Thermoregulatory sudomotor dysfunction and diabetic neuropathy develop in parallel in at-risk feet

An overview of current developments and methods for identifying diabetic foot ulcers: A survey

Diabetic foot ulcers (DFUs) present a substantial health risk across diverse age groups, creating challenges for healthcare professionals in the accurate classification and grading. DFU plays a crucial role in automated health monitoring and diagnosis systems, where the integration of medical imaging, computer vision, statistical analysis, and gait information is essential for comprehensive understanding and effective management. Diagnosing DFU is imperative, as it plays a major role in the processes of diagnosis, treatment planning, and neuropathy research within automated health monitoring and diagnosis systems. To address this, various machine learning and deep learning‐based methodologies have emerged in the literature to support healthcare practitioners in achieving improved diagnostic analyses for DFU. This survey paper investigates various diagnostic methodologies for DFU, spanning traditional statistical approaches to cutting‐edge deep learning techniques. It systematically reviews key stages involved in diabetic foot ulcer classification (DFUC) methods, including preprocessing, feature extraction, and classification, explaining their benefits and drawbacks. The investigation extends to exploring state‐of‐the‐art convolutional neural network models tailored for DFUC, involving extensive experiments with data augmentation and transfer learning methods. The overview also outlines datasets commonly employed for evaluating DFUC methodologies. Recognizing that neuropathy and reduced blood flow in the lower limbs might be caused by atherosclerotic blood vessels, this paper provides recommendations to researchers and practitioners involved in routine medical therapy to prevent substantial complications. Apart from reviewing prior literature, this survey aims to influence the future of DFU diagnostics by outlining prospective research directions, particularly in the domains of personalized and intelligent healthcare. Finally, this overview is to contribute to the continual evolution of DFU diagnosis in order to provide more effective and customized medical care.

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Screening tools for diabetic foot ulcers: a narrative review

The prevalence of diabetic foot ulcers (DFUs) is 4 to 10% among people with diabetes mellitus. DFUs are associated with increased morbidity and mortality as well as reduced quality of life and have a significant impact on overall healthcare expenditure. The main predisposing factors for DFU are diabetic neuropathy, peripheral arterial disease, and trauma. The fact that a range of tests can be used to identify patients at risk for DFU often causes confusion among practitioners regarding which screening tests should be implemented in clinical practice. Herein we sought to determine whether tests of somatic nerve function, such as pinprick sensation, thermal (cold/hot) test, ankle reflexes, vibration perception, 10-g monofilament, Ipswich touch test, neuropathy disability score, and nerve conduction studies, predict the development of DFUs. In addition, we examined whether sudomotor function screening tests, such as Neuropad, sympathetic skin response, and other tests, such as elevated plantar pressure or temperature measurements, can be used for DFU screening. If not treated properly, DFUs can have serious consequences, including amputation, early detection and treatment are vital for patient outcomes.

Frontiers in diagnostic and therapeutic approaches in diabetic sensorimotor neuropathy (DSPN)

Diabetes sensory polyneuropathy (DSPN) is a significant complication of diabetes affecting up to 50% of patients in their lifetime and approximately 20% of patients suffer from painful diabetes neuropathic pain. DSPN - both painless and painful - leads to considerable morbidity including reduction of quality of life, increased lower limb amputations and is associated with worsening mortality. Significant progress has been made in the understanding of pathogenesis of DSPN and the last decade has seen newer techniques aimed at its earlier diagnosis. The management of painful DSPN remains a challenge despite advances made in the unravelling the pathogenesis of pain and its transmission. This article discusses the heterogenous clinical presentation of DSPN and the need to exclude key differential diagnoses. Furthermore, it reviews in detail the current diagnostic techniques involving both large and small neural fibres, their limitations and advantages and current place in the diagnosis of DSPN. Finally, the management of DSPN including newer pharmacotherapies are also discussed.

Prediction of the Efficacy of Lumbar Sympathetic Block in Patients with Lower Extremity Complex Regional Pain Syndrome Type 1 Based on the Sympathetic Skin Response

INTRODUCTION

Complex regional pain syndrome type 1 (CRPS-1) is prevalent after trauma, with intractable pain being the most prominent clinical symptom. The impact of sympathetic block on CRPS is unclear. The goal of this study was to explore the characteristics that predict successful symptom relief with lumbar sympathetic block (LSB) in patients with lower extremity CRPS-1.

METHODS

The study was designed as a prospective cohort study. Ninety-eight patients diagnosed with lower extremity CRPS-1 between March 2021 and March 2022 were enrolled as participants. All of the patients received two LSB treatments within a month. Sympthetic skin response (SSR) and numeric rating scale (NRS) were recorded before and after LSB treatment. The procedure was judged as a clinically positive response if the patients a 50% or greater reduction in NRS scores. Patients were divided into positive response and negative response groups after LSB treatment: LSB (+) and LSB (-), and the different characteristics and examination findings of the two groups of patients were compared. Furthermore, a multivariable logistic regression model was utilized to evaluate the predictors of successful symptom relief following LSB treatment.

RESULTS

A total of 43.9% (43/98) of patients experienced successful symptom relief, while 56.1% (55/98) had unsuccessful symptom relief. After LSB treatment of all subjects, the overall NRS score decreased, the SSR amplitude increased, and the SSR latency shortened in the affected extremity (P < 0.05). There was a significant difference in the change in SSR amplitude between the LSB (-) and LSB (+) groups (P = 0.000). A 12-month disease duration had an OR (odds ratio) of 4.477 (P = 0.009), and a 510-µV baseline SSR amplitude of the affected extremity had an OR of 7.508 (P = 0.000) in the multivariable analysis that included these explanatory variables.

