Barbara Griefahn

Bio: Barbara Griefahn is an academic researcher from Technical University of Dortmund. The author has contributed to research in topics: Noise & Annoyance. The author has an hindex of 30, co-authored 118 publications receiving 3307 citations.

Event-related awakenings caused by nocturnal transportation noise.

Abstract: The present study focussed on awakenings caused by nocturnal noises emitted from aircraft, road and rail vehicles with maximum levels ranging from 40 to 76 dBA. A laboratory study with 24 participants (12 male, 12 female, 19-28 years) was performed with polysomnographic recordings during 13 nights (including a preceding habituation night). Multivariable random subject effect logistic regression models containing acoustical, situational and individual parameters were used to determine the probability of event-related awakenings for each traffic mode. Awakening probability increased significantly with maximum sound pressure level (SPL), slope of rise (dB/s), noise duration and the noise-free interval between noise events. Gender, noise sensitivity and age did not influence awakening probability significantly (the latter only in a combined model). Awakening probability increased with elapsed time after sleep onset, and was significantly lower during slow wave sleep compared to S2 sleep, but not during REM sleep. After adjusting for differences in study design (acoustical macrostructure), awakening probability decreased in the order rail, road and air traffic noise, but only rail and air traffic noise differed significantly (p= 0.002). After further adjusting for slope of rise and noise duration (acoustical microstructure), differences between traffic modes decreased, but rail and air traffic noise still differed significantly (p=0.044). Acoustical properties other than slope of rise and noise duration may account for the residual difference. The results of this study suggest that the reduction of maximum SPLs, rise slopes, and traffic volume during the second part of the night might reduce the number of noise-induced awakenings.

An ECG-based Algorithm for the Automatic Identification of Autonomic Activations Associated with Cortical Arousal

Abstract: Objectives: EEG arousals are associated with autonomic activations. Visual EEG arousal scoring is time consuming and suffers from low interob-server agreement. We hypothesized that information on changes in heart rate alone suffice to predict the occurrence of cortical arousal. Methods: Two visual AASM EEG arousal scorings of 56 healthy subject nights (mean age 37.0 ± 12.8 years, 26 male) were obtained. For each of 5 heartbeats following the onset of 3581 consensus EEG arousals and of an equal number of control conditions, differences to a moving median were calculated and used to estimate likelihood ratios (LRs) for 10 categories of heartbeat differences. Comparable to 5 consecutive diagnostic tests, these LRs were used to calculate the probability of heart rate responses being associated with cortical arousals. Results: EEG and ECG arousal indexes agreed well across a wide range of decision thresholds, resulting in a receiver operating characteristic (ROC) with an area under the curve of 0.91. For the decision threshold chosen for the final analyses, a sensitivity of 68.1% and a specificity of 95.2% were obtained. ECG and EEG arousal indexes were poorly correlated (r = 0.19, P <0.001, ICC = 0.186), which could in part be attributed to 3 outliers. The Bland-Altman plot showed an unbiased estimation of EEG arousal indexes by ECG arousal indexes with a standard deviation of ± 7.9 arousals per hour sleep. In about two-thirds of all cases, ECG arousal scoring was matched by at least one (22.2%) or by both (42.5%) of the visual scorings. Sensitivity of the algorithm increased with increasing duration of EEG arousals. The ECG algorithm was also successfully validated with 30 different nights of 10 subjects (mean age 35.3 □ 13.6 years, 5 male). Conclusions: In its current version, the ECG algorithm cannot replace visual EEG arousal scoring. Sensitivity for detecting <10-s EEG arousals needs to be improved. However, in a nonclinical population, it may be valuable to supplement visual EEG arousal scoring by this automatic, objective, reproducible, cheap, and time-saving method.

