Cold feet and prolonged sleep-onset latency in vasospastic syndrome

[Glaucoma Patient with Suspected Flammer Syndrome: Diagnostic Procedures and Therapeutic Implications]

If glaucoma damage develops despite normal intraocular pressure or if the damage progresses despite well-controlled intraocular pressure, we usually find other risk factors. One important group are the vascular factors. We should focus not only on the classical risk factors of atherosclerosis, such as arterial hypertension or dyslipidaemia, but also on dysregulation of blood flow, especially on primary vascular dysregulation (PVD). Low blood pressure, either current or in adolescence, low body mass index or frequently cold hands and feet may provide important hints. Very often PVD is coupled with a number of other symptoms and signs, and we then speak of a Flammer Syndrome (FS). If there is any indication of FS, we take a targeted patient history, undertake 24 h blood pressure monitoring, measure retinal venous pressure, and perform a dynamic retinal vessel analysis or nail fold capillary microscopy. This is especially recommended if the patient is relatively young or the damage is progressing rapidly. If the suspicion is confirmed, we then try to reduce the drops in blood pressure, lower the retinal venous pressure, improve the regulation of blood flow and reduce the oxidative stress in the mitochondria.

Effects of bathing-induced changes in body temperature on sleep

BACKGROUND

Passive body heating before sleep is well known to lead to improved sleep. However, the effects of the degree of change in body temperature by bathing on sleep quality are unclear. The present study aimed to clarify the effects on sleep of bathing-induced changes in body temperature.

METHODS

Twenty-three healthy males and females in their 20 s to 50 s bathed in their homes 1.5-2 h before bedtime under three bathing conditions: showering only; short bathing in a bathtub; and long bathing in a bathtub. Sublingual and skin temperatures and thermal sensation before and after bathing, sleep indices such as sleep onset latency, time in bed, sleep efficiency, and wake after sleep onset, all of which were evaluated using an actimeter, and subjective evaluations of sleep were compared among conditions.

RESULTS

Sublingual temperature just after bathing was significantly higher with long bathing than with other conditions, and the fall in sublingual temperature from after bathing to before sleep was significantly larger with long bathing than with short bathing. Sleep onset latency by actimeter was significantly reduced with long bathing compared to showering. In addition, subjective evaluations of falling asleep and sleep quality were better with long bathing than with showering or short bathing.

CONCLUSIONS

In conclusion, bathing conditions that produce a 0.9 °C increase in sublingual temperature appear effective for falling asleep and sleep quality, because core temperature shows a greater drop to before sleep than those producing an increase of about 0.3 °C increase in sublingual temperature.

Circadian rhythms of risk factors and management in atherosclerotic and hypertensive vascular disease: Modern chronobiological perspectives of an ancient disease

Atherosclerosis, a chronic inflammatory disease of the arteries that appears to have been as prevalent in ancient as in modern civilizations, is predisposing to life-threatening and life-ending cardiac and vascular complications, such as myocardial and cerebral infarctions. The pathogenesis of atherosclerosis involves intima plaque buildup caused by vascular endothelial dysfunction, cholesterol deposition, smooth muscle proliferation, inflammatory cell infiltration and connective tissue accumulation. Hypertension is an independent and controllable risk factor for atherosclerotic cardiovascular disease (CVD). Conversely, atherosclerosis hardens the arterial wall and raises arterial blood pressure. Many CVD patients experience both atherosclerosis and hypertension and are prescribed medications to concurrently mitigate the two disease conditions. A substantial number of publications document that many pathophysiological changes caused by atherosclerosis and hypertension occur in a manner dependent upon circadian clocks or clock gene products. This article reviews progress in the research of circadian regulation of vascular cell function, inflammation, hemostasis and atherothrombosis. In particular, it delineates the relationship of circadian organization with signal transduction and activation of the renin-angiotensin-aldosterone system as well as disturbance of the sleep/wake circadian rhythm, as exemplified by shift work, metabolic syndromes and obstructive sleep apnea (OSA), as promoters and mechanisms of atherogenesis and risk for non-fatal and fatal CVD outcomes. This article additionally updates advances in the clinical management of key biological processes of atherosclerosis to optimally achieve suppression of atherogenesis through chronotherapeutic control of atherogenic/hypertensive pathological sequelae.

Partial sleep restriction-induced changes in stress, quality of life, and lipid metabolism in relation to cold hypersensitivity: A before-and-after intervention study

Sleep disturbances are associated with cold hypersensitivity (CH) and characterized by excessive cold sensation in specific body parts and cold thermal discomfort. This study investigated the effects of short-term sleep restriction followed by a recovery phase on subjective health status, inflammation, and lipid metabolism in different types of CH. A total of 118 healthy adults aged 35 to 44 years without sleep disturbances were enrolled. Participants underwent 4-hour sleep restrictions per day for 3 days at a hospital and then returned to their daily lives for 4 days of rest. CH was assessed using a structured questionnaire with eight characteristic symptoms. A questionnaire and blood tests were administered baseline, after sleep restriction, and follow-up to assess cortisol, lipid profiles, and self-reported stress and quality of life (QOL). Participants were divided into CH (44.1%) and non-CH (55.9%) groups. The CH group showed increased stress, impaired QOL, and decreased low-density lipoprotein-cholesterol (LDL-C) levels compared to the non-CH group after sleep restriction. The variance for QOL (effect size = 0.07), subjective stress (effect size = 0.053), and LDL-C (effect size = 0.029) among time points depended on the group. Short-term sleep restriction was associated with deterioration of subjective health and reduced lipid metabolism; such changes were more evident in the CH group. Our findings suggest the need to consider an individual's CH status to assess the clinical risk associated with insufficient sleep.

Ocular and Systemic Factors Associated with Glaucoma

Glaucoma is one of the leading causes of irreversible blindness in the world. Although numerous factors have been implicated in the pathogenesis of glaucoma, the main focus of management still remains lowering the intraocular pressure (IOP) by medical or surgical therapy. However, a major challenge is that many glaucoma patients continue to progress despite good control of IOP. In this regard, the importance of other coexisting factors that may contribute to disease progression needs to be explored. Ophthalmologists need to be aware of ocular risk factors and the impact of systemic diseases and their medications, along with lifestyle modifications on the course of glaucomatous optic neuropathy and adopt a holistic approach in treating the eye as well as the patient to alleviate the suffering from glaucoma in a comprehensive manner.

How to cite this article

Dada T, Verma S, Gagrani M, et al. Ocular and Systemic Factors associated with Glaucoma. J Curr Glaucoma Pract 2022;16(3):179-191.

Do ginger footbaths improve symptoms of insomnia more than footbaths with warm water only? - A randomized controlled study

OBJECTIVES

To compare the effects between warm water (WW) and ginger footbaths (WW+ginger) on sleep quality and warmth regulation in adults with self-reported insomnia symptoms.

METHODS

A prospective randomized-controlled study in which 28 participants (mean age 50.9 years, 64.3% women, insomnia symptom duration 11.4 years) were randomized to receive WW (n = 13) or WW+ginger (n = 15) daily for 2 weeks. Treatment involved nightly footbaths (12 liters of 38-42 °C warm tap water, maximum duration 20 min) with and without topical ginger (80 g of powdered ginger rhizomes).

MAIN OUTCOME MEASURES

The primary outcome measure was self-reported sleep quality (global score from Pittsburgh Sleep Quality Index, PSQI) at 2 weeks. Secondary outcomes included measures of insomnia severity (Insomnia Severity Index, ISI) and warmth regulation (Herdecke Warmth Perception Questionnaire, HWPQ and 24-hour distal-proximal skin temperature gradient, DPG).

