Biphasic sleep describes a sleeping schedule with two segments. Polyphasic is a pattern with more than two sleeping periods throughout the day.

Biphasic sleep is a sleep pattern which is also called bimodal, diphasic, segmented, or divided sleep. Biphasic sleep refers to sleep habits that involve a person sleeping for two segments per day. Sleeping during nighttime hours and taking a midday nap.

Most people are monophasic sleepers. Monophasic sleep patterns involve only one segment of sleep, usually during nighttime hours. It’s thought that the custom of sleeping for one 6- to 8-hour segment per day may have been shaped by the modern industrial workday.

Biphasic vs. polyphasic sleep

The terms “segmented” or “divided” sleep can also refer to polyphasic sleep. Biphasic sleep describes a sleeping schedule with two segments. Polyphasic is a pattern with more than two sleeping periods throughout the day.

People might actively pursue a biphasic or polyphasic sleep lifestyle because they believe it makes them more productive. It creates more time for certain tasks and activities during the day, while maintaining the same benefits of monophasic sleeping at night.

It may also come to them more naturally.

People may voluntarily or naturally follow biphasic or polyphasic sleep schedules. However, in some cases, polyphasic sleep is the result of a sleep disorder  or disability.

Irregular sleep-wake syndrome is one example of polyphasic sleep. Those who have this condition tend to go to sleep and wake up at scattered and irregular intervals. They usually have difficulty feeling well-rested and awake.

What does science have to say?

While many people report positive personal experiences with biphasic sleep, the research on whether there are true health benefits — or detriments — is mixed.

The rise of the modern work day, along with artificial illumination technology, herded most cultures in the developing world toward 8-hour monophasic sleep schedules at night. Before the industrial era, it’s argued that biphasic and even polyphasic patterns weren’t unusual.

Short naps of around 5 to 15 minutes were reviewed as beneficial and associated with better cognitive function, as were naps of longer than 30 minutes. However, the review did note that more studies were needed at a deeper level.

In adults, napping can be associated with or increase the risk of poor sleep patterns or sleep deprivation.

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