A laboratory study on the effects of wind turbine noise on sleep: results of the polysomnographic WiTNES study

Noise-induced sleep disruption from wind turbines: scientific updates and acoustical standards

Wind energy appears to place global environmental benefits against local human health, particularly sleep. The result is a significant challenge to wind-energy development for the achievement of large-scale alternative energy. Our purpose is to examine noise from wind turbines and its potential to disrupt sleep, to examine the human health literature addressing these concerns, and to provide insight into how developers and communities can employ these concepts to pursue wind energy without impacting human health. The latest and most rigorous research on noise from wind turbines points to healthy sleep, when turbines are sited reasonably. This includes audible noise, low-frequency noise, and infrasound. Recent advances in acoustical standards provide practical methods to ensure adherence to these scientific findings. There now exist key data concerning wind-turbine noise, and its impact on sleep. Knowing that information, and how to deploy it with modern engineering standards should simultaneously facilitate wind development and protect human health.

Establishing the acute physiological and sleep disruption characteristics of wind farm versus road traffic noise disturbances in sleep: a randomized controlled trial protocol

Study Objectives

Despite the global expansion of wind farms, effects of wind farm noise (WFN) on sleep remain poorly understood. This protocol details a randomized controlled trial designed to compare the sleep disruption characteristics of WFN versus road traffic noise (RTN).

Methods

This study was a prospective, seven night within-subjects randomized controlled in-laboratory polysomnography-based trial. Four groups of adults were recruited from; <10 km away from a wind farm, including those with, and another group without, noise-related complaints; an urban RTN exposed group; and a group from a quiet rural area. Following an acclimation night, participants were exposed, in random order, to two separate nights with 20-s or 3-min duration WFN and RTN noise samples reproduced at multiple sound pressure levels during established sleep. Four other nights tested for continuous WFN exposure during wake and/or sleep on sleep outcomes.

Results

The primary analyses will assess changes in electroencephalography (EEG) assessed as micro-arousals (EEG shifts to faster frequencies lasting 3-15 s) and awakenings (>15 s events) from sleep by each noise type with acute (20-s) and more sustained (3-min) noise exposures. Secondary analyses will compare dose-response effects of sound pressure level and noise type on EEG K-complex probabilities and quantitative EEG measures, and cardiovascular activation responses. Group effects, self-reported noise sensitivity, and wake versus sleep noise exposure effects will also be examined.

Conclusions

This study will help to clarify if wind farm noise has different sleep disruption characteristics compared to road traffic noise.

Association between exposure to wind turbines and sleep disorders: A systematic review and meta-analysis

To date, there is scarce evidence on the association between sleep disorders and noise generated by wind turbines. We searched six relevant electronic databases from the inception to May 2023 for relevant articles. The methodological quality of the included articles was evaluated using the US National Institutes of Health tool. Fifteen articles met the inclusion criteria. The overall prevalence of sleep disorders among residents close to wind turbines was 34% (95% Confidence Interval, 0.22-0.47). Univariate meta-regressions for distance and sound power level showed that at higher distance the prevalence of sleep disorders decreases (p = 0.010) and with a higher sound power level the prevalence increases (p = 0.037). Furthermore, this systematic review and meta-analysis highlighted that the overall quality of current research on this topic is poor, and the methods to measure the results are often based on subjective assessments and not validated questionnaires. In conclusion, our preliminary findings suggest that there may be a possible relation between exposure to wind turbines and sleep disorders, although no conclusions can be drawn in terms of causality due to the nature of the retrieved data and the poor quality of current evidence. Future studies should adopt a longitudinal design and focus on objective measurements, supported by validated subjective methods such as questionnaires.

