Before the industrial revolution, many people slept in two chunks. They'd go to bed around 9 PM, wake up around midnight for an hour or two (called "first sleep" and "second sleep"), then sleep again until morning. This pattern was documented in hundreds of historical accounts from Europe, Africa, the Middle East, and South America. Is biphasic sleep actually better than our modern 8-hour block?
Biphasic sleep means sleeping in two periods per 24 hours. There are two main patterns:
Countries with siesta cultures (Greece, Spain, Italy) traditionally had lower rates of heart disease. A 2007 study in the Archives of Internal Medicine found that regular napping (30+ minutes, 3+ times per week) was associated with a 37% lower risk of heart disease death. However, this may be confounded by other lifestyle factors (diet, stress, social connection).
Historian Roger Ekirch documented that segmented sleep was the norm before electric lighting. People went to bed at dusk, woke for 1-2 hours around midnight (used for prayer, reflection, sex, or small tasks), then slept again until dawn. There's limited modern research on this pattern, but some sleep scientists believe it may be more aligned with natural circadian rhythms than our modern consolidated 8-hour block.
If you want to experiment with biphasic sleep:
Biphasic sleep isn't inherently better or worse than monophasic (one block) sleep. What matters is getting enough total sleep (7-9 hours) with adequate deep sleep and REM. If a biphasic pattern fits your lifestyle and you feel rested, it can work. But don't force it if a monophasic pattern works fine for you.
Whether you sleep in one block or two, use our free Sleep Calculator to optimize your timing.
There's no strong evidence that one is healthier than the other. What matters is total sleep time and quality. Some research suggests that a short afternoon nap can reduce cardiovascular risk, but this doesn't mean sleeping in two blocks is necessary.
No. Your sleep need is genetically determined. Biphasic sleep distributes your sleep across two periods, but it doesn't reduce the total amount you need. If you need 8 hours, you need 8 hours whether it's in one block or two.
Polyphasic sleep (Uberman schedule: six 20-minute naps, etc.) is extremely difficult to maintain and has no scientific support for safety or effectiveness. Most people who try it experience severe sleep deprivation, cognitive impairment, and eventually crash. It's not recommended.
They serve different purposes. A 20-minute nap improves alertness and mood without grogginess. A 90-minute nap allows a full sleep cycle (including deep sleep and REM) and is better for physical recovery and memory consolidation. A 2-hour nap enters a second cycle but may cause grogginess upon waking.
Electric lighting. Before the light bulb, people had limited evening activities and went to bed shortly after dark. With artificial light, evening activities extended, and the two-block pattern naturally consolidated into one longer block. Industrialization and fixed work schedules further cemented the 8-hour block pattern.