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How A e Adolescen s Sleeping? Adolescen Sleep Pa e ns and Sociodemog aphic
Di e ences in 24 Eu opean and No h Ame ican Coun ies
© 2020 Else ie
Published e sion
Ga iepy, Gene ie e; Danna, So ia; Gobiņa, Inese; Rasmussen, Me e; Gaspa de
Ma os, Ma ga ida; Tynjälä, Jo ma; Janssen, Ian; Kalman, Michal; Ville uša, Ani a;
Husa o a, Daniela; B ooks, Fiona; Elga , F ank J.; Kla ina-Mak ecka, Sol i a;
Šmigelskas, Kas y is; Gaspa , Tania; Schnoh , Ch is ina
Ga iepy, G., Danna, S., Gobiņa, I., Rasmussen, M., Gaspa de Ma os, M., Tynjälä, J., Janssen, I.,
Kalman, M., Ville uša, A., Husa o a, D., B ooks, F., Elga , F. J., Kla ina-Mak ecka, S., Šmigelskas,
K., Gaspa , T., & Schnoh , C. (2020). How A e Adolescen s Sleeping? Adolescen Sleep Pa e ns
and Sociodemog aphic Di e ences in 24 Eu opean and No h Ame ican Coun ies. Jou nal o
Adolescen Heal h, 66(6, Supplemen ), S81-S88.
h ps://doi.o g/10.1016/j.jadoheal h.2020.03.013
2020
O iginal a icle
How A e Adolescen s Sleeping? Adolescen Sleep Pa e ns and
Sociodemog aphic Di e ences in 24 Eu opean and No h
Ame ican Coun ies
Gene ie e Ga iepy, Ph.D.
a
,
*
,Sofia Danna, M.Sc.
b
, Inese Gobin¸ a, Ph.D.
c
, Me e Rasmussen, Ph.D.
d
,
Ma ga ida Gaspa de Ma os, Ph.D.
e
, Jo ma Tynjälä, Ph.D.
, Ian Janssen Ph.D.
g
, Michal Kalman Ph.D.
h
,
Ani a Ville u
sa, M.D.
i
, Daniela Husa o a, Ph.D.
j
, Fiona B ooks, Ph.D.
k
, F ank J. Elga , Ph.D.
l
,
Sol i a Kla ina-Mak ecka M.Sc.
m
, Kas y is 
Smigelskas, Ph.D.
n
, Tania Gaspa , Ph.D.
o
, and
Ch is ina Schnoh , Ph.D.
p
a
Depa men o Social and P e en i e Medicine, Uni e si y o Mon eal, Mon eal, Canada
b
Douglas Men al Heal h Uni e si y Ins i u e, Mon eal, Canada
c
Depa men o Public Heal h and Epidemiology, Ins i u e o Public Heal h, Riga S adins Uni e si y, Riga, La ia
d
Na ional Ins i u e o Public Heal h, Uni e si y o Sou he n Denma k, Copenhagen, Denma k
e
Ins i u e o En i onmen al Heal h, School o Human Kine ics, Uni e si y o Lisbon, Lisbon, Po ugal
Facul y o Spo and Heal h Sciences, Uni e si y o Jy askyla, Jy askyla, Finland
g
Depa men o Public Heal h Sciences, School o Kinesiology and Heal h S udies, Queen's Uni e si y, Kings on, Canada
h
Depa men o Rec ea ion and Leisu e S udies, Facul y o Physical Cul u e, Palacky Uni e si y Olomouc, Olomouc, Czech Republic
i
Depa men o Public heal h and Epidemiology, Ins i u e o Public Heal h, Riga S adins Uni e si y, Riga, La ia
j
Depa men o Heal h Psychology, Facul y o Medicine, PJ Sa a ik Uni e si y, Kosice, Slo akia
k
O fice o he Depu y Vice-Chancello Resea ch, Uni e si y o Technology Sydney, Ul imo, Sydney, Aus alia
l
Ins i u e o Heal h and Social Policy, McGill Uni e si y, Mon eal, Canada
m
Depa men o Public Heal h and Epidemiology, Riga S adins Uni e si y, Riga, La ia
n
Heal h Resea ch Ins i u e, Li huanian Uni e si y o Heal h Sciences, Kaunas, Li huania
o
Psychology and Educa ional Sciences Ins i u e, Lusiada Uni e si y/CLISSIS, ISAMB/Lisbon Uni e si y, Lisbon, Po ugal
p
Depa men o Public Heal h, Uni e si y o Copenhagen, Copenhagen, Denma k
A icle his o y: Recei ed Oc obe 1, 2019; Accep ed Ma ch 10, 2020
Keywo ds: Sleep pa e ns; Sleep; Adolescen s; In e na ional su eys; Epidemiology; Public Heal h; Age dispa i ies; Socioeconomic
di e ences
ABSTRACT
Pu pose: Insu ficien and poo sleep pa e ns a e common among adolescen s wo ldwide. Up o
now, he e idence on adolescen sleep has been mos ly in o med by coun y-specific s udies ha
used di e en measu es and age g oups, making di ec compa isons di ficul . C oss-na ional da a on
adolescen sleep ha could in o m na ions and in e na ional discussions a e lacking. We examined
he sleep pa e ns o adolescen s ac oss 24 coun ies and by gende , age, and a fluence g oups.
