The Relationship Between Alcohol and Sleep: Does a 'Nightcap' Really Help You Sleep Better?
It is often said that having a drink before bed helps you sleep well. Many people make it a habit to have a drink before getting into bed to soothe the fatigue of the day. However, that 'nightcap' might actually be significantly lowering the quality of your sleep. In this article, we will explain the surprising relationship between alcohol and sleep in an easy-to-understand way.
● The habit of a nightcap is common among Japanese people
According to a survey by the Ministry of Health, Labour and Welfare, approximately 30% of adult men and 10% of adult women in Japan responded that they 'sometimes drink alcohol to help them sleep.' Even from a global perspective, Japan is one of the countries with a high rate of nightcap consumption. Compared to figures of around 10% in France and Germany, and about 20% in the United States, Japan's numbers are notable.
Why has the nightcap become so widespread in Japan? The background includes difficulty falling asleep due to long working hours, resistance to sleep-inducing medication, and the long-held belief that 'alcohol is medicine.' Medical texts from the Edo period also contain descriptions stating that 'a small amount of alcohol circulates energy and induces sleep,' and having a drink before bed has become rooted as a part of Japanese culture.
● Alcohol helps you fall asleep faster, but makes your sleep shallower
It is true that drinking alcohol helps you fall asleep faster. This is because alcohol has the effect of suppressing the central nervous system, which calms brain activity. Experimental data shows that drinking about one medium bottle of beer (500mL) reduces the time it takes to fall asleep by an average of about 10 minutes.
However, this is where the problem begins! In the process of alcohol being broken down, a substance called 'acetaldehyde' is produced in the body. This is a component that also causes hangovers, and it works to stimulate the sympathetic nervous system, increase heart rate, and awaken the brain. As a result, 3 to 4 hours after falling asleep, your sleep becomes shallower and you are more likely to wake up in the middle of the night.
Furthermore, it has been reported that the duration of 'non-REM sleep' (sleep where the brain and body are resting deeply), which is deep sleep, becomes about 20% shorter compared to when you do not drink. While you may fall asleep faster, the quality of your sleep in the latter half of the night drops significantly.
● Diuretic effects and snoring also hinder sleep
Alcohol also has another strong diuretic effect. It is known that if you drink 1L of beer, about 1.1L of water is excreted as urine. In other words, more water is lost from the body than the amount you drank. This increases the number of times you wake up to go to the bathroom in the middle of the night, causing your sleep to be fragmented.
In addition, alcohol relaxes the throat and surrounding muscles, making snoring and apnea more likely to occur. Even people who do not usually snore may find it easier to snore after drinking, and oxygen intake can be impaired. There are many cases where this leads to headaches and lethargy the next morning.
● Tips for enjoying alcohol wisely
So, what can you do to enjoy alcohol while protecting the quality of your sleep? The key is the amount you drink and the timing.
First, it is ideal not to drink alcohol for 3 hours before going to bed. It takes about 3 hours for alcohol to leave the body for a person weighing 60kg per medium bottle of beer. It is ideal to enjoy it during dinner and finish the breakdown process before bedtime.
As for a guideline for quantity, about 20g per day in terms of pure alcohol is considered 'moderate drinking.' This is equivalent to one medium bottle of beer, one go (180mL) of sake, two glasses of wine (200mL), or one double shot of whiskey (60mL). Within this range, you can minimize the impact on the next day's sleep.
Also, the habit of having a 'chaser,' which is drinking the same amount of water as alcohol, is recommended. It prevents dehydration and slows down the absorption of alcohol. Asking for water at a bar is by no means embarrassing.
● Alcohol is a pleasure to enjoy, not a sleeping pill
The habit of 'sleeping with a nightcap' may feel effective in the short term, but if continued for a long time, it will definitely lower the quality of your sleep. Furthermore, if you continue to have a nightcap every night, your body will get used to it, leading to the problem of 'tolerance,' where you can no longer sleep with the same amount and end up drinking more.
Alcohol is best enjoyed as a pleasure to enrich meals and conversation, not as a tool for falling asleep. Why not enjoy your drink tonight slowly during dinner instead of right before bed? You will surely feel a difference when you wake up the next morning.