The Benefits Of Biphasic Sleep: Humans' Natural Sleep Pattern?

Humans have a long and fascinating history with biphasic sleep, or sleeping twice a day. This sleep pattern involves two sleep sessions in a 24-hour period, either at night or with a longer session at night and a shorter nap during the day. While it may seem unusual to modern sleepers, biphasic sleep was the norm for most of human history, with people sleeping for around four hours early in the night, then waking up for an hour or two, before heading back to sleep for another four hours or so.

References to this cultural sleeping pattern can be found in historical art, literature, diaries, and even medical texts, with mentions by historical figures such as Virgil, Homer, and Chaucer. It was practised in many parts of the world, including Europe, Africa, Australia, Latin America, and the Middle East, and continued until the late 19th century when the invention of artificial lighting and the Industrial Revolution led to a shift towards monophasic sleep, or sleeping for one extended session, usually at night.

Today, biphasic sleep is still evident in cultures that take afternoon siestas, such as in Spain, Italy, and Scandinavian countries. Modern research suggests that biphasic sleep may offer benefits such as increased energy levels, alertness, cognitive function, and productivity. However, there is limited research on its long-term effects, and it may not be feasible for everyone due to work or family commitments.

The history of biphasic sleep

Biphasic sleep, or sleeping in two phases, was a common practice in many parts of the world before the late 19th century. This sleep pattern typically involved a "first sleep" in the evening, followed by a period of wakefulness, and then a "second sleep" in the morning.

The Pre-Industrial Era

During the pre-industrial era, people often slept communally, snuggled up with family members, friends, servants, and even strangers when travelling. To minimise awkwardness, there were designated sleeping positions and strict social conventions, such as avoiding physical contact and too much fidgeting.

The "first sleep" usually began around 9 pm or 10 pm and lasted a couple of hours. People would then wake up naturally, without the need for an alarm, and engage in various activities during "the watch". This period of wakefulness was a time for socialising, sex, religious practices, household chores, or criminal activities.

After a couple of hours, people would go back to bed for their "second sleep", which might last until dawn or later, depending on when they went to bed.

Evidence in Literature and Historical Records

References to biphasic sleep can be found in literature and historical records from various cultures, including Europe, Africa, North America, South Asia, Latin America, the Middle East, and Australia.

In medieval literature, biphasic sleep is mentioned in Geoffrey Chaucer's "The Canterbury Tales" and William Baldwin's "Beware the Cat". It also appears in ballads, such as "Old Robin of Portingale", where the lyrics refer to waking up from the "first sleepe" and "next sleepe".

In France, the initial sleep was called the "premier somme", while in Italy, it was known as "primo sonno".

The Industrial Revolution

The Industrial Revolution brought about a shift in sleeping habits, primarily due to the introduction of artificial lighting, such as gas lighting and electric lighting. This allowed people to stay up later, truncating their overall sleep and compressing it into a single block of time.

The invention of the light bulb by Thomas Edison in the late 19th century played a significant role in this transition, as people could now work, be productive, or enjoy nighttime activities for longer before going to bed.

Modern-Day Biphasic Sleep

While biphasic sleep is not as common today, it still exists in some cultures, particularly in the form of a midday nap. This is prevalent in countries like Spain, Italy, China, and Scandinavian nations like Finland, Denmark, and Sweden.

In conclusion, biphasic sleep was a widespread practice in pre-industrial societies, shaped by social conventions and natural sleep patterns. The Industrial Revolution and the introduction of artificial lighting led to a shift towards monophasic sleep, with people sleeping in a single block of time rather than two separate phases.

The benefits of biphasic sleep

Biphasic sleep, or sleeping in two phases, is a sleep pattern where a person gets two sleep periods in a day. While this sleep pattern is unpopular in the 21st century, it was more widely adopted before the late 19th century. However, recent studies have shown that sleeping in multiple phases within a 24-hour period may adversely affect physical and mental health, and it is not recommended for most people. Nevertheless, biphasic sleep offers several benefits.

Firstly, biphasic sleep may improve cognitive function by reducing feelings of tiredness and enhancing focus and concentration. This increase in alertness and productivity is not accompanied by a greater sense of tiredness or burnout.

Secondly, biphasic sleep can improve productivity, especially for those with unusual work or family schedules. The two sleep periods in a day can create more flexibility for juggling work, family, and other responsibilities.

Thirdly, biphasic sleep may help reduce stress. The nighttime wakefulness session practiced during the biphasic sleep patterns of yore was considered a highly relaxing way for people to manage their stress.

Fourthly, biphasic sleep yields all the benefits of power napping. Research suggests that power naps can boost learning, creative problem-solving, logical reasoning, memory formation, and greater cognitive performance overall. Power naps may also increase mental alertness, reduce fatigue, decrease the risk of making errors on the job, improve mood, and reduce stress.

Fifthly, biphasic sleep may improve dream recall. Research suggests that biphasic sleeping may improve our ability to remember our dreams, which can give us greater access to our subconscious minds and yield personal insights into our feelings and thoughts.

Lastly, biphasic sleep may help people cope with insomnia. When people who are suffering from insomnia learn that humans long woke up in the middle of the night, it can help them feel less anxious about their condition, leading to improved sleep.

In conclusion, while biphasic sleep may not be suitable or feasible for everyone, it offers several benefits, including improved cognitive function, productivity, and stress reduction.

The downsides of biphasic sleep

While biphasic sleep may have been the norm for most of human history, it does come with some potential downsides. Firstly, transitioning to a biphasic sleep schedule can be challenging and may involve an adjustment period during which individuals may experience increased tiredness, grogginess, and irritability. This new sleep schedule may also disrupt social dynamics, requiring individuals to spend less time with friends or causing conflicts at work.