RESULTS

WW+ginger had no greater effect on PSQI (mean between-difference 0.0 [95% CI -3.0 to 2.9], Cohen's d=0.0) or ISI (-0.2 [-3.9 to 3.4], 0.0) than WW. Nor were there any significant differences in HWPQ perceived warmth (0.1 ≥d≥0.5) or DPG (0.1 ≥d≥0.4) between WW and WW+ginger. Both groups improved over time in PSQI (WW+ginger: d=0.7, WW: d=1.3) and ISI (WW+ginger: d=0.8, WW: d=1.0). Perceived warmth of the feet increased only in WW+ginger over time (d=0.6, WW: d=0.0).

CONCLUSIONS

This dose of ginger (6.67 g/liter) did not have greater effects on sleep quality, insomnia severity or warmth regulation than WW. Considering effect sizes, costs and risks, the use of WW would be recommended over WW+ginger in this patient population.

The history of sleep research and sleep medicine in Europe

Sleep became a subject of scientific research in the second half of the 19th century. Since sleep, unlike other physiological functions, cannot be attributed to a specific organ, there was no distinct method available to study sleep until then. With the development of physiology and psychology, and a rapidly increasing knowledge of the structure and functioning of the nervous system, certain aspects of sleep became accessible to objective study. A first step was to measure responsiveness to external stimuli systematically, during sleep, allowing a first representation of the course of sleep (Schlaftiefe = sleep depth). A second method was to register continuously the motor activity across the sleep-wake cycle, which allowed the documentation in detail of rest-activity patterns of monophasic and polyphasic sleep-wake rhythms, or between day or night active animals. The central measurement for sleep research, however, became the electroencephalogram in the 1930s, which allowed observation of the sleeping brain with high temporal resolution. Beside the development of instruments to measure sleep, prolonged sleep deprivation was applied to study physiological and psychological effects of sleep loss. Another input came from clinical and neuropathological observations of patients with pronounced disorders of the sleep-wake cycle, which for the first time allowed localisation of brain areas that are essentially involved in the regulation of sleep and wakefulness. Experimental brain stimulation and lesion studies were carried out with the same aim at this time. Many of these activities came to a halt on the eve of World War II. It was only in the early 1950s, when periods with rapid eye movements during sleep were recognised, that sleep became a research topic of itself. Jouvet and his team explored the brain mechanisms and transmitters of paradoxical sleep, and experimental sleep research became established in all European countries. Sleep medicine evolving simultaneously in different countries, with early centres in Italy and France. In the late 1960s sleep research and chronobiology began to merge. In recent decades, sleep research, dream research, and sleep medicine have benefited greatly from new methods in genetic research and brain imaging techniques. Genes were identified that are involved in the regulation of sleep, circadian rhythms, or sleep disorders. Functional imaging enabled a high spatial resolution of the activity of the sleeping brain, complementing the high temporal resolution of the electroencephalogram.

Bioheat Transfer Basis of Human Thermoregulation: Principles and Applications

Thermoregulation is a process that is essential to the maintenance of life for all warm-blooded mammalian and avian species. It sustains a constant core body temperature in the face of a wide array of environmental thermal conditions and intensity of physical activities that generate internal heat. A primary component of thermoregulatory function is the movement of heat between the body core and the surface via the circulation of blood. The peripheral vasculature acts as a forced convection heat exchanger between blood and local peripheral tissues throughout the body enabling heat to be convected to the skin surface where is may be transferred to and from the environment via conduction, convection, radiation, and/or evaporation of water as local conditions dictate. Humans have evolved a particular vascular structure in glabrous (hairless) skin that is especially well suited for heat exchange. These vessels are called arteriovenous anastomoses (AVAs) and can vasodilate to large diameters and accommodate high flow rates. We report herein a new technology based on a physiological principle that enables simple and safe access to the thermoregulatory control system to allow manipulation of thermoregulatory function. The technology operates by applying a small amount of heating local to control tissue on the body surface overlying the cerebral spine that upregulates AVA perfusion. Under this action, heat exchangers can be applied to glabrous skin, preferably on the palms and soles, to alter the temperature of elevated blood flow prior to its return to the core. Therapeutic and prophylactic applications are discussed.

The Circadian Rhythm of Thermoregulation Modulates both the Sleep/Wake Cycle and 24 h Pattern of Arterial Blood Pressure

Borbély proposed an interacting two-component model of sleep regulation comprising a homeostatic Process S and a circadian Process C. The model has provided understanding of the association between core body temperature (CBT) as a key element of Process C that is deterministic of sleep onset and offset. However, it additionally provides a new perspective of the importance of the thermoregulatory mechanisms of Process C in modulating the circadian rhythm of arterial blood pressure (ABP). Herein, we examine the circadian physiology of thermoregulation, including at the end of the activity span the profound redistribution of cardiac output from the systemic circulation to the arteriovenous anastomoses of the glabrous skin that markedly enhances convective transfer of heat from the body to the environment to cause (i) decrease of the CBT as a pathway to sleep onset and (ii) attenuation of the asleep ABP mean and augmentation of the ABP decline (dipping) from the wake-time mean, in combination the strongest predictors of the risk for blood vessel and organ pathology and morbid and mortal cardiovascular disease events. We additionally review the means by which blood perfusion to the glabrous skin can be manipulated on demand by selective thermal stimulation, that is, mild warming, on the skin of the cervical spinal cord to intensify Process C as a way to facilitate sleep induction and promote healthy asleep ABP. © 2021 American Physiological Society. Compr Physiol 11:1-14, 2021.

Role of the Preoptic Area in Sleep and Thermoregulation

Sleep and body temperature are tightly interconnected in mammals: warming up our body helps to fall asleep and the body temperature in turn drops while falling asleep. The preoptic area of the hypothalamus (POA) serves as an essential brain region to coordinate sleep and body temperature. Understanding how these two behaviors are controlled within the POA requires the molecular identification of the involved circuits and mapping their local and brain-wide connectivity. Here, we review our current understanding of how sleep and body temperature are regulated with a focus on recently discovered sleep- and thermo-regulatory POA neurons. We further discuss unresolved key questions including the anatomical and functional overlap of sleep- and thermo-regulatory neurons, their pathways and the role of various signaling molecules. We suggest that analysis of genetically defined circuits will provide novel insights into the mechanisms underlying the coordinated regulation of sleep and body temperature in health and disease.

Hot-water bathing before bedtime and shorter sleep onset latency are accompanied by a higher distal-proximal skin temperature gradient in older adults

STUDY OBJECTIVES

Passive body heating in controlled settings could shorten sleep onset latency (SOL). The hypothesized mechanism is vasodilation-induced heat loss before bedtime. However, this evidence is based on small sample-sized studies in specific populations. Thus, we analyzed the association of hot-water bathing and its before-bedtime timing with SOL and heat loss in a large study population of older adults.

METHODS

We conducted a longitudinal analysis using repeated measurements of hot-water bathing and sleep among 1,094 older adults (mean age, 72.0 years). SOL was recorded using actigraphy and self-reported sleep estimates and was categorized into conditions (intervals of 1-60, 61-120, 121-180, and > 181 minutes between hot bath and bedtime) and compared with the control condition of no bathing. The heat-loss indicator, distal-proximal skin temperature gradient, was examined in the same categorization.

