-density lipoprotein cholesterol, ACE inhibitors/angiotensin receptor blockers and glucagon-like peptide-1 receptor agonists were independent protective factors for elevated uACR (HR=0.96, 0.25, and 0.07, respectively; all p<0.05).

Conclusion

Cardiovascular autonomic neuropathy is a potential indicator of DKD. Comprehensive management of DKD in the early stages of CAN may prevent microalbuminuria.

Detecting and treating the protean manifestations of diabetic autonomic neuropathy

The manifestations of diabetic autonomic neuropathy (DAN) are protean and clinically involve multiple systems, including the cardiovascular system, the gastrointestinal system, the genitourinary system as well as the sweat glands (sudomotor dysfunction) and the gallbladder. In addition, cardiac autonomic neuropathy (CAN) is associated with a correctible inability to appreciate and correct hypoglycaemia. While not a clinical problem, pupillary involvement should be the clue and the catalyst to investigate for other manifestations of DAN. This review outlines a practical approach to detecting and investigating the manifestations of DAN. Of particular importance is early detection of cardiovascular involvement where prompt therapy through glycaemic control can decrease the severity of CAN and decelerate the frequency and severity of retinopathy and nephropathy in addition to decreasing cardiovascular events and mortality. CAN also plays a role in accelerating other diabetic complications such as acute ischaemic stroke, heart failure, medial artery calcinosis, foot ulcers, peripheral artery disease and Charcot joints. Many therapies of DAN are available, which should not only decrease morbidity and mortality from DAN, but also improve the patient's quality of life. However, the therapies available are largely symptomatic.

Cardiac Autonomic Nerve Dysfunction Predicts Incident Retinopathy and Early Kidney Dysfunction in Adolescents With Type 1 Diabetes

OBJECTIVE

Cardiac autonomic neuropathy (CAN) may contribute to vascular complications in diabetes. We hypothesized that adolescents with CAN are at greater risk of diabetic retinopathy and early kidney dysfunction.

RESEARCH DESIGN AND METHODS

In this prospective longitudinal study of 725 adolescents with type 1 diabetes without retinopathy and albuminuria at baseline, early CAN was defined as one or more abnormalities in seven heart rate tests derived from a 10-min electrocardiogram. Retinopathy was defined as the presence of one or more microaneurysms, early kidney dysfunction as an albumin excretion rate (AER) >7.5 μg/min, and albuminuria as an AER >20 μg/min. Multivariable generalized estimating equations were used to examine the association between CAN and retinopathy or early kidney dysfunction. Cox proportional hazards regression analysis was used to assess cumulative risks of incident retinopathy and albuminuria.

RESULTS

At baseline, the mean age of the sample was 13.6 ± 2.6 years, 52% were male, and mean diabetes duration was 6.1 ± 3.3 years. Over a median follow-up of 3.8 (interquartile range 2.2-7.5) years, the complication rate 27% for retinopathy, 16% for early kidney dysfunction, and 3% for albuminuria. The mean study HbA1c was 72.3 ± 16 mmol/mmol (8.6 ± 1.4%). CAN predicted incident retinopathy (odds ratio 2.0 [95% CI 1.4, 2.9]) and early kidney dysfunction (1.4 [1.0, 2.0]) after adjusting for HbA1c and diabetes duration. CAN also predicted retinopathy (hazard ratio 1.57 [95% CI 1.09, 2.26]) and albuminuria (2.30 [1.05, 5.04]) independently of HbA1c.

CONCLUSIONS

CAN predicted incident retinopathy and kidney dysfunction in adolescents with type 1 diabetes, likely reflecting autonomic microvascular dysregulation contributing to complications. Therefore, screening and interventions to reduce CAN may influence the risk of complications.

Pupillary Responses Reveal Autonomic Regulation Impairments in Patients With Central Serous Chorioretinopathy

Purpose

This study assessed the autonomic nervous system in patients with central serous chorioretinopathy (CSC) by simultaneously measuring pupillary responses and heart rate variability (HRV).

Methods

We recruited 33 patients with CSC and 26 age- and sex-matched healthy controls. Using a pupillometry and acceleration plethysmography system, we measured the participants’ pupillary light reflex and HRV simultaneously, and compared the following parameters between the two groups: the pupil diameters, diameter changes, and time and frequency domain HRV indices (high frequency power: HF; low frequency power: LF; log LF/HF ratio). Additional data from the Profile of Mood States (POMS) and pupillary responses during mental tasks were also analyzed.

Results

The CSC group had a significantly lower constriction amplitude and a higher re-dilation ratio compared with the control group, indicating parasympathetic inhibition and sympathetic activation. For the HRV measures, the CSC group demonstrated significantly lower HF and higher LF and log LF/HF ratio, indicative of higher sympathetic activity. The CSC group also showed significantly larger pupil dilation during tasks of moderate difficulty, and higher negative/lower positive POMS mood scores. Further analyses also revealed that the baseline pupil diameter was significantly larger in patients with active as opposed to chronic CSC.

Conclusions

Pupillary responses and HRV measures both revealed sympathetic activation and parasympathetic attenuation in patients with CSC. Larger pupil dilation during mental tasks in CSC could be a potential marker of psychophysiological stress.

