Effects of train noise and vibration on human heart rate during sleep: an experimental study

OBJECTIVES Transportation of goods on railways is increasing and the majority of the increased numbers of freight trains run during the night. Transportation noise has adverse effects on sleep structure, affects the heart rate (HR) during sleep and may be linked to cardiovascular disease. Freight trains also generate vibration and little is known regarding the impact of vibration on human sleep. A laboratory study was conducted to examine how a realistic nocturnal railway traffic scenario influences HR during sleep. DESIGN Case-control. SETTING Healthy participants. PARTICIPANTS 24 healthy volunteers (11 men, 13 women, 19-28 years) spent six consecutive nights in the sleep laboratory. INTERVENTIONS All participants slept during one habituation night, one control and four experimental nights in which train noise and vibration were reproduced. In the experimental nights, 20 or 36 trains with low-vibration or high-vibration characteristics were presented. PRIMARY AND SECONDARY OUTCOME MEASURES Polysomnographical data and ECG were recorded. RESULTS The train exposure led to a significant change of HR within 1 min of exposure onset (p=0.002), characterised by an initial and a delayed increase of HR. The high-vibration condition provoked an average increase of at least 3 bpm per train in 79% of the participants. Cardiac responses were in general higher in the high-vibration condition than in the low-vibration condition (p=0.006). No significant effect of noise sensitivity and gender was revealed, although there was a tendency for men to exhibit stronger HR acceleration than women. CONCLUSIONS Freight trains provoke HR accelerations during sleep, and the vibration characteristics of the trains are of special importance. In the long term, this may affect cardiovascular functioning of persons living close to railways.