RESULTS

Mixed-effects linear regression models suggested that the bathing conditions of 61-120 minutes and 121-180 minutes showed significantly shorter log-transformed actigraphic SOL by 0.23 log-minutes (95% confidence interval (CI), 0.03-0.42) and 0.32 log-minutes (95% CI, 0.09-0.56), shorter self-reported SOL by 0.16 log-minutes (95% CI, 0.02-0.30) and 0.18 log-minutes (95% CI, 0.01-0.35), and higher distal-proximal skin temperature gradient for 30 minutes before bedtime by 0.49°C (95% CI, 0.22-0.75) and 0.51°C (95% CI, 0.20-0.83), respectively, independent of potential confounders.

CONCLUSIONS

Hot-water bathing before bedtime is significantly associated with shorter SOL and higher distal-proximal skin temperature gradient among the large-scale older population. This finding could enhance the generalizability of hot-water bathing habits for ameliorating sleep initiation difficulty.

Periocular skin warming promotes body heat loss and sleep onset: a randomized placebo-controlled study

Periocular skin warming was reported to have favorable effects on subjective and objective sleep quality. We hypothesized that enhancing body heat loss by periocular skin warming would reduce sleep onset and improve sleep quality. Eighteen healthy volunteers were asked to maintain wakefulness with their eyes closed for 60 min after applying either a warming or sham eye mask, followed by a 60-min sleep period. Compared to the sham, periocular warming increased the distal skin temperature and distal-proximal skin temperature gradient only during the 30-min thermal manipulation period. In the subsequent sleep period, periocular warming facilitated sleep onset, increased stage 2 sleep and electroencephalographic delta activity during the first half of the sleep period relative to the sham. These results suggest that periocular skin warming may accelerate and deepen sleep by enhancing physiological heat loss via the distal skin, mimicking physiological conditions preceding habitual sleep.

From Nanowarming to Thermoregulation: New Multiscale Applications of Bioheat Transfer

This review explores bioheat transfer applications at multiple scales from nanoparticle (NP) heating to whole-body thermoregulation. For instance, iron oxide nanoparticles are being used for nanowarming, which uniformly and quickly rewarms 50-80-mL (≤5-cm-diameter) vitrified systems by coupling with radio-frequency (RF) fields where standard convective warming fails. A modification of this approach can also be used to successfully rewarm cryopreserved fish embryos (∼0.8 mm diameter) by heating previously injected gold nanoparticles with millisecond pulsed laser irradiation where standard convective warming fails. Finally, laser-induced heating of gold nanoparticles can improve the sensitivity of lateral flow assays (LFAs) so that they are competitive with laboratory tests such as the enzyme-linked immunosorbent assay. This approach addresses the main weakness of LFAs, which are otherwise the cheapest, easiest, and fastest to use point-of-care diagnostic tests in the world. Body core temperature manipulation has now become possible through selective thermal stimulation (STS) approaches. For instance, simple and safe heating of selected areas of the skin surface can open arteriovenous anastomosis flow in glabrous skin when it is not already established, thereby creating a convenient and effective pathway to induce heat flow between the body core and environment. This has led to new applications of STS to increase or decrease core temperatures in humans and animals to assist in surgery (perioperative warming), to aid ischemic stress recovery (cooling), and even to enhance the quality of sleep. Together, these multiscale applications of nanoparticle heating and thermoregulation point to dramatic opportunities for translation and impact in these prophylactic, preservative, diagnostic, and therapeutic applications of bioheat transfer.

The Temperature Dependence of Sleep

Mammals have evolved a range of behavioural and neurological mechanisms that coordinate cycles of thermoregulation and sleep. Whether diurnal or nocturnal, sleep onset and a reduction in core temperature occur together. Non-rapid eye movement (NREM) sleep episodes are also accompanied by core and brain cooling. Thermoregulatory behaviours, like nest building and curling up, accompany this circadian temperature decline in preparation for sleeping. This could be a matter of simply comfort as animals seek warmth to compensate for lower temperatures. However, in both humans and other mammals, direct skin warming can shorten sleep-latency and promote NREM sleep. We discuss the evidence that body cooling and sleep are more fundamentally connected and that thermoregulatory behaviours, prior to sleep, form warm microclimates that accelerate NREM directly through neuronal circuits. Paradoxically, this warmth might also induce vasodilation and body cooling. In this way, warmth seeking and nesting behaviour might enhance the circadian cycle by activating specific circuits that link NREM initiation to body cooling. We suggest that these circuits explain why NREM onset is most likely when core temperature is at its steepest rate of decline and why transitions to NREM are accompanied by a decrease in brain temperature. This connection may have implications for energy homeostasis and the function of sleep.

Residual vision activation and the brain-eye-vascular triad: Dysregulation, plasticity and restoration in low vision and blindness - a review

Vision loss due to ocular diseases such as glaucoma, optic neuropathy, macular degeneration, or diabetic retinopathy, are generally considered an exclusive affair of the retina and/or optic nerve. However, the brain, through multiple indirect influences, has also a major impact on functional visual impairment. Such indirect influences include intracerebral pressure, eye movements, top-down modulation (attention, cognition), and emotionally triggered stress hormone release affecting blood vessel dysregulation. Therefore, vision loss should be viewed as the result of multiple interactions within a “brain-eye-vascular triad”, and several eye diseases may also be considered as brain diseases in disguise. While the brain is part of the problem, it can also be part of the solution. Neuronal networks of the brain can “amplify” residual vision through neuroplasticity changes of local and global functional connectivity by activating, modulating and strengthening residual visual signals. The activation of residual vision can be achieved by different means such as vision restoration training, non-invasive brain stimulation, or blood flow enhancing medications. Modulating brain functional networks and improving vascular regulation may offer new opportunities to recover or restore low vision by increasing visual field size, visual acuity and overall functional vision. Hence, neuroscience offers new insights to better understand vision loss, and modulating brain and vascular function is a promising source for new opportunities to activate residual vision to achieve restoration and recovery to improve quality of live in patients suffering from low vision.

Risks associated with the stroke predisposition at young age: facts and hypotheses in light of individualized predictive and preventive approach

Stroke is one of the most devastating pathologies of the early twenty-first century demonstrating 1-month case-fatality rates ranging from 13 to 35% worldwide. Though the majority of cases do occur in individuals at an advanced age, a persistently increasing portion of the patient cohorts is affected early in life. Current studies provide alarming statistics for the incidence of "young" strokes including adolescents. Young stroke is a multifactorial disease involving genetic predisposition but also a number of modifiable factors, the synergic combination of which potentiates the risks. The article analyzes the prevalence and impacts of "traditional" risk factors such as sedentary lifestyle, smoking, abnormal alcohol consumption, drug abuse, overweight, hypertension, abnormal sleep patterns, and usage of hormonal contraceptives, among others. Further, less explored risks such as primary vascular dysregulation and associated symptoms characteristic for Flammer syndrome (FS) are considered, and the relevance of the FS phenotype for the stroke predisposition at young age is hypothesized. Considering the high prevalence of known genetic and modifiable risk factors in the overall predisposition to the young stroke, the risk mitigating measures are recommended including innovative screening programs by application of specialized questionnaires and biomarker panels as well as educational programs adapted to the target audiences such as children, adolescents, and young adults.

Transient visual field impairment after cold provocation in glaucoma patients with Flammer syndrome

Background:

It is still debatable whether visual field defects in glaucoma have a reversible component and to what extent a temporary loss can be provoked.

Objective:

To investigate the response of the visual function to a cold provocation in glaucoma patients, particularly to test whether subjects with Flammer syndrome (FS) behaved differently from subjects without FS.

Methods:

Ten (10) primary open-angle glaucoma (POAG) patients with FS, 7 POAG patients without FS, and 11 healthy controls were tested with program G2 on the Octopus 101 perimeter before and after putting one hand in cold water (4°C) for 2 min. The mean sensitivity (MS) of each visual field was included in the statistical analysis.