Me hods: We ob ained sleep da a on 165,793 adolescen s (mean age 13.5 yea s; 50.5% gi ls) in 24
Eu opean and No h Ame ican coun ies om he ecen c oss-sec ional Heal h Beha iou in
School-aged Child en su eys (2013e2014 and 2017e2018). Fo each coun y, we calcula ed he
age-s anda dized mean in sleep du a ion, iming, and consis ency and he p opo ions mee ing
IMPLICATIONS AND
CONTRIBUTION
The sleep pa e ns o ado-
lescen s a y ac oss coun-
ies and by
sociodemog aphic g oups.
Insu ficien sleep on
school days is p e alen
c oss-na ionally. Na ional
policies and s a egies ha
Conflic s o in e es : The au ho s ha e no conflic s o in e es o disclose.
Disclosu e: This supplemen was suppo ed by he Wo ld Heal h O ganiza ion
Eu opean O fice and he Uni e si y o Glasgow. The a icles ha e been pee -
e iewed and edi ed by he edi o ial s a o he Jou nal o Adolescen Heal h. The
opinions o iews exp essed in his supplemen a e hose o he au ho s and do
no necessa ily ep esen he o ficial posi ion o he unde .
*Add ess co espondence o: Gene ie e Ga iepy, Ph.D., Depa men o Social
and P e en i e Medicine, Uni e si y o Mon eal, 7101 du Pa c, Mon eal, QC H3N
1X9, Canada.
E-mail add ess: gene ie [email p o ec ed] (G. Ga iepy).
www.jahonline.o g
1054-139X/Ó2020 Published by Else ie Inc. on behal o Socie y o Adolescen Heal h and Medicine. This is an open access a icle unde he CC BY-NC-ND license (h p://
c ea i ecommons.o g/licenses/by-nc-nd/4.0/).
h ps://doi.o g/10.1016/j.jadoheal h.2020.03.013
Jou nal o Adolescen Heal h 66 (2020) S81eS88
sleep ecommenda ions on school and nonschool days om sel - epo ed bed imes and wake
imes. We conduc ed s a ified analyses by gende , age, and amily a fluence g oup.
Resul s: Adolescen sleep pa e ns a ied c oss-na ionally. The a e age sleep du a ion anged
be ween 7:47 and 9:07 hou s on school days and be ween 9:31 and 10:22 hou s on nonschool
days, and he p opo ion o adolescen s mee ing sleep ecommenda ions anged be ween 32% and
86% on school days and be ween 79% and 92% on nonschool days. Sleep pa e ns by gende and
a fluence g oups we e la gely simila , bu olde adolescen s slep less and wen o bed la e on
school days han younge adolescen s in all coun ies.
Conclusions: The sleep pa e ns o adolescen s a y ac oss coun ies and sociodemog aphic
g oups. Insu ficien sleep on school days is common in many coun ies. Public heal h and policy
e o s o p omo e heal hy adolescen sleep a e encou aged.
Ó2020PublishedbyElse ie Inc.onbehal o Socie y o Adolescen Heal handMedicine.Thisisanopen
access a icle unde he CC BY-NC-NDlicense (h p://c ea i ecommons.o g/licenses/by-nc-nd/4.0/).
suppo adolescen sleep
a e encou aged.
Adolescen sleep is a public heal h conce n in many coun ies.
Poo sleep pa e nsdincluding sleep ha is insu ficien , incon-
sis en , non es o a i e, dis up ed, o poo ly imed (e.g., la e
bed ime)da ec some 30%e70% o adolescen s in Eu ope and
No h Ame ica [1,2], whe e a leas one ou h o adolescen s
ha e di ficul y alling asleep a nigh and eel i ed du ing he day
[1]. Sleep pa e ns o adolescen s di e on school and nonschool
days, and hei ci cadian sleepewake cycle is delayed by 2e
3 hou s ela i e o adul s [1,3]. Ea ly school s a imes conflic
wi h his ci cadian shi [3,4], leading o unca ed sleep du ing
he week [5e7]. On weekends and holidays, adolescen s end o
sleep longe and la e [1]. This disc epancy in sleep imes is
called social je lag [8] and has been associa ed wi h heal h,
beha io al, and cogni i e issues [9e11]. O e all, poo sleep is
linked o physical heal h p oblems such as colds, headaches, and
obesi y [12,13], emo ional p oblems such as anxie y, dep ession,
and suicidal hough s [10,12,14], isky beha io s [15], poo aca-
demic pe o mance [9,12], and wo se quali y o li e [13]. Poo
sleep also ela es o physical inac i i y, seden a y beha io s
including excessi e sc een ime, and poo die [12], unde sco ing
he need o include heal hy sleep in o you h heal h p omo ion
e o s.