The immediate effect of a single session of pain neuroscience education on pain and the autonomic nervous system in subjects with persistent pain, a pilot study

BACKGROUND

The autonomic nervous system is a system that operates at the subconscious level and has been associated with neurobehavioral aspects of pain. Overall, persistent pain has a stimulating effect on the sympathetic nervous system. A promising emerging nonpharmacological treatment to manage persistent pain is neuroscience-based pain education. The overarching goal of neuroscience-based pain education is to change cognitions about pain and the pain experience through education. The aim was to determine the immediate and short-term impact of a neuroscience-based pain education video on the autonomic nervous system and pain in a subgroup of individuals with persistent pain.

METHODS

A convenience sample of 26 subjects were recruited for this study. Each subject indicated their pain level at the time of testing using a Visual Analogue Scale. Automated pupillometry was utilized to measure pupil diameter. After two minutes of accommodation to the goggles, the pupil was measured continuously for 60 s. Following this a 5-minute video presentation "Understanding Pain" was watched, followed by a continuous pupil measurement for 60 s. Three minutes after this measure, the final pupil diameter measurement was taken for 60 s. After completing the final pupil measure, the subject was asked to fill out a second Visual Analogue Scale and a Global Rate of Change.

OUTCOMES

Each subject completed a Global Rating of Change Scale and the mean score was 1.14 (SD = 1.61 and a SEM = 0.), supporting the hypothesis of an overall self-perceived benefit from the intervention. There was a statistically significant difference in pain following the video, P < 0.01. A significant correlation was observed between the self-perceived decrease in pain level and the Global Rating of Change score, p = 0.02. There was no statistically significant difference in the mean pupil diameter following the video with p = 0.76 for the right eye and p = 0.250 for the left eye.

DISCUSSION

This pilot study demonstrated that a 5-minute neuroscience-based pain education video reduced perceived pain in a small sample of subjects with persistent pain. Watching the neuroscience-based pain education video did not seem to result in an immediate generalized autonomic nervous system response. However, it resulted in a different reaction on each eye. This unequal response might be the result of the hemispheric lateralization of the ANS. This study supports the fact that the pain experience is determined by the balance between conscious cognitive processes and subconscious processes based on previous psychological experiences.

Static and Dynamic Pupillary Responses in Patients with Different Stages of Diabetic Retinopathy

This study aimed to investigate pupillary involvement in patients with type 2 diabetes mellitus (DM) and to evaluate whether there is a relationship between severity of diabetic retinopathy (DR) and pupillary responses. The study included 133 individuals in four groups: proliferative DR, non-proliferative DR, DM group without retinal involvement and a control group. Static pupillometry measurements including scotopic pupil diameter (PD), mesopic PD, low photopic PD, high photopic PD, and dynamic pupillometry measurements, including resting diameter, amplitude, latency, velocity, duration of pupil contraction and latency, duration, and velocity of pupil dilatation were taken using an automated quantitative pupillometry system. The correlations between glycosylated haemoglobin values and duration of DM with these parameters were also investigated. The study showed that patients with DR may also have diabetic autonomic neuropathy and pupillometry can be a useful screening tool for detecting diabetic autonomic neuropathy.

Geometry of the Poincaré plot can segregate the two arms of autonomic nervous system - A hypothesis

Autonomic Nervous System (ANS) operates to achieve the optimum physiological functioning and maintains homeostasis in a tonic and continuous manner. Evaluation of ANS profile is crucial in assessing autonomic dysfunction. Conventional ANS evaluation procedures fail to capture minute dynamic alterations of ANS activities. The ANS output pattern is appropriately reflected in the fine alteration of the resting heart rate (HR). HR is a non-stationary variable, results from the dynamic interplay between the multiple physiologic mechanisms. The control of cardiac rate or the chronotropic regulation of heart is considered as a coupled network of oscillators, each representing a specific facet of the cardiovascular reflex. The slower vasomotor oscillation via sympathetic system is combined with rapid respiratory oscillation by parasympathetic system to modulate the intrinsic oscillation pattern of the SA Node. Heart Rate Variability (HRV) is used to understand the autonomic influence on cardiovascular system in health and disease. Fourier decomposition of HRV offers us mainly two different frequency components. High frequency (HF) variation indicates parasympathetic variability due to respiration and Low frequency (LF) mainly implicates tonic sympathetic influence, due to slower vasomotor modulation of heart rate. However, different studies show conflicting results and direct recording of sympathetic nerve activity also failed to correlate with LF power in either healthy subjects or in patients with increased cardiac sympathetic drive. A scatter-plot where each R-R interval is plotted against the preceding R-R interval forms a distributed elliptic point cloud in two dimensional plane. The phase space realization of this plot with dimension two and delay one is referred to as Poincaré plot analysis, an emerging quantitative-visual technique where the shape of the plot is categorized into different functional classes. The plot provides summary as well as detailed beat-to-beat information of the heart. This plot can be extended to three dimensions and with multi-lag, offering more insight and information. A mathematical expression was developed by an interventional study by Toichi et al., using pharmacological blockers during different physiological variables that calculated the lengths of transverse and longitudinal axes of the Poincaré plot to derive two quantitative expressions of sympathetic and vagal influence on HRV: 'cardiac sympathetic index' (CSI)) and 'cardiac vagal index' (CVI). In the present study, we emulate Poincaré plot patterns seen in normal range of sympatho-vagal balances and also in Diabetes Mellitus (DM), known to cause autonomic dysfunction. The emerging pattern of R-R interval time series would provide valuable insight into the altered temporal dynamics and also extract crucial features embedded within. DM is a major public health crisis globally and particularly in Indian population. We hypothesize that, CSI and CVI will effectively segregate the two arms of ANS and can be utilized as an effective evaluation tool to explore the disease status in patients of Diabetes Mellitus. We also propose that, the dynamics of fluctuations in physiological rhythms that exhibit long-term correlation and memory, can also be explored and expressed quantitatively by incorporating various degrees of 'lag' in these recurrence plots.