Prediction of the average skin temperature in warm and hot environments

Abstract: The prediction of the mean skin temperature used for the Required Sweat Rate index was criticised for not being valid in conditions with high radiation and high humidity. Based on a large database provided by 9 institutes, 1999 data points obtained using steady-state conditions, from 1399 experiments and involving 377 male subjects, were used for the development of a new prediction model. The observed mean skin temperatures ranged from 30.7 degrees C to 38.6 degrees C. Experimental conditions included air temperatures (Ta) between 20 and 55 degrees C, mean radiant temperatures (Tr) up to 145 degrees C, partial vapour pressures (Pa) from 0.2 to 5.3 kPa, air velocities (v(a)) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (T(re)) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation, I(cl), < or = 0.2 clo, where 1 clo = 0.155 m2 x degrees C x W(-1), which is equivalent to the thermal insulation of clothing necessary to maintain a resting subject in comfort in a normally ventilated room, air movement = 10 cm/s, at a temperature of 21 degrees C and a humidity of less than 50%) and clothed (0.6 < or = I(cl) < or = 1.0 clo) subjects using a multiple linear regression technique with re-sampling (non-parametric bootstrap). The following expressions were obtained for nude and clothed subjects, respectively: T(sk) = 7.19 + 0.064Ta + 0.061Tr + 0.198Pa - 0.348v(a) + 0.616T(re) and T(sk) = 12.17 + 0.020Ta + 0.044Tr + 0.194Pa - 0.253v(a) + 0.0029M + 0.513T(re). For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range of +/- 1 degree C of the observed skin temperatures. It is concluded that the proposed models for the prediction of the mean skin temperature are valid for a wide range of warm and hot ambient conditions in steady-state conditions, including those of high radiation and high humidity.

Melatonin production during childhood and adolescence: a longitudinal study on the excretion of urinary 6-hydroxymelatonin sulfate.

Abstract: Cross-sectional data on urinary 6-hydroxymelatonin sulfate (6-OHMS) excretion in children suggest a constant melatonin secretion during growth The present longitudinal study concerned, accordingly, the intra-individual stability of melatonin production during childhood and adolescence Urine samples collected during a longitudinal investigation of healthy white children and adolescents were analyzed Forty-six boys and 38 girls were chosen for the present study They had passed 3-15 annual examinations between their 3rd and 18th yr of age Each examination included the collection of urine over 24 hr The daily urinary output of 6-OHMS of the overall 621 samples was quantified by enzyme-linked immunosorbent assay The analyses clearly revealed for the first time that, despite huge inter-individual differences, melatonin production remains constant in one and the same individual during childhood and adolescence Additionally, neither a significant sex difference was observed nor was the 6-OHMS output affected by season The dramatic decrease of plasma melatonin levels as described in the literature is mainly related to an increase in body size rather than to decreasing pineal secretion

Aircraft noise effects on sleep: Mechanisms, mitigation and research needs

Abstract: There is an ample number of laboratory and field studies which provide sufficient evidence that aircraft noise disturbs sleep and, depending on traffic volume and noise levels, may impair behavior and well-being during the day. Although clinical sleep disorders have been shown to be associated with increased risk of cardiovascular diseases, only little is known about the long-term effects of aircraft noise disturbed sleep on health. National and international laws and guidelines try to limit aircraft noise exposure facilitating active and passive noise control to prevent relevant sleep disturbances and its consequences. Adopting the harmonized indicator of the European Union Directive 2002/49/EC, the WHO Night Noise Guideline for Europe (NNG) defines four Lnight , outside ranges associated with different risk levels of sleep disturbance and other health effects ( 55 dBA). Although traffic patterns differing in number and noise levels of events that lead to varying degrees of sleep disturbance may result in the same Lnight , simulations of nights with up to 200 aircraft noise events per night nicely corroborate expert opinion guidelines formulated in WHO's NNG. In the future, large scale field studies on the effects of nocturnal (aircraft) noise on sleep are needed. They should involve representative samples of the population including vulnerable groups like children and chronically ill subjects. Optimally, these studies are prospective in nature and examine the long-term consequences of noise-induced sleep disturbances. Furthermore, epidemiological case-control studies on the association of nocturnal (aircraft) noise exposure and cardiovascular disease are needed. Despite the existing gaps in knowledge on long-term health effects, sufficient data are available for defining limit values, guidelines and protection concepts, which should be updated with the availability of new data.