Results:

In glaucoma patients with FS, the mean MS significantly decreased after cold provocation (delta MS = –0.91 dB, CI = –1.43 to –0.39, p = 0.0014). In contrast, the mean MS in glaucoma patients without FS did not change significantly (delta MS = 0.17 dB, CI = –0.43 to 0.78, p = 0.56). Likewise, the mean MS did not change significantly in the healthy controls (delta MS = 0.23 dB, CI = –0.27 to 0.72, p = 0.36).

Conclusions:

Cold provocation induced a transient visual field deterioration in the glaucoma patients with FS but not in the glaucoma patients without FS or in the healthy controls. We assume this effect to be the result of a transient reduction of ocular blood flow.

Are cold extremities an issue in women's health? Epidemiological evaluation of cold extremities among Japanese women

Background

Unlike traditional East Asian medicine, the necessity of health care services for cold extremities is yet to be acknowledged in Western medicine. In this study, we aimed to conduct an epidemiological evaluation of this unremarkable symptom among women in Japan.

Materials and methods

A cross-sectional study was conducted from February 2016 to April 2017, and data of 238 women throughout Japan were analyzed. Questionnaires were used to examine participants’ demographics, health-related behaviors, health status, and frequency of subjective symptoms over the past 1 year. The association between cold extremities and other subjective symptoms was examined by the multiple logistic regression analysis.

Results

The prevalences of mild and severe cold extremities were 49.6% and 35.3%, respectively. Temperature and utilization of health care services were not significantly different by the severity of cold extremities. The accompanying symptoms that were significantly associated with the cold extremities were shoulder stiffness, fatigue, low back pain, headache, nasal congestion, itching, injury, and difficulty hearing. After multiple logistic regression analysis, low back pain (OR: 4.91) and difficulty hearing (OR: 4.84) kept the significance. Factors related to cold extremities including mental quality of life, sleep quality, and habitual drinking were significantly associated with other accompanying symptoms.

Conclusion

Women with cold extremities have various accompanying symptoms and health-risk behaviors. Symptomatic treatment for cold extremities may not be sufficient, and comprehensive care would be required.

Normal-tension glaucoma: Pathogenesis and genetics

Normal-tension glaucoma (NTG) is a multifactorial optic neuropathy which, similar to open-angle glaucomas, is characterized by progressive retinal ganglion cell death and glaucomatous visual field loss. The major distinction of NTG from open-angle glaucomas is that the intraocular pressure (IOP) does not exceed the normal range. Missing the major risk factor and target of therapy, the elevated IOP, NTG poses a clinical challenge. Several insightful reviews have been published on the pathophysiology of NTG describing the possible underlying mechanisms. The current literature available also suggests that a significant percentage of patients with NTG (as high as 21%) have a family history of glaucoma, indicating a genetic predisposition to the disease. These facts strengthen the indication that NTG remains an enigmatic process. The aim of this review was to summarize the vascular, mechanical and genetic components considered to be responsible for NTG development and to discuss the mechanisms through which they are involved in the pathogenesis of NTG.

From Nanowarming to Thermoregulation: New Multiscale Applications of Bioheat Transfer

This review explores bioheat transfer applications at multiple scales from nanoparticle (NP) heating to whole-body thermoregulation. For instance, iron oxide nanoparticles are being used for nanowarming, which uniformly and quickly rewarms 50-80-mL (≤5-cm-diameter) vitrified systems by coupling with radio-frequency (RF) fields where standard convective warming fails. A modification of this approach can also be used to successfully rewarm cryopreserved fish embryos (∼0.8 mm diameter) by heating previously injected gold nanoparticles with millisecond pulsed laser irradiation where standard convective warming fails. Finally, laser-induced heating of gold nanoparticles can improve the sensitivity of lateral flow assays (LFAs) so that they are competitive with laboratory tests such as the enzyme-linked immunosorbent assay. This approach addresses the main weakness of LFAs, which are otherwise the cheapest, easiest, and fastest to use point-of-care diagnostic tests in the world. Body core temperature manipulation has now become possible through selective thermal stimulation (STS) approaches. For instance, simple and safe heating of selected areas of the skin surface can open arteriovenous anastomosis flow in glabrous skin when it is not already established, thereby creating a convenient and effective pathway to induce heat flow between the body core and environment. This has led to new applications of STS to increase or decrease core temperatures in humans and animals to assist in surgery (perioperative warming), to aid ischemic stress recovery (cooling), and even to enhance the quality of sleep. Together, these multiscale applications of nanoparticle heating and thermoregulation point to dramatic opportunities for translation and impact in these prophylactic, preservative, diagnostic, and therapeutic applications of bioheat transfer.

Skin temperature, sleep, and vigilance

A large number of studies have shown a close association between the 24-hour rhythms in core body temperature and sleep propensity. More recently, studies have have begun to elucidate an intriguing association of sleep with skin temperature as well. The present chapter addresses the association of sleep and alertness with skin temperature. It discusses whether the association could reflect common underlying drivers of both sleep propensity and skin vasodilation; whether it could reflect efferents of sleep-regulating brain circuits to thermoregulatory circuits; and whether skin temperature could provide afferent input to sleep-regulating brain circuits. Sleep regulation and concomitant changes in skin temperature are systematically discussed and three parallel factors suggested: a circadian clock mechanism, a homeostatic hourglass mechanism, and a third set of sleep-permissive and wake-promoting factors that gate the effectiveness of signals from the clock and hourglass in the actual induction of sleep or maintenance of alert wakefulness. The chapter moreover discusses how the association between skin temperature and arousal can change with sleep deprivation and insomnia. Finally it addresses whether the promising laboratory findings on the effects of skin temperature manipulations on vigilance can be applied to improve sleep in everyday life.

Retinal venous pressure measurements in patients with Flammer syndrome and metabolic syndrome

Background

The purpose of this research is to analyze retinal venous pressure (RVP) of both eyes of patients who visited a Swiss ophthalmic practice and compare values among the following groups of patients with primary open-angle glaucoma (POAG), Flammer syndrome (FS), and metabolic syndrome (MetS).

Methods

RVP was measured in both eyes of all patients who visited a Swiss ophthalmic practice during March 2016 till November 2016, and the results were analyzed retrospectively. All measurements were performed by one physician by means of ophthalmodynamometry. Ophthalmodynamometry is done by applying an increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

Results

Spontaneous central retinal venous pulsation was present in the majority of the patients (192 out of 357, 53.8%). Spontaneous RVP rate was significantly negatively correlated with age (r = -0.348, p < 0.001). A significantly increased RVP was noted in FS, MetS, and POAG patients, particularly those POAG patients who also suffered from FS (p < 0.005).

Conclusions

Although most patients had a spontaneous RVP, those with FS, POAG, and MetS had increased RVP. Measuring RVP by means of ophthalmodynamometry provides predictive information about certain ocular diseases and aids in instituting adequate preventive measures.

Acupuncture benefits for Flammer syndrome in individuals with inherited diseases of the retina

BACKGROUND

Patients with inherited diseases of the retina (IRD) often exhibit signs and symptoms of Flammer syndrome (FS). Acupuncture treatment has shown its positive effect on visual function in patients with IRD. The aim of the present study is to examine the effect of acupuncture on signs and symptoms of FS in a cohort of patients suffering simultaneously FS and IRD.

