Wind Turbine Noise Effects on Sleep: The WiTNES study 

ABSTRACT —
Onshore wind turbines are becoming increasingly widespread globally, with the associated net effect that a greater number of people will be exposed to wind turbine noise (WTN). Sleep disturbance by WTN has been suggested to be of particular importance with regards to a potential impact on human health. Within the Wind Turbine Noise Effects on Sleep (WiTNES) project, we have experimentally investigated the physiological effects of night time WTN on sleep using polysomnography and self-reporting protocols. Fifty participants spent three nights in the sound exposure laboratory. To examine whether habituation or sensitisation occurs among populations with long-term WTN exposure, approximately half of the participants lived within 1km of at least one turbine. The remaining participants were not exposed to WTN at home. The first night served for habituation and one WTN-free night served to measure baseline sleep. Wind turbine noise (L_{AEq,indoor,night}=31.9 dB) was introduced in one night. This exposure night included variations in filtering, corresponding to a window being fully closed or slightly open, and variations in amplitude modulation

Michael Smith, Mikael Ögren, Laith Hussain-Alkhateeb, Julia Ageborg Morsing, Kerstin Persson Waye
Department of Occupational and Environmental Medicine, Institute of Medicine, University of Gothenburg, Sweden

Pontus Thorsson, Jens Forssén
Division of Applied Acoustics, Department of Civil and Environmental Engineering, Chalmers University of Technology, Gothenburg, Sweden

Eja Pedersen
Department of Architecture and the Built Environment, Lund University, Sweden

Presented at the 12th ICBEN Congress on Noise as a Public Health Problem, 18–22 June, Zurich

INTRODUCTION

Sleep is vital for adequate health and wellbeing, yet by its very definition is reversible. Such reversibility presents the opportunity for external factors, including noise, to disrupt sleep as the brain awakes the body following environmental intrusion. The link between traffic noise and sleep disruption is well established, yet the effects of noise from wind turbines is comparatively under-examined, although the body of research is growing. There is some evidence for an association between sleep disturbance and wind turbine noise (WTN) levels, but there has also been recent work finding no link between one-year WTN averages and sleep outcomes.

Response to a sound is not wholly dependent on the acoustical characteristics such as level, duration and frequency content. An individual’s tolerance and attitude to a certain sound can moderate their response, and persistent exposure may lead to an increase or a decrease in reaction. In the case of habituation, repeated exposure over time results in an individual reacting less strongly than previously to an exposure of the same amplitude. For example, long-term behavioural adaptation to noise occurs in fish following repeated motorboat noise exposure following an initial increase in hiding. It is unclear however whether behavioural changes such as these in humans may reflect true habituation, involving synaptic plasticity mechanisms such as long-term depression, or if these changes are instead indicative of coping strategies. In the opposite direction to habituation, sensitisation occurs when repeated exposure leads to a stronger response over time. For instance, in the famous example of a dripping tap, the sound may be innocuous at first but can become unbearable after persistent exposure.

Possible habituation or sensitisation to WTN represents a potential explanation for the disparity in findings from research into the effects of WTN on human response. This paper therefore describes a study performed to investigate the physiological impact on sleep from WTN exposure. The Wind Turbine Noise Effects on Sleep (WiTNES) project was performed with the aims of investigating the physiological or psychological impact of WTN on sleep, and whether repeated WTN exposure at home may lead to habituation or sensitisation. …

Self-reported outcomes

The results of the models for each outcome, which includes WTN exposure night alone as a predictor, are presented in Table 4. All response items excepting tenseness, perceived sleep depth and social orientation were significantly negatively affected following nights with WTN exposure. Furthermore, the exposed study group differed from the control group in the majority of the response items, rating their sleep as worse even in the absence of WTN exposure. There was a significant effect of sex for sleep depth and WTN causing difficulty falling back asleep, in both instances with men having worse sleep. Effects of noise sensitivity were seen for WTN causing tiredness and both mood items. Regular sleep difficulties was a significant predictor for around half of all outcomes, including difficulty sleeping, one of the three outcomes for which no effect of WTN exposure was seen. No significant effects of age were found for any of the outcomes, and no WTN exposure × group interactions were observed.

DISCUSSION

Almost all measures of self-reported sleep were negatively impacted following nights with wind turbine noise. The WTN nights lead to increased sleep disturbance, reduced sleep quality, increased tiredness, increased irritation, awakenings, increased difficulty to sleep, sleeping worse than usual, and decreased mood. Subjects dwelling close to wind turbines, and consequently potentially exposed to WTN at home, repeatedly scored their sleep and restoration lower than the reference group following the WTN nights. However, their baseline sleep and restoration scored after the quiet WTN-free night were also generally scored lower than by the reference group. Although efforts were made during recruitment to obtain as similar a study sample from both the exposed and reference groups, a larger proportion of participants in the exposed group reported excessive tiredness at least once a month (58% vs. 20%) or difficulties sleeping at home at least several times a month (61% vs. 41%). Nevertheless, the effect of WTN exposure on sleep remained even after correcting for regular sleep difficulties and tiredness. … Despite the limitations of questionnaires and the study design, the present paper provides evidence that a single night of wind turbine noise at indoor levels of L_AEq,8h=31.9 dB negatively impacts self-reported sleep.

Download original document: “Wind Turbine Noise Effects on Sleep: The WiTNES study”