3 pages writing

Major Article

Napping in College Students and Its Relationship With Nighttime Sleep

Lichuan Ye, PhD, RN; Stacy Hutton Johnson, MS/MBA, RN, NE-BC; Kathleen Keane, MS, RN; Michael Manasia, BSN, RN; Matt Gregas, PhD

Abstract. Objective: To examine the habit of napping and its relationship with nighttime sleep in college students. Participants: Four hundred and forty undergraduate students who responded to an anonymous online survey in April 2010. Methods: Three questions were asked to determine the frequency, length, and timing of napping during the past month. Sleep quality was measured by the Pittsburgh Sleep Quality Index (PSQI). Results: The PSQI score significantly differed among self- reported nap-frequency (p D .047) and nap-length (p D .017) groups, with those who napped more than 3 times per week and those who napped more than 2 hours having the poorest sleep quality. Students who napped between 6 and 9 PM had shorter sleep on school nights compared with students in other nap-timing groups (p D .002). Conclusions: College students who are self- reported frequent, long, and late nappers may have a higher risk of poor nighttime sleep quality and more severe sleep deprivation.

Keywords: academic performance, college students, napping, sleep deprivation, sleep habits, sleep quality

A dequate sleep is integral to the well-being of indi-viduals, and it is of critical importance to adoles-cents and young adults. Insufficient and irregular sleep has been well documented among college students.

1

Poor sleep quality in college students, particularly caused

by self-imposed sleep deprivation and irregular sleep

schedules, can lead to significant emotional imbalance,

fatigue, poor concentration, impaired memory, and gener-

ally lower life satisfaction. 2–6

In fact, sleep disturbance has

been consistently rated as a top impediment to academic

performance in college students. 7–9

College students are known to voluntarily restrict their

sleep, and their flexible schedules may permit more day-

time napping. 10

Although napping is not a well-understood

sleep practice, with cultural norms differing dramatically,

napping has been suggested to be a common way for col-

lege students to cope with insufficient sleep and daytime

sleepiness across cultures. 11,12

The benefits of napping for

waking performance such as improved neurobehavioral

performance and alertness have been systematically

reviewed in healthy adults. 13

However, longer naps (eg, 30

minutes or longer) can cause sleep inertia, which is associ-

ated with confusion, grogginess, and deficits to cognitive

performance. 14

Some important factors, such as frequency,

length, and temporal placement of naps should be taken

into consideration in order to understand the consequences

of napping. 13

Napping behavior and its effect on nighttime sleep

remain less well studied in the college population. Few

researchers have considered how napping behavior is

related to nighttime sleep. The goal of the present study

was to characterize the habit of napping, including self-

reported nap frequency, length, and timing, and examine its

relationship with nighttime sleep (as measured by self-

reported sleep duration and quality) in a group of college

students in the United States. Understanding the effect of

napping on nighttime sleep will help planners develop strat-

egies to promote sleep quality and, ultimately, improve

overall health and academic performance in young adults.

METHODS

Data Collection

This study used a Web-based survey (Qualtrics Survey

Program) to characterize the self-reported habit of napping

Dr Ye, Ms Hutton Johnson, and Ms Keane are with the William F. Connell School of Nursing at Boston College in Chestnut Hill, Massachusetts. Mr Manasia is with the Memorial Sloan-Kettering Cancer Center in New York, New York. Dr Gregas is with Research Services at Boston College in Chestnut Hill, Massachusetts.

Copyright � 2015 Taylor & Francis Group, LLC

88

JOURNAL OF AMERICAN COLLEGE HEALTH, VOL. 63, NO. 2

and its relationship with nocturnal sleep in college students.

Undergraduate students were invited via e-mail to partici-

pate in an anonymous online survey. With the approval of

the university’s Institutional Review Board, e-mail

addresses of 2,000 undergraduate students were obtained

from the Office of Institutional Research. This was a ran-

dom sample of currently registered undergraduates in terms

of sex, race, and enrolled schools. Following principles out-

lined by Dillman and colleagues, 15

4 e-mails were sent out

to these students: an introductory e-mail on day 1 that intro-

duced the study and advised that another e-mail would

arrive with participation details, an e-mail on day 4 that

included the link to the survey, a reminder e-mail on day 7

encouraging participation, and the final reminder on day

11. Each participant gave informed consent by reading the

consent form online and putting his or her initials in a des-

ignated box to indicate agreement to participate. Partici-

pants who completed the survey were invited to enter a

lottery to receive an online gift certificate. The survey was

conducted in April 2010, at least 1 month prior to the week

of final examinations so that students’ responses were not

influenced by potentially severe sleep deprivation before

final examinations. A total of 440 students participated and

completed the survey, yielding a response rate of 22%.

