Effects of Varying Duration of Naps on Cognitive Performance and Memory Encoding

Comparing the Effects of 10, 30 and 60 Minute Naps on Cognitive Performance and Memory Encoding

To evaluate the nap duration that achieves maximal cognitive gain with practicality of implementation, the present work employs a within-subject design comparing nap durations of 10 minutes, 30 minutes, and 60 minutes with a no nap condition on benefits to alertness, vigilance, mood, speed of processing and memory over post-nap intervals of 5 minutes, 30 minutes, 60 minutes and 240 minutes. The effect of nap duration on memory encoding will also be examined.

Study Overview

• Status: Completed
• Conditions: Sleep
• Intervention / Treatment: Behavioral: Nap duration

Detailed Description

Naps are a global phenomenon and a commonly adopted lifestyle countermeasure to reduce sleepiness and performance impairments. Experimental studies have also shown that naps can improve cognitive functioning and enhance memory and mood. However, the implementation of naps is highly varied amongst individuals, and it remains uncertain what duration of naps achieves the greatest cognitive benefit. Given the potential for naps to boost productivity in societies such as ours where insufficient nocturnal sleep is prevalent and where work hours are long, an investigation of the optimal nap duration is warranted.

Previous studies suggest that the benefits of brief naps (5-15 minutes) occur immediately after the nap and last a limited period (1-3 hours). Longer naps (>30 minutes) are more likely to produce some temporary decrements due to sleep inertia but have the potential to improve cognitive performance for a more sustained period. These findings need to be strengthened through replication and extended to include memory measures that are evaluated over a longer post-nap testing period. To evaluate the nap duration that achieves maximal cognitive gain with practicality of implementation, the present work employs a within-subject design comparing nap durations of 10 minutes, 30 minutes, and 60 minutes with a no nap condition on benefits to alertness, vigilance, mood, speed of processing and memory over post-nap intervals of 5 minutes, 30 minutes, 60 minutes and 240 minutes. The effect of nap duration on memory encoding will also be examined.

The investigator's findings are expected to inform theoretical models of sleep and cognition and will aid in the design of practical lifestyle strategies to alleviate sleepiness and improve cognitive performance that may be adopted in an everyday context to boost societal well-being and productivity.

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Singapore
  • Singapore, Singapore, 117549
    • Yong Loo Lin School of Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years to 35 years (ADULT)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Participants aged from 21 - 35 years and who have an average sleep duration of 6-6.5 h are eligible for this study.

Exclusion Criteria:

• Participants who have an average sleep duration of less than 6 h or more than 6.5 h, who report sleep apnea symptoms, who report drinking more than 5 cups of caffeinated drinks a day, who have a BMI greater or equal to 30, or report elevated depression or anxiety symptoms will be excluded.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: BASIC_SCIENCE
• Allocation: RANDOMIZED
• Interventional Model: CROSSOVER
• Masking: TRIPLE

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
NO_INTERVENTION: No nap group; No nap opportunity will be given in this condition.
EXPERIMENTAL: 10 minute nap; Participants will be given a 10 minute nap.	Behavioral: Nap duration; A cognitive battery which will be repeated at 1505, 1530, 1600 and 1900. Material for the picture encoding task will be learned at 1630 and will be tested at 2000.
EXPERIMENTAL: 30 minute nap; Participants will be given a 30 minute nap.	Behavioral: Nap duration; A cognitive battery which will be repeated at 1505, 1530, 1600 and 1900. Material for the picture encoding task will be learned at 1630 and will be tested at 2000.
EXPERIMENTAL: 60 minute nap; Participants will be given a 60 minute nap.	Behavioral: Nap duration; A cognitive battery which will be repeated at 1505, 1530, 1600 and 1900. Material for the picture encoding task will be learned at 1630 and will be tested at 2000.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Picture encoding task	Participants will observe pictures of non-famous people, landscapes, scenes and objects. Later they are tested on whether they remember seeing the picture previously or not. The encoding session will take 20-30 min, and the retrieval session will take 15 min.	In total: 35-45 min
Levels of sleepiness	Karolinska Sleepiness Scale. Participants rated their level of subjective sleepiness on a 9-point Likert scale (1 - very alert, 9 - very sleepy, great effort to keep awake).	1 min
Mood	Positive and Negative Affect Scale. On the Positive and Negative Affect Scale (PANAS), participants responded to 20 adjectives describing positive and negative mood states on a 5-point Likert scale (1 - very slightly, 5 - extremely). Positive and negative affect scores are represented by the sum of the item responses.	1 min
Vigilance	Psychomotor Vigilance Test. The 3-min PVT assessed levels of sustained attention. At intervals varying randomly from 2000 ms to 10000 ms, a counter on the screen appeared and participants were to press a key as quickly as possible. Lapses were defined as responses exceeding 500 ms.	3 min
Speed of processing	Digit Symbol Substitution Test. The 2-min DSST was used as a measure of speed of processing. In this task, participants were required to match symbols to digits as quickly as possible following a key shown on screen. The total number of correct trials was used as the critical measure.	2 min

Collaborators and Investigators

• Sponsor: Duke-NUS Graduate Medical School
• Investigators: Principal Investigator: Michael Chee, MBBS, National University of Singapore

Study record dates

Study Major Dates

• Study Start (ACTUAL): November 1, 2020
• Primary Completion (ACTUAL): June 15, 2021
• Study Completion (ACTUAL): June 15, 2021

Study Registration Dates

• First Submitted: March 15, 2021
• First Submitted That Met QC Criteria: July 28, 2021
• First Posted (ACTUAL): August 2, 2021

Study Record Updates

• Last Update Posted (ACTUAL): August 2, 2021
• Last Update Submitted That Met QC Criteria: July 28, 2021
• Last Verified: July 1, 2021

More Information

Terms related to this study

• Other Study ID Numbers: NapTitration

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No