The e idence on adolescen sleep is mos ly in o med by
coun y-specific s udies ha in ol e di e en measu es and age
g oups o e he las ew decades, making di ec compa isons
di ficul [1,2,16e18]. None heless, he e a e indica ions ha
adolescen sleep a ies ac oss egions and cul u es. A 2011 sys-
ema ic e iew o 41 s udies ound la e bed imes in Eu ope han
in No h Ame ica (22:46 s. 22:06) and longe sleep on school
days (8:26 s. 7:28 hou s) and weekends (10:01 s. 8:48 hou s)
[1]. The e iewalso ound ha going o bed abou 2 hou s la e on
weekends han on school days was common ac oss egions.
Mo eo e , con empo a y in o ma ion on c oss-na ional sleep
pa e ns is sca ce and mos ly desc ibes sleep du a ion, whe eas
new e idence shows ha o he sleep pa e ns also a ec heal h
[11].
Social pa e ns in sleep a e ound be ween age, gende , and
socioeconomic g oups. Olde adolescen s go o bed la e , sleep
less on school days, and sleep mo e on weekendsda common
end in Eu ope, No h Ame ica, and Asia [1,18,19]da ibu able
o biological [3,4], beha io al [20], and social changes [21] du ing
adolescence. Some s udies ound ha boys sleep less and go o
bed la e han gi ls [16,19,22], pa icula ly on weekends [19],
whe eas o he s ound ha boys sleep mo e [2,16,17]. Fu he -
mo e, s udies om Canada, he U.S., Aus alia, and No way ound
ha sho e and poo e quali y sleep is mo e common in lowe
socioeconomic g oups [2,16,23], bu compa able da a om o he
coun ies a e sca ce.
Using da a on sleep collec ed in school-based su eys o ad-
olescen s in Eu ope and Canada, we examined c oss-na ional
di e ences in sleep du a ion, sleep imes, and social je lag and
di e ences by gende , age, and socioeconomic g oups. We hy-
po hesized ha sleep pa e ns would a y ac oss coun ies and
be ween sociodemog aphic subg oups. Specifically, we an ici-
pa ed ha olde adolescen s would go o bed la e , sleep less on
school days, and sleep mo e on weekends han younge adoles-
cen s, and ha lowe socioeconomic g oups would sleep less
han highe socioeconomic g oups, bu we we e agnos ic abou
gende di e ences, gi en he mixed findings in he li e a u e.
Me hods
Sample and p ocedu e
The Heal h Beha iou in School-aged Child en (HBSC) s udy is
a Wo ld Heal h O ganiza ion collabo a i e c oss-sec ional s udy
cu en ly conduc ed in 47 coun ies ac oss Eu ope and No h
Ame ica (h p://www.hbsc.o g)[24]. Da a collec ion p ocedu es
in all coun ies we e conduc ed in acco dance wi h a s anda d-
ized in e na ional p o ocol [24]. Each membe coun y ob ained
e hics clea ance o conduc he su ey om a uni e si y-based
e iew boa d o equi alen egula o y body. Da a a e collec ed
in school se ings e e y 4 yea s om a na ionally ep esen a i e
andom clus e sample o 11-,13-, and 15-yea -old adolescen s in
each pa icipa ing coun y. The HBSC su ey uses a wo-s age
sampling o ec ui s uden s wi hin s a ified samples o
schools ha ep esen ed he egional, economic, and public-
p i a e dis ibu ion in each coun y. The p ima y sampling
uni s a e schools. Mo e de ailed in o ma ion abou me hodology
o he HBSC s udy is epo ed elsewhe e [24]. Fo he fi s ime in
2013e2014 and again in 2017e2018, he HBSC su ey included
sleep i ems in one o he su ey's op ional ques ionnai e pack-
ages. HBSC coun ies could choose o add his op ional package
o su ey i ems on sleep o he HBSC manda o y ques ionnai e,
depending on hei needs and p io i ies. Twen y- ou coun ies
elec ed o include sleep i ems in hei 2013e2014 o 2017e2018
na ional su ey and we e included in his s udy (n ¼185,278).