Measurements

Participants completed a survey including multiple-

choice items and open-ended questions. The open-ended

questions asked for descriptions of perceived benefits, bar-

riers encountered, and suggested interventions to improve

sleep quality, and will be reported separately. The current

report provides results from the multiple-choice items in

the survey, examining the habit of self-reported napping

and sleep quality in college students.

Sleep quality was measured using the Pittsburgh Sleep

Quality Index (PSQI). 16

It is a 19-item self-rating question-

naire designed to assess sleep quality and disturbances over

a 1-month time interval and includes 7 “components”: sub-

jective sleep quality, sleep latency, sleep duration, habitual

sleep efficiency, sleep disturbances, use of sleeping medica-

tion, and daytime dysfunction. The sum of the component

scores yields 1 global score, ranging from 0 to 21. At the

cutoff point of 5, the PSQI has a sensitivity of 89.6% and a

specificity of 86.5% in distinguishing good (PSQI global

score � 5) and poor sleepers (PSQI global score > 5).16 The PSQI has a high degree of internal constancy and test-

retest reliability. 16

The PSQI has been used to examine

sleep quality in the college student population. 17,18

In this

study, only the PSQI global score was reported and used in

data analyses. In addition to administering the PSQI, sup-

plemental survey questions were added to gain more infor-

mation about students’ weekday versus weekend sleep

schedules and students’ self-identification of “early bird”

(go to bed early and get up early) or “night owl” (go to bed

late and get up late) routines.

Three questions elicited descriptions of nap habits,

including napping frequency, average length, and typical

time of naps. Participants were first asked, “Do you usually

take naps?” with 4 possible responses: not during the past

month, less than once per week, once or twice per week,

and 3 or more times per week. Those who responded other

than “not during the past month” were then asked to spec-

ify: “How long were your naps on average?” (0.5 hours or

less, 1 hour, 1.5 hours, 2 hours, over 2 hours) and “What

was the typical time for you to take naps?” (morning,

12–3 PM, 3–6 PM, and 6–9 PM).

The survey included questions about demographics,

general health (excellent, very good, good, fair, or

poor), and mood/energy level (using a 10-point scale,

with ¡5 being very depressed or fatigued and C5 very elated or energetic). Academic performance was ascer-

tained by self-reported grade point average (GPA) on a

4.0 scale. The students were also asked how satisfied

they were with their amount of sleep on nights before

class and if they missed class or were late for school

because of oversleeping.

Statistical Analysis

The sample characteristics were evaluated using sum-

mary statistics, with means, standard deviations, or pro-

portions as appropriate. For each continuous variable, an

analysis of variance was performed with napping fre-

quency, length, and timing as predictors. If the likeli-

hood-ratio test for the predictors was significant,

pairwise contrasts were examined. Tukey’s honest signif-

icant difference method was used to adjust for multiple

comparisons. 19

Counts among student groups were com-

pared using chi-square analyses. Pearson correlations

were used to examine the associations between continu-

ous variables. Multiple regression analyses were per-

formed to determine the relationship between self-

reported napping habits and sleep quality, controlling for

identified pertinent covariates including age and sex. For

all analyses, a 2-sided significance level of a D .05 was used. Data analyses were conducted using the Statistical

Package for the Social Sciences version 18.0 software

(SPSS, Chicago, Illinois).

RESULTS

Sample Demographic Characteristics and Sleep Habits

As indicated in Table 1, the majority of the sample

consisted of college-aged (20.0 § 1.3 years) female (66.4%), white (80.2%), non-Hispanic (90.9%) students.

Approximately 19% of the students were overweight or

obese, with a body mass index (BMI), calculated based

upon self-reported height and weight, greater than or

equal to 25 kg/m 2 . Over half (58.7%) self-rated their

general health as very good or excellent. On a scale of

¡5 to 5, the students rated their average mood/energy

Napping and Nighttime Sleep

VOL 63, FEBRUARY/MARCH 2015 89

level as 1.6 § 2.0, with the majority (81.8%) rating the level equal to or higher than 0.

Sleeping habits and sleep quality for the entire sample

are described in the column of “Total cohort” of Table 2.

Over half of the respondents (59.7%) were classified as

poor sleepers because they had a PSQI score higher than 5.