PATIENTS AND METHODS

A prospective pilot study was performed on 17 patients with FS and IRD: rod-cone dystrophy, Nr: 12 (RCD); cone-rod dystrophy, Nr: 3 (CRD) and inherited macular dystrophy, Nr: 2 (IMD; 12♀, 5♂; mean age: 44.19 y; SD ±17.09 y). Acupuncture treatment was done applying needle acupuncture of the body and the ears. The treatment was scheduled at 10 half-hour sessions over 5 weeks. Primary outcome was evaluation of the post-acupuncture effect on the signs and symptoms of FS in IRD patients using multiple-choice questionnaires.

RESULTS

Following acupuncture, we found improvement in signs and symptoms of FS in patients suffering simultaneously IRD, as for instance (Nr. patients: improvement/suffering/total): a reduced tiredness (10/11/17), shorter sleep onset time (10/11/17), warmer feet and hands (10/10/17) and reduced frequency of headache attacks (9/11/17). Surprisingly, in four RCD patients and in one IMD patient, a reduction of macular edema was documented.

CONCLUSIONS

The applied acupuncture protocol for FS in IRD patients showed improvement in FS signs and symptoms and was tolerated well. Nevertheless, the objective evaluation of this complementary therapy on FS in IRD patients remains to be elucidated.

Relationship between normal tension glaucoma and Flammer syndrome

BACKGROUND

Besides intraocular pressure, vascular factors play a role in the pathogenesis of glaucomatous optic neuropathy. One of these potential vascular factors is Flammer syndrome. The purpose of the present study was to determine in a Korean population whether signs and symptoms of Flammer syndrome occur more often in normal tension glaucoma patients than in control subjects.

METHODS

Two hundred forty-six normal tension glaucoma patients and 1116 control subjects responded to a multiple-choice questionnaire asking about 15 signs and symptoms of Flammer syndrome.

RESULTS

Seven of the 15 signs and symptoms of Flammer syndrome (increased drug sensitivity, good smell perception, reversible skin blotches, tinnitus, long sleep onset time, tendency to perfectionism, and cold hands/feet) were significantly more often positive in normal tension glaucoma patients than in controls. Six additional signs and symptoms (migraines, low blood pressure, headaches, dizziness, increased pain sensation, and feeling cold) also occurred more often, but did not reach statistical significance. Only two items (low body weight and reduced feeling of thirst) were more frequently (not significant) positive in the controls.

CONCLUSION

There is an association between normal tension glaucoma and Flammer syndrome. If future studies confirm this relationship, treatment of Flammer syndrome may help to prevent normal tension glaucoma or to slow down its progression.

The discovery of the Flammer syndrome: a historical and personal perspective

This review describes the clinical and basic research that led to the description of Flammer syndrome. It is narrated from a personal perspective. This research was initiated by the observation of an increased long-term fluctuation of visual fields in a subgroup of glaucoma patients. As these patients had strikingly cold hands, peripheral blood flow was tested with a capillary microscopy, and vasospastic syndrome (VS) was diagnosed. Further studies on these patients revealed frequently weakened autoregulation of ocular blood flow and increased flow resistivity in retroocular vessels. Their retinal vessels were more rigid and irregular and responded less to flickering light. Holistic investigation demonstrated low blood pressure, silent myocardial ischaemia, altered beat-to-beat variation, altered gene expression in the lymphocytes, slightly increased plasma endothelin level and increased systemic oxidative stress. This combination of signs and symptoms was better described by the term primary vascular dysregulation (PVD) than by VS. Subsequent studies showed additional symptoms frequently related to PVD, such as low body mass index, cold extremities combined with slightly increased core temperature, prolonged sleep onset time, reduced feelings of thirst, increased sensitivity to smell and also for certain drugs and increased retinal venous pressure. To better characterise this entire syndrome, the term Flammer syndrome (FS) was introduced. Most subjects with FS were healthy. Nevertheless, FS seemed to increase the risk for certain eye diseases, particularly in younger patients. This included normal-tension glaucoma, anterior ischaemic optic neuropathy, retinal vein occlusions, Susac syndrome and central serous chorioretinopathy. Hereditary diseases, such as Leber’s optic neuropathy or retinitis pigmentosa, were also associated with FS, and FS symptoms and sings occurred more frequent in patients with multiple sclerosis or with acute hearing loss. Further research should lead to a more concise definition of FS, a precise diagnosis and tools for recognizing people at risk for associated diseases. This may ultimately lead to more efficient and more personalised treatment.

[Centrally acting cholinomimetics in the complex therapy of progressive glaucomatous optic neuropathy]

Many factors exist that are associated with higher risk of glaucoma progression. Arterial hypotension, low perfusion pressure, vasospastic syndrome, diabetes mellitus, myopia, etc. increase the need for neuroprotective therapy, which is aimed at stabilizing the pathological process and creating favorable conditions for maintaining visual functions. The aim of this study was to assess the therapeutic efficacy of Gliatilin as part of the complex treatment of progressive glaucomatous optic neuropathy.

MATERIAL AND METHODS

A total of 240 patients were randomly selected and divided into 2 groups, 120 patients each. Both groups were matched for age, somatic comorbidity, and the gravity of the glaucomatous process. Patient age averaged 71.3±1.6 years. Advanced glaucoma prevailed in both groups: 70.0 and 76.6% correspondingly. Neuroprotective therapy included drugs from different pharmacological classes so that different aspects of pathogenesis were addressed. Apart from that, patients from Group I first received intravenous Gliatilin (1000 mg/4ml, 12--15 doses) and then switched to oral (1 capsule b.i.d. for 4 months). All patients underwent standard ophthalmic examination and static perimetry.

RESULTS

No adverse effects were observed over the first two weeks of Gliatilin course, during which the patients stayed in the hospital. IOP level was normal and stable. Although neuroprotective therapy does not directly affect IOP, stability of the latter describes the dynamics of the glaucomatous process. When assessing changes in visual functions, particular attention was paid to the central visual field, foveolar and total light sensitivity, peripheral visual field, and MD and PSD indices. All mean values showed a tendency toward improvement, more pronounced in the Gliatilin group.

CONCLUSION

A complex therapy cannot be limited to a single drug only, and to make better decisions, one should consider not only ocular, but also general condition of the patient. Adjuvant Gliatilin in the complex therapy of progressive glaucoma is appropriate and efficient, especially in case of systemic atherosclerosis and cerebrovascular insufficiency. The frequency of stabilization therapy depends on the efficacy of the latest course and clinical manifestations of the glaucomatous process.

The trilateral link between anaesthesia, perioperative visual loss and Flammer syndrome

Background

A variety of factors have been linked to perioperative visual loss during or directly after nonocular and ocular surgeries. Prolonged immobilization, biochemical factors and hemodynamic instability have been discussed as factors in the pathogenesis of this devastating complication. Perioperative visual loss in four consecutive patients, all featuring Flammer syndrome, is reported herein. To our knowledge, we present the first case series, which associates perioperative visual loss with Flammer syndrome. We assume that a low perfusion pressure, disturbed autoregulation of the ocular blood flow and altered drug sensitivity in such subjects, play significant role in the pathogenesis of this dreaded complication.

Cases presentation

We analysed the medical records of four consecutive patients with permanent perioperative visual loss and complemented our findings with additional history taking and clinical examinations. A variety of tests was performed, including colour Doppler ultrasonography of the retroocular vessels, static and dynamic retinal vessel analysis. The visual loss was unilateral in three patients and bilateral in one. An extensive review of published perioperative vision loss cases was conducted.

All four patients were male Caucasians, and exhibited prominent signs and symptoms of Flammer syndrome. The visual loss originated from a propensity for unstable ocular blood flow, combined with hyperreactivity toward pharmacological stimuli, leading together to disturbed autoregulation of the blood supply, and subsequently - to ocular hypoxia. An identified intrinsic hypoperfusion diathesis was a crucial pathophysiologic link in all of the patients. Other, yet unknown systemic or local factors may also be involved in this process.