Additionally, there is a lack of long-term research on the effects of biphasic sleep. Sleep scientists are unsure if there are negative consequences to adopting this sleep pattern over an extended period. Experts recommend that healthy adults get between 7-9 hours of sleep per night, and a biphasic sleep schedule may make it difficult to achieve this recommended amount. Not getting enough sleep can lead to short- and long-term side effects, including increased risk for heart disease, diabetes, stroke, high blood pressure, and depression.

Furthermore, artificial light exposure at night, which is common in today's society, can disrupt circadian rhythms and make it challenging to fall and stay asleep during the second sleep session. This can lead to sleep deprivation and its associated negative health outcomes.

Finally, while biphasic sleep can offer increased flexibility and improved productivity for some individuals, it may not suit everyone's body clock or work schedule. For those with strict work schedules or caregivers who need to be available throughout the day, maintaining a biphasic sleep schedule may not be feasible.

The transition to monophasic sleep

Monophasic sleep, or sleeping in one continuous block, is the most common sleep pattern in modern society. This transition from biphasic sleep, or sleeping in two phases, can be attributed to a combination of historical, cultural, and biological factors. Here is an exploration of the shift to monophasic sleep and its implications.

Historical and Cultural Influences

The Industrial Revolution played a pivotal role in shaping sleep habits. With the advent of artificial lighting, particularly the invention of the light bulb, people could stay awake longer and work extended hours. This disrupted the natural inclination towards biphasic sleep, as longer continuous work periods aligned with the consolidation of sleep into one uninterrupted phase. The demands of industrial work hours and the formalisation of the working day further solidified the monophasic sleep schedule as the norm.

Additionally, cultural factors and societal norms have influenced sleep behaviours. Western cultural models have historically isolated sleep from its social dimension, promoting a schedule of daytime wakefulness and nocturnal rest. The industrial and technological revolutions standardised sleep schedules, and global capitalism has threatened the tradition of the 'siesta' in many cultures.

Biological Mechanisms

Health Implications

The shift to monophasic sleep has had both positive and negative health consequences. On the one hand, monophasic sleep provides simplicity and stability, making it easier for individuals to establish a regular sleep routine. It aligns with the typical 9-to-5 workday, promoting improved focus and productivity during waking hours. Consistency in sleep and wake times is associated with better long-term health outcomes, as irregular sleep patterns are linked to various health issues.

However, the rigidity of monophasic sleep can be challenging for those with non-traditional work schedules, such as shift workers or those who travel across time zones. This inflexibility can lead to sleep deprivation and a misalignment of the body's natural circadian rhythm, potentially causing health issues. Additionally, adhering strictly to a monophasic sleep schedule may contribute to the risk of oversleeping, which has been associated with cardiovascular disease, diabetes, and obesity.

In conclusion, the transition to monophasic sleep is influenced by a complex interplay of historical, cultural, and biological factors. While it offers simplicity and aligns with societal norms, it may not be the optimal sleep pattern for everyone, particularly those with non-traditional schedules or unique lifestyle demands.

Biphasic sleep in modern times

Biphasic sleep, or sleeping in two phases, is a sleep pattern where a person gets two sleep periods in a day. While this sleep pattern is unpopular in the 21st century, it was more widely adopted before the late 19th century, when Thomas Edison invented the lightbulb. The discovery of artificial lighting allowed people to carry on working into the later evening hours, be more productive, and enjoy nighttime activities, thus dropping the first sleep and adopting one long sleep shift instead of two shorter ones.

Nowadays, there is a lot of research supporting the benefits of monophasic sleep, or sleeping in one block, and the disadvantages of multiphase sleep patterns. Recent studies show that sleeping in multiple phases within a 24-hour period may adversely affect physical and mental health and is not recommended for most people.

However, biphasic sleep is still evident in modern society, in the form of a nap, usually less than an hour, in the middle of the day. This sleeping habit is widespread in Spain, Italy, China, and Scandinavian countries like Finland, Denmark, and Sweden. In 2015, the Mayor of Ador, a small town in Valencia, ordered a compulsory afternoon three-hour nap, where businesses close and everyone takes a break or rests from 2 pm to 5 pm.

Some people in modern society have also adopted this type of biphasic sleep schedule as it provides two periods of increased activity, creativity, and alertness across the day, rather than having a long wake period where sleepiness builds up across the day and productivity wanes. Biphasic sleep may also be a more natural rhythm for some people, as there is growing evidence suggesting that naps can have important benefits for memory and learning, increasing alertness, and improving mood states.

Additionally, split sleep schedules have recently begun to emerge as a potential alternative to continuous night shift work. Working at night has the combined problems of prolonged wakefulness and circadian misalignment. Shift workers frequently complain of fatigue and reduced productivity at work, and they are at increased risk for chronic diseases such as obesity, type 2 diabetes, and heart disease. Split sleep/work schedules divide the day into multiple work/rest cycles so employees work multiple short shifts, broken up with short off-duty periods every 24 hours. Studies have found that split sleep provides comparable benefits for performance to one big sleep if the total sleep time per 24 hours is maintained (at around 7 to 8 hours total sleep time).

However, as might be expected, performance and safety can still be impaired if wake-up and start work times are in the early hours of the morning. It is also not known if these schedules afford any benefits for health and reduce the risk for chronic disease. While the challenges of night shift work cannot be eliminated, the advantage of some split shift schedules is that all workers get at least some opportunity to sleep at night and do not have to sustain alertness for longer than 6 to 8 hours.

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