Too hot to sleep?

If a loved one or resident at the aged care facility where you’re employed is restless during summer nights, Ron Grunstein, Professor of Sleep Medicine at Sydney Medical School, may be able to help.

“Sleep and body control of temperature are intimately connected. Body temperature follows a 24 hour cycle linked with the sleep wake rhythm,” he writes.

According to Professor Grunstein, body temperature decreases during the night time sleep phase and rises during the wake phase.

Sleep is most likely to occur when core temperature decreases, and much less likely to occur during the rises.

He adds the hands and feet play a key role in facilitating sleep as they permit the heated blood from the central body to lose heat to the environment through the skin surface.

The sleep hormone melatonin plays an important part of the complex loss of heat through the peripheral parts of the body, Professor Grunstein explains.

“At sleep onset, core body temperature falls but peripheral skin temperature rises. But temperature changes become more complex during sleep as our temperature self regulation varies according to sleep stage,” he says.

Research has shown how environmental heat can disturb this delicate balance between sleep and body temperature. For instance, an ambient temperature of 22 or 23 degrees Celsius is ideal. Any major variation in this leads to disturbance of sleep with reduced slow wave sleep (a stage of sleep where the brain’s electrical wave activity slows and the brain ‘rests’), and also results in less dreaming sleep (rapid eye movement or REM sleep).

According to Professor Grunstein, during REM sleep, our ability to regulate body temperature is impaired.

“So, in a clever sort of way the body ‘avoids’ this stage of sleep during extreme cold or heat. A heat wave may cause several nights of fragmented sleep with less slow wave and REM sleep. This will certainly cause a correct perception of bad, restless sleep with consequent negative effects on mood and alertness.”

Restless sleep may contribute to problems with complex memory retention, higher judgement (poorer decision making and increased risk taking behaviour), blood pressure control and regulation of glucose in the body.

More than half of men and women aged over 65 years complain of at least one sleep problem. Many older people experience insomnia and other sleep difficulties on a regular basis.

As we age, our sleep patterns change. In general, older people sleep less, experience more fragmented sleep, and spend less time in stages 3 & 4 and REM sleep (deep sleep and dream sleep) than younger people.

“The clear message is this: if you’re going to make some big decisions during a heatwave, sleep in a carefully controlled air conditioned environment,” Professor Grunstein says.

How to have a better sleep (without air conditioning):

• Sleep in the lateral position (on your side) with less contact with the mattress may be good.
• Cooling the central body with a wet cloth or towel makes sense. A cool shower may also help.
• It is important to avoid doing anything too strenuous in the hours before bedtime as this will make it harder for the body temperature to fall during sleep.