The students in the sample slept an average of 1.7 hours

longer during the weekend than on weekdays (8.3 § 1.4 vs 6.7 § 1.2; p < .001). Approximately two thirds of the stu- dents (66.3%) identified themselves as “night owls.” The

self-reported GPA was negatively correlated with the PSQI

score (r D ¡.163, p D .002), indicating that self-reported poorer sleep quality was associated with poorer academic

performance. In addition, higher PSQI score (poorer sleep

quality) was significantly correlated with shorter self-

reported nightly sleep duration (r D ¡.516, p < .001) and greater difference in sleep hours between school days and

weekends (r D .224, p < .001).

Frequency of Naps and Sleep Quality

Sleep quality and sleep habits for groups by self-reported

napping frequency are reported in Table 2. Taking naps

during the month prior to completing the survey was

reported in 75% of the participants, with 42.9% reporting

having napped at least once per week. The PSQI score sig-

nificantly differed among the 4 nap-frequency groups

(p D .047). Students who reported napping 3 or more times per week during the month prior to completing the survey

had the highest PSQI score, indicating the poorest sleep

quality (7.0 § 2.5), which was, on average, 1.2 points

higher than those who reported they did not nap (5.8 § 3.3; p D .052).

Among the 4 nap-frequency groups, significant differen-

ces were also observed in the disparities in self-reported

sleep hours between school days and the weekend

(p D .039), in the rate of being “night owls” (p < .001), being satisfied with the amount of sleep on nights before

class (p D .002), and missing or being late for school because of oversleeping (p D .008). Frequent nappers (� 3/ week) had a significantly greater difference in self-reported

school day sleep hours and weekend sleep hours than non-

nappers (2.1 § 2.1 vs 1.3 § 1.6; p D .029). In addition, among the 4 nap-frequency groups, frequent nappers were

the most likely to identify themselves as “night owls”

(77.6%) and report missing or being late for school because

of oversleeping (62.7%), but were the least likely to feel

satisfied with the amount of sleep they got on nights before

class (25.4%).

Length of Naps and Sleep Quality

Among those who reported napping during the month

prior to completing the survey (n D 330 of 440), sleep qual- ity and sleep habit for 5 nap-length groups are reported in

Table 3. The mean PSQI score was significantly different

among the groups (p D .017). Students who reported nap- ping over 2 hours on average had a 2-point higher PSQI

score compared with those who reported napping for 1 hour

(7.9 § 3.8 vs 5.9 § 2.4; p D .036). Compared with shorter nappers, students who self-

reported taking longer naps slept less during school nights

(p D .011) but slept longer during the weekend (p D .001), had a greater difference in sleep duration between school

days and weekends (p < .001), and were more likely to

identify themselves as “night owls” (p D .004). For exam- ple, 87% of the students who reported napping for longer

than 2 hours per day considered themselves “night owls,”

but this dropped to 53.4% for those who reported napping

0.5 hours or less. In addition, longer nappers were less

likely to be satisfied with the amount of sleep they had dur-

ing the nights before class (p D .001) and were more likely to be late to or miss class because of oversleeping (p D .001). Additionally, the GPA was significantly different

among nap-length groups (p D .008), with students who napped longer having a lower GPA.

Timing of Naps and Sleep Quality

Sleep quality and sleep habits based on the timing of

naps among students who napped during the month prior to

completing the survey are reported in Table 4. The majority

of students reported napping in the afternoon, with 23%

between 12 and 3 PM and 67% between 3 and 6 PM. Students

who napped between 6 and 9 PM reported fewer hours of

sleep (5.7 § 1.2) on school nights compared with students who napped at other times (p D .002), namely, those who

TABLE 1. Demographic Characteristics of the Study Sample (N D 440) Characteristic % M SD

Female 66.4 White 80.2 Hispanic 9.1 Age, years 20.0 1.3 Body mass index, kg/m

2 23.0 3.2

Overweight or obese 19.3 Year in school Freshman 26.1 Sophomore 29.3 Junior 19.8 Senior 24.8

Self-rated general health Excellent 11.4 Very good 47.3 Good 33.8 Fair 6.6 Poor 0.7

Mood/Energy level 1.6 2.0

Ye et al

90 JOURNAL OF AMERICAN COLLEGE HEALTH

T A B L E 2 . S le e p Q u a li ty

a n d S le e p H a b it fo r th e E n ti re

C o h o rt a n d b y N a p p in g F re q u e n c y

T o ta l c o h o rt

(N D

4 4 0 ; 1 0 0 % )

N o n a p p in g

(n D

1 1 0 ; 2 5 % )

N a p p in g

< 1 /w e e k

(n D

1 4 1 ; 3 2 % )

N a p p in g

1 – 2 /w e e k

(n D

1 2 2 ; 2 7 .7 % )