Fo he nine coun ies ha collec ed sleep da a in hei 2013e
2014 and 2017e2018 su eys, we combined he samples o bo h
su eys o maximize he use o he a ailable da a and he s a-
is ical powe o es ima e subg oup di e ences wi hin each
coun y. Sleep pa e ns ac oss he 2013e2014 and 2017e2008
G. Ga iepy e al. / Jou nal o Adolescen Heal h 66 (2020) S81eS88S82
su eys we e compa able. Pa icipan s who did no espond o
any sleep i em (n ¼18,489) o did no epo hei age (n ¼996)
we e excluded, lea ing a final sample o 165,793 pa icipan s
om 24 coun ies (Table 1 and Supplemen a y Table 1).
Measu es
Sleep pa e ns we e de e mined using ou i ems ha asked,
“When do you usually go o bed?”and “When do you usually
wake up?”on school days and weekends o holidays (nonschool
days). Bed imes anged in hal -hou in e als om “No la e han
21:00” o “2:00 o la e ” o school days and o “4:00 o la e ” o
nonschool days. Wake imes anged in hal -hou in e als om
“No la e han 5:00” o “8:00 o la e ” o school days and om
“No la e han 7:00” o “14:00 o la e ” o nonschool days. We
calcula ed sleep du a ion on school and nonschool days using
bed and wake imes. Fo each hal -hou in e al, we used he
ime a midpoin in ou calcula ions (e.g., 22:15 i he bed ime
esponse was “be ween 22:00 and 22:30”). Fo esponses a he
ends o he scale, we used he minimum/maximum s a ed ime
(e.g., 14:00 i he wake ime esponse was “14:00 o la e ”and
5:00 i he wake ime esponse was “No la e han 5:00”). We
calcula ed social je lag using he di e ence in bed imes on
nonschool and school days [25]. We also assessed whe he s u-
den s me he minimum sleep ecommenda ion o hei age
using cu en in e na ional guidelines [26,27], which ecom-
mend a leas 9 hou s o hose aged 5e13 yea s (op imal ange
9e11 hou s) and 8 hou s o hose aged 14e17 yea s (op imal
ange 8e10 hou s).
Socioeconomic s a us (SES) was assessed using he Family
A fluence Scale, a checklis o six amily asse s: numbe o ca s,
ha ing own bed oom, numbe o compu e s, numbe o ba h-
ooms, amily holidays in he pas yea , and ha ing a dishwashe .
The Family A fluence Scale is a alida ed scale o compa a i e
measu es o amily a fluence o Eu opean and No h Ame ican
adolescen s [28]. We ca ego ized s uden s in o e ile g oups o
low, medium, o high amily a fluence ela i e o he dis ibu ion
o o al sco es om he same age, gende , coun y, and su ey
yea . We also used sel - epo ed age and gende (boy o gi l).
S a ified analyses used he h ee sampled age g oups in HBSC
[24], 11-yea -olds (10.5e12.4 yea s), 13-yea -olds (12.5e
14.4 yea s), and 15-yea -olds (14.5e16.5 yea s).
S a is ical analysis
All analyses we e un sepa a ely o each coun y. We fi s
conduc ed a desc ip i e analysis o he sample cha ac e is ics.
We hen es ima ed he age-s anda dized a e age sleep du a-
ions, bed imes, wake imes, and social je lag. We s anda dized
he esul s o age using he age dis ibu ion o all coun ies
combined as a e e ence o accoun o he di e en age dis i-
bu ions ac oss coun ies. Finally, we conduc ed s a ified ana-
lyses by gende , age, and amily a fluence g oups in each coun y.
We s a is ically compa ed di e ences in subg oups using he
adjus ed Wald es o con inuous sleep ou comes and he co -
ec ed weigh ed Pea son chi-squa e s a is ic o ca ego ical sleep
ou comes o accoun o he complex su ey design. Because o
he a ying sample sizes ac oss coun ies (n ange om 2,667 o
15,432), we in e p e ed he s a is ical significance wi h cau ion
and wi h conside a ion o he public heal h ele ance o he
es ima es. Analyses we e done using S a a/SE 15 (S a aCo p LLC,
College S a ion, TX). We accoun ed o clus e ing a he school
le el and inco po a ed sampling weigh s whe e ele an o
ensu e esul s we e ep esen a i e o he coun y using he s y
op ion in S a a.
Resul s
A e age sleep pa e ns on school and nonschool days by
coun y a e p esen ed in Figu es 1 and 2, espec i ely, and in
Supplemen a y Table 2. School day sleep du a ion anged om
7:47 hou s in Poland o 9:07 hou s in Flemish Belgium, whe eas
on nonschool days, i anged om 9:31 hou s in G eece o
10:22 hou s in Flemish Belgium. School day bed imes anged
om 21:42 hou s in Flemish Belgium o 23:18 hou s in G eece,
whe eas nonschool day bed imes anged om 23:14 hou s in
Flemish Belgium o 0:54 hou s in Spain. School day wake imes
anged om 06:18 hou s in Hunga y o 07:23 hou s in Spain.
