Wind turbine noise shown to affect people’s sleep

Wind turbine noise (WTN) influences how well people feel they have rested after sleep, as well as having a small impact on dream sleep, or rapid eye movement (REM) sleep, a new study has claimed.

Scientists from the University of Gothenburg, Sweden, have been studying the impact of wind turbine noise on sleep using polysomnography, a method of sleep recording that uses electrodes attached to the head and chest to record brain activity, eye movement, heart rate and other factors during sleep.

50 people participated in the study: 24 of them had been living within one kilometre of one or more wind turbines for at least a year. The other 26 people did not live near wind turbines.

“We wanted to find out whether people exposed to noise from wind turbines over time become more sensitive or more habituated to WTN, so that their sleep may be affected differently than someone who doesn’t live near any turbines,” said corresponding author Kerstin Persson Waye.

The participants spent three nights in the Sound Environment Laboratory, one for acclimatisation and then, in a random order, one quiet night and one with four separate periods of WTN.

The sounds that were used were modelled on outdoor measurements from several wind turbines, and was filtered to correspond with the sound insulation of a typical Swedish wooden house.

Exposure was further modelled, to correspond to sleeping with a closed window and window ajar respectively.

The sounds were chosen to represent relatively unfavourable conditions, with a slightly higher average outdoor noise level than is currently permitted in Sweden. However, this level corresponded with a low indoor noise level below the levels at which sleep had previously been found to be affected by traffic noise or other common noises.

During the night with WTN, according to the physiological measures, the participants spent an average of 11.1 minutes less in REM sleep, which they entered 16.8 minutes later, than during the quiet night.

The proportion of time they spent in REM sleep was 18.8 per cent for the night with WTN, compared with 20.6 per cent for the quiet night—a small but statistically significant difference that, moreover, was independent from habituation to WTN.

There were no statistically significant differences in other sleep parameters, such as number of awakenings, total sleep time, time in deeper (non-REM) sleep stages or fragmentation of deep sleep, and heart rate. However, rhythmic sound variations appeared to disturb sleep, especially with closed windows.

Besides the physiologically based measurements, participants filled out a questionnaire on their sleep quality and how tired or rested they felt. Both groups reported that they slept worse during nights with WTN.

The study gave no indication of the habituation effect or increased sensitivity in the participants exposed to wind turbines in their home environment. However, the group that lived close to wind turbines reported worse sleep overall, even during the quiet night.

“Sleep disturbance, a negative health effect according to the World Health Organisation (WHO), can in itself contribute to chronic diseases. However, we can’t draw conclusions from this study on long-term health impact. Further studies should, if possible, investigate sleep in people’s home environments and include longer exposure time,” Persson Waye said.

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