Sleep disorders in chronic pain and its neurochemical mechanisms: a narrative review

Chronic pain (CP) is a prevalent problem, and more than half of patients with CP have sleep disorders. CP comorbidity with sleep disorders imposes immense suffering and seriously affects the patient's quality of life, which is a challenging issue encountered by clinicians. Although the reciprocal interactions between pain and sleep have been studied to some degree, there is still a lack of awareness and comprehensive description of CP comorbidity with sleep disorders. In this narrative review article, we summarize the current knowledge about the present estimates of the prevalence of comorbid sleep disorders in CP patients, sleep detection methods, sleep characterization in CP, and the effect of sleep disorders on CP and current therapies. We also summarize current knowledge of the neurochemical mechanisms of CP comorbidity with sleep disorders. In conclusion, insufficient attention has been paid to the role of sleep disorders in CP patients, and CP patients should be screened for sleep disorders in the clinic. Special attention should be given to a possible risk of drug-drug interaction when using two types of drugs targeting pain and sleep simultaneously. The current insight into the neurobiological mechanisms underlying CP comorbidity with sleep disorders is still rather limited.

The Health Effects of 72 Hours of Simulated Wind Turbine Infrasound: A Double-Blind Randomized Crossover Study in Noise-Sensitive, Healthy Adults

BACKGROUND

Large electricity-generating wind turbines emit both audible sound and inaudible infrasound at very low frequencies that are outside of the normal human range of hearing. Sufferers of wind turbine syndrome (WTS) have attributed their ill-health and particularly their sleep disturbance to the signature pattern of infrasound. Critics have argued that these symptoms are psychological in origin and are attributable to nocebo effects.

OBJECTIVES

We aimed to test the effects of 72 h of infrasound (1.6-20 Hz at a sound level of ∼90 dB pk re 20μPa, simulating a wind turbine infrasound signature) exposure on human physiology, particularly sleep.

METHODS

We conducted a randomized double-blind triple-arm crossover laboratory-based study of 72 h exposure with a >10-d washout conducted in a noise-insulated sleep laboratory in the style of a studio apartment. The exposures were infrasound (∼90  dB pk), sham infrasound (same speakers not generating infrasound), and traffic noise exposure [active control; at a sound pressure level of 40-50 dB LAeq,night and 70 dB LAFmax transient maxima, night (2200 to 0700 hours)]. The following physiological and psychological measures and systems were tested for their sensitivity to infrasound: wake after sleep onset (WASO; primary outcome) and other measures of sleep physiology, wake electroencephalography, WTS symptoms, cardiovascular physiology, and neurobehavioral performance.

RESULTS

We randomized 37 noise-sensitive but otherwise healthy adults (18-72 years of age; 51% female) into the study before a COVID19-related public health order forced the study to close. WASO was not affected by infrasound compared with sham infrasound (-1.36 min; 95% CI: -6.60, 3.88, p=0.60) but was worsened by the active control traffic exposure compared with sham by 6.07 min (95% CI: 0.75, 11.39, p=0.02). Infrasound did not worsen any subjective or objective measures used.

DISCUSSION

Our findings did not support the idea that infrasound causes WTS. High level, but inaudible, infrasound did not appear to perturb any physiological or psychological measure tested in these study participants. https://doi.org/10.1289/EHP10757.

Health effects of wind turbines: a review of the literature between 2010-2020

Although wind power is more acceptable in terms of its environmental impact, possible risks to human health are still being discussed. The aim of this study is to systematically evaluate the methodology and the outcomes of the articles that investigate the health effects of wind turbines on humans. Combinations of keywords were entered into the PubMed database. The search resulted in a total of 141 hits, 22 were included. It had been noticed that the most common problems in those living around the wind turbines are noise annoyance(n=18), risk perception and attitude towards wind turbines(n=11), general health symptoms and quality of life(n=11), sleep disturbance(n=10), annoyance(n=7) and shadow flicker effect(n=4). General annoyance is adversely affected by the noise level and sensitivity to noise. We can conclude that the knowledge of and attitude towards wind turbines can turn into annoyance and symptoms if the audio-visual effects of turbines limit daily life activities.