Time effect for in-situ dry needling on the autonomic nervous system, a pilot study

Study design: Pilot study.Background: Dry needling has been an emerging treatment option for physical therapists over the last decade. Despite the fact that studies have demonstrated the overall benefit of dry needling, there is no clear understanding how long needles should be left in place (situ). This pilot study investigated the effects of needles remaining in situ based on autonomic responses over time.Methods: A convenience sample of 21 subjects were recruited for this study. Automated pupillometry was utilized to obtain a direct measure of autonomic nervous system activity. Directly following a baseline measurement, 8 type J Seirin Acupuncture needles were inserted paravertebral at the C7-T3 segments. A total of 8 post-needling 60 seconds pupil measurements were taken at 3 minutes intervals for 24 minutes post needling.Outcomes: A statistical significant difference in mean pupil diameter was found following the needle intervention (p < .01), which implies an increased sympathetic activity. This subject sample had a statistically significantly larger mean pupil diameter immediately after the needling, which lasted until measure point 7, at 18 minutes (P < .05). At measure point 8 there was no longer a statistical significant difference compared to the premeasurement measure.Discussion: The results of this study provide evidence that dry needling results in a significant increased activity of the sympathetic nervous system for up to 18 minutes. Between 18 and 21 minutes autonomic activity returned to a non-significant difference compared to baseline. The results of this study could assist clinicians in clinical decision making to determine needle placement time.

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.

Cardiovascular autonomic dysfunction predicts increasing albumin excretion in type 1 diabetes

OBJECTIVE

To determine the potential role of cardiovascular autonomic dysfunction in the development of renal complications in young people with type 1 diabetes (T1D).

METHODS

In this prospective study, 199 children and adolescents recruited to the Oxford Regional Prospective Study underwent assessment of autonomic function ~5 years after diagnosis, and were subsequently followed with longitudinal assessments of HbA_1c and urine albumin-creatinine ratio (ACR) over 8.6 ± 3.4 years. Autonomic function was assessed with 4 standardized tests of cardiovascular reflexes: heart rate (HR) response to (1) Valsalva Maneuver, (2) deep breathing, (3) standing, and (4) blood pressure (BP) response to standing. Linear mixed models were used to assess the association between autonomic parameters and future changes in ACR.

RESULTS

Independent of HbA_1c , each SD increase in HR response to Valsalva Maneuver predicted an ACR increase of 2.16% [95% CI: 0.08; 4.28] per year (P = .04), while each SD increase in diastolic BP response to standing predicted an ACR increase of 2.55% [95% CI: 0.37; 4.77] per year (P = .02). The effect of HR response to standing on ACR reached borderline significance (-2.07% [95% CI: -4.11; 0.01] per year per SD increase, P = .051).

CONCLUSIONS

In this cohort of young people with T1D, enhanced cardiovascular reflexes at baseline predicted future increases in ACR. These results support a potential role for autonomic dysfunction in the pathogenesis of diabetic nephropathy.

Association of Heart Rate Recovery With Microalbuminuria in Non-Obstructive Coronary Artery Disease

Background

Non-obstructive coronary artery disease (CAD) is associated with significantly increased risk for myocardial infarction. Heart rate recovery (HRR), a measure of autonomic function, is a strong predictor of all-cause mortality. Microalbuminuria, a marker of early arterial disease, is an independent risk factor for cardiovascular disease and mortality. We aimed to investigate HRR and determine its relationship with microalbuminuria in patients with non-obstructive CAD.

Methods

We prospectively studied 565 patients who underwent elective coronary angiography. All participants underwent urinary analysis and then an exercise test. Microalbuminuria was defined as an urinary albumin-to-creatinine ratio (UACR) of 30 - 299 mg/g. The HRR was abnormal if ≤ 12 beats/min during the first minute after exercise. First, all patients were divided into two groups, patients with microalbuminuria (n = 152) and patients without microalbuminuria (n = 413). Then, all patients were re-divided into two groups, those with lower HRR (≤ 12 beats/min, n = 126) and those with higher HRR (> 12 beats/min, n = 439).

Results

Patients with microalbuminuria had lower HRR and patients with lower HRR had higher UACR. While UACR was negatively correlated with HRR in patients with microalbuminuria (r = -0.424; P < 0.001) and in patients with lower HRR (r = -0.192; P= 0.042), there was no correlation of UACR with HRR in neither patients with normoalbuminuria nor patients with higher HRR, respectively. In the all study population, there was a significant inverse association between UACR and HRR (r = -0.445, P < 0.001), and UACR independently predicted the presence of lower HRR (P < 0.001).

Conclusions

Our findings showed that there was a significant inverse association between UACR and HRR in patients especially with microalbuminuria, and that albuminuria might predict cardiac autonomic imbalance evaluated by HRR in patients with non-obstructive CAD.