Nonschool day wake imes anged om 09:11 hou s in Hunga y
o 10:36 hou s in Spain. The pe cen age o adolescen s mee ing
sleep ecommenda ions on school days anged om 32.0% in
Poland o 86.3% in Flemish Belgium and on nonschool days om
79.2% in G eece o 92.4% in Flemish Belgium (Figu e 3). Social
je lag anged om 1:11 hou s in Moldo a o 2:12 hou s in
Sweden.
Boys epo ed longe sleep du a ion on school days han gi ls
in wo hi ds o coun ies (15/24 coun ies), al hough di e ences
we e small (10 minu es), e en i s a is ically significan . On
nonschool days, gi ls slep longe in all coun ies, om 4 minu es
mo e in Swi ze land o 34 minu es mo e in Slo enia. Boys had
sligh ly la e bed imes on school days (2e10 minu es) and
nonschool days (1e27 minu es). On school days, gi ls woke
ea lie han boys in all coun ies, bu on nonschool days, boys
woke ea lie han gi ls in abou wo hi ds o coun ies. Al hough
boys we e mo e likely o mee sleep ecommenda ions on school
days in mos coun ies (17/24 coun ies), gi ls we e mo e likely
o mee sleep ecommenda ions on nonschool days in all coun-
ies. Boys had abou he same o sligh ly mo e social je lag han
Table 1
Su ey yea s and sample size o Heal h Beha iou in School-aged Child en
coun ies wi h sleep da a
Coun y Su ey yea s Sample size
Flemish Belgium 2017e2018 4,305
F ench Belgium 2013e2014, 2017e2018 9,791
Canada 2013e2014 11,295
Czech Republic 2013e2014, 2017e2018 15,432
Denma k 2013e2014, 2017e2018 6,019
Es onia 2013e2014, 2017e2018 8,633
Finland 2013e2014, 2017e2018 7,975
G eece 2017e2018 3,817
Hunga y 2013e2014, 2017e2018 7,397
Iceland 2017e2018 6,967
La ia 2013e2014, 2017e2018 9,887
The Ne he lands 2017e2018 4,634
No way 2017e2018 3,085
Poland 2017e2018 5,205
Po ugal 2017e2018 2,971
Republic o Moldo a 2017e2018 4,682
Sco land 2013e2014, 2017e2018 8,794
Slo akia 2013e2014, 2017e2018 10,736
Slo enia 2013e2014 4,982
Spain 2013e2014 7,576
Sweden 2013e2014 7,511
Swi ze land 2013e2014 2,667
Uk aine 2017e2018 6,600
Wales 2013e2014 4,832
G. Ga iepy e al. / Jou nal o Adolescen Heal h 66 (2020) S81eS88 S83
gi ls, anging om no di e ence in Uk aine o 22 minu es in
Sweden.
Olde adolescen s slep less in all coun ies (Supplemen a y
Table 3). On school days, di e ences be ween he younges and
oldes g oups anged om 54 minu es in Slo akia o 1:44 hou s
in Slo enia. On nonschool days, he smalles di e ence was
11 minu es in Flemish Belgium, and he g ea es di e ence was
52 minu es in Uk aine. Mos coun ies also saw longe delays in
bed imes in olde adolescen s, bo h on school days ( om
52 minu es in Flemish Belgium o 1:35 hou s in Iceland) and
nonschool days ( om 1:15 minu es in Flemish Belgium and
Uk aine o 2:00 hou s in Sweden). Al hough age di e ences in
wake imes on school days a ied conside ably be ween coun-
ies, wake imes on nonschool days we e consis en ly la e in
olde adolescen s, wi h 15-yea -olds waking 23 minu es la e
han 11-yea -olds in Uk aine and up o 1:22 hou s la e in No -
way. Age di e ences we e also ound in he pe cen age o ado-
lescen s who me sleep ecommenda ions. On school days, 11-
yea -olds we e mos likely o ge he ecommended amoun o
sleep, anging om 42.8% in Poland o 92.9% in Flemish Belgium,
whe eas on nonschool days, 15-yea -olds we e mos likely o
mee ecommenda ions, anging om 83.7% in G eece o 96.3%
in Iceland. Finally, mo e social je lag was obse ed in he oldes
g oup compa ed wi h he younges in all coun ies.