Considerations on environmental, economic, and energy impacts of wind energy generation: Projections towards sustainability initiatives

The energy sector contributes significantly to the emission of greenhouse gases (GHGs) due to the use of fossil fuels which leads to climate change problems. Worldwide, there is a shift from fossil fuel-based energy to cleaner energy sources such as solar, wind, geothermal, and biomass. Wind energy is one of the promising cleaner energy sources as it is feasible and cost-effective. However, the development of wind farms causes impacts on sustainability aspects. This article aims to review the impacts of wind energy generation on environmental, economic, and social aspects of sustainability and their mitigation strategies. The aim was achieved by reviewing recent research papers on different aspects of wind energy sustainability. The environmental impacts reviewed include the effects on avian life, noise pollution, visual impacts, microclimate and vegetation. Apart from environmental impacts, wind energy generation faces issues in energy and financial sustainability, such as the wind power fluctuation, technology lagging and use of fixed feed-in tariff contracts that do not consider wind energy advancement and end-of-life management. We discussed that turbine deterrents, automatic curtailment, low gloss blades and sustainable siting of wind farms as some of the effective ways to combat wind energy environmental impacts. In addition, we discussed that energy storage systems, setting up microgrids, combination of solar, wind and energy storage, and renewable energies policies are some of the ways to combat wind energy's economic and energy impacts. Lastly, the recommendations, and future perspectives on wind energy generation sustainability are discussed.

Impact of Noise Exposure on Risk of Developing Stress-Related Metabolic Effects: A Systematic Review and Meta-Analysis

Background

Exposure to noise can increase biological stress reactions, which may increase adverse health effects, including metabolic disorders; however, the certainty in the association between exposure to noise and metabolic outcomes has not been widely explored. The objective of this review is to evaluate the evidence between noise exposures and metabolic effects.

Materials and Methods

A systematic review of English and comparative studies available in PubMed, Cochrane Central, EMBASE, and CINAHL databases between January 1, 1980 and December 29, 2021 was performed. Risk of Bias of Nonrandomized Studies of Exposures was used to assess risk of bias of individual studies and certainty of the body of evidence for each outcome was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

Results

Fifty-six primary studies reporting on cortisol, cholesterol levels, waist circumference, glucose levels, and adrenaline and/or noradrenaline were identified. Although meta-analyses suggested that there may be an increase in waist circumference and adrenaline with increased noise exposure, the certainty in the evidence is very low. Overall, the certainty in the evidence of an effect of increased noise on all the outcomes were low to very low due to concerns with risk of bias, inconsistency across exposure sources, populations, and studies, and imprecision in the estimates of effects.

Conclusions

The certainty of the evidence of increased noise on metabolic effects was low to very low, which likely reflects the inability to compare across the totality of the evidence for each outcome. The findings from this review may be used to inform policies involving noise reduction and mitigation strategies, and to direct further research in areas that currently have limited evidence available.

An experimental investigation on the impact of wind turbine noise on polysomnography-measured and sleep diary-determined sleep outcomes

Study Objectives

Carefully controlled studies of wind turbine noise (WTN) and sleep are lacking, despite anecdotal complaints from some residents in wind farm areas and known detrimental effects of other noises on sleep. This laboratory-based study investigated the impact of overnight WTN exposure on objective and self-reported sleep outcomes.

Methods

Sixty-eight participants (38 females) aged (mean ± SD) 49.2 ± 19.5 were recruited from four groups; N = 14, living &lt;10 km from a wind farm and reporting WTN related sleep disruption; N = 18, living &lt;10 km from a wind farm and reporting no WTN sleep disruption; N = 18, reporting road traffic noise-related sleep disruption; and N = 18 control participants living in a quiet rural area. All participants underwent in-laboratory polysomnography during four full-night noise exposure conditions in random order: a quiet control night (19 dB(A) background laboratory noise), continuous WTN (25 dB(A)) throughout the night; WTN (25 dB(A)) only during periods of established sleep; and WTN (25 dB(A)) only during periods of wake or light N1 sleep. Group, noise condition, and interaction effects on measures of sleep quantity and quality were examined via linear mixed model analyses.

Results

There were no significant noise condition or group-by-noise condition interaction effects on polysomnographic or sleep diary determined sleep outcomes (all ps &gt; .05).

Conclusions

These results do not support that WTN at 25 dB(A) impacts sleep outcomes in participants with or without prior WTN exposure or self-reported habitual noise-related sleep disruption. These findings do not rule out effects at higher noise exposure levels or potential effects of WTN on more sensitive markers of sleep disruption.