N a p p in g

�3 /w e e k

(n D

6 7 ; 1 5 .2 5 % )

S a m p le c h a ra c te ri st ic

% M

S D

% M

S D

% M

S D

% M

S D

% M

S D

p v a lu e

P S Q I g lo b a l

6 .4

2 .9

5 .8

a 3 .3

6 .6

2 .9

6 .2

2 .5

7 .0

a 2 .5

.0 4 7

P o o r sl e e p e r (P S Q I

g lo b a l > 5 )

5 9 .7

4 8 .9

6 6 .1

5 8 .9

6 4 .8

.0 7 7

A v e ra g e sl e e p

d u ra ti o n

6 .9

1 .2

6 .8

1 .2

7 .0

1 .2

7 .0

1 .1

6 .8

1 .1

.3 2 9

S le e p h o u rs – sc h o o l

n ig h t

6 .7

1 .2

6 .7

1 .2

6 .7

1 .2

6 .6

1 .2

6 .5

1 .1

.7 0 1

S le e p h o u rs – w e e k e n d

8 .3

1 .4

8 .1

1 .3

8 .3

1 .3

8 .4

1 .4

8 .6

1 .5

.0 5 9

D if fe re n c e in

sl e e p

h o u rs b e tw e e n

sc h o o l d a y s a n d

w e e k e n d

1 .7

1 .7

1 .3

b 1 .6

1 .6

1 .6

1 .8

1 .7

2 .1

b 2 .1

.0 3 9

N ig h t o w l

6 6 .3

5 3 .6

6 1 .4

7 7 .0

7 7 .6

.0 0 0

S a ti sfi e d w it h th e

a m o u n t o f sl e e p o n

n ig h ts b e fo re

c la ss ?

4 1 .9

5 4 .5

3 9 .7

4 2 .1

2 5 .4

.0 0 2

M is se d /l a te fo r c la ss

b e c a u se

o f

o v e rs le e p in g

4 9 .1

3 8 .2

4 6 .8

5 4 .1

6 2 .7

.0 0 8

G P A

3 .4

0 .4

3 .4

0 .3

3 .4

0 .3

3 .4

0 .4

3 .3

0 .4

.1 0 1

N o te . P S Q I D

P it ts b u rg h S le e p Q u a li ty

In d e x ; G P A = g ra d e p o in t a v e ra g e .

a T h e

P S Q I

g lo b a l

sc o re

w a s

lo w e r

in th o se

w h o

d id

n o t

n a p

d u ri n g

th e

p a st

m o n th

c o m p a re d

w it h

th o se

w h o

n a p p e d

3 o r

m o re

ti m e s

p e r

w e e k

(p D

.0 5 2 ).

b T h e d if fe re n c e in

sl e e p h o u rs b e tw e e n w e e k e n d a n d w e e k d a y s w a s si g n ifi c a n tl y g re a te r in

th o se

w h o d id

n o t n a p d u ri n g th e p a st m o n th

c o m p a re d w it h th o se

w h o n a p p e d 3 o r m o re

ti m e s p e r w e e k (p

D .0 2 9 ).

VOL 63, FEBRUARY/MARCH 2015 91

Napping and Nighttime Sleep

T A B L E 3 . S le e p Q u a li ty

a n d S le e p H a b it b y L e n g th

o f N a p s

0 .5

h o u rs

o r le ss

(n D

5 9 ; 1 7 .9 %

a m o n g a ll n a p p e rs )

1 h o u r

(n D

1 1 5 ; 3 4 .8 %

a m o n g a ll n a p p e rs )

1 .5

h o u rs

(n D

8 5 ; 2 5 .8 %

a m o n g a ll n a p p e rs )

2 h o u rs

(n D

4 7 ; 1 4 .2 %

a m o n g a ll n a p p e rs )

