Our bodies are governed by genetically-determined biological clocks that are vital for our wellbeing. Our bodies’ natural cycles are controlled by a master clock in the brain which connects to the pineal gland behind the eyes.
Incoming light switches off melatonin, the sleep hormone that governs our best known circadian (around 24 hours) rhythm. This makes us more active during daylight and influences our hormones, metabolism, muscle strength and even hair growth.
Some body cycles are shorter (ultradian) – around 100,000 times a second for brainwaves, 60-100 times a minute for heartbeats. ‘Infradian’ rhythms are longer — for example; menstrual cycles or animals’ hibernation/mating seasons.
Normal sleep in Circadian Rhythm
Adults need seven to nine hours’ sleep per night, but pineal aging or visual impairment may reduce night time sleep and increase daytime napping. If you’re an early riser, your circadian rhythm is probably less than 24 hours, while for ‘night owls’ it’s usually longer. Sleep itself cycles through deep sleep and REM (rapid eye movement/dreaming) and is deepest between around 2am and 4am. Many of us notice an afternoon energy dip, especially if we’re short on sleep.
Our blood pressure and body temperature fall during sleep, our kidneys make less urine, growth hormone levels rise to help repair cell damage and glucose/cholesterol metabolism improves.
However some anti-inflammatory proteins are suppressed, so we may get morning stiffness. Levels of cortisol – ‘stress’ hormone – and our blood pressure start to rise before waking in preparation for the day’s challenges. We’re most alert around noon and 6pm.
Lifestyles, anxiety, depression, pain, sleep apnoea (blocked breathing) and frequent disturbances can play havoc with our sleep-wake cycle, making us lethargic, irritable and prone to ‘dropping off’ next day. Like shift work (whether rotating shifts or permanent nights), this can affect our hormones and repair systems, increasing our risk of obesity, diabetes, heart disease and some cancers. Jet lag causes sleep disturbance and fatigue until our body clocks catch up with new time zones. Seasonal affective disorder (SAD), linked to winter fatigue and low mood, may be a brain disorder; rarely, tumours can disrupt sleep, too.
Studying how our natural rhythms affect our health and response to treatment (chronotherapy) should lead to better prevention and treatment for a wide range of diseases.
Side-effects from corticosteroids used to treat inflammatory conditions can be reduced by taking them in the morning when cortisol levels are already high.
People with raised blood pressure that doesn’t ‘dip’ at night may benefit from bedtime medication (known as ‘sartans’). This may also be the best time to take cholesterol lowering statins and drugs for rheumatoid arthritis, or those that switch off stomach acid.
Circadian rhythms can also affect our immune systems and cancer cells. Research suggests some cancer drugs may be more effective or may have fewer side effects if given at specific times.
8 Ways To Improve Your Biological-clock Sleep-Wake Cycle
1. Stick to a regular bedtime and getting-up time, even if you’ve had a bad night.
2. Avoid caffeine, alcohol and eating after 6pm.
3. Start your bedtime routine 1-2 hours before you plan to sleep. Switch off computers/phones/TVs, have a warm drink and/or bath and make sure your bed and bedroom are at a comfortable temperature.
4. Exclude light completely with black-out blinds and with no stand-by lights or illuminated screens.
5. For short trips abroad, try sticking to your usual timetable; for longer ones, adopt the new time zone immediately.
6. Write down any worries before sleep, then use relaxation techniques or mindfulness to switch off.
7. Prescription melatonin may re-set older body clocks or help jet lag.
8. Light therapy may help seasonal affective disorder.
E269 – Diabetics and the Circadian Rhythm – www.diabetic.today