Clinical Trial Registration

ACTRN12619000501145, UTN U1111-1229-6126. Establishing the physiological and sleep disruption characteristics of noise disturbances in sleep. https://www.anzctr.org.au/. This study was prospectively registered on the Australian and New Zealand Clinical Trial Registry.

Hair cortisol as a viable tool for the assessment of an association between environmental noise exposure and chronic stress

Entrenched in the well-established link between stress and health, noise exposure as a potential contributor to stress-related health effects receives tremendous attention. Indeed, exposure to noise can act as a stressor as evidenced through increased heart rate, blood pressure, adrenaline, epinephrine, and cortisol. Cortisol is secreted from the adrenal glands in response to stressor-induced activation of the hypothalamic-pituitary-adrenal axis. For assessment of environmental noise and stress, repeated sampling in blood, saliva, or urine is necessary to evaluate the association between environmental noise exposure and protracted changes in cortisol. Controlling for the many variables that influence the secretion of cortisol at discrete sampling intervals is challenging. Studies suggest that systemically produced cortisol integrates and remains in hair as it grows, providing a measure that integrates a cortisol response over a longer period, circumventing several limitations associated with multiple sampling. Robust evidence supports the integration of cortisol into hair, yet recent studies call into question the notion that cortisol is retained with growth. The current paper discusses the strengths and limitations of hair cortisol analysis with an emphasis on its utility as a measure of chronic stress in environmental noise studies.

Environmental Noise and Effects on Sleep: An Update to the WHO Systematic Review and Meta-Analysis

BACKGROUND

Nighttime noise carries a significant disease burden. The World Health Organization (WHO) recently published guidelines for the regulation of environmental noise based on a review of evidence published up to the year 2015 on the effects of environmental noise on sleep.

OBJECTIVES

This systematic review and meta-analysis will update the WHO evidence review on the effects of environmental noise on sleep disturbance to include more recent studies.

METHODS

Investigations of self-reported sleep among residents exposed to environmental traffic noise at home were identified using Scopus, PubMed, Embase, and PsycINFO. Awakenings, falling asleep, and sleep disturbance were the three outcomes included. Extracted data were used to derive exposure-response relationships for the probability of being highly sleep disturbed by nighttime noise [average outdoor A-weighted noise level (Lnight) 2300-0700 hours] for aircraft, road, and rail traffic noise, individually. The overall quality of evidence was assessed using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) criteria.

RESULTS

Eleven studies (n=109,070 responses) were included in addition to 25 studies (n=64,090 responses) from the original WHO analysis. When sleep disturbance questions specifically mentioned noise as the source of disturbance, there was moderate quality of evidence for the probability of being highly sleep disturbed per 10-dB increase in Lnight for aircraft [odds ratio (OR)=2.18; 95% confidence interval (CI): 2.01, 2.36], road (OR=2.52; 95% CI: 2.28, 2.79), and railway (OR=2.97; 95% CI: 2.57, 3.43) noise. When noise was not mentioned, there was low to very low quality of evidence for being sleep disturbed per 10-dB increase in Lnight for aircraft (OR=1.52; 95% CI: 1.20, 1.93), road (OR=1.14; 95% CI: 1.08, 1.21), and railway (OR=1.17; 95% CI: 0.91, 1.49) noise. Compared with the original WHO review, the exposure-response relationships closely agreed at low (40 dB Lnight) levels for all traffic types but indicated greater disturbance by aircraft traffic at high noise levels. Sleep disturbance was not significantly different between European and non-European studies.

DISCUSSION

Available evidence suggests that transportation noise is negatively associated with self-reported sleep. Sleep disturbance in this updated meta-analysis was comparable to the original WHO review at low nighttime noise levels. These low levels correspond to the recent WHO noise limit recommendations for nighttime noise, and so these findings do not suggest these WHO recommendations need revisiting. Deviations from the WHO review in this updated analysis suggest that populations exposed to high levels of aircraft noise may be at greater risk of sleep disturbance than determined previously. https://doi.org/10.1289/EHP10197.