> 2 h o u rs

(n D

2 3 ; 7 .0 %

a m o n g a ll n a p p e rs

S a m p le c h a ra c te ri st ic

% M

S D

% M

S D

% M

S D

% M

S D

% M

S D

p v a lu e

P S Q I g lo b a l

6 .5

2 .5

5 .9

a 2 .4

7 .0

2 .5

6 .9

3 .1

7 .9 a

3 .8

.0 1 7

P o o r sl e e p e r

6 5 .2

6 0 .2

6 6 .2

6 5 .8

6 1 .1

.9 3 4

A v e ra g e sl e e p

d u ra ti o n

7 .0

1 .1

7 .1

1 .0

6 .9

1 .1

6 .8

1 .2

6 .7

1 .5

.3 0 0

S le e p h o u rs – sc h o o l

n ig h t

6 .7

1 .1

6 .8

b 1 .1

6 .7

1 .2

6 .3

1 .1

6 .1 b

1 .2

.0 1 1

S le e p h o u rs – w e e k e n d

8 .1

c 1 .2

8 .3

c 1 .4

8 .3

1 .3

9 .0

c 1 .4

9 .2 c

1 .6

.0 0 1

D if fe re n c e in

sl e e p

h o u rs b e tw e e n

sc h o o l d a y s a n d

w e e k e n d

1 .5

1 .6

1 .4

1 .6

1 .6

1 .8

2 .6 d

1 .9

3 .1 d

1 .5

.0 0 0

N ig h t o w l

5 3 .4

6 7 .0

7 7 .6

7 8 .7

8 7 .0

.0 0 4

S a ti sfi e d w it h th e

a m o u n t o f sl e e p o n

n ig h ts b e fo re

c la ss ? (y e s)

3 3 .9

4 4 .3

4 7 .1

1 7 .4

1 7 .4

.0 0 1

M is se d /l a te fo r c la ss

b e c a u se

o f

o v e rs le e p in g (y e s)

4 4 .1

4 4 .3

5 2 .9

7 2 .3

7 8 .3

.0 0 1

G P A

3 .5

0 .3

3 .5

0 .3

3 .4

0 .4

3 .3

0 .5

3 .3

0 .4

.0 0 8

N o te . P S Q I D

P it ts b u rg h S le e p Q u a li ty

In d e x ; G P A D

g ra d e p o in t a v e ra g e .

a T h o se

w h o n a p p e d lo n g e r th a n 2 h o u rs h a d a si g n ifi c a n tl y h ig h e r P S Q I g lo b a l sc o re

th a n th o se

w h o n a p p e d fo r 1 h o u r (p

D .0 3 6 ).

b T h o se

w h o n a p p e d lo n g e r th a n 2 h o u rs h a d si g n ifi c a n tl y sh o rt e r sl e e p d u ra ti o n d u ri n g sc h o o l n ig h t th a n th o se

w h o n a p p e d fo r 1 h o u r (p

D .0 3 5 ).

c T h o se

w h o n a p p e d fo r h a lf a n h o u r o r le ss

h a d a si g n ifi c a n tl y le ss

sl e e p h o u r d u ri n g w e e k e n d th a n th o se

w h o n a p p e d 2 h o u rs (p

D .0 1 3 ) o r w h o n a p p e d lo n g e r th a n 2 h o u rs (p

D .0 1 2 ). T h o se

w h o n a p p e d fo r

1 h o u r h a d a si g n ifi c a n tl y le ss

sl e e p h o u r d u ri n g w e e k e n d th a n th o se

w h o n a p p e d 2 h o u rs (p

D .0 2 4 ) o r w h o n a p p e d lo n g e r th a n 2 h o u rs (p

D .0 2 2 ).

d T h o se

w h o n a p p e d fo r 2 h o u rs o r lo n g e r h a d si g n ifi c a n tl y g re a te r d if fe re n c e s in

sl e e p h o u rs b e tw e e n sc h o o l d a y s a n d w e e k e n d c o m p a re d w it h th o se

w h o n a p p e d 0 .5

h o u rs o r le ss , 1 h o u r, o r 1 .5

h o u rs (a ll p

v a lu e s <

.0 1 ).

92 JOURNAL OF AMERICAN COLLEGE HEALTH

Ye et al

T A B L E 4 . S le e p Q u a li ty

a n d S le e p H a b it b y T im

in g o f N a p s

M o rn in g

(n D

7 ; 2 .1 %

a m o n g

a ll n a p p e rs )

1 2 – 3

P M

(n D

7 6 ; 2 3 .0 %

a m o n g a ll n a p p e rs )

3 – 6

P M

(n D

2 2 1 ; 6 7 .0 %

a m o n g a ll n a p p e rs )

6 – 9

P M

(n D

2 1 ; 6 .4 %

a m o n g a ll

n a p p e rs )

