Think Your Nightcap is Helping You Sleep? Think Again

2020 has started off as a stressful time throughout the world with many complaining of anxiety, isolation, frustration, and ensuing sleep disturbances. It is an old belief that having an alcoholic beverage will help with sleep. In fact, the concept of a ‘nightcap’ (an alcoholic drink to aid sleep) dates back to 1818! But is there any truth to this?

What does alcohol do to our body? In short, alcohol is a depressant. This means it slows down the function of our central nervous system manifesting in slurred speech, impaired memory, delayed reactions, and mild sedation. As such, it makes sense that we think it may help sleep. Let’s review the evidence-based effects of alcohol on sleep.

1. Alcohol can reduce the time to fall asleep

Based on its sedative qualities, alcohol can in fact slow us down helping to wind down for bed. Stress has become a modern-day plague, especially in Hong Kong, interfering with immunity, weight regulation, hormones, and sleep. A survey on well-being in Hong Kong reported 92% of people in Hong Kong experience stress on a daily basis.1 When we are stressed it is often difficult to fall asleep and some may reach for an alcoholic beverage to “relax”. However, while research backs alcohol’s ability to induce sleepiness and dull senses,2 there is more to sleep than falling asleep.

2. Alcohol reduces sleep quality

We all know that getting 7-8 hours of shut-eye per night is essential for health. However, quantity is only half the battle. The National Sleep Foundation (NSF) outlines 4 key indices to determine sleep quality: 1) falling asleep in 30 minutes or less, 2) being asleep for at least 85% of time spent in bed, 3) waking up no more than once per night, and 4) being awake for less than 20 minutes after falling asleep.3 While alcohol might help with #1, drinking causes frequent night-time and early morning awakenings4 (even if you don’t consciously register them or remember them in the morning). This means your sleep is interrupted, breaking the natural cycles of sleep and impairing your body and mind’s ability to rest, repair, and reset for the following day. In fact, many attribute the common hangover feelings more to a lack of restful sleep than the alcohol itself, although this has yet to be determined.

3. Alcohol blocks REM sleep

Sleep can be broadly categorized into rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep, which cycles roughly every 90 minutes. Studies show that alcohol dramatically reduces REM sleep – with an increased time to get to the first REM cycle as well as a total reduction in REM sleep.5 This effect becomes more pronounced, the more you drink. REM sleep is when we dream, but it is also when the brain is most active and is decompressing and processing the day’s events. Studies show it is linked to memory, learning, and emotional processing.6

4. Alcohol makes you hot (= poor sleep)

Our body temperature fluctuates throughout the day but every night it drops 2-3 degrees while we sleep. This daily temperature cycle is termed our circadian temperature rhythm and is a key component of our sleep-wake cycle. It is the reason why having a slightly cooler environment (18-22°C) promotes sleep.

If you get rosy cheeks and feel hot and sweaty when drinking, it isn’t just the Hong Kong heat. Alcohol interferes with our thermoregulation, resulting in increased skin blood flow and chest sweating just 10 minutes after drinking.7 For sleep, this equates to a 43% decrease in the amplitude of our circadian temperature rhythm.8 As alcohol will keep prevent our natural drop in temperature at night, it can make it difficult to fall asleep and descend into that deep sleep that is so vital for rest and recuperation.

5. Other not-so-fun effects

For sleep, alcohol also increases the risk of sleep disorders such as sleep apnea.9 We also know that alcohol taxes our liver, interferes with our gut microbiome, increases risk of respiratory problems and influences mood. Interestingly, many of these effects differ by age and even gender. For example, alcohol intake can predict lower happiness the following day in women but more anger the following day in men.10

The Verdict

Looking at the research on sleep and alcohol, although alcohol might help make you sleepy, it interrupts many key functions of a good night’s sleep. This means you are going to feel extra groggy, tired, and potentially irritable or low the next day. At LifeHub we are all for moderation, just keep in mind alcohol’s effects on sleep, especially if you have sleep conditions, are intolerant to alcohol (test your DNA to find out!) or experience sleeping difficulties. If you do have trouble sleeping, we recommend a personalized lifestyle approach to bring your sleeping patterns back to optimal functioning.


Rachel Erwin, Nutritionist & Content Writer

Rachel is a Nutritionist with a BSc in Biology and Global Health from the University of Toronto, and a Postgraduate Diploma in Human Nutrition from the University of Ulster. She has counselled and educated clients in Hong Kong, whose health goals ranged from weight loss to detox and hormone balancing. Her love of writing led her to complete ‘Writing in the Sciences’, offered by Stanford University, and since then she has contributed several evidence-based health articles to various publications.

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