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The vital importance of full sleep cycles

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Adolescents undergo hormone changes and a shift in their circadian rhythm, from the early sleep of a child to a bedtime past their parents’. Modern life and particularly early school times are denying their biological clocks as well as robbing them of early-morning, REM-heavy sleep. Data shows that early school starts are bad for teenagers’ health, academic performance, and even mortality figures.

One of Massey University sleep researcher Philippa Gander’s students did research a few years ago on changes in sleep time associated with hormonal changes at Wellington High School. She found Year 9 students suffer some social jetlag but Year 12s were much worse – so the senior school made the first period of the day a study period. Results improved. Although the picture is now complicated by more devices in the bedroom, Gander says, “what it looked like was that later start for the senior school had protected the kids from the adverse effects of their technology”.

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It’s a myth that older adults need less sleep, says University of California professor of neuroscience and psychology Matthew Walker. Although REM sleep remains largely stable in midlife, the deep-NREM sleep that stabilises after adolescence begins to decline, due to changes in parts of the brain as we age. The deep NREM brainwaves become smaller, fewer, and less powerful. The circadian rhythm and melatonin release become weaker.

Older people also frequently suffer fragmentation of their sleep, including from medications, physical ailments and ills such as depression, and a weaker bladder. Sleep doesn’t refresh as it did when people were teenagers.

Poorer sleep efficiency, as it’s known, is associated with higher mortality risk, worse physical and mental health, lower energy and more forgetfulness.

However, the connection between poor health and poorer sleep quality is often not made or mentioned to GPs.

What can be done? Walker has a few suggestions. In the bedroom, an easy-to-reach side lamp, a phone by the bed in case of emergencies, dim or motion-detecting night-lights, and removing obstacles en route to the bathroom.

Wear sunglasses during morning exercise to reduce light to your inner clock; wear sunscreen but not sunglasses in the afternoon outside to delay the release of melatonin; talk to your GP about taking melatonin in the evening. In older people, melatonin has been shown to improve circadian rhythms, improving sleep patterns and quality, and morning alertness, says Walker.

Alice Gregory, a professor of psychology at Goldsmiths, University of London, notes that women approaching or experiencing menopause often report poorer sleep duration and quality. Some studies suggest that hormone replacement therapy can improve sleep – but do talk to your GP.

Gregory also notes that the lenses of our eyes yellow as we age, and cataracts often develop, both cutting the amount of blue light that gets through. Gander says scheduling light treatment and exercise can help older people hold their body clock in a regular pattern and improve working functions.

This article was first published in the January 5, 2019 issue of the New Zealand Listener.