S a m p le c h a ra c te ri st ic

% M

S D

% M

S D

% M

S D

% M

S D

p v a lu e

P S Q I g lo b a l

7 .3

2 .7

6 .6

2 .4

6 .4

2 .8

7 .3

2 .7

.5 1 0

P o o r sl e e p e r

8 3 .3

6 9 .4

5 8 .1

7 8 .9

.0 9 9

A v e ra g e sl e e p

d u ra ti o n

6 .6

0 .8

7 .0

1 .3

7 .0

1 .0

6 .5

1 .4

.1 7 6

S le e p h o u rs – sc h o o l

n ig h t

6 .6

0 .7

6 .7

a 1 .2

6 .7

a 1 .1

5 .7

a 1 .2

.0 0 2

S le e p h o u rs – w e e k e n d

7 .9

0 .9

8 .6

1 .4

8 .4

1 .3

8 .1

1 .8

.4 0 1

D if fe re n c e in

sl e e p

h o u rs b e tw e e n

sc h o o l d a y s a n d

w e e k e n d

1 .3

0 .6

1 .8

1 .8

1 .7

1 .7

2 .4

2 .6

.2 5 5

N ig h t o w l

2 8 .6

7 1 .1

7 0 .5

8 1 .0

.0 9 2

S a ti sfi e d w it h th e

a m o u n t o f sl e e p o n

n ig h ts b e fo re

c la ss ? (y e s)

2 8 .6

3 5 .5

4 1 .4

1 4 .3

.0 6 3

M is se d /l a te fo r c la ss

b e c a u se

o f

o v e rs le e p in g (y e s)

5 7 .1

5 7 .9

4 7 .5

8 5 .7

.0 0 4

G P A

3 .6

0 .2

3 .5

0 .4

3 .4

0 .4

3 .3

0 .5

.3 2 4

N o te . P S Q I D

P it ts b u rg h S le e p Q u a li ty

In d e x ; G P A D

g ra d e p o in t a v e ra g e .

a S tu d e n ts w h o n a p p e d b e tw e e n 6 a n d 9

P M h a d a si g n ifi c a n tl y sh o rt e r sl e e p d u ra ti o n d u ri n g sl e e p n ig h t c o m p a re d w it h th o se

w h o n a p p e d b e tw e e n 1 2 a n d 3

P M (p

D .0 0 2 ) a n d th o se

w h o n a p p e d b e tw e e n 3 a n d

6 P M (p

D .0 0 1 ).

VOL 63, FEBRUARY/MARCH 2015 93

Napping and Nighttime Sleep

napped between 12 and 3 PM (6.7 § 1.2; p D .002) and between 3 and 6 PM (6.7 § 1.1; p D .001). In addition, these late nappers were significantly more likely to miss or be

late for class due to oversleeping compared with students in

other nap-timing groups (p D .004).

Overall Napping Habits (Frequency, Length, and Timing) and Sleep Quality

Among all the students who reported napping in the

month prior to the survey, the relationships of 3 aspects of

self-reported napping habits with nocturnal sleep quality

were concurrently examined using multiple regression anal-

yses. Among the demographic variables (including age,

sex, BMI, race, ethnicity, year in school, and enrolled

school), only age and sex were significantly associated with

the PSQI score and remained as covariates in the final

regression model (Table 5). Controlling for age and sex,

the greater average length of nap was significantly associ-

ated with a higher PSQI score (b D .187, p D .003). We also found that self-rated general mood and energy level

significantly differed among the 5 nap-length groups, with

those who reported napping longer having a lower mood

and energy level (p D .007).

COMMENT

This study characterized 3 important aspects of self-

reported napping behavior, including frequency, length,

and timing, and its relationship with nighttime sleep in a

group of American college students. Special attention needs

to be given to frequent (3 or more times per week), long

(over 2 hours), or late (between 6 and 9 PM) nappers who

have a high risk of suffering poor nighttime sleep quality,

severe sleep deprivation, and the associated poor academic

performance.

This study provides further evidence that napping is a

common behavior in college students. The majority of the

sample (75%) reported napping during the month prior to

completing the survey, with 42.9% reported having napped

at least once per week. This is similar to previous reports

from college students in Spain 11

and Hong Kong. 20

Although it has been estimated that as many as 75% of

healthy adults take naps, people choose to nap for a variety

of reasons: replacement naps in response to perceived

sleepiness; appetitive naps without regard to insufficient

sleep but for enjoyment; and prophylactic naps in advance

of sustained wakefulness or in preparation for sleep loss. 21

In our study, self-reported nappers, particularly those fre-

quent, long, and late nappers, reported less sleep on school

nights and tended to sleep longer during the weekend. This

lends support to the premise that these naps could be

replacement naps, which are likely to be used as a coping

strategy against weeknight insufficient sleep and daytime

sleepiness by college students. As supported by a previous

epidemiological survey on sleep in a representative sample

of Italian adolescents, an evening circadian preference—or

being a “night owl”—can be significantly associated with

napping. 22

The majority of the students in our study

(66.3%) self-identified as “night owls,” and this rate was

even higher for those who reported being frequent (77.6%),

long (87%), and late (81%) nappers. Being “night owls”

can predispose students to partial sleep deprivation, result-

ing in an increased reliance on replacement naps. In addi-

tion, underlying sleep disorders may contribute to daytime

sleepiness and poor daily functioning, and students tend to

compensate by napping. This is supported by the observed

strong association of napping with sleep apnea in a popula-

tion-based study in Spain. 23

Why college students nap and

whether napping could be regarded as a marker of underly-

ing sleep disorders deserve further investigation.