CONCLUSIONS

Patients with lower extremity CRPS-1 can experience significant pain relief after LSB treatment. The predictors of successful symptom relief after LSB treatment were a baseline SSR amplitude of the affected extremity < 510 µV and a disease duration < 12 months.

TRIAL REGISTRATION

The study was registered in the Chinese Clinical Trial Registry (ID: ChiCTR2000037755, date of registration: September 4, 2020).

The Impact of Heatwaves on Mortality and Morbidity and the Associated Vulnerability Factors: A Systematic Review

BACKGROUND

This study aims to investigate the current impacts of extreme temperature and heatwaves on human health in terms of both mortality and morbidity. This systematic review analyzed the impact of heatwaves on mortality, morbidity, and the associated vulnerability factors, focusing on the sensitivity component.

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 flow checklist. Four databases (Scopus, Web of Science, EBSCOhost, PubMed) were searched for articles published from 2012 to 2022. Those eligible were evaluated using the Navigation Guide Systematic Review framework.

RESULTS

A total of 32 articles were included in the systematic review. Heatwave events increased mortality and morbidity incidence. Sociodemographic (elderly, children, male, female, low socioeconomic, low education), medical conditions (cardiopulmonary diseases, renal disease, diabetes, mental disease), and rural areas were crucial vulnerability factors.

CONCLUSIONS

While mortality and morbidity are critical aspects for measuring the impact of heatwaves on human health, the sensitivity in the context of sociodemographic, medical conditions, and locality posed a higher vulnerability to certain groups. Therefore, further research on climate change and health impacts on vulnerability may help stakeholders strategize effective plans to reduce the effect of heatwaves.

The Effects of Skin Temperature Changes on the Integrity of Skin Tissue: A Systematic Review

OBJECTIVE

To determine whether changes in skin temperature can affect the integrity of skin.

METHODOLOGY

The authors conducted a systematic literature search as per the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. They searched the CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, MEDLINE Complete, Academic Search Ultimate, and HyDi databases for articles examining the effects of skin temperature on skin integrity published through April 2020. Two independent reviewers scored the methodologic quality of the 13 included studies.

RESULTS

Only 11 studies were included in the qualitative analysis, as the other two articles had a critical risk of bias. There is strong evidence to indicate that an increase in skin temperature leads to changes in skin structure and function. However, ulcer formation was more affected by intrinsic and extrinsic factors, rather than by temperature alone.

CONCLUSION

Further high-quality randomized controlled trials are required to investigate the direct effect of skin temperature on ulceration.

Concordance between sudomotor disorder and the clinical diagnosis of diabetic peripheral neuropathy, according to various clinical guidelines

AIM

To assess the concordance between variations in Neuropad® results and the those in different diagnostic criteria of Diabetic Peripheral Neuropathy, according to various clinical guidelines.

METHODS

A descriptive observational study was conducted of 111 patients with a confirmed diagnosis of diabetes mellitus. The criteria for inclusion in the study were that patients should be aged 18 years or more and have at least 10 years' history of diabetes mellitus.

RESULTS

73 (65.8%) were male and 38 (34.2%) were female. Their mean age was 57.92 ± 13.24 years (95% CI 55.45-60.38). Healthy Neuropad® findings were obtained for 35 right feet (31.5%) and 31 left feet (27.9%).

CONCLUSION

Neuropad® is an effective instrument for detecting macro and microvascular complications such as early-stage neuropathy, although its use should always be accompanied by a clinical examination of the foot.

Heat-related mortality at the beginning of the twenty-first century in Rio de Janeiro, Brazil

Temperature record-breaking events, such as the observed more intense, longer-lasting, and more frequent heat waves, pose a new global challenge to health sectors worldwide. These threats are of particular interest in low-income regions with limited investments in public health and a growing urban population, such as Brazil. Here, we apply a comprehensive interdisciplinary climate-health approach, including meteorological data and a daily mortality record from the Brazilian Health System from 2000 to 2015, covering 21 cities over the Metropolitan Region of Rio de Janeiro. The percentage of absolute mortality increase due to summer extreme temperatures is estimated using a negative binomial regression modeling approach and maximum/minimum temperature-derived indexes as covariates. Moreover, this study assesses the vulnerability to thermal stress for different age groups and both genders and thoroughly analyzes four extremely intense heat waves during 2010 and 2012 regarding their impacts on the population. Results showed that the highest absolute mortality values during heat-related events were linked to circulatory illnesses. However, the highest excess of mortality was related to diabetes, particularly for women within the elderly age groups. Moreover, results indicate that accumulated heat stress conditions during consecutive days preferentially preceded by persistent periods of moderate-temperature, lead to higher excess mortality rather than sporadic single hot days. This work may provide directions in human health policies related to extreme climate events in large tropical metropolitan areas from developing countries, contributing to altering the historically based purely reactive response.

Use of Noncontact Infrared Skin Thermometer for Peripheral Arterial Disease Screening in Patients With and Without Diabetes

Peripheral arterial disease (PAD) poses a threat of limb amputation and cardiovascular events. However, PAD diagnostic procedure requiring time, cost, and technical skills preclude its application as a screening test in the general population. Although PAD tends to be associated with lower foot skin temperature, none has yet to appreciate its usefulness for diagnosis/screening. We measured foot skin temperatures at the first and fifth metatarsal head and heel areas using noncontact infrared thermometer at the time of ankle brachial pressure index (ABI) measurement and limb arterial ultrasonography in 176 patients (345 legs) in participants. Foot skin temperatures correlated with ABI and showed distinctly lower levels in legs with ultrasound-confirmed arterial stenosis/occlusion and in those with ABI ≤0.90. Receiver operating characteristics analyses revealed that the lowest temperature value of the 3-foot locations had a higher sensitivity than every single location in detecting lower extremity PAD. Diagnostic efficiency for the ABI cutoff of 0.90 showed sensitivity/specificity of 41%/94%, while that for the lowest skin temperature cutoff of 30.8°C showed sensitivity/specificity of 60%/64%. In conclusion, an accurate skin temperature measurement using noncontact handheld infrared skin thermometer could serve as a new, cost-effective screening strategy for earlier diagnosis of PAD.