Beyond traditional wind farm noise characterisation using transfer learning

This study proposes an approach for the characterisation and assessment of wind farm noise (WFN), which is based on extraction of acoustic features between 125 and 7500 Hz from a pretrained deep learning model (referred to as deep acoustic features). Using data measured at a variety of locations, this study shows that deep acoustic features can be linked to meaningful characteristics of the noise. This study finds that deep acoustic features can reveal an improved spatial and temporal representation of WFN compared to what is revealed using traditional spectral analysis and overall noise descriptors. These results showed that this approach is promising, and thus it could provide the basis for an improved framework for WFN assessment in the future.

A holistic environmental investigation of complementary energy in Alberta

As Canada progresses toward its pledge of net-zero carbon emissions by the year 2050, it is worthwhile to thoughtfully examine the current energy landscape and how one might hope to achieve decarbonization within this timeframe. This examination is of particular importance in a fossil fuel producing region such as Alberta. Through an analysis of renewable energy strategies as well as the potential difficulties in this transition, an appropriate strategy may be devised. A combinatorial approach of wind, solar, and geothermal energy sources in the residential, commercial, and industrial spheres may serve as a transition measure, and eventually supplant fossil fuels as the dominant source of energy produced in Alberta with appropriate incentivization. Decarbonization is a pressing need given the imminent climate crisis the world is encountering, and these technologies are capable of serving as a step toward lower carbon emissions and ultimately curbing human-accelerated climate change.

Environmental noise-induced cardiovascular responses during sleep

STUDY OBJECTIVES

This study was designed to test the utility of cardiovascular responses as markers of potentially different environmental noise disruption effects of wind farm compared to traffic noise exposure during sleep.

METHODS

Twenty participants underwent polysomnography. In random order, and at six sound pressure levels from 33 dBA to 48 dBA in 3 dB increments, three types of wind farm and two types of road traffic noise recordings of 20-sec duration were played during established N2 or deeper sleep, each separated by 20 seconds without noise. Each noise sequence also included a no-noise control. Electrocardiogram and finger pulse oximeter recorded pulse wave amplitude changes from the pre-noise onset baseline following each noise exposure and were assessed algorithmically to quantify the magnitude of heart rate and finger vasoconstriction responses to noise exposure.

RESULTS

Higher sound pressure levels were more likely to induce drops in pulse wave amplitude. Sound pressure levels as low as 39 dBA evoked a pulse wave amplitude response (Odds ratio [95% confidence interval]; 1.52 [1.15, 2.02]). Wind farm noise with amplitude modulation was less likely to evoke a pulse wave amplitude response than the other noise types, but warrants cautious interpretation given low numbers of replications within each noise type.

CONCLUSION

These preliminary data support that drops in pulse wave amplitude are a particularly sensitive marker of noise-induced cardiovascular responses during. Larger trials are clearly warranted to further assess relationships between recurrent cardiovascular activation responses to environmental noise and potential long-term health effects.

The effect of wind turbine noise on polysomnographically-measured and self-reported sleep latency in wind turbine noise naïve participants

STUDY OBJECTIVES

Wind turbine noise exposure could potentially interfere with the initiation of sleep. However, effects on objectively assessed sleep latency are largely unknown. This study sought to assess the impact of wind turbine noise on polysomnographically-measured and sleep diary-determined sleep latency compared to control background noise alone in healthy good sleepers without habitual prior wind turbine noise exposure.

METHODS

Twenty-three wind turbine noise naïve urban residents (mean±standard deviation age: 21.7±2.1 years, range 18-29, 13 females) attended the sleep laboratory for two polysomnography studies, one week apart. Participants were blind to noise conditions and only informed that they may or may not hear noise during each night. During the sleep onset period, participants were exposed to counterbalanced nights of wind turbine noise at 33 dB(A), the upper end of expected indoor values; or background noise alone as the control condition (23 dB(A)).

RESULTS

Linear mixed model analysis revealed no differences in log10 normalized objective or subjective sleep latency between the wind turbine noise versus control nights (median [interquartile range] objective 16.5 [11.0 to 18.5] versus 16.5 [10.5 to 29.0] minutes, p = 0.401; subjective 20.0 [15.0 to 25.0] versus 15.0 [10.0 to 30.0] minutes, p = 0.907).

CONCLUSIONS

Although undetected small effects cannot be ruled out, these results do not support that wind turbine noise extends sleep latency in young urban dwelling individuals without prior wind turbine noise exposure.