Our findings offer empirical support for the association

between the habit of napping and sleep quality. There is a

growing concern about college students’ poor sleep quality,

with irregular sleep patterns and sleep deprivation being

very common in these young adults. 12,20

It is alarming that

based upon PSQI scores, 59.7% of the students in our sam-

ple were classified as poor sleepers, and that sleep quality

was even worse for those who reported napping during the

month prior to completing the survey. The underlying

causes for the poor sleep in college students may be multi-

factorial. Individual factors such as poor sleep hygiene

associated with inadequate sleep knowledge could lead to

poor sleep quality in college students. 24 The early start time

of morning classes can also contribute to shorter sleep

TABLE 5. Relationship Between Napping Habits (Frequency, Length, and Timing) and Sleep Quality

Variable Standardized coefficient (b) Significance (p value)

Sex ¡.151 .015* Age .161 .008

*

Napping frequency ¡.012 .846 Length of nap(s) .187 .003

*

Timing of nap(s) .009 .878

Note. For the regression model, total R 2 D .074, F D 4.083 (df D 5), p D .001.

* p < .05.

94 JOURNAL OF AMERICAN COLLEGE HEALTH

Ye et al

length on weekdays and compensatory sleep during

weekends. 25

The effect of napping on nighttime sleep may be com-

plex. Napping can alter the sleep–wake cycle, which is

associated with hypothalamic–pituitary–adrenal axis dysre-

gulation in young adults, and may lead to negative health

consequences such as depression, decreased glucose toler-

ance and insulin sensitivity, altered adrenal function, and

increased evening cortisol levels. 26,27

When considering

frequency, length, and timing of napping concurrently, we

found that longer naps were significantly associated with

poorer overall sleep quality when controlling for age and

sex. Long naps have been shown to be less efficient than

short naps in improving cognitive performance and subjec-

tive alertness. 28 Sleep inertia is more likely to follow longer

naps, which consist of more slow wave sleep. 29

Sleep iner-

tia is the experience of impaired performance and/or dis-

orientation immediately after awaking from sleep. 30

The

effect of sleep inertia can last up to 4 hours after awaken-

ing 31

and may influence nocturnal sleep quality particularly

for those late nappers who take long naps. In addition, tak-

ing long naps can be a sign of depression, which may

directly impair sleep quality. This is supported by our

observation that students who reported napping longer

reported a lower mood and energy level.

Our findings suggest that for those who nap habitually,

taking a shorter nap should be considered to enhance night-

time sleep quality. Healthy young adults should ideally nap

for approximately 10 to 20 minutes, with benefits in mood,

alertness, and cognitive performance. 32,33

Taking short

naps has been recommended in workplace settings, where

performance immediately upon awakening is normally

required. 13

Power naps, typically defined as sleep episodes

of less than 20 minutes, have been discussed as a potential

countermeasure to fatigue and sleepiness. 34

Amin et al 35

reported that a short (up to 20 minutes) mid-day nap

improved cognitive functioning and alertness among medi-

cal residents. Pilcher and colleagues 34

found that in a group

of healthy young and middle-aged adults, approximately

half of the participants reported napping for less than 20

minutes. In contrast, the majority of the students in our

sample reported napping much longer. It is possible that the

participants were less likely to remember short naps when

they were surveyed about their sleep habits. A daily log, as

adopted in the study by Pilcher and colleagues, 34

may have

allowed a more accurate assessment of sleep habits.

The timing of a nap also is known to have a significant

effect on nighttime sleep. An evening nap can alter one’s

circadian rhythms, leading to disrupted sleep and less noc-

turnal sleep. 36 Although sleep tendency usually increases in

the afternoon, researchers studying healthy young adults

have not identified a “best” time to nap. As suggested by

Milner and Cote, 13

the best time to nap might depend on

various factors, such as individual sleep need, morning-

ness-eveningness tendencies, quality of sleep during the

nap, and sleep quality of the previous night.