Dryness of Foot Skin Assessed by the Visual Indicator Test and Risk of Diabetic Foot Ulceration: A Prospective Observational Study

Research Question: Previous cross-sectional studies have shown an association between sudomotor dysfunction and diabetic foot ulceration (DFU). The aim of this prospective multicenter study was to determine the role of dryness of foot skin and of established neurological modalities in the prediction of risk for foot ulceration in a cohort of individuals with diabetes mellitus (DM). Design: The study was conducted from 2012 to 2017. A total of 308 subjects with DM without history of DFU or critical limb ischemia completed the study. Diabetic neuropathy was assessed using the neuropathy symptom score (NSS) and neuropathy disability score (NDS). In a subset of participants, vibration perception threshold (VPT) was evaluated. Dryness of foot skin was assessed by the visual indicator plaster method (IPM). The diagnostic performance of the above neurological modalities for prediction of DFU was tested by receiver operating characteristic curve (ROC) analysis. Results: During the 6-year follow-up, 55 patients (annual ulceration incidence 2.97%) developed DFU. Multivariate Cox-regression analysis after controlling for the effect of age, gender, and DM duration demonstrated that the risk (hazard ratio, 95% confidence intervals) of DFU increased significantly with either abnormal IPM (3.319, 1.460-7.545, p = 0.004) or high (≥6) NDS (2.782, 1.546-5.007, p = 0.001) or high (≥25 volts) VPT (2.587, 1.277-5.242, p = 0.008). ROC analysis showed that all neurological modalities could discriminate participants who developed DFU (p < 0.001). IPM testing showed high sensitivity (0.86) and low specificity (0.49), while high vs. low NDS and VPT showed low sensitivity (0.40 and 0.39, respectively) and high specificity (0.87 and 0.89, respectively) for identification of patients at risk for DFU. Conclusion: Dryness of foot skin assessed by the IPM predicts the development of DFU. IPM testing has high sensitivity, whereas high NDS and VPT have high specificity in identifying subjects at risk for DFU. The IPM can be included in the screening methods for identification of the foot at risk.

Heatwaves and diabetes in Brisbane, Australia: a population-based retrospective cohort study

Background

Available data on the effects of heatwaves on hospitalizations for diabetes and the post-discharge status of diabetics are scarce. This study aimed to assess the effects of heatwaves on hospitalizations and post-discharge deaths for diabetes, and to identify the individual- and community-level characteristics [i.e. age, gender, Socio-economic Indexes for Areas (SEIFA), and normalized difference vegetation index (NDVI)] that modified heatwave effects.

Methods

Health data were extracted from a cohort study which included patients in Brisbane, Australia, who were hospitalized due to diabetes from 1st January 2005 to 31st December 2013, and died within 2 months after they were discharged. Data on community-level modifiers, including SEIFA and NDVI (i.e. urban vegetation), were obtained from Australian Bureau of Statistics and Australian Bureau of Meteorology, respectively. Case-crossover design was used to quantify the effects of heatwaves on hospitalizations and post-discharge deaths due to diabetes. Four heatwave definitions incorporating both intensity (i.e. 90th, 95th, 97th and 99th percentiles of mean temperature distribution) and duration (2 days), as well as excess heat factor (EHF), were used. A case-only design was adopted to identify the modifiers of heatwave effects.

Results

There were 10 542 hospitalizations for diabetes, and 513 patients died due to diabetes within 2 months after discharge. During low-intensity heatwave days (i.e. 90th percentile & 2 days), we did not observe a significant increase in hospitalizations for diabetes [9% at lag 0; 95% confidence interval (CI): –3%, 23%; P = 0.146], but we observed a significant increase in post-discharge deaths (46% at lag 2; 95% CI: 3%, 107%; P = 0.036). During middle-intensity heatwave days (i.e. 95th percentile & 2 days), hospitalizations for diabetes increased by 19% at lag 0 (95% CI: 2%, 39%; P = 0.026), and post-discharge deaths increased by 64% at lag 0 (95% CI: 6%, 154%; P = 0.027). During high-intensity heatwave days (i.e. 97th percentile & 2 days), hospitalizations for diabetes increased by 37% at lag 1 (95% CI: 11%, 69%; P = 0.004) and post-discharge deaths increased by 137% at lag 1 (95% CI: 39%, 303%; P = 0.002). When heatwave intensity increased to 99th percentile, we did not observe a significant increase in hospitalizations (–1% at lag 0; 95% CI: –38%, 59%; P = 0.870) or post-discharge deaths (79% at lag 0; 95% CI: –39%, 431%; P = 0.301). When we used EHF to define heatwaves, we observed significant increases of hospitalizations (7%; 95% CI: 1%, 15%; P = 0.039) and post-discharge deaths (68%, 95% CI: 10%, 158%; P = 0.017) during heatwave days, compared with non-heatwave days. Children and male diabetics were particularly vulnerable to heatwave effects, but we did not find any significant modification effect of SEIFA or NDVI on the associations of heatwaves with hospitalizations and post-discharge deaths due to diabetes.

Conclusion

Heatwaves may lead to hospitalizations of diabetics and their premature deaths. Heat-related diabetes burden in children may increase as climate warms and with increasing obesity rates in adolescents.