Conclusions

A review of numerous publications of perioperative visual loss and our data, support our hypothesis for a novel pathophysiologic model and incorporate Flammer syndrome as a distinct risk factor for paradoxical visual loss, during nonocular and ocular surgeries, or invasive procedures. To prevent the complications produced by disturbed blood flow autoregulation in such patients, guidelines for screening and tailored preoperative approach are given.

Effect of Triflusal on Primary Vascular Dysregulation Compared with Aspirin: A Double-Blind, Randomized, Crossover Trial

PURPOSE

Primary vascular dysregulation (PVD) is a condition in which the response to cold temperature or external stimuli is abnormal. We investigated whether triflusal use results in amelioration of PVD symptoms and improvement of several related parameters compared with aspirin.

MATERIALS AND METHODS

Eighty-eight PVD patients (54% female, 56±8 years) were randomly selected to receive either triflusal (300 mg, b.i.d.) or aspirin (150 mg, b.i.d.) for a period of 6 weeks followed by crossover. PVD was defined as both red-blood-cell standstill in video-assisted microscopic capillaroscopy during cold stimulation using carbon dioxide gas and a score of more than 7 points in a validated questionnaire. Efficacy of treatment was assessed by 1) cold intolerance symptom severity (CISS) score, 2) finger Doppler indices, and 3) indocyanine green perfusion imaging.

RESULTS

The use of triflusal resulted in a greater improvement in CISS score (44.5±18.4 vs. 51.9±16.2; p<0.001) and in mean radial peak systolic velocity (69.8±17.2 vs. 66.1±16.4; p=0.011) compared to aspirin. Furthermore, significant differences were also observed in perfusion rates on indocyanine green perfusion imaging between triflusal and aspirin (45.6±25.8 vs. 51.6±26.9; p=0.020).

CONCLUSION

Triflusal was more effective and demonstrated a more consistent impact on the improvement of symptoms and blood flow in patients with PVD than aspirin.

The effect of nifedipine on retinal venous pressure of glaucoma patients with the Flammer-Syndrome

PURPOSE

The purpose was to measure the retinal venous pressure (RVP) in both eyes of primary open-angle glaucoma (POAG) patients before and 3 weeks after treatment with low-dosed Nifedipine.

METHODS

This retrospective study included 20 POAG patients who were treated with Nifedipine (5 mg daily) and 20 untreated control POAG patients. In both the treated and untreated control group, a distinction was made between those patients who had the Flammer-Syndrome (FS) and those who did not. The RVP was measured in all patients bilaterally at baseline and 3 weeks later by means of contact lens ophthalmodynamometry and the RVP measurements of the treated POAG patients were compared to the RVPs of the untreated POAG controls. Ophthalmodynamometry is done by applying an increasing force on the eye via a contact lens. The minimum force required to induce a venous pulsation is called the ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

RESULTS

The RVP decreased significantly after 3 weeks in both eyes of patients treated with low-dosed Nifedipine compared to the untreated group (mean decrease of 12.5 mmHg (SD 12.5), P < 0.001). A larger response to therapy was found in patients with the FS compared to patients lacking the FS (mean decrease of 16.07 vs. 7.28 mmHg, confidence Interval (CI): 5.2 to 9.3 vs. 12.3 to 19.7; P < 0.001). No significant differences were accounted for in the IOP's of the patients after treatment. In the untreated control group, no significant differences were accounted for either in the RVP or the IOP after 3 weeks.

CONCLUSIONS

Treatment with low-dosed Nifedipine decreases RVP in both eyes of glaucoma patients, particularly in those with the Flammer-Syndrome. This effect may be due to the partial inhibition of Endothelin-1 (ET-1) by Nifedipine.

The effect of flammer-syndrome on retinal venous pressure

BACKGROUND

The purpose of the study was to measure the retinal venous pressure (RVP) in the eyes of primary open-angle glaucoma (POAG) patients and healthy subjects with and without a Flammer-Syndrome (FS).

METHODS

RVP was measured in the following four groups of patients and age- and sex-matched healthy controls: (a) 15 patients with a POAG and a FS (POAG/FS+); (b) 15 patients with a POAG but without a FS (POAG/FS-); (c) 14 healthy subjects with a FS (healthy/FS+) and (d) 16 healthy subjects without a FS (healthy/FS-). RVP was measured in all participants bilaterally by means of contact lens ophthalmodynamometry. Ophthalmodynamometry is done by applying increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

RESULTS

The participants with a FS (whether patients with POAG or healthy subjects), had a significantly higher RVP compared to subjects without a FS (p = 0.0103). Patients with a POAG and FS (POAG/FS+) had a significantly higher RVP compared to patients without a FS (POAG/FS-) (p = 0.0301). There was a notable trend for a higher RVP in the healthy/FS + group compared to the healthy/FS - group, which did not reach statistical significance (p = 0.0898).

CONCLUSIONS

RVP is higher in subjects with a FS, particularly in glaucoma patients. The causal relationship needs to be further evaluated.

Association between zolpidem use and glaucoma risk: a Taiwanese population-based case-control study

Background

To date, the relationship between zolpidem use and subsequent risk of glaucoma in a Taiwanese population has not been assessed.

Methods

We used data from the National Health Insurance system to investigate whether zolpidem use was related to glaucoma risk. A 1:4 matched case-control study was conducted. The cases were patients newly diagnosed with glaucoma from 2001 to 2010. The controls were randomly selected non-glaucoma subjects matched by sex and age (±5 years). Zolpidem exposure and/or the average dosage of zolpidem used (mg/year) were evaluated. Medical comorbidities were considered as confounding factors. Multiple logistic regression models were used to evaluate the potential risk of zolpidem exposure on glaucoma with/without adjustment for the effects of confounding variables.

Results

The exposure rate of zolpidem use in the glaucoma group was significantly higher than that of the control group (2.8% vs. 2.0%, P < 0.0001). The adjusted odds ratio (OR) of the risk of glaucoma for those with zolpidem use vs. those without was 1.19 (95% confidence interval [CI], 1.02–1.38). Compared to non-zolpidem users, zolpidem users with an average dose of more than 200 mg/year had significantly increased risk of glaucoma (OR 1.31, 95% CI 1.03–1.68).

Conclusions

This study suggests that the use of zolpidem might increase the risk of subsequent glaucoma. Further confirmatory studies are recommended to clarify this important issue.

The primary vascular dysregulation syndrome: implications for eye diseases

Vascular dysregulation refers to the regulation of blood flow that is not adapted to the needs of the respective tissue. We distinguish primary vascular dysregulation (PVD, formerly called vasospastic syndrome) and secondary vascular dysregulation (SVD). Subjects with PVD tend to have cold extremities, low blood pressure, reduced feeling of thirst, altered drug sensitivity, increased pain sensitivity, prolonged sleep onset time, altered gene expression in the lymphocytes, signs of oxidative stress, slightly increased endothelin-1 plasma level, low body mass index and often diffuse and fluctuating visual field defects. Coldness, emotional or mechanical stress and starving can provoke symptoms. Virtually all organs, particularly the eye, can be involved. In subjects with PVD, retinal vessels are stiffer and more irregular, and both neurovascular coupling and autoregulation capacity are reduced while retinal venous pressure is often increased. Subjects with PVD have increased risk for normal-tension glaucoma, optic nerve compartment syndrome, central serous choroidopathy, Susac syndrome, retinal artery and vein occlusions and anterior ischaemic neuropathy without atherosclerosis. Further characteristics are their weaker blood–brain and blood-retinal barriers and the higher prevalence of optic disc haemorrhages and activated astrocytes. Subjects with PVD tend to suffer more often from tinnitus, muscle cramps, migraine with aura and silent myocardial ischaemic and are at greater risk for altitude sickness. While the main cause of vascular dysregulation is vascular endotheliopathy, dysfunction of the autonomic nervous system is also involved. In contrast, SVD occurs in the context of other diseases such as multiple sclerosis, retrobulbar neuritis, rheumatoid arthritis, fibromyalgia and giant cell arteritis. Taking into consideration the high prevalence of PVD in the population and potentially linked pathologies, in the current article, the authors provide recommendations on how to effectively promote the field in order to create innovative diagnostic tools to predict the pathology and develop more efficient treatment approaches tailored to the person.