Health Effects Related to Wind Turbine Sound: An Update

Commissioned by the Swiss Federal Office for the Environment, an update of an earlier narrative review was prepared for the literature published between 2017 and mid-2020 about the effects of wind turbine sound on the health of local residents. Specific attention was hereby given to the health effects of low-frequency sound and infrasound. The Netherlands Institute for Public Health and the Environment and Mundonovo sound research collected the scientific literature on the effect of wind turbines on annoyance, sleep disturbance, cardiovascular disease, and metabolic effects, as well as mental and cognitive impacts. It also investigated what is known about annoyance from visual aspects of wind turbines and other non-acoustic factors, such as the local decision-making process. From the literature study, annoyance again came forward as the most important consequence of sound: the louder the sound (in dB) of wind turbines, the stronger the annoyance response was. The literature did not show that "low-frequency sound" (sound with a low pitch) results in extra annoyance on top of normal sound. Results of scientific research for other health effects are either not available or inconsistent, and we can conclude that a clear association with wind turbine related sound levels cannot be confirmed. There is evidence that long-term effects are related to the annoyance people experience. These results confirm earlier conclusions. There is increasing evidence that annoyance is lower when people can participate in the siting process. Worries of residents should be addressed in an early stage, by involving them in the process of planning and decision making.

Self-reported health in the vicinity of five wind power production areas in Finland

In many countries, some people living in the vicinity of wind power production areas report having symptoms that they intuitively associate with wind turbines. Recently public discussions have focused especially on wind turbine infrasound. However, scientific evidence supporting an association is lacking. The aim of this study was to assess the association between exposure to wind turbines and the prevalence of self-reported symptoms, diseases and medications. A cross-sectional questionnaire study (n = 2,828) was conducted in the vicinity of five wind power production areas in Finland in 2015-2016. Each area had 3-16 turbines with a nominal power of 2.4-3.3 MW. The response rate was 50% (n = 1,411). Continuous and categorised (≤ 2.5, > 2.5-5, > 5-10 km) distance between the respondents' home and the closest wind turbine was used to represent exposure to wind turbines. Wind turbine sound pressure level outdoors could be reliably modelled only for the closest distance zone where the yearly average was 34 dB and maximum 43 dB. The data on symptoms (headache, nausea, dizziness, tinnitus, ear fullness, arrhythmia, fatigue, difficulties in falling asleep, waking up too early, anxiety, stress), diseases (hypertension, heart insufficiency, diabetes), and medications (analgesics for headache, joint/muscle pain and other pain, and medication for sleep disturbance, anxiety and depression, and hypertension) was obtained from the questionnaire. Logistic regression analyses were adjusted for age, sex, marital status, education, work situation, smoking, alcohol consumption, physical activity, body mass index, and hearing problems. Annoyance and sleep disturbance due to wind turbine noise were inversely associated with the distance to the closest wind turbine. The prevalence of symptoms, diseases and medications was essentially the same in all distance categories. In multivariate regression modelling, the odds ratio estimates were generally close to unity and statistically non-significant. Beyond annoyance and sleep disturbance, there were no consistent associations between exposure to wind turbines and self-reported health problems. The results do not support the hypothesis that broadband sound or infrasound from wind turbines could cause the proposed health problems.

Sleep actigraphy time-synchronized with wind turbine output

Studies have yielded inconsistent evidence for an association between long-term average wind turbine sound pressure level (SPL) and disturbed sleep. Transient changes in sleep may be more susceptible to short-term variations in wind turbine SPL throughout the sleep period time. We analyzed sleep actigraphy data (subject sleep nights=2094, males=151, females=192) in 10 min intervals time-synchronized to wind turbine supervisory control and data acquisition. Calculated indoor wind turbine SPL was considered after adjusting for turbine rotor speed and closed/open bedroom windows. Maximum calculated nightly average wind turbine SPL reached 44.7 dBA (mean=32.9, SD=6.4) outdoors, and 31.4 dBA (mean=12.5, SD=8.3) indoors. Wind turbine SPL in 10 min intervals, and nightly averages, were not statistically associated with actigraphy outcomes. However, the variability in wind turbine SPL due to changes in wind turbine operation across the sleep period time, as measured by the difference between the 10 min SPL and the nightly average SPL (∆SPL), was statistically related to awakenings (p=0.028) and motility (p=0.015) rates. These diminutive differences translate to less than 1 min of additional awake and motility time for a 5 dBA increase over a 450 min sleep period time. Overall results showed that wind turbine SPL below 45 dBA was not associated with any consequential changes in actigraphy-measured sleep. Observations based on ∆SPL provided some indication that a more sensitive assessment of sleep may be one that considers variations in wind turbine SPL throughout the sleep period time.