Mortality burden attributable to heatwaves in Thailand: A systematic assessment incorporating evidence-based lag structure

BACKGROUND

Available information on the acute and cumulative effects of heatwaves on cause-specific mortality in Thailand is scarce.

OBJECTIVES

To quantify the acute and cumulative effects of heatwaves on mortality in Thailand, and assess heatwave-related mortality burden.

METHODS

Thirty heatwave definitions were used and categorized into three groups: low intensity heatwaves (HW_low), middle intensity heatwaves (HW_middle), and high intensity heatwaves (HW_high). Time-series analyses were conducted to examine the acute and cumulative effects of HW_low, HW_middle, and HW_high on total and cause-specific mortality in 60 provinces of Thailand, incorporating an optimal lag for each cause and each province. Random-effects meta-analyses were performed to pool provincial estimates to national estimates for both acute and cumulative effects. Meta-regressions were conducted to identify the possible factors contributing to the spatial heterogeneity of heatwave vulnerability.

RESULTS

The cumulative effects of HW_low and HW_middle on total and cause-specific mortality were greater than HW_high. Both acute and cumulative effects of HW_low, HW_middle and HW_high on neoplasms and certain infectious and parasitic diseases were among the highest across all death causes. Effects of heatwaves on deaths from endocrine, nutritional and metabolic diseases appeared to be longer-lasting, and effects of heatwaves on deaths from ischaemic heart diseases and pneumonia occurred more rapidly. Northern and Central Thailand were the regions vulnerable to heatwaves, and proportion of elderly population was the major driver behind the spatial heterogeneity of heatwave vulnerability.

CONCLUSIONS

More attention needs to be paid to mild heatwaves. Future heatwave-related mortality burden due to neoplasms and infectious diseases in Thailand may increase as climate change continues.

The relationship between sudomotor function and skin microvascular reactivity in individuals with type 1 diabetes of long duration

AIM

The aim of this study was to assess the relationship between sudomotor function and microvascular perfusion in patients with type 1 diabetes (DM1).

METHODS

We evaluated 415 patients (206 women), with DM1, median age of 41 (IQR: 33-53) years, disease duration of 25 (IQR: 20-32) years. We assessed metabolic control of diabetes and the presence of peripheral and cardiac autonomic neuropathy. Sudomotor function was assessed using Sudoscan device by electrochemical skin conductance (ESC). Microvascular function was measured by laser-Doppler flowmetry with basal perfusion, the peak flow after occlusion (PORHpeak) and THmax which is the percentage change between basal perfusion and the peak flow during thermal hyperemia (TH). The accumulation of advanced glycation end products in the skin was assessed by skin autofluorescence (AF) measurement using AGE Reader. We subdivided patients based on the presence of diabetic peripheral neuropathy (DPN), cardiac autonomic neuropathy (CAN) and according to normal value of ESC.

RESULTS

Patients with abnormal ESC had higher skin AF [2.5 (2.1-2.9) vs 2.1 (1.9-2.5) AU, p < 0.001], lower eGFR [83 (72-96) vs 98 (86-108) ml/min/1.73 m2, p < 0.001], higher basal perfusion [25 (12-81) vs 14 (7-43) PU, p < 0.001], lower THmax [664 (137-1461) vs 1115 (346-1933) %, p = 0.002], higher PORHpeak [104 (59-167) vs 70 (48-135) PU, p < 0.001] as compared to subjects with normal ESC results. We found negative correlation between THmax and TG level (Rs = -0.14, p < 0.005), AF (Rs = -0.19, p = 0.001), vibration perception threshold - VPT (Rs = -0.24, p < 0.001) and positive correlation with HDL level (Rs = 0.14, p = 0.005), Feet ESC (Rs = 0.21, p < 0.001) and Hands ESC (Rs = 0.14, p = 0.004). We found positive correlation between PORHpeak and TG level (Rs = 0.14, p = 0.003), skin AF (Rs = 0.29, p < 0.001), VPT (0.27, p < 0.001) and negative correlation with eGFR (Rs = -0.2, p < 0.001), HDL (Rs = -0.12, p = 0.01), Feet ESC (Rs = -0.27, p < 0.001) and Hand ESC (Rs = -0.16, p = 0.002).

CONCLUSION

Impaired microvascular reactivity is associated with sudomotor dysfunction in patients with type 1 diabetes.

The role of the microbiome in nonhealing diabetic wounds

Wound healing is a highly coordinated and complex process, and there can be devastating consequences if it is interrupted. It is believed that, in combination with host factors, microorganisms in a wound bed can not only impair wound healing but can lead to stalled, chronic wounds. It is hypothesized that the wound microbiota persists in chronic wounds as a biofilm, recalcitrant to antibiotic and mechanical intervention. Cultivation-based methods are the gold standard for identification of pathogens residing in wounds. However, these methods are biased against fastidious organisms, and do not capture the full extent of microbial diversity in chronic wounds. Thus, the link between specific microbes and impaired healing remains tenuous. This is partially because local infection and, more specifically, the formation of a biofilm, is difficult to diagnose. This has led to research efforts aimed at understanding if biofilm formation delays healing and leads to persistent and chronic infection. Circumventing challenges associated with culture-based estimations, advances in high-throughput sequencing analysis has revealed that chronic wounds are host to complex, diverse microbiomes comprising multiple species of bacteria and fungi. Here, we discuss how the use of genomic methodologies to study wound microbiomes has advanced the current understanding of infection and biofilm formation in chronic wounds.

