Why deep sleep is so good for us

We all know that sleep is good for us—and now we know it’s more than we had realised.

Scientists have tracked the neural circuits that get fired in deep sleep that impact on so many aspects of our health.

When we reach the deep sleep state, all sorts of health-supporting activities are kickstarted: muscles are strengthened, bone growth begins, and you start burning fat.  If you’re a teenager, deep sleep helps you grow taller.

It’s all to do with growth hormones that get activated in deep sleep.  Researchers at the University of California, Berkeley, have mapped the brain circuits that control growth hormone release during sleep and identified a new feedback system that keeps those levels in balance.  Conversely, insomnia and poor sleep increase the risk of obesity, diabetes, and heart disease.

The system behind this process is buried deep in the hypothalamus, an ancient part of the brain shared by all mammals. Here, specialized neurons release signals that either trigger or suppress growth hormone.  Two key players are growth hormone releasing hormone (GHRH), which stimulates release, and somatostatin, which inhibits it. Together, they coordinate hormone activity across the sleep-wake cycle.

In tests on mice, the researchers found that GHRH and somatostatin behave differently depending on whether the brain is in REM or non-REM sleep.  REM is the stage of lighter sleeping before deep sleep takes over.

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