FIND THE RHYTHM, AVOID THE BLUES

1. UNDERSTAND YOUR CIRCADIAN BIOLOGY

This is controlled by the suprachiasmatic nucleus, a tiny region of the hypothalamus that receives the day-night signal from light coming through our eyes and optic nerve, says Dr Bentley. It controls the network of other clocks in almost every organ, even your liver and ovaries, switching on and off a slew of clock genes and timekeeping proteins that rise and fall in virtually all your body cells every 24 hours, like the sun. In 2017 a group of researchers won a Nobel Prize for uncovering how clock genes control our daily rhythms through a protein, PER, which with other proteins accumulates at night and diminishes by day in a feedback loop, controlling everything from when we sleep, to our heart rate, blood pressure, metabolism, body temperature, hormones and immune system.

2. UNDERSTAND THE COST OF DISRUPTING YOUR CIRCADIAN RHYTHM

By overriding your internal clock with your lifestyle, you’re raising your risk of obesity, diabetes, heart disease, some cancers, depression, gut disorders, allergies, infections, premature ageing as well as early death.

3. GIVE ‘CIRCADIAN EATING’ A TRY

Limit your eating and drinking to eight or 10 hours of daylight. In a recent meta-review of studies at Johns Hopkins University, this intermittent fasting approach was found to lower blood pressure, lipid level and heart rate. Research by scientists at Harvard found that early eaters (those who have their main meal before 3pm) lost 25 percent more weight, and more quickly, than those who ate late. And in a Salk Institute for Biological Studies study, people with metabolic syndrome who restricted food and beverage intake to a 10-hour window over a period of three months reported major improvements in body composition and levels of cholesterol. ‘One of the circadian rhythms involves the gut resting at

night – the body is not designed to deal with food at night,’ says Dr Bentley. ‘Eating at night results in changed management of that food in the body.’

4. GET YOUR LIGHTING RIGHT

At night, turn off bright lights, especially short-wavelength bluelight ones. If possible, install dimmers, and fit warm yellow, orange or red-toned longerwavelength bulbs in a few lamps (‘think campfire at dusk’ says McGroarty), and use only those. Switch off all light-emitting electronics at least an hour before you go to bed; read a book, listen to the radio, music or soothing sound apps. Use dark curtains or blinds to block out street lights or the glare of city lights, or wear a sleep mask. In the morning, open the curtains or blinds, or turn on bright, blue-light bulbs.

5. SUPPORT YOUR CIRCADIAN RHYTHMS TO KEEP JETLAG AT BAY

Jetlag is the result of our 24-hour sleep-wake, dark-light cycle being shifted as we speed across time zones; it takes a toll on our mood, sleep and digestion. ‘To help counter this, plan your trip and understand how your circadian rhythms are going to have to change,’ Dr Bentley says. Control your exposure to light by wearing a sleep mask in-flight, and sunglasses in the airport. When you need to be awake, expose yourself to bright light by watching a movie on a brightly lit screen. The Timeshifter app (on Google Play) is helpful: you enter your usual sleep pattern and your itinerary, and it gives you a schedule of when to avoid or prioritise light and take in small amounts of caffeine and a melatonin supplement. Timeshifter won last year’s National Sleep Foundation SleepTech Award.