Novel methods of imaging and analysis for the thermoregulatory sweat test

The thermoregulatory sweat test (TST) can be central to the identification and management of disorders affecting sudomotor function and small sensory and autonomic nerve fibers, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. A high-resolution, quantitative, clean and simple assay of sweating could significantly improve identification and management of these disorders. Images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. First, using the standard indicator powder, skin surface sweat distributions were determined algorithmically for each patient. Second, a fundamentally novel method using thermal imaging of forced evaporative cooling was evaluated through comparison with the standard technique. Correlation and receiver operating characteristic analyses were used to determine the degree of match between these methods, and the potential limits of thermal imaging were examined through cumulative analysis of all studied patients. Algorithmic encoding of sweating and nonsweating regions produces a more objective analysis for clinical decision-making. Additionally, results from the forced cooling method correspond well with those from indicator powder imaging, with a correlation across spatial regions of -0.78 (confidence interval: -0.84 to -0.71). The method works similarly across body regions, and frame-by-frame analysis suggests the ability to identify sweating regions within ~1 s of imaging. Although algorithmic encoding can enhance the standard sweat testing protocol, thermal imaging with forced evaporative cooling can dramatically improve the TST by making it less time consuming and more patient friendly than the current approach. NEW & NOTEWORTHY The thermoregulatory sweat test (TST) can be central to the identification and management of several common neurological disorders, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. In this study, images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. Our results suggest that these improved methods could make sweat testing more reliable and acceptable for screening and management of a range of neurological disorders.

Computer aided diagnosis of diabetic foot using infrared thermography: A review

Diabetes mellitus (DM) is a chronic metabolic disorder that requires regular medical care to prevent severe complications. The elevated blood glucose level affects the eyes, blood vessels, nerves, heart, and kidneys after the onset. The affected blood vessels (usually due to atherosclerosis) may lead to insufficient blood circulation particularly in the lower extremities and nerve damage (neuropathy), which can result in serious foot complications. Hence, an early detection and treatment can prevent foot complications such as ulcerations and amputations. Clinicians often assess the diabetic foot for sensory deficits with clinical tools, and the resulting foot severity is often manually evaluated. The infrared thermography is a fast, nonintrusive and non-contact method which allows the visualization of foot plantar temperature distribution. Several studies have proposed infrared thermography-based computer aided diagnosis (CAD) methods for diabetic foot. Among them, the asymmetric temperature analysis method is more superior, as it is easy to implement, and yielded satisfactory results in most of the studies. In this paper, the diabetic foot, its pathophysiology, conventional assessments methods, infrared thermography and the different infrared thermography-based CAD analysis methods are reviewed.

Post-occlusive reactive hyperaemia of skin microvasculature and foot complications in type 2 diabetes

AIMS

Diabetes-related microvascular disease has been implicated in the development of foot ulceration and amputation. Assessment of microvascular function may be effective in identifying those at risk of diabetic foot complications. We investigated the relationship between active or previous foot complication and post-occlusive reactive hyperaemia (PORH) measured by laser-Doppler fluxmetry (LDF) in people with type 2 diabetes.

METHODS

PORH measures were obtained from the hallux apex in 105 people with type 2 diabetes. Associations were investigated between active or previous foot complication and PORH measures: time to peak (TtPeak) and peak as a percentage of baseline (P%BL). Multinomial logistic regression was used to determine the association of PORH with the likelihood of active foot ulcer or previous foot complication.

RESULTS

For each second increase in TtPeak, the likelihood of a participant having a history of foot complication is increased by 2% (OR=1.019, p=0.01). This association was not reflected in people with an active foot ulcer (OR=1.003, p=0.832). P%BL was not found to be significantly different between those with a current or previous foot complication and those without (p=0.404).

CONCLUSIONS

This investigation in a cohort with type 2 diabetes has demonstrated that longer TtPeak is associated with history of diabetic foot complications.

Ambient high temperature and mortality in Jinan, China: A study of heat thresholds and vulnerable populations

BACKGROUND

Understanding the health consequences of continuously rising temperatures-as is projected for China-is important in terms of developing heat-health adaptation and intervention programs. This study aimed to examine the association between mortality and daily maximum (T_max), mean (T_mean), and minimum (T_min) temperatures in warmer months; to explore threshold temperatures; and to identify optimal heat indicators and vulnerable populations.

METHODS

Daily data on temperature and mortality were obtained for the period 2007-2013. Heat thresholds for condition-specific mortality were estimated using an observed/expected analysis. We used a generalised additive model with a quasi-Poisson distribution to examine the association between mortality and T_max/T_min/T_mean values higher than the threshold values, after adjustment for covariates.

RESULTS

T_max/T_mean/T_min thresholds were 32/28/24°C for non-accidental deaths; 32/28/24°C for cardiovascular deaths; 35/31/26°C for respiratory deaths; and 34/31/28°C for diabetes-related deaths. For each 1°C increase in T_max/T_mean/T_min above the threshold, the mortality risk of non-accidental-, cardiovascular-, respiratory, and diabetes-related death increased by 2.8/5.3/4.8%, 4.1/7.2/6.6%, 6.6/25.3/14.7%, and 13.3/30.5/47.6%, respectively. Thresholds for mortality differed according to health condition when stratified by sex, age, and education level. For non-accidental deaths, effects were significant in individuals aged ≥65 years (relative risk=1.038, 95% confidence interval: 1.026-1.050), but not for those ≤64 years. For most outcomes, women and people ≥65 years were more vulnerable.

CONCLUSION

High temperature significantly increases the risk of mortality in the population of Jinan, China. Climate change with rising temperatures may bring about the situation worse. Public health programs should be improved and implemented to prevent and reduce health risks during hot days, especially for the identified vulnerable groups.