Supplemen a y Table 4 shows c oss-na ional sleep pa e ns
by amily a fluence g oups. An equal mix o posi i e and nega i e
a fluence g adien s was obse ed o sleep du a ion. Howe e ,
mos di e ences be ween a fluence g oups we e small. On
school days, he di e ence in sleep du a ion be ween he leas
and mos a fluen adolescen s anged om 31 minu es in
Moldo a o þ10 minu es in Sco land and Swi ze land. On
nonschool days, sleep du a ion be ween he leas and mos
a fluen adolescen s anged om 22 minu es less sleep in
Moldo a o þ13 minu es mo e sleep in Sco land. On school days,
bed imes we e la e in he high a fluence g oup compa ed wi h
he low a fluence g oup in mos coun ies. The g ea es di e -
ence was in Moldo a (þ31 minu es). In con as , he high a flu-
ence g oup wen o bed ea lie in F ench Belgium, Denma k,
Sco land, Wales, and Swi ze land, up o 19 minu es ea lie in
Swi ze land. On nonschool days, bed imes we e la e in he high
a fluence g oup in hal he coun ies, wi h he la ges di e ence
in Moldo a (þ54 minu es) and ea lie in o he coun ies, he
la ges di e ence in Sco land (30 minu es). The e was li le
a iabili y in wake imes among a fluence g oups. On school
days, he di e ence anged om þ5 minu es la e in Canada and
Hunga y o 10 minu es ea lie in Swi ze land. The e was also
no domina ing end on nonschool days. The di e ence be ween
he high and low a fluence g oups anged om þ32 minu es in
Moldo a o 18 minu es ea lie in Sco land. On school days,
mo e low a fluence adolescen s me sleep ecommenda ions in
abou hal he coun ies. The g ea es di e ence was in Moldo a
(þ19.1 pe cen age poin s). The high a fluence g oup be e me
sleep ecommenda ions in o he coun ies, wi h he highes
di e ence ound in Sco land (þ7.2 pe cen age poin s). Simila
ends we e obse ed on nonschool days. The p opo ion
mee ing sleep ecommenda ions on nonschool days was highe
in he high a fluence g oup in some coun ies, wi h he la ges
di e ence in F ench Belgium (þ5.2 pe cen age poin s), and
highe in he low a fluence g oup in o he coun ies, wi h he
la ges di e ence epo ed in Moldo a (þ6.5 pe cen age poin s).
Mo e a fluen adolescen s epo ed mo e social je lag in mos
coun ies. The g ea es inc ease was in Swi ze land, whe e high
a fluence adolescen s had 35 minu es mo e social je lag han low
a fluence adolescen s. Con e sely, low a fluence adolescen s had
Figu e 1. A e age sleep imes and sleep du a ion on school days by coun y.
G. Ga iepy e al. / Jou nal o Adolescen Heal h 66 (2020) S81eS88S84

g ea e social je lag in o he coun ies, up o 25 minu es in
F ench Belgium.
Discussion
This s udy examined sleep du a ion, iming, and consis ency
in o e 165,000 adolescen s om 24 p ima ily Eu opean coun-
ies. Sleep du a ion anged om 7:47 o 9:07 hou s on school
days and om 9:31 o 10:22 hou s on nonschool days. A
conside ably smalle p opo ion o s uden s me sleep du a ion
ecommenda ions on school days ( ange 32%e86%) han on
nonschool days ( ange 79%e92%). Social je lag was obse ed in
all coun ies, as bed imes we e consis en ly la e and sleep du-
a ions consis en ly longe on nonschool han school days. These
di e ences be ween school and nonschool days a e consis en
wi h adolescen sleep pa e ns p e iously obse ed in he li e -
a u e [1].
In line wi h p e ious s udies, sleep iming and du a ion
changed wi h age [1,18,19] bu we e only sligh ly di e en be-
ween boys and gi ls [2,16,17,19,22]. Olde adolescen s slep less,
wen o bed la e , and expe ienced g ea e social je lag han
younge adolescen s. These changes eflec he no ma i e
de elopmen al cou se o he ci cadian clock, which shi s owa d
e eningness a ound pube y, peaks a a ound age 16 yea s, and
shi s back in ea ly adul hood [3,4]. The inc eased demands o
schoolwo k and he use o social media and elec onic de ices
[20] u he delay sleep imes and add o he biological endency
o olde adolescen s o all asleep la e , a a ime when pa en al
con ol o e sleep imes diminishes [21].
Howe e , we examined di e ences in sleep pa e ns ac oss
age and no pube al de elopmen . Pube al s age was no
assessed in mos HBSC coun ies. P e ious s udies no e ha
changes in sleep du ing adolescence a e a ibu able o a ious
physiological and ho monal changes ela ed o pube y and less
so wi h age pe se [29,30]. Fu u e s udies could add nuance o
hese analyses by add essing pube al de elopmen in addi ion
o age.
Al hough we ound li le o e all gende di e ences in sleep
pa e ns, he e we e no able coun y-specific di e ences. Fo
example, boys slep 10 minu es longe on school days han gi ls
in Poland, and gi ls slep 34 minu es longe on nonschool days in
Slo enia, sugges ing ha gende di e ences in beha io al pa -
e ns, oles, o esponsibili ies may influence adolescen sleep in
some coun ies.