QT interval, corrected for heart rate, is associated with HbA1c concentration and autonomic function in diabetes

AIMS

To examine QT intervals corrected for heart rate (QTc) in adolescents with Type 1 diabetes compared with control subjects, and to determine associations with metabolic control and autonomic function.

METHODS

Resting electrocardiogram recordings of 142 adolescents with Type 1 diabetes [mean (sd) age 15.3 (2.0) years, diabetes duration 9.0 (3.5) years, HbA1c 71 (17) mmol/mol or 8.7 (1.6)%] and 125 control subjects [mean (sd) age 15.7 (2.5) years] were used to calculate QTc duration and derive mean heart rate and heart rate variability (HRV) values. Linear and logistic regression models were used to examine the associations between QTc, metabolic control and autonomic function (HRV and pupillary function).

RESULTS

QTc duration was not significantly different between subjects with Type 1 diabetes and control subjects (mean duration 392 vs 391 ms; P = 0.65). In the Type 1 diabetes group, QTc was positively associated with HbA1c [β = 4 (95% CI 2, 6); P < 0.001] and inversely associated with severe hypoglycaemic events [β = -10 (95% CI -20,-2); P = 0.01], less insulin/kg [β = -12 (95% CI -22, -2); P = 0.024] and less HRV. In the Type 1 diabetes group, QTc in the highest quintile (≥409 ms) vs quintiles 1-4 had more pupillary abnormalities (83 vs 56%; P = 0.03), lower pupillary maximum constriction velocity (4.8 vs 5.3 mm/s; P = 0.04), higher heart rate (78 vs 72 beats per min; P = 0.02) and lower HRV (standard deviation of mean NN intervals 4.0 vs 4.3 ms, P = 0.004 and root-mean-square difference of successive NN intervals 3.7 vs 4.1 ms; P = 0.004).

CONCLUSIONS

Although there are concerns about hypoglycaemia in general in people with Type 1 diabetes, chronic hyperglycaemia, rather than intermittent hypoglycaemia, appears to be more deleterious to autonomic cardiac function, even in adolescence. Longer QTc was associated with higher HbA1c concentration, lower risk of hypoglycaemia and autonomic dysfunction. Longitudinal studies are warranted.

Cardiovascular autonomic neuropathy associates with nephropathy lesions in American Indians with type 2 diabetes

AIMS

Cardiovascular autonomic neuropathy (CAN) predicts clinical diabetic nephropathy (DN). We investigated the relationship between DN structural lesions and CAN.

METHODS

Sixty three Pima Indians with type 2 diabetes underwent kidney biopsies following a 6-year clinical trial testing the renoprotective efficacy of losartan vs. placebo. CAN was assessed a median 9.2years later. CAN variables included expiration/inspiration ratio (E/I), standard deviation of the normal R-R interval (sdNN), and low and high frequency signal power and their ratio (LF, HF, LF/HF); lower values reflect more severe neuropathy. Associations of CAN with renal structural variables were assessed by linear regression adjusted for age, sex, diabetes duration, blood pressure, HbA1c, glomerular filtration rate, and treatment assignment during the trial.

RESULTS

Global glomerular sclerosis was negatively associated with sdNN (partial r=-0.35, p=0.01) and LF (r=-0.32, p=0.02); glomerular basement membrane width was negatively associated with all measures of CAN except for LF/HF (r=-0.28 to -0.42, p<0.05); filtration surface density was positively associated with sdNN, LF, and HF (r=0.31 to 0.38, p<0.05); and cortical interstitial fractional volume was negatively associated with HF (r=-0.27, p=0.04).

CONCLUSIONS

CAN associates with DN lesions.

Autonomic nervous system function assessed by conventional and spectral analysis might be useful in terms of predicting retinal deterioration in persons with type 1 diabetes mellitus

AIMS

To determine whether cardiac autonomic dysfunction represents a risk factor for diabetic retinopathy (DR) development and progression in persons with type 1 diabetes mellitus (T1DM).

METHODS

The study comprised 154 normoalbuminuric persons with T1DM divided into two groups according to the DR presence: with and without DR. Cardiovascular autonomic functioning was measured at baseline using conventional and spectral analysis. Participants were re-examined for the DR presence 18months after.

RESULTS

The group with DR had longer disease duration compared to the group without DR (20 vrs 11.5years, p<0.001), heart rate coefficient of variation (HRV-CV) at rest and during deep breathing were lower in participants with DR (p=0.001 and 0.004), as well did spectral indices of HRV: low frequency (LF) band, high frequency (HF) band (p=0.003 and 0.022) while LF/HF ratio indicating sympathovagal balance was higher (p=0.037). No difference in glycaemic control or blood pressure value were observed. Twenty-one (13.36%) participants developed non proliferative DR or progressed to proliferative DR. Cox proportional regression showed that the 18months risk from retinal deterioration was reduced by 33.4% by each increase in the HRV-CV of 1%, 12.7% for the same HRV-CV increase during deep breathing while LF band of 1ms(2) results in 8.6% risk reduction.

CONCLUSIONS

This study provides evidence that DR should not be considered merely a metabolic control manifestation and that HRV-CV as well as spectral indices of HRV might serve as a practical tool to identify a subgroup of T1DM patients with higher risk of retinal deterioration.

