Monday, June 12, 2006

Short Naps are Better

Thinking about taking a nap, but not sure how much napping will help you wake up refreshed? A new study finds that ten minutes may be the magic number when it comes to napping. The study of 24 healthy, young adults who were good sleepers and not regular nappers investigated what would be most effective after a night of five hours of sleep – no nap, a five minute, ten minute, twenty minute or thirty minute nap. Participants took afternoon naps at 3 p.m., and their performance post-nap was measured for three hours. Benefits of the five-minute nap were similar to taking no nap, while twenty and thirty-minute naps offered improvements up to an hour and a half after the nap, though immediately following these naps there was a period of reduced performance, sleep inertia and sleepiness. In the end, the ten-minute nap yielded the most benefits with the least side effects. This nap triggered improvements in cognitive function, sleepiness, fatigue, vigor, etc., and the effects lasted for up to 155 minutes. Researchers believe further investigation is needed to understand what processes occur in the first ten minutes of sleep and how they may provide benefit.
From the National Sleep Foundation. Here is the actual abstract:

A Brief Afternoon Nap Following Nocturnal Sleep Restriction: Which Nap Duration is Most Recuperative?
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Amber Brooks, PhD; Leon Lack, PhD
School of Psychology, Flinders University, Adelaide, SA, Australia

Study Objectives: The purposes of this study were to compare the benefits of different length naps relative to no nap and to analyze the electroencephalographic elements that may account for the benefits. Design: A repeated-measures design included 5 experimental conditions: a no-nap control and naps of precisely 5, 10, 20, and 30 minutes of sleep. Setting: Nocturnal sleep restricted to about 5 hours in participants’ homes was followed by afternoon naps at 3:00 PM and 3 hours of postnap testing conducted in a controlled laboratory environment. Participants: Twenty-four healthy, young adults who were good sleepers and not regular nappers. Measurements and Results: The 5-minute nap produced few benefits in comparison with the no-nap control. The 10-minute nap produced immediate improvements in all outcome measures (including sleep latency, subjective sleepiness, fatigue, vigor, and cognitive performance), with some of these benefits maintained for as long as 155 minutes. The 20- minute nap was associated with improvements emerging 35 minutes after napping and lasting up to 125 minutes after napping. The 30-minute nap produced a period of impaired alertness and performance immediately after napping, indicative of sleep inertia, followed by improvements lasting up to 155 minutes after the nap. Conclusions: These findings suggest that the 10-minute nap was overall the most effective afternoon nap duration of the nap lengths examined in this study. The implications from these results also suggest a need to consider a process occurring in the first 10 minutes of sleep that may account for the benefits associated with brief naps.

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