Abstract
Some studies have shown that people living near a mobile phone base station may report sleep disturbances and discomfort. Using a rat model, we have previously shown that chronic exposure to a low-intensity radiofrequency electromagnetic field (RF-EMF) was associated with paradoxical sleep (PS) fragmentation and greater vasomotor tone in the tail. Here, we sought to establish whether sleep disturbances might result from the disturbance of thermoregulatory processes by a RF-EMF. We recorded thermal preference and sleep stage distribution in 18 young male Wistar rats. Nine animals were exposed to a low-intensity RF-EMF (900 MHz, 1 V.m−1) for five weeks and nine served as non-exposed controls. Thermal preference was assessed in an experimental chamber comprising three interconnected compartments, in which the air temperatures (Ta) were set to 24°C, 28°C and 31°C. Sleep and tail skin temperature were also recorded. Our results indicated that relative to control group, exposure to RF-EMF at 31°C was associated with a significantly lower tail skin temperature (−1.6°C) which confirmed previous data. During the light period, the exposed group preferred to sleep at Ta = 31°C and the controls preferred Ta = 28°C. The mean sleep duration in exposed group was significantly greater (by 15.5%) than in control group (due in turn to a significantly greater amount of slow wave sleep (SWS, +14.6%). Similarly, frequency of SWS was greater in exposed group (by 4.9 episodes.h−1). The PS did not differ significantly between the two groups. During the dark period, there were no significant intergroup differences. We conclude that RF-EMF exposure induced a shift in thermal preference towards higher temperatures. The shift in preferred temperature might result from a cold thermal sensation. The change in sleep stage distribution may involve signals from thermoreceptors in the skin. Modulation of SWS may be a protective adaptation in response to RF-EMF exposure.
Highlights
People living near mobile phone base stations may be concerned about the health effects of the associated radiofrequency electromagnetic fields (RF-EMFs)
We found that rats exposed to low-intensity RFEMF (900 MHz, 1 V.m21) at an ambient temperature (Ta) of 31uC exhibited (i) unusually high peripheral vasoconstrictor tone and (ii) fragmentation of their paradoxical sleep [4]
Few experiments have been performed with low-intensity RF-EMFs and it is still not clear whether and how behavioral thermal responses are elicited in this context
Summary
People living near mobile phone base stations may be concerned about the health effects of the associated radiofrequency electromagnetic fields (RF-EMFs). With a viewing to probing the impact of a putative change in peripheral sensitivity induced by a chronic low-level RFEMF exposure on the thermoregulatory behavioral response, we monitored the thermal preference of exposed young rats. Our experiments were performed in an environmental chamber in which the rat was free to choose between three Ta values (24uC, 28uC and 31uC, corresponding to the lower boundary, midpoint and upper boundary of the rat’s thermoneutral zone [11,12]) Within this zone, homeothermia can be maintained by controlling changes in peripheral vasomotor tone and by modulating wakefulness (W) and sleep stage distribution (which in turn modulate metabolic heat production) [13,14,15]. The present study aimed at assessing the changes in thermal preference and sleep stage distribution that may potentially be influenced by a difference in skin temperature [11,16]
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