Pupillary Light Reflexes are Associated with Autonomic Dysfunction in Bolivian Diabetics But Not Chagas Disease Patients

Autonomic dysfunction is common in Chagas disease and diabetes. Patients with either condition complicated by cardiac autonomic dysfunction face increased mortality, but no clinical predictors of autonomic dysfunction exist. Pupillary light reflexes (PLRs) may identify such patients early, allowing for intensified treatment. To evaluate the significance of PLRs, adults were recruited from the outpatient endocrine, cardiology, and surgical clinics at a Bolivian teaching hospital. After testing for Chagas disease and diabetes, participants completed conventional autonomic testing (CAT) evaluating their cardiovascular responses to Valsalva, deep breathing, and orthostatic changes. PLRs were measured using specially designed goggles, then CAT and PLRs were compared as measures of autonomic dysfunction. This study analyzed 163 adults, including 96 with Chagas disease, 35 patients with diabetes, and 32 controls. PLRs were not significantly different between Chagas disease patients and controls. Patients with diabetes had longer latency to onset of pupil constriction, slower maximum constriction velocities, and smaller orthostatic ratios than nonpatients with diabetes. PLRs correlated poorly with CAT results. A PLR-based clinical risk score demonstrated a 2.27-fold increased likelihood of diabetes complicated by autonomic dysfunction compared with the combination of blood tests, CAT, and PLRs (sensitivity 87.9%, specificity 61.3%). PLRs represent a promising tool for evaluating subclinical neuropathy in patients with diabetes without symptomatic autonomic dysfunction. Pupillometry does not have a role in the evaluation of Chagas disease patients.

Impaired Awareness of Hypoglycemia in Adults With Type 1 Diabetes Is Not Associated With Autonomic Dysfunction or Peripheral Neuropathy

OBJECTIVE

Impaired awareness of hypoglycemia (IAH) is a risk factor for severe hypoglycemia in people with insulin-treated diabetes; autonomic neuropathy has been suggested to underlie its development. The aim was to evaluate a putative association between IAH and autonomic dysfunction using novel and sensitive measures of autonomic neural function.

RESEARCH DESIGN AND METHODS

Sixty-six adults with type 1 diabetes were studied, 33 with IAH and 33 with normal awareness of hypoglycemia (NAH), confirmed by formal testing. Participants were matched for age, sex, and diabetes duration. Clinical and laboratory evaluations included extensive autonomic function testing, peripheral nerve conduction studies, and quantitative sensory testing. Composite abnormality Z scores were used for group comparisons.

RESULTS

The IAH and NAH group had similar median (interquartile range) age of 48 (14.5) vs. 47 (14.5) years, diabetes duration of 30 (13.5) vs. 31 (13.5) years, and mean ± SD HbA1c 7.8 ± 2.2% vs. 8.1 ± 1.9%, respectively. The autonomic composite Z score did not differ between the two groups (mean difference -0.15, 95% CI -0.46, 0.16; P = 0.33), nor did the thermal detection (mean difference 0.15, 95% CI -0.31, 0.61; P = 0.51) or nerve conduction scores (mean difference 0.03, 95% CI -0.43, 0.49; P = 0.89).

CONCLUSIONS

In adults with type 1 diabetes, IAH was not associated with autonomic dysfunction or peripheral neuropathy.

Cardiac autonomic neuropathy and early progressive renal decline in patients with nonmacroalbuminuric type 1 diabetes

BACKGROUND AND OBJECTIVES

Cardiac autonomic neuropathy predicts future adverse renal outcomes in the general population. This study sought to determine its relationship with early progressive renal decline in type 1 diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A subset of participants with normoalbuminuria (n=204) or microalbuminuria (n=166) from the First Joslin Kidney Study underwent assessment for cardiac autonomic neuropathy using heart rate variability during baseline visits performed from January 1991 to April 1992. Cardiac autonomic neuropathy was defined as an R-R variation (mean circular resultant) <20. Participants also had baseline and follow-up measurement of eGFR. Early progressive renal decline was evaluated according to two definitions: early GFR loss (slope of eGFR estimated by cystatin C <-3.3%/year) and incident advanced CKD (stage ≥3, defined by eGFR [calculated by Modification of Diet in Renal Disease method] <60 ml/min per 1.73 m(2)). Association with baseline cardiac autonomic neuropathy was assessed by adjusted logistic regression and Cox proportional hazards.

RESULTS

Among the 370 participants, 47 (13%) had baseline cardiac autonomic neuropathy, 51 (14%) had early GFR loss, and 68 (18%) had incident advanced CKD over a median 14-year follow-up. Early GFR loss occurred in 15 (32%) of the 47 patients with baseline autonomic neuropathy and in 32 (10%) of the 323 without baseline autonomic neuropathy (P<0.001). Baseline autonomic neuropathy was strongly associated with odds of early GFR loss (adjusted odds ratio, 4.09; 95% confidence interval, 1.65 to 10.12; P=0.002). Incident advanced CKD was observed in 22 (47%) of those with baseline autonomic neuropathy and 46 (14%) of those without baseline autonomic neuropathy (P<0.001). Autonomic neuropathy was independently associated with incident advanced CKD (adjusted hazard ratio, 2.76; 95% confidence interval, 1.44 to 5.30; P=0.002).

CONCLUSIONS

Cardiac autonomic neuropathy was a strong independent predictor of the long-term risk of early progressive renal decline in type 1 diabetes. Future research should explore the mechanisms by which autonomic neuropathy may be associated with renal function loss.