We obse ed some socioeconomic g adien s in sleep mea-
su es, bu hey ended o be small and fluc ua e be ween coun-
ies (i.e., posi i e in some coun ies and nega i e in o he s). Ou
esul s di e om p e ious s udies epo ing an associa ion be-
ween lowe SES and sho e sleep among adolescen s [2,16,23].
Howe e , p e ious e idence s emmed om smalle , na ional
samples and used di e en SES measu es. Fu he mo e, a e o-
spec i e coho s udy om No way ound ha sleep p oblems
we e mo e common in adolescen s who expe ienced downwa d
socioeconomic mobili y compa ed wi h s able o upwa d
mobili y [31]. The disc epancy wi h ou findings may he e o e
poin o me hodological di e ences bu also sugges ha he
ela ionship be ween SES and sleep is complex and a ies ac oss
na ional and cul u al se ings.
This s udy ound significan c oss-na ional a ia ions in sleep
pa e ns, sugges ing ha coun y-le el ac o s may play a ole in
p o ec ing and p omo ing adolescen sleep. One de e minan
may be di e ences in school s a imes. A g owing body o e -
idence finds ha la e school s a imes a e associa ed wi h
longe sleep du a ions, p ima ily by delaying wake imes [5e7].
Figu e 2. A e age sleep imes and sleep du a ion on nonschool days by coun y.
G. Ga iepy e al. / Jou nal o Adolescen Heal h 66 (2020) S81eS88 S85
In e en ion s udies ha e eplica ed hese findings [32], sup-
po ing he implemen a ion o his policy o p o ec adolescen
sleep. The HBSC su eys did no collec in o ma ion on school
s a imes, and na ional da a on school s a imes a e no
a ailable. Howe e , a s udy om Canada ound a na ional
a e age school s a ime o 08:43 hou s in 2013e2014 [6],
whe eas a s udy om he U.S. ound an a e age na ional s a
ime o 08:03 hou s in 2011e2012 [7], indica ing a iabili y in
school s a imes ac oss coun ies. Commu ing ime o school
may also a ec he sleep pa e ns o adolescen s and a y be-
ween coun ies [33]. The esul s om a ime use s udy on
Ame ican high school s uden s sugges ha each addi ional
minu e spen commu ing o school was associa ed wi h 1.3 ewe
minu es sleeping [34]. The mode o anspo a ion o commu e
o school (e.g., walking s. d i ing) ha is no ma i e o accessible
in di e en coun ies may also a ec sleep. In addi ion, ime
spen on homewo k is associa ed wi h sho e sleep in adoles-
cen s [14] and a ies ac oss coun ies [35]. Mo eo e , cul u al
di e ences in bed imes and meal imes [36] and in heal h and
li es yle no ms, such as physical ac i i y and heal hy ea ing [20],
may con ibu e o di e ences in adolescen sleep pa e ns ac oss
coun ies. Finally, geog aphic di e ences could also add o c oss-
na ional sleep a ia ions. Fo ins ance, in coun ies si ua ed a
highe la i udes, changes in dayligh iming and du a ion
h oughou he yea end o co ela e wi h sleep imes, such ha
he la e and longe dayligh o he summe ela es o la e
bed imes and less sleep compa ed wi h he win e [37].
A no able s eng h o ou s udy is he use o an in e na ional
s anda dized p o ocol o da a collec ion, he eby ensu ing high
alidi y o c oss-na ional compa isons. By using la ge, na ionally
ep esen a i e samples om a o al o 24 coun ies, he p esen
s udy adds significan ly o he li e a u e on sociodemog aphic
di e ences in adolescen sleeping pa e ns by documen ing a
numbe o obus di e ences ac oss na ional se ings and by
highligh ing he ele ance o na ional influences o sleep.
Ou s udy used sel - epo ed sleep da a. Al hough some
s udies ound ha sel - epo ed sleep co ela es highly wi h
ac ig aphy da a [38], o he s ha e ound disc epancies ha sug-
ges cau ion wi h in e p e a ion [39,40]. Howe e , sleep da a
we e measu ed using s anda dized sleep ques ions making
ela i e c oss-na ional compa isons mo e likely o be alid
despi e imp ecisions. Fu he mo e, sel - epo ed sleep da a
gene ally o e es ima e sleep du a ions because sleep onse ends
o be la e han bed ime, he e o e esul ing in mo e conse a-
i e es ima es in ou s udy. The cu poin s used o define minimal
sleep ecommenda ions [26,27] we e based on a sys ema ic e-
iew o he bes a ailable e idence [13]. Howe e , much o his
e idence was no o high quali y [13], and i is possible ha he
cu poin s could change in he u u e as he quan i y and quali y
o e idence imp o e. None heless, sleep du a ion ecommen-
da ions, e en when based on weake e idence, a e impo an
om a popula ion heal h pe spec i e, as hey play an impo an
ole in su eillance and public heal h policy o ma ion. Finally,
ou da a a e limi ed o s uden s a ending school and may no be
gene alizable o adolescen s ou side he school se ing.