The effect of ambient temperature on diabetes mortality in China: A multi-city time series study

Few multi-city studies have been conducted to investigate the acute health effects of low and high temperatures on diabetes mortality worldwide. We aimed to examine effects of ambient temperatures on city-/gender-/age-/education-specific diabetes mortality in nine Chinese cities using a two-stage analysis. Distributed lag non-linear model was first applied to estimate the city-specific non-linear and delayed effects of temperatures on diabetes mortality. Pooled effects of temperatures on diabetes mortality were then obtained using meta-analysis, based on restricted maximum likelihood. We found that heat effects were generally acute and followed by a period of mortality displacement, while cold effects could last for over two weeks. The pooled relative risks of extreme high (99th percentile of temperature) and high temperature (90th percentile of temperature) were 1.29 (95%CI: 1.11-1.47) and 1.11 (1.03-1.19) over lag 0-21 days, compared with the 75th percentile of temperature. In contrast, the pooled relative risks over lag 0-21 days were 1.44 (1.25-1.66) for extreme low (1st percentile of temperature) and 1.20 (1.12-1.30) for low temperature (10th percentile of temperature), compared to 25th percentile of temperature. The estimate of heat effects was relatively higher among females than that among males, with opposite trend for cold effects, and the estimates of heat and cold effects were particularly higher among the elderly and those with low education, although the differences between these subgroups were not statistically significant (P>0.05). These findings have important public health implications for protecting diabetes patients from adverse ambient temperatures.

Peripheral sensory neuropathy is associated with altered postocclusive reactive hyperemia in the diabetic foot

OBJECTIVE

This study examined whether the presence of peripheral sensory neuropathy or cardiac autonomic deficits is associated with postocclusive reactive hyperemia (reflective of microvascular function) in the diabetic foot.

RESEARCH DESIGN AND METHODS

99 participants with type 2 diabetes were recruited into this cross-sectional study. The presence of peripheral sensory neuropathy was determined with standard clinical tests and cardiac autonomic function was assessed with heart rate variation testing. Postocclusive reactive hyperemia was measured with laser Doppler in the hallux. Multiple hierarchical regression was performed to examine relationships between neuropathy and the peak perfusion following occlusion and the time to reach this peak.

RESULTS

Peripheral sensory neuropathy predicted 22% of the variance in time to peak following occlusion (p<0.05), being associated with a slower time to peak but was not associated with the magnitude of the peak. Heart rate variation was not associated with the postocclusive reactive hyperemia response.

CONCLUSIONS

This study found an association between the presence of peripheral sensory neuropathy in people with diabetes and altered microvascular reactivity in the lower limb.

Extremely cold and hot temperatures increase the risk of diabetes mortality in metropolitan areas of two Chinese cities

BACKGROUND

Numerous studies have reported the association between ambient temperature and mortality. However, few studies have focused on the effects of extreme temperatures on diabetes mortality, particularly in China. The objective of the present study was to assess the effects of extremely cold and hot temperatures on diabetes mortality in urban areas of Harbin and Chongqing in China to provide scientific evidence for public health policy implementation to respond to challenges in diabetes mortality because of extreme temperature events.

METHODS

A double threshold B-spline distributed lag non-linear model (DLNM) was used to investigate the effects of extremely cold and hot temperatures on diabetes mortality from lag 0 to 30 days, after controlling for potential confounders including air pollutants. The unit risk, which is the elevated cumulative risk of diabetes mortality caused by each 1 °C change in extremely cold and hot temperatures during certain lag days, was estimated for extreme cold and heat using simple regression analysis.

RESULTS

Significant associations between both extreme hot and cold temperatures and diabetes mortality were observed in Harbin and Chongqing for different lag lengths. In Harbin, the extreme cold effects on diabetes mortality were delayed by three days and lasted for six days (lag 3-8), with the highest risk (RR 95% CI: 1.223,1.054-1.418 for -23 °C) at lag 5. The hot effects were delayed one day and lasted for three days (lag 1-3), with the peak RR (1.343: 1.080-1.670 for 37 °C) at lag 2. In Chongqing, the cold effects on diabetes mortality were delayed by seven days and lasted for four days (lag 7-10), with the highest risk (1.201: 1.006-1.434 for 4 °C) at lag 7. The hot effects peaked (1.811: 1.083-3.027 for 41 °C) at lag 0 and lasted for 2 days (lag 0-1). The unit risk for cold and hot effects was 12.9% (95% CI: 2.5-33.7%) and 16.5% (95% CI: 3.8-39.1%) in Harbin and 12.5% (95% CI: -4.7 to 47.5%) and 19.7% (95% CI: 3.9-48.5%) in Chongqing, respectively.

CONCLUSIONS

The results indicate that both extremely cold and hot temperatures increase diabetes mortality in different manners in Harbin and Chongqing. Diabetes education programs should include information on either managing or combating the effects of extreme hot and cold weather.

Correlation between sudomotor function, sweat gland duct size and corneal nerve fiber pathology in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION

To study the correlation between sudomotor function, sweat gland duct size and corneal nerve fiber pathology in type 2 diabetes.

MATERIALS AND METHODS

Sudomotor function was quantified by Neuropad test, and sweat gland duct and corneal nerve fibers were visualized by confocal microscopy in 78 patients with type 2 diabetes stratified by diabetic neuropathy and 28 control participants.

RESULTS

In patients with diabetic neuropathy, sudomotor function, as judged by the time required for complete color change of a Neuropad, was impaired compared with that of controls (P < 0.0001), thereby showing deterioration was related to the severity of diabetic neuropathy (P < 0.0001). Sweat gland ducts were smaller in patients without neuropathy than in controls (P < 0.0001), and further shrinking was seen in patients with severe diabetic neuropathy (P < 0.05). Patients without diabetic neuropathy showed reduced density and length (P < 0.001) of corneal nerve fibers and beading frequency (P < 0.0001), and increased tortuosity (P < 0.0001) compared with controls, and these changes deteriorated in patients with severe diabetic neuropathy. Sudomotor function was negatively associated with corneal nerve fibers (P < 0.002) and branches (P < 0.01), and influenced by the severity of diabetic neuropathy (P < 0.0001); sweat gland duct size correlated with serum triglycerides (P < 0.02), uric acid (P < 0.01), corneal nerve branch (P < 0.03), sudomotor function (P < 0.03) and severity of neuropathy (P < 0.03).