Cardiac autonomic dysfunction is associated with high-risk albumin-to-creatinine ratio in young adolescents with type 1 diabetes in AdDIT (adolescent type 1 diabetes cardio-renal interventional trial)

OBJECTIVE

This study examined the association between cardiac autonomic dysfunction and high albumin-to-creatinine ratio (ACR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Adolescents recruited as part of a multicenter screening study (n = 445, 49% female, aged 10-17 years, mean duration 6.9 years; mean HbA1c 8.4%, 68 mmol/mol) underwent a 10-min continuous electrocardiogram recording for heart rate variability analysis. Time-domain heart rate variability measures included baseline heart rate, SD of the R-R interval (SDNN), and root mean squared difference of successive R-R intervals (RMSSD). Spectral analysis included sympathetic (low-frequency) and parasympathetic (high-frequency) components. Standardized ACR were calculated from six early morning urine collections using an established algorithm, reflecting age, sex, and duration, and stratified into ACR tertiles, where the upper tertile reflects higher nephropathy risk.

RESULTS

The upper-tertile ACR group had a faster heart rate (76 vs. 73 bpm; P < 0.01) and less heart rate variability (SDNN 68 vs. 76 ms, P = 0.02; RMSSD 63 vs. 71 ms, P = 0.04). HbA1c was 8.5% (69 mmol/mmol) in the upper tertile vs. 8.3% (67 mmol/mol) in the lower tertiles (P = 0.07). In multivariable analysis, upper-tertile ACR was associated with faster heart rate (β = 2.5, 95% CI 0.2-4.8, P = 0.03) and lower RMSSD (β = -9.5, 95% CI -18.2 to -0.8, P = 0.03), independent of age and HbA1c.

CONCLUSIONS

Adolescents at potentially higher risk for nephropathy show an adverse cardiac autonomic profile, indicating sympathetic overdrive, compared with the lower-risk group. Longitudinal follow-up of this cohort will further characterize the relationship between autonomic and renal dysfunction and the effect of interventions in this population.

The association between abnormal heart rate variability and new onset of chronic kidney disease in patients with type 2 diabetes: a ten-year follow-up study

AIMS

We investigated the association between cardiovascular autonomic neuropathy (CAN) and the future development of chronic kidney disease (CKD) in patients with type 2 diabetes.

METHODS

From Jan 2003 to Dec 2004, 1117 patients with type 2 diabetes without CKD (estimated glomerular filtration rate [eGFR] ≥ 60 ml/min/1.73 m(2)), aged 25-75 years, were consecutively enrolled. A cardiovascular autonomic function test (AFT) was performed using heart rate variability parameters. The eGFR was measured at least more than once every year, and new onset CKD was defined as eGFR < 60 ml/min/1.73 m(2) using a Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

RESULTS

Among the 755 (67.6%) patients who completed the follow-up evaluation for 9.6 years, 272 patients (36.0%) showed a CKD stage ≥3. The patients who developed CKD were older, had a longer duration of diabetes, had hypertension, received more insulin and ACE inhibitor/angiotensin receptor blocker (ARB) treatment, and exhibited lower baseline eGFR, HbA1c, and albuminuria levels. Compared to patients without CKD, more patients with CKD at follow-up had CAN at baseline. In a multivariate analysis, after adjustment for age, sex, diabetes duration, presence of hypertension, mean HbA1c, diabetic complications, use of insulin, ACE inhibitor/ARB, statin, and baseline eGFR, the development of CKD was significantly associated with the presence of CAN (HR 2.62, 95% CI 1.87-3.67, P<0.001).

CONCLUSIONS

In this prospective, longitudinal, observational cohort study, we demonstrated that diabetic CAN was an independent prognostic factor for the future development of CKD in type 2 diabetes.

Cardiovascular autonomic dysfunction predicts severe hypoglycemia in patients with type 2 diabetes: a 10-year follow-up study

OBJECTIVE The aim of this study was to investigate the development of severe hypoglycemia (SH) in the presence of cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS From January 2001 to December 2002, a total of 894 patients with type 2 diabetes were enrolled. A cardiovascular autonomic function test (AFT) was performed using the following heart rate variability parameters: expiration-to-inspiration ratio, response to Valsalva maneuver, and standing. From the results for each of the three tests (0 for normal, 1 for abnormal), a total AFT score of 1 was defined as early CAN, and an AFT score of ≥2 was defined as definite CAN. RESULTS The median follow-up time was 9.5 years. The mean age was 54.5 ± 10.1 years, and the mean duration of diabetes was 8.9 ± 6.3 years. One hundred ninety-six patients (31.4%) showed an abnormal cardiovascular AFT score at baseline. Sixty-two patients (9.9%) experienced 77 episodes of SH (1.33 per 100 patient-years). The number of SH events increased as the CAN score increased (23 patients [5.4%] with normal score; 17 patients [17.2%] with early CAN; and 22 patients [22.7%] with definite CAN; P for trends < 0.001). Cox proportional hazards regression analysis revealed that SH was associated with definite CAN (normal vs. definite CAN: hazard ratio 2.43 [95% CI 1.21-4.84]; P = 0.012). CONCLUSIONS Definite CAN was an independent prognostic factor for the development of SH in patients with type 2 diabetes.