The eye and the heart

The vasculature of the eye and the heart share several common characteristics. The easily accessible vessels of the eye are therefore-to some extent-a window to the heart. There is interplay between cardiovascular functions and risk factors and the occurrence and progression of many eye diseases. In particular, arteriovenous nipping, narrowing of retinal arteries, and the dilatation of retinal veins are important signs of increased cardiovascular risk. The pressure in the dilated veins is often markedly increased due to a dysregulation of venous outflow from the eye. Besides such morphological criteria, functional alterations might be even more relevant and may play an important role in future diagnostics. Via neurovascular coupling, flickering light dilates capillaries and small arterioles, thus inducing endothelium-dependent, flow-mediated dilation of larger retinal vessels. Risk factors for arteriosclerosis, such as dyslipidaemia, diabetes, or systemic hypertension, are also risk factors for eye diseases such as retinal arterial or retinal vein occlusions, cataracts, age-related macular degeneration, and increases in intraocular pressure (IOP). Functional alterations of blood flow are particularly relevant to the eye. The primary vascular dysregulation syndrome (PVD), which often includes systemic hypotension, is associated with disturbed autoregulation of ocular blood flow (OBF). Fluctuation of IOP on a high level or blood pressure on a low level leads to instable OBF and oxygen supply and therefore to oxidative stress, which is particularly involved in the pathogenesis of glaucomatous neuropathy. Vascular dysregulation also leads to a barrier dysfunction and thereby to small retinal haemorrhages.

Retinitis pigmentosa and ocular blood flow

Is the concept of integrative, preventive and personalised medicine applicable to the relationship between retinitis pigmentosa (RP) and ocular blood flow (OBF)? RP encompasses a group of hereditary diseases of the posterior segment of the eye characterised by degeneration, atrophy and finally loss of photoreceptors and retinal pigment epithelium, leading to progressive visual loss. Many different mutations affecting different genes can lead to the clinical picture of RP. Even though the disease has a clear genetic background, there are obviously other factors influencing the manifestation and progression of RP. In this review, we focus on the role of OBF. There is evidence that, in PR patients, OBF is more reduced than one would expect secondary to the retinal atrophy. The main cause of this additional component seems to be primary vascular dysregulation (PVD) syndrome. As PVD syndrome is partly treatable, a vascular evaluation of RP patients is meaningful. Based on the outcome, a targeted individualised, preventive or supportive treatment might be introduced in selected RP patients.

New insights in the pathogenesis and treatment of normal tension glaucoma

Increased intraocular pressure (IOP) is a major risk factor for glaucomatous damage and reducing IOP improves prognosis. Nevertheless, there is little doubt that other risk factors besides IOP such as unstable ocular perfusion are involved. Blood flow is unstable if either the IOP fluctuates at a high level (or blood pressure fluctuates at a low level) or if the autoregulation of blood flow disturbed. A common cause for a disturbed OBF autoregulation is a primary vascular dysregulation (PVD) frequently observed in normal tension glaucoma patients. An unstable blood flow leads to recurrent mild reperfusion injury (chronic oxidative stress) affecting particularly the mitochondria of the optic nerve head. OBF regulation can be improved by magnesium, calcium channel blockers as well as with carbonic anhydrase inhibitors.

Sleep, vigilance, and thermosensitivity

The regulation of sleep and wakefulness is well modeled with two underlying processes: a circadian and a homeostatic one. So far, the parameters and mechanisms of additional sleep-permissive and wake-promoting conditions have been largely overlooked. The present overview focuses on one of these conditions: the effect of skin temperature on the onset and maintenance of sleep, and alertness. Skin temperature is quite well suited to provide the brain with information on sleep-permissive and wake-promoting conditions because it changes with most if not all of them. Skin temperature changes with environmental heat and cold, but also with posture, environmental light, danger, nutritional status, pain, and stress. Its effect on the brain may thus moderate the efficacy by which the clock and homeostat manage to initiate or maintain sleep or wakefulness. The review provides a brief overview of the neuroanatomical pathways and physiological mechanisms by which skin temperature can affect the regulation of sleep and vigilance. In addition, current pitfalls and possibilities of practical applications for sleep enhancement are discussed, including the recent finding of impaired thermal comfort perception in insomniacs.

Thermal discomfort with cold extremities in relation to age, gender, and body mass index in a random sample of a Swiss urban population

Background

The aim of this epidemiological study was to investigate the relationship of thermal discomfort with cold extremities (TDCE) to age, gender, and body mass index (BMI) in a Swiss urban population.

Methods

In a random population sample of Basel city, 2,800 subjects aged 20-40 years were asked to complete a questionnaire evaluating the extent of cold extremities. Values of cold extremities were based on questionnaire-derived scores. The correlation of age, gender, and BMI to TDCE was analyzed using multiple regression analysis.

Results

A total of 1,001 women (72.3% response rate) and 809 men (60% response rate) returned a completed questionnaire. Statistical analyses revealed the following findings: Younger subjects suffered more intensely from cold extremities than the elderly, and women suffered more than men (particularly younger women). Slimmer subjects suffered significantly more often from cold extremities than subjects with higher BMIs.

Conclusions

Thermal discomfort with cold extremities (a relevant symptom of primary vascular dysregulation) occurs at highest intensity in younger, slimmer women and at lowest intensity in elderly, stouter men.

Relationship between optic nerve head and finger blood flow

PURPOSE

To examine the relationship between optic nerve head (ONH) and finger blood flow in subjects with and without a primary vascular dysregulation (PVD).

METHODS

ONH blood flow and finger blood flow was measured in 15 subjects with PVD and in 24 subjects without PVD. PVD was defined as being present if it was detected in patient history as well as by nailfold capillaromicroscopy. PVD was defined as being absent if the patient history for PVD was negative and the results of nailfold capillaromicroscopy were negative. Scanning laser Doppler flowmetry (LDF) was used to measure ONH and finger blood flow. Finger temperature was measured in all subjects using a contact sensor.

RESULTS

ONH blood flow is significantly related to finger blood flow in subjects with PVD (p<0.01), but not in subjects without a PVD. Subjects with PVD had a significantly lower finger skin temperature in comparison to those without PVD (p<0.01)

CONCLUSIONS

The present study indicates a relationship between ONH and finger blood flow in subjects with PVD. This might be an indirect sign of a disturbed autoregulation of ocular blood flow in PVD subjects.