CONCLUSIONS

Type 2 diabetic patients had sudomotor dysfunction and smaller sweat gland ducts compared with controls. The stage of diabetic neuropathy and corneal nerve fiber pathology were independent predictors of sudomotor dysfunction, and serum triglycerides, uric acid, corneal nerve branch, stage of diabetic neuropathy and sudomotor function were predictors of sweat gland duct size.

Morphological pattern classification system for plantar thermography of patients with diabetes

BACKGROUND

A plantar temperature distribution can be obtained by thermography; however, the advantage has not been effectively utilized in the past. We previously proposed a classification method based on the angiosome concept, but the method was insufficient because it was too subjective and complicated for clinicians. In this study, we propose a new classification system of plantar forepart thermographic patterns using an image segmentation technique.

METHODS

A cross-sectional observational study was conducted including 32 healthy volunteers and 129 patients with diabetes mellitus (DM). Individual thermographic variations and trends were evaluated. A comparison was conducted between the patterns obtained by our previous angiosome-based research and the patterns found by the new classification system.

RESULTS

The system objectively found wider variations of the plantar forepart thermographic patterns in the patients with DM compared with those in the control subjects. In patients with DM, the system showed that the whole-high pattern was most frequent (46%), followed by the butterfly pattern (12%). In the control group, the butterfly pattern was most frequent (44%), followed by the whole-high pattern (19%). Both ankle and toe brachial indices were higher in feet with high temperature area in the inner side of the plantar.

CONCLUSIONS

Thermographic patterns found by the new computer-based system were similar to those obtained in our previous subjective work. The classification system found forefoot-low pattern and tiptoe-low pattern objectively. The system based on infrared thermography will be a screening tool to assess circulatory status in daily foot care of patients with DM.

Microcirculatory vasomotor changes are associated with severity of peripheral neuropathy in patients with type 2 diabetes

Systemic microvascular complications are related to the presence of diabetic neuropathy. This study investigated the associations of blood flow oscillations with peripheral neuropathy in 25 controls and 3 diabetic groups including clinical (24), subclinical (27) and without neuropathy (26). Laser Doppler skin perfusion was transformed into three low-frequency subintervals corresponding to endothelial, neurogenic and myogenic vasomotor controls. The average vasomotion was significantly reduced in clinical neuropathy group and characterized by endothelial and neural but not smooth muscle-related changes. The normalized spectrums revealed a relative increase of myogenic and decrease of neurogenic activity in subclinical neuropathy group. The myogenic component showed a statistically inverse correlation with postural fall in systolic blood pressure (r = -0.32, p < 0.01). The diabetic patients with decreased low-frequency vasomotor responses were associated with increased odds ratio of peripheral neuropathy [odds ratio = 3.51 (95% confidence interval = 1.19-10.31), p = 0.02]. This study elucidated possible interaction between impaired microvascular flow motion and diabetic peripheral neuropathy. The vasomotor changes of skin microcirculation could be detected even in the absence of overt cardiovascular dysfunction.

Screening for the high-risk foot of ulceration: tests of somatic and autonomic nerve function

Diabetic foot ulcers affect almost 5% of the patients with diabetes and carry a huge physical, emotional, and financial burden. Almost 80% of amputations in patients with diabetes are preceded by a foot ulcer. The need for simple screening methods for prevention of foot ulcers and amputations is indisputable. Simple tests such as monofilament, tuning fork, vibration perception threshold determination, ankle reflexes, and pinprick sensation alone or in combination have been studied prospectively and can be used for identification of patients at risk. Newer tests examining sudomotor dysfunction and skin dryness have been introduced in recent years. In cross-sectional studies sudomotor dysfunction assessed by either sympathetic skin response or NEUROPAD™ (Miro Verbandstoffe GmbH, Wiehl-Drabenderhöhe, Germany) testing has been consistently associated with foot ulceration. In addition, NEUROPAD™ testing is simple, reproducible, and widely available and has a high sensitivity for the diagnosis of clinical or subclinical diabetic polyneuropathy. Prospective studies are required to establish whether sudomotor dysfunction can predict foot ulcers and if simple methods assessing sudomotor dysfunction (eg, NEUROPAD™ testing) can be included in the screening tests for the prevention of this complication.

Non-invasive and quantitative assessment of sudomotor function for peripheral diabetic neuropathy evaluation

AIMS

Perturbation of pain sensation is considered one of the major initiating risk factors for diabetic foot ulcer. Sweat dysfunction leading to abnormal skin conditions, including dryness and fissures, can increase foot ulcer risk. The aim of this study was to evaluate Sudoscan™, a new, quick, non-invasive and quantitative method of measuring sudomotor dysfunction as a co-indicator of the severity of diabetic polyneuropathy (DPN).

METHODS

A total of 142 diabetic patients (age 62±18 years, diabetes duration 13±14 years, HbA(1c) 8.9±2.5%) were measured for vibration perception threshold (VPT), using a biothesiometer, and for sudomotor dysfunction, using electrochemical sweat conductance (ESC) based on the electrochemical reaction between sweat chloride and electrodes in contact with the hands and feet. Retinopathy status was also assessed, as well as reproducibility between two ESC measurements and the effect of glycaemia levels.