Autonomic neuropathy in young people with type 1 diabetes: a systematic review

Autonomic neuropathy is an under-recognized complication of diabetes, although it affects multiple organ systems and has widespread clinical manifestations including orthostatic hypotension, exercise intolerance, gastroparesis, diarrhea, constipation, and urinary incontinence. The most severe consequences include hypoglycemia unawareness and cardiovascular dysfunction. Autonomic neuropathy is also implicated in sudden unexplained deaths in otherwise healthy young people--the ‘dead in bed syndrome’. In adults, cardiovascular autonomic neuropathy is an independent predictor of mortality, predominantly due to cardiovascular disease, nephropathy, and hypoglycemia. While overt autonomic neuropathy is rare in childhood and adolescence, subclinical signs of autonomic dysfunction are common, and can be found soon after diabetes diagnosis. Risk factors for autonomic neuropathy in young people include diabetes duration, poor glycemic control, and presence of aldose reductase gene (AKR1B1) polymorphisms, specifically the Z-2/Z-2 genotype. Autonomic dysfunction is accelerated by puberty.

Laboratory evaluation of pediatric autonomic disorders

The autonomic nervous system controls a variety of fundamental physiological processes in the human body including regulation of breathing, heart rate, blood pressure, temperature, and gastrointestinal motility. Although, methods of testing autonomic function have been developed and normative data have been collected in adults, development of child-friendly testing and the field of pediatric autonomic medicine is just beginning. These noninvasive testing methods serve to identify changes in autonomic functioning and to clarify whether dysfunction is isolated or crosses into multiple systems. Methods for testing cardiovagal, adrenergic, sudomotor, pupillary, enteric, and bladder function need to be refined and made more child friendly at the same time that age and gender appropriate normative values are developed for children.

Immediate effects of a thoracic spine thrust manipulation on the autonomic nervous system: a randomized clinical trial

Thoracic spine manipulation has been shown to be effective for the management of neck pain. The purpose of this study was to investigate the immediate effect of a T3-T4 spinal thrust manipulation on autonomic nervous system activity in subjects with chronic cervical pain. An additional aim was to determine if the manipulation resulted in an immediate pain relief in patients with chronic neck pain when compared to a placebo intervention. One hundred subjects with chronic neck pain were randomly assigned to receive either a thoracic thrust manipulation or a placebo intervention. The Friedman's test was used to evaluate the change in pupil diameter within both groups. The Wilcoxen signed-ranks test was used to explore pupil changes over time and to make paired comparisons of the pupil change between the groups. The Mann-Whitney U test was used to compare the change in pain perception for the chronic cervical pain group subjects receiving either the thrust manipulation or the placebo intervention. The results demonstrated that manipulation did not result in a change in sympathetic activity. Additionally, there was no significant difference in the subject's pain perception (P = 0.961) when comparing the effects of the thrust manipulation to the placebo intervention within this group of subjects with chronic neck pain. The clinical impression of this study is that manipulation of the thoracic spine may not be effective in immediately reducing pain in patients with chronic neck pain.

Medial arterial calcification in diabetes and its relationship to neuropathy

Calcification of the media of arterial walls is common in diabetes and is particularly associated with distal symmetrical neuropathy. Arterial calcification also complicates chronic kidney disease and is an independent risk factor for cardiovascular and all-cause mortality. The term calcification is not strictly accurate because the morphological changes incorporate those of new bone formation, i.e. ossification. The processes are complex, but are closely related to those involved in bone homeostasis, and it is relevant that calcification of the arterial wall and osteopenia often co-exist. One particular factor linked to the development of arterial calcification is distal symmetrical neuropathy; indeed, it has been suggested that neuropathy explains the distal distribution of arterial calcification in diabetes. It has also been suggested that the link with neuropathy results from loss of neuropeptides, such as calcitonin gene-related peptide, which are inherently protective. The association between distal symmetrical neuropathy and calcification of the arterial wall highlights the fact that neuropathy may be an independent risk factor for cardiovascular mortality.

Diabetic retinopathy is associated with early autonomic dysfunction assessed by exercise-related heart rate changes

Diabetic retinopathy has been associated with cardiac autonomic dysfunction in both type 1 and type 2 diabetes mellitus (DM) patients. Heart rate (HR) changes during exercise testing indicate early alterations in autonomous tonus. The aim of the present study was to investigate the association of diabetic retinopathy with exercise-related HR changes. A cross-sectional study was performed on 72 type 2 and 40 type 1 DM patients. Autonomic dysfunction was assessed by exercise-related HR changes (Bruce protocol). The maximum HR increase, defined as the difference between the peak exercise rate and the resting rate at baseline, and HR recovery, defined as the reduction in HR from the peak exercise to the HR at 1, 2, and 4 min after the cessation of the exercise, were determined. In type 2 DM patients, lower maximum HR increase (OR = 1.62, 95%CI = 1.03-2.54; P = 0.036), lower HR recovery at 2 (OR = 2.04, 95%CI = 1.16-3.57; P = 0.012) and 4 min (OR = 2.67, 95%CI = 1.37-5.20; P = 0.004) were associated with diabetic retinopathy, adjusted for confounding factors. In type 1 DM, the absence of an increase in HR at intervals of 10 bpm each during exercise added 100% to the odds for diabetic retinopathy (OR = 2.01, 95%CI = 1.1-3.69; P = 0.02) when adjusted for DM duration, A1c test and diastolic blood pressure. In conclusion, early autonomic dysfunction was associated with diabetic retinopathy. The recognition of HR changes during exercise can be used to identify a high-risk group for diabetic retinopathy.