We found that students who reported napping more fre-

quently, or who reported being long or late nappers, had

either a lower GPA or were more likely to miss or be late to

class due to oversleeping. The effect of napping on aca-

demic performance in college students is likely to be medi-

ated by nighttime sleep quality, sleep duration, and sleep/

wake schedules. Consistent with our findings, poor sleep

quality, together with shortened sleep duration, late to-bed

and rise times, and erratic sleep/wake schedules, has been

demonstrated to negatively affect academic performance

for adolescents from middle school through college. 9,37

Poorer nighttime sleep quality and worse sleep deprivation

in frequent, long, and late nappers may lead to overall

poorer daily functioning and cognitive performance, which

can contribute to impaired academic performance, among

other negative consequences.

Limitations

Some limitations in this study need to be considered. A

causal relationship cannot be inferred from the cross-

sectional survey data collected in this study. The bidirec-

tional relationship between the napping behavior and night-

time sleep should be noted. In the present study,

retrospective subjective reports of napping and sleep pat-

terns were utilized. Although it has been suggested that

self-reported sleep survey data are as reliable as objective

measures in adolescents, 38

sleep–wake diaries, polysom-

nography, or actigraphy measurements could possibly pro-

vide more valid assessments for napping and nighttime

sleep. Other aspects of napping, such as the number of naps

per day and the individual experience of napping, may also

have an effect on nighttime sleep. Further studies could be

designed to examine these issues. We compared our final

sample with the undergraduate student population in this

university and noticed that the proportion of females in the

sample was higher compared with that in the overall student

body (66.4% vs 52%). It is possible that females were more

likely to respond to the online survey. Although the major-

ity of the questions of the online survey were from the

highly validated PSQI, the reliability or validity for other

survey questions were not tested, including the 3 questions

describing napping habits, the supplemental questions of

sleep habits (eg, weekday vs weekend sleep schedules,

being “early bird” or “night owl”), and questions about gen-

eral health and mood/energy level. Future studies using val-

idated instruments are needed to confirm our findings. It is

hoped that our study can guide the development of a valid

and reliable questionnaire evaluating napping behavior for

future investigations.

Conclusion

In summary, this study documented the habit of napping

by frequency, length, and timing and assessed how napping

VOL 63, FEBRUARY/MARCH 2015 95

Napping and Nighttime Sleep

may affect nighttime sleep in a selected group of college

students. Given its high prevalence and association with

nighttime sleep, napping behavior should be assessed for

college students, at least for those who show an unexpected

change in their academic performance. One of the most

interesting findings is the demonstrated worse nighttime

sleep quality, more severe sleep deprivation, and overall

poorer academic performance in students who were self-

reported frequent, long, or late nappers. Notably, the signif-

icant implications of napping habits to college students’

nighttime sleep quality, their GPA, and class absence or tar-

diness should be taken seriously by academic administra-

tors and health providers. Although napping has been

routinely assessed in students presenting with sleep and/or

mood disturbance, current practice is largely limited to sim-

ply asking whether or not the students take naps. We rec-

ommend that it is critical to include specific questions

examining frequency, length, and timing of napping. A

valid and reliable questionnaire evaluating these aspects of

napping is needed for future research and practice. Further

evaluation and tailored interventions are needed for college

students who are identified to be frequent, long, or late nap-

pers. Educational and behavioral programs aiming to

improve sleep quality in college students can also benefit

from specific instructions about napping. Researchers

should examine the impetus for napping and the underlying

causes of differences in self-reported sleep habits and qual-

ity, including the role of consumption of caffeine, alcohol,

and recreational drugs, as well as the influence of technol-

ogy use late into night (eg, cell phones, social media, Inter-

net) on college campuses. Based on a more nuanced

understanding of these factors, interventional strategies at

the individual and institutional levels aimed at improving

college students’ sleep could be created and tested for

effectiveness.

FUNDING

No funding was used to support this research and/or the

preparation of the manuscript.

CONFLICT OF INTEREST DISCLOSURE

The authors have no conflicts of interest to report.

The authors confirm that the research presented in this

article met the ethical guidelines, including adherence to

the legal requirements, of the United States and received

approval from the Institutional Review Board of Boston

College.

NOTE

For comments and further information, address corre-

spondence to Lichuan Ye, PhD, RN, Assistant Professor,

Boston College, William F. Connell School of Nursing,

Cushing Hall 423, 140 Commonwealth Avenue, Chestnut

Hill, MA 02467, USA (e-mail: [email protected]).

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Received: 7 April 2014 Revised: 1 October 2014

Accepted: 12 October 2014

VOL 63, FEBRUARY/MARCH 2015 97

Napping and Nighttime Sleep

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