RESULTS

ESC measurements in the feet of patients showed a descending trend from 66±17 μS to 43±39 μS, corresponding to an ascending trend in VPT threshold from <15 V to >25 V (P=0.001). Correlation between VPT and ESC was -0.45 (P<0.0001). Foot ESC was lower in patients with fissures, while VPT was comparable. Both VPT and foot ESC correlated with retinopathy status. Bland-Altman plots indicated good reproducibility between two measurements, and between low and high glycaemia levels.

CONCLUSION

Sudoscan™ is a reproducible technique with results that are not influenced by blood glucose levels. Sweating status may be a quantitative indicator of the severity of polyneuropathy that may be useful for the early prevention of foot skin lesions.

Neuropad as a diagnostic tool for diabetic autonomic and sensorimotor neuropathy

AIMS

The aim of the present study was to determine the diagnostic accuracy of the Neuropad sudomotor test for diabetic cardiovascular autonomic neuropathy (CAN) and diabetic polyneuropathy (DPN), the latter assessed using a multi-level diagnostic approach.

METHODS

In 51 diabetic patients, CAN, symptoms and signs of DPN, vibration perception threshold (VPT), cold (CTT) and warm thermal perception thresholds (WTT) were measured. Neuropad response was determined as normal (complete colour change) or abnormal (absent or incomplete colour change). The time until the complete colour change (CCC time) was recorded.

RESULTS

CCC time showed significant correlations with all the neurological parameters, the strongest of which were with Valsalva ratio (rho = -0.64, P < 0.0001), symptoms of DPN (rho = 0.66, P < 0.0001), postural hypotension (rho = 0.54, P = 0.0001) and CTT (rho = -0.54, P = 0.0001). CCC time showed moderate diagnostic accuracy for both CAN and DPN: the areas under the receiver operating characteristic (ROC) curves were 0.71 and 0.76, respectively. The diagnostic characteristics of three cut-off values of CCC time, identified by ROC analysis (i.e. 10, 15 and 18 min), were analysed. Compared with 10 min, the 15-min cut-off value provided better specificity (from 27% to 52% and from 31% to 62% for CAN and DPN, respectively) and a better likelihood ratio for negative result (from 0.67 to 0.34 and from 0.58 to 0.33) without lowering sensitivity (from 82% to 82% and from 85% to 80%).

CONCLUSIONS

Neuropad is a reliable diagnostic tool for both CAN and DPN, albeit of only moderate accuracy. Extending the observation period to 15 min provides greater diagnostic usefulness.

Impaired distal thermoregulation in diabetes and diabetic polyneuropathy

OBJECTIVE

To determine how thermoregulation of the feet is affected by diabetes and diabetic polyneuropathy in both wakefulness and sleep.

RESEARCH DESIGN AND METHODS

Normal subjects, diabetic subjects without neuropathy, diabetic subjects with small-fiber diabetic polyneuropathy, and those with advanced diabetic polyneuropathy were categorized based on neurological examination, nerve conduction studies, and quantitative sensory testing. Subjects underwent foot temperature monitoring using an iButton device attached to the foot and a second iButton for recording of ambient temperature. Socks and footwear were standardized, and subjects maintained an activity diary. Data were collected over a 32-h period and analyzed.

RESULTS

A total of 39 normal subjects, 28 patients with diabetes but without diabetic polyneuropathy, 14 patients with isolated small-fiber diabetic polyneuropathy, and 27 patients with more advanced diabetic polyneuropathy participated. No consistent differences in foot temperature regulation between the four groups were identified during wakefulness. During sleep, however, multiple metrics revealed significant abnormalities in the diabetic patients. These included reduced mean foot temperature (P < 0.001), reduced maximal temperature (P < 0.001), increased rate of cooling (P < 0.001), as well as increased frequency of variation (P = 0.005), supporting that patients with diabetic polyneuropathy and even those with only diabetes but no diabetic polyneuropathy have impaired nocturnal thermoregulation.

CONCLUSIONS

Nocturnal foot thermoregulation is impaired in patients with diabetes and diabetic polyneuropathy. Because neurons are highly temperature sensitive and because foot warming is part of the normal biology of sleep onset and maintenance, these findings suggest new potentially treatable mechanisms of diabetes-associated nocturnal pain and sleep disturbance.

Sudomotor dysfunction is associated with foot ulceration in diabetes

AIM

To examine the relationship between sudomotor dysfunction and foot ulceration (FU) in patients with diabetes.

METHODS

Ninety patients with either Type 1 or Type 2 diabetes [30 without peripheral sensorimotor neuropathy (PN), 30 with PN but without FU and 30 with FU] were recruited in this cross-sectional study. Assessment of PN was based on neuropathy symptom score (NSS), neuropathy disability score (NDS) and vibration perception threshold (VPT). Sudomotor dysfunction was assessed using the sympathetic skin response (SSR). Cardiac autonomic nervous system activity was assessed by the battery of the classical autonomic function tests.

RESULTS

Patients with foot ulcers had longer duration of diabetes, higher values of VPT and NDS and lower values of the autonomic functions tests in comparison with the other study groups. Sudomotor dysfunction and cardiac autonomic neuropathy were significantly more common in the FU group. Multivariate logistic regression analysis after adjustment for gender, body mass index, duration of diabetes and glycated haemoglobin (HbA(1c)) demonstrated that the odds ratio (95% confidence intervals) of FU increased with measures of neuropathy such as NDS >or= 6 (10.2, 6.2-17.3) and VPT >or= 25 volts (19.8, 9.9-47.5), but was also significantly increased with absent SSR (15.3, 5.3-38.4).

CONCLUSIONS

Sudomotor dysfunction is associated with increased risk of FU and should be included in the screening tests for identification of diabetic patients at risk of ulceration.