K-complexes are a sensitive marker of noise-related sensory processing during sleep: A pilot study

STUDY OBJECTIVES

The primary aim of this study was to examine dose-response relationships between sound pressure levels (SPLs) and K-complex occurrence probability for wind farm and road traffic noise. A secondary aim was to compare K-complex dose-responses to manually scored EEG arousals and awakenings.

METHODS

Twenty-five participants underwent polysomnography recordings and noise exposure during sleep in a laboratory. Wind farm and road traffic noise recordings of 20-sec duration were played in random order at 6 SPLs between 33 - 48 dBA during established N2 or deeper sleep. Noise periods were separated with periods of 23 dBA background noise. K-complexes were scored using a validated algorithm. K-complex occurrence probability was compared between noise types controlling for noise SPL, subjective noise sensitivity and measured hearing acuity.

RESULTS

Noise-induced K-complexes were observed in N2 sleep at SPLs as low as 33 dBA (Odds ratio, 33dBA vs 23 dBA, mean (95% confidence interval); 1.75 (1.16, 2.66)) and increased with SPL. EEG arousals and awakenings were only associated with noise above 39 dBA in N2 sleep. K-complexes were 2 times more likely to occur in response to noise than EEG arousals or awakenings. Subjective noise sensitivity and hearing acuity were associated with K-complex occurrence, but not arousal or awakening. Noise type did not detectably influence K-complexes, EEG arousals or awakening responses.

CONCLUSION

These findings support that K-complexes are a sensitive marker of sensory processing of environmental noise during sleep and that increased hearing acuity and decreased self-reported noise sensitivity increase K-complex probability.

A systematic review and meta-analysis of wind turbine noise effects on sleep using validated objective and subjective sleep assessments

Little is known about the potential impacts of wind turbine noise (WTN) on sleep. Previous research is limited to cross-sectional studies reporting anecdotal impacts on sleep using inconsistent sleep metrics. This meta-analysis sought to comprehensively review studies evaluating the impact of WTN using widely accepted and validated objective and subjective sleep assessments. Search terms included: "wind farm noise", "wind turbine noise", "wind turbine sound", "wind turbine noise exposure" AND "sleep". Only original articles published in English published after the year 2000 and reporting sleep outcomes in the presence of WTN using polysomnography, actigraphy or psychometrically validated sleep questionnaires were included. Uniform outcomes of the retrieved studies were meta-analysed to examine WTN effects on objective and subjective sleep outcomes. Nine studies were eligible for review and five studies were meta-analysed. Meta-analyses (Hedges' g; 95% confidence interval [CI]) revealed no significant differences in objective sleep onset latency (0.03, 95%  CI -0.34 to 0.41), total sleep time (-0.05, 95%  CI -0.77 to 0.67), sleep efficiency (-0.25, 95%  CI -0.71 to 0.22) or wake after sleep onset (1.25, 95%  CI -2.00 to 4.50) in the presence versus absence of WTN (all p > .05). Subjective sleep estimates were not meta-analysed because measurement outcomes were not sufficiently uniform for comparisons between studies. This systematic review and meta-analysis suggests that WTN does not significantly impact key indicators of objective sleep. Cautious interpretation remains warranted given variable measurement methodologies, WTN interventions, limited sample sizes, and cross-sectional study designs, where cause-and-effect relationships are uncertain. Well-controlled experimental studies using ecologically valid WTN, objective and psychometrically validated sleep assessments are needed to provide conclusive evidence regarding WTN impacts on sleep.