The relationship between insomnia and body temperatures

Sleepiness and sleep propensity are strongly influenced by our circadian clock as indicated by many circadian rhythms, most commonly by that of core body temperature. Sleep is most conducive in the temperature minimum phase, but is inhibited in a "wake maintenance zone" before the minimum phase, and is disrupted in a zone following that phase. Different types of insomnia symptoms have been associated with abnormalities of the body temperature rhythm. Sleep onset insomnia is associated with a delayed temperature rhythm presumably, at least partly, because sleep is attempted during a delayed evening wake maintenance zone. Morning bright light has been used to phase advance circadian rhythms and successfully treat sleep onset insomnia. Conversely, early morning awakening insomnia has been associated with a phase advanced temperature rhythm and has been successfully treated with the phase delaying effects of evening bright light. Sleep maintenance insomnia has been associated not with a circadian rhythm timing abnormality, but with nocturnally elevated core body temperature. Combination of sleep onset and maintenance insomnia has been associated with a 24-h elevation of core body temperature supporting the chronic hyper-arousal model of insomnia. The possibility that these last two types of insomnia may be related to impaired thermoregulation, particularly a reduced ability to dissipate body heat from distal skin areas, has not been consistently supported in laboratory studies. Further studies of thermoregulation are needed in the typical home environment in which the insomnia is most evident.

Live to the rhythm, slave to the rhythm

Circadian rhythms in health and disease have most often been described in terms of their phases and amplitudes, and how these respond to a single exposure to stimuli denoted as zeitgebers. The present paper argues that it is also important to consider the 24-h regularity in the repeated occurrence of the zeitgebers. The effect of the regularity of stimulation by light, melatonin, physical activity, body temperature, corticosteroids and feeding on synchronization within and between the central circadian clock and peripheral oscillators is discussed. In contrast to the phase shifts that can be recorded acutely after a single zeitgeber pulse, the effects of irregularly versus regularly timed zeitgeber can be studied only in long-term protocols and may develop slowly, which is a possible reason why they have received relatively little attention. Several observations indicate a reciprocal relation between the robustness of the endogenous circadian timing system and its dependency on regularly timed zeitgebers. Especially at old age and in disease, proper functioning of the circadian timing system may become more dependent on regularly timed exposure to zeitgeber stimuli. in such conditions, regularly timed exposure to zeitgeber appears to be highly important for health. After a concise introduction on inputs to the central and peripheral oscillators of the circadian timing system, the paper discusses the responses of the circadian timing system and health to (1) a chronic lack of zeitgeber stimuli; (2) fragmented or quasi-ultradian stimuli and (3) repeated phase shifts in stimuli. Subsequently, the specific relevance to aging is discussed, followed by an overview of the effects of experimentally imposed regularly timed stimuli. Finally, a possible mechanism for the gradually evolving effects of repeated regularly timed stimuli on the circadian timing system is proposed.

What is the present pathogenetic concept of glaucomatous optic neuropathy?

Glaucomatous optic neuropathy implies loss of neural tissue, activation of glial cells, tissue remodeling, and change of blood flow. The blood flow reduction is not only secondary but has a primary component. Activation of astrocytes leads to an altered microenvironment. An unstable ocular perfusion, either due to IOP fluctuation or a disturbed autoregulation (due to primary vascular dysregulation syndrome) leads to a mild reperfusion injury. The superoxide (O(2)(-)) anion produced in the mitochondria of the axons, fuses with the nitric oxide (NO) diffusing from the astrocytes, leading to the damaging peroxynitrite (ONOO(-)). It is possible that the diffusion of endothelin and metalloproteinases to the surrounding of the optic nerve head leads to a local vasoconstriction and thereby increases the risk for venous occlusion and weakens the blood-brain barrier, which in extreme situations results in splinter hemorrhages. Activated retinal astrocytes can be visualized clinically. The involvement of primary vascular dysregulation in the pathogenesis of glaucomatous optic neuropathy may explain why women, as well as Japanese, suffer more often from normal-tension glaucoma.

Does the blood-brain barrier play a role in Glaucoma?

The optic nerve head, although part of the central nervous system, lacks classical blood-brain barrier properties. The tissue of Elschnig does not totally separate the optic nerve head from fenestrated peripapillary choriocapillaries. The microvessels in the prelaminar region of the optic nerve head have less effective barriers than those in the laminar or retrolaminar regions. In glaucoma, the blood-brain barrier in the optic nerve head may even be weaker. Incomplete blood-brain barrier renders circulating molecules, such as endothelin-1 (ET-1), direct access to smooth vascular muscle cells and pericytes both in the prelaminar part of the optic nerve head and to adjacent retinal tissue. This potentially leads to some vasoconstriction as observed in the peri-papillary retinal vessel in glaucoma patients. In extreme situations, this may provoke retinal vein occlusion. The direct access of these molecules also influences the barrier function. If, simultaneously, ET-1 reduces endothelial tight-junctions and matrix-metalloproteinase (MMP)-9 degrades the basement membrane, not only macromolecules but even red blood cells may cross the blood-brain barrier and lead to what is clinically observed as optic disk hemorrhages.

What is the link between vascular dysregulation and glaucoma?

The need of blood flow to different organs varies rapidly over time which is why there is sophisticated local regulation of blood flow. The term dysregulation simply means that blood flow is not properly adapted to this need. Dysregulative mechanisms can lead to an over- or underperfusion. A steady overperfusion may be less critical for long-term damage. A constant underperfusion, however, can lead to some tissue atrophy or in extreme situations to infarction. Unstable perfusion (underperfusion followed by reperfusion) leads to oxidative stress. There are a number of causes that lead to local or systemic vascular dysregulation. Systemic dysregulation can be primary or secondary of nature. A secondary dysregulation is due to other autoimmune diseases such as rheumatoid arthritis, giant cell arteritis, systemic lupus erythematodes, multiple sclerosis, colitis ulcerosa, or Crohns disease. Patients with a secondary vascular dysregulation normally have a high level of circulating endothelin-1 (ET-1). This increased level of ET-1 leads to a reduction of blood flow both in the choroid and the optic nerve head but has little influence on autoregulation. In contrast, primary vascular dysregulation has little influence on baseline ocular blood flow but interferes with autoregulation. This, in turn, leads to unstable oxygen supply, which seems to be a relevant component in the pathogenesis of glaucomatous optic neuropathy.

Chronobiological characterization of women with primary vasospastic syndrome: body heat loss capacity in relation to sleep initiation and phase of entrainment

Women with primary vasospastic syndrome (VS), but otherwise healthy, exhibit a functional disorder of vascular regulation (main symptom: cold extremities) and often suffer from difficulties initiating sleep (DIS). Diverse studies have shown a close association between distal vasodilatation before lights off and a rapid onset of sleep. Therefore, we hypothesized that DIS in women with VS could be due to a reduced heat loss capacity in the evening, i.e., subjects are physiologically not ready for sleep. The aim of the study was to elucidate whether women having both VS and DIS (WVD) or not (controls) show different circadian characteristics (e.g., phase delay of the circadian thermoregulatory system with respect to the sleep-wake cycle). Healthy young women (n = 9 WVD and n = 9 control) completed a 40-h constant routine protocol (adjusted to habitual bedtime) before and after an 8-h sleep episode. Skin temperatures [off-line calculated as distal-proximal skin temperature gradient (DPG)] and core body temperature (CBT; rectal) were continuously recorded. Half-hourly saliva samples were collected for melatonin assay and subjective sleepiness was assessed on the Karolinska Sleepiness Scale (KSS). Compared with control, WVD showed no differences in habitual bed times, but a 1-h circadian phase delay of dim light-melatonin onset (hours after lights on: WVD 14.6 +/- 0.3 h; control 13.5 +/- 0.2 h; P = 0.01). Similar phase shifts were observed in CBT, DPG, and KSS ratings. In conclusion, WVD exhibit a phase delay of the endogenous circadian system with respect to their habitual sleep-wake cycle, which could be a cause of DIS.