Peripheral sensory neuropathy associates with micro- or macroangiopathy: results from a population-based study of type 2 diabetic patients in Sweden

OBJECTIVE

To assess associations between peripheral sensory neuropathy (PSN) and other diabetes-related complications.

RESEARCH DESIGN AND METHOD

In an area-based cohort of type 2 diabetic subjects, we investigated 156 subjects (age 61.7 +/- 7.2 years and diabetes duration 7.0 +/- 5.7 years) by questionnaires, clinical examinations, blood and urine sampling, and review of medical records.

RESULTS

Prevalence of PSN, assessed by monofilament and neurothesiometer testing, increased with severity of retinopathy (50% frequency in moderate and 100% in severe or proliferative retinopathy; P = 0.02). Vibration perception threshold was higher in subjects with retinopathy (25.6 +/- 8.9 vs. 20.5 +/- 8.9 V; P = 0.007). PSN was more common in subjects with overt nephropathy, with higher vibration perception thresholds, than in subjects without overt nephropathy. Subjects with PSN but no retinopathy had twice the prevalence of peripheral vascular disease (PVD) (52%) as subjects with both PSN and retinopathy (19%; P = 0.05). In subjects with PSN alone, PVD was three times more likely (52%) than in subjects without PSN (16%; P = 0.001). In multivariate analysis, PSN was independently associated with PVD (odds ratio 2.31; P = 0.007), age (1.12; P = 0.008), male sex (2.01; P = 0.02), and HDL cholesterol (0.21; P < 0.05) and tended to be independently associated with IGF-1 binding protein (1.03; P = 0.05) but not with diabetes duration or A1C.

CONCLUSIONS

In a representative population of type 2 diabetes, PSN is related to microvascular and macrovascular pathology. PSN is possibly affected by the IGF axis.

Plantar fascia thickness, a measure of tissue glycation, predicts the development of complications in adolescents with type 1 diabetes

OBJECTIVE

Direct measurement of collagen glycation requires skin biopsy, which is invasive. We hypothesized that measurement of plantar fascia thickness (PFT) by ultrasound is an alternative index of tissue glycation and a marker of microvascular disease.

RESEARCH DESIGN AND METHODS

This was a prospective longitudinal study of microvascular complications in 344 adolescents with type 1 diabetes, whose PFT was assessed by ultrasound at baseline. Retinopathy was assessed by seven-field fundal photography, albumin excretion rate (AER) measured from three consecutive timed overnight urine specimens, autonomic neuropathy by pupillometry and cardiovascular tests, and peripheral neuropathy by vibration and thermal thresholds. Longitudinal analysis was performed using generalized estimating equations with baseline PFT, duration, and A1C as explanatory variables.

RESULTS

At first assessment, median (interquartile range) age was 15.1 (13.5-17.2) years and diabetes duration was 8.5 (6.0-11.5) years. Median follow up was 3.2 (2.1-4.5) years with a median of 4 (2-13) complications assessments per patient. In multivariate analysis, baseline PFT (abnormal in 132 subjects, 38%) predicted subsequent development of retinopathy (odds ratio 2.4 [95% CI 1.1-5.0]), elevated AER (2.24 [1.05-5.11]), peripheral neuropathy (2.3 [1.2-4.41]), and autonomic neuropathy (4.94 [2.46-9.91]). Limited joint mobility was present in only 4%.

CONCLUSIONS

PFT is a significant predictor of the subsequent development of complications in type 1 diabetes, suggesting that glycation and oxidation of collagen in soft tissues may be independent risk factors for microvascular complications.

Dysfunction of the pupillary light reflex in experimental autoimmune autonomic ganglionopathy

Autoimmune autonomic ganglionopathy (AAG) is an antibody-mediated form of severe autonomic failure. AAG is associated with serum antibodies against ganglionic acetylcholine receptors (AChR) and appears to result from impaired synaptic transmission in autonomic ganglia. The rabbit model of experimental AAG (EAAG), induced by immunization, reproduces the cardinal features of the human disease. Pupillary dysfunction is a prominent and defining feature in both AAG and EAAG. We adapted infrared computer-assisted video pupillometry to record direct pupil light responses in control and EAAG rabbits. Offline analysis algorithms were used to determine latency, velocity and amplitude of the constriction and redilation phases of the light reflex. Following immunization, pupillary abnormalities were the earliest sign of evolving autonomic failure. EAAG rabbits showed significant reduction in velocity and amplitude of pupil constriction while redilation parameters were only mildly affected. Fatigue in pupillary constriction, evidenced by premature redilation of the pupil prior to termination of the light stimulus, was observed only in seropositive rabbits. The severity of pupillary abnormalities was significantly correlated with ganglionic AChR antibody level. In chronic EAAG, treatment with pyridostigmine produced a partial recovery of pupil function. We conclude that pupillometry is a robust and sensitive diagnostic tool to assess autonomic dysfunction, distinguish AAG from other disorders, and assess responses to therapy. In EAAG, pupillary dysfunction is partially reversible, parasympathetic pupil function is more severely compromised than sympathetic function, and fatigue of pupillary constriction may be seen. These characteristic abnormalities of the pupillary light reflex may prove to have diagnostic value.