Auditory and non-auditory eff ects of noise on health

Abstract: Noise is pervasive in everyday life and can cause both auditory and non-auditory health eff ects. Noise-induced hearing loss remains highly prevalent in occupational settings, and is increasingly caused by social noise exposure (eg, through personal music players). Our understanding of molecular mechanisms involved in noise-induced haircell and nerve damage has substantially increased, and preventive and therapeutic drugs will probably become available within 10 years. Evidence of the non-auditory eff ects of environmental noise exposure on public health is growing. Observational and experimental studies have shown that noise exposure leads to annoyance, disturbs sleep and causes daytime sleepiness, aff ects patient outcomes and staff performance in hospitals, increases the occurrence of hypertension and cardiovascular disease, and impairs cognitive performance in schoolchildren. In this Review, we stress the importance of adequate noise prevention and mitigation strategies for public health.

Circadian typology: a comprehensive review.

Abstract: The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep-wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.

Sleep and circadian rhythm disruption in psychiatric and neurodegenerative disease

Abstract: Sleep and circadian rhythm disruption are frequently observed in patients with psychiatric disorders and neurodegenerative disease. The abnormal sleep that is experienced by these patients is largely assumed to be the product of medication or some other influence that is not well defined. However, normal brain function and the generation of sleep are linked by common neurotransmitter systems and regulatory pathways. Disruption of sleep alters sleep-wake timing, destabilizes physiology and promotes a range of pathologies (from cognitive to metabolic defects) that are rarely considered to be associated with abnormal sleep. We propose that brain disorders and abnormal sleep have a common mechanistic origin and that many co-morbid pathologies that are found in brain disease arise from a destabilization of sleep mechanisms. The stabilization of sleep may be a means by which to reduce the symptoms of--and permit early intervention of--psychiatric and neurodegenerative disease.

Melatonin: Nature's most versatile biological signal?

Abstract: Melatonin is a ubiquitous molecule and widely distributed in nature, with functional activity occurring in unicellular organisms, plants, fungi and animals. In most vertebrates, including humans, melatonin is synthesized primarily in the pineal gland and is regulated by the environmental light/dark cycle via the suprachiasmatic nucleus. Pinealocytes function as 'neuroendocrine transducers' to secrete melatonin during the dark phase of the light/dark cycle and, consequently, melatonin is often called the 'hormone of darkness'. Melatonin is principally secreted at night and is centrally involved in sleep regulation, as well as in a number of other cyclical bodily activities. Melatonin is exclusively involved in signaling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. Synthesis of melatonin also occurs in other areas of the body, including the retina, the gastrointestinal tract, skin, bone marrow and in lymphocytes, from which it may influence other physiological functions through paracrine signaling. Melatonin has also been extracted from the seeds and leaves of a number of plants and its concentration in some of this material is several orders of magnitude higher than its night-time plasma value in humans. Melatonin participates in diverse physiological functions. In addition to its timekeeping functions, melatonin is an effective antioxidant which scavenges free radicals and up-regulates several antioxidant enzymes. It also has a strong antiapoptotic signaling function, an effect which it exerts even during ischemia. Melatonin's cytoprotective properties have practical implications in the treatment of neurodegenerative diseases. Melatonin also has immune-enhancing and oncostatic properties. Its 'chronobiotic' properties have been shown to have value in treating various circadian rhythm sleep disorders, such as jet lag or shift-work sleep disorder. Melatonin acting as an 'internal sleep facilitator' promotes sleep, and melatonin's sleep-facilitating properties have been found to be useful for treating insomnia symptoms in elderly and depressive patients. A recently introduced melatonin analog, agomelatine, is also efficient for the treatment of major depressive disorder and bipolar affective disorder. Melatonin's role as a 'photoperiodic molecule' in seasonal reproduction has been established in photoperiodic species, although its regulatory influence in humans remains under investigation. Taken together, this evidence implicates melatonin in a broad range of effects with a significant regulatory influence over many of the body's physiological functions.