You may be aware that seven to eight hours of good quality sleep is what experts recommend for adults. But does that mean you can achieve these goals by sleeping at any hour of the night? Not quite.
Sleep has many benefits: it improves memory, promotes emotional stability and reboots cellular metabolism. But going to sleep late at night, even if you complete the recommended hours, may not have the desired positive effects on your body.
With the lockdown impacting our lifestyles, about 67 per cent of people in India are now sleeping after 11 pm. Even otherwise, a 2018 study found that about 53 per cent of Indians sleep late at night after scrolling through social media, while 18 per cent revealed that work or finance-related issues kept them awake at night, as reported by Economic Times. Studies, however, have argued that the timing of sleep is as important as the number of hours you sleep.
What is the best time to sleep?
Dr Joy Desai, director, neurology, Jaslok Hospital and Research Centre, told, “There is a master clock in the suprachiasmatic nucleus (SCN), which is a region of the brain in the hypothalamus. This is meant to sychronise with the clock in your other bodily systems. All biological functions have a circadian rhythm that is primarily determined by daylight — also known as Zeitgeber — that provides the setting for the biological clock.”
The human brain is actually wired to sleep after three-and-a-half to four hours after sunset. So, if the sunset is between 6:30-7pm, you are actually wired to sleep by 10-10:30 pm, the doctor emphasised. When light levels drop, it stimulates the cells in the retina that signal the hypothalamus. There is a peptide called pituitary adenylate cyclase-activating peptide (PACAP) which makes the SCN signal to other body parts by secreting melatonin, a hormone that regulates the sleep-wake cycle. If you start sleeping late every night, the body stops making melatonin at the right time.
Melatonin production is supposed to start by 9 pm which then peaks by 1 am. But if you get into the practice of being awake and looking at the television screen or phone till late at night, over a period of time the brain stops making melatonin at the right time. If this starts in your youth, by the time you are older, you are unable to sleep even if you go to bed early, Dr Desai warned.
Many of us, however, tend to go to bed late owing to various reasons, from job stress to excess screen time. On weekends, we try to make up for our sleep deprivation by waking up late. This is known as what professor of chronobiology Till Roenneberg called “social jetlag” or the discrepancy between work and free days, or social and biological time.
Social jetlag is correlated with obesity. So, despite good diet and exercise, people experiencing social jetlag are at risk of becoming obese. That is because the peripheral clock in your other body systems are not in sync with the brain’s clock, Dr Desai explained. The desynchronised system of energy metabolism negatively impact peptides in the body — leptine and ghreline — that determine our hunger and satiety. Sleep harmonises energy metabolism in the body. So, when you sleep late at night, it is likely to increase the risk of various disorders like diabetes, obesity, mood disorders and memory issues in older people.
In a 2011 Norwegian study that followed about 49,000 nurses, researchers further found a link between night work (with altered sleep cycle) and the risk of breast cancer, with increased risks being observed in nurses who worked for five years or more with four to five or more consecutive night shifts.
Researchers argued that shift work implied exposure to light at night resulting in reduction in the synthesis of melatonin, which has been suggested as a contributing cause or the cancer. “Research shows The genetic makeup of our cells get damaged during the day and is repaired during our sleep at night. So if you are not sleeping at the right time, the DNA repair is not going to happen, which could result in oncogene upregulation, predisposing cells to cancer,” stated the neurologist.
How does one correct the time of sleeping?
For this, one should try and get into the habit of sleeping at 10:30 pm and waking up at 6:30 am. Here are some things to keep in mind to get good quality sleep at night. Besides exercising, having a regular bowel movement and an early breakfast are some other ways to get your sleep cycle on track.
“If you are waking up at 6:30 am, you should have breakfast by 7 am, which signals the body that the day has begun, thereby reinforcing the circadian rhythm. Again, when you exercise in the evening, you feel energetic for the next few hours which can delay sleep. So it is recommended that you exercise in the morning. If not, then you can exercise early evening,” Dr Desai advised. “These are all secondary signals to the body that your daylight cycle is in sync,” he added.