This s udy p o ides he la ges c oss-na ional accoun o
adolescen sleep and sociodemog aphic pa e ning o da e. The
esul s show ha , al hough he sleep pa e ns o adolescen s
a y ac oss coun ies and sociodemog aphic subg oups, insu fi-
cien sleep and poo sleep pa e ns a e p e alen among ado-
lescen s in mos coun ies and subg oups. These esul s build on
p e ious e idence om coun y-specific s udies and poin o
na ional se ings and sociodemog aphic g oups as s ong in-
fluences o conside in he p omo ion o heal hy adolescen
sleep. Because good sleep is essen ial o se e al aspec s o a
heal hy adolescen de elopmen , public heal h policies should
Figu e 3. Pe cen age o adolescen s ha mee sleep ecommenda ions on school days and nonschool days by coun y.
G. Ga iepy e al. / Jou nal o Adolescen Heal h 66 (2020) S81eS88S86
include c oss-sec o al in e en ions ha a ge adolescen sleep.
These policies should consis o modifiable, policy-le el mea-
su es ha suppo heal hy adolescen sleep, such as delaying
school s a imes and educa ing adolescen s, pa en s, and
eache s abou he impo ance o sleep hygiene. Fu he esea ch
on c oss-na ional di e ences o o he aspec s o sleep, such as
sleeping di ficul ies and subjec i e sleep quali y, is wa an ed, as
hey a e impo an componen s o o e all sleep. Fu u e esea ch
is also needed o unde s and he c oss-coun y beha io al ac o s
and he social, s uc u al, and cul u al de e minan s ha influ-
ence sleep pa e ns, such as school and wo k schedules.
Acknowledgmen s
The Heal h Beha iou in School-aged Child en is an in e na-
ional s udy ca ied ou in collabo a ion wi h WHO/EURO. The
In e na ional Coo dina o was Candace Cu ie (Uni e si y o S
And ews) o he 2013/2014 su ey and Jo Inchley (Uni e si y o
Glasgow) o he 2017/2018 su ey. The Da a Bank Manage was
P o esso Odd un Samdal (Uni e si y o Be gen). The 2013/2014
and 2017/2018 su eys included in his s udy we e conduc ed by
he ollowing p incipal in es iga o s in he 24 coun ies: Flemish
Belgium (Ba De Cle cq and Anne Huble ), F ench Belgium (Ka ia
Cas e bon and Danielle Pie e), Canada (William Picke and
Wendy C aig), Czech Republic (Michal Kalman), Denma k (Me e
Rasmussen), Es onia (Leila Oja and Ka in Aas ee), Finland
(Jo ma Tynjälä), G eece (Anna Kokke i), Hunga y (Ágnes Ném-
e h), Iceland (A saell M. A na sson), La ia (I e a Pudule), he
Ne he lands (Gonneke S e ens, Saskia an Do sselae , Wilma
Vollebe gh, and Tom de Bog ), No way (Odd un Samdal), Poland
(Joanna Mazu ), Po ugal (Ma ga ida Gaspa de Ma os), Republic
o Moldo a (Galina Lesco), Sco land (Jo Inchley, Candace Cu ie),
Slo akia (And ea Mada aso a Gecko a), Slo enia (Helena Je -
icek), Spain (Ca men Mo eno), Sweden (Pe a Lo s ed and Lilly
Augus ine), Swi ze land (Ma ina Delg ande-Jo dan, He é
Kuendig, and Emmanuelle Kun sche), Uk aine (Olga Balaki e a),
and Wales (Ch is Robe s).
Funding Sou ces
The wo k was suppo ed by he Eu opean Regional De elop-
men Fund-P ojec "E ec i e Use o Social Resea ch S udies o
P ac ice" (No. CZ.02.1.01/0.0/0.0/16_025/0007294) and by unding
om he Technology Agency o he Czech Republic (ÉTA
TL01000335) and he Minis y o Educa ion, You h and Spo s, In-
e -Excellence, LTT18020 (HBSC Czech Republic); he Public Heal h
Agency o Canada (HBSC Canada); he Juho Vainio Founda ion and
he Uni e si y o Jy askyla (HBSC Finland); and he Po ugal- Na-
ional Founda ion o Science and Technology (HBSC Po ugal).
Supplemen a y Da a
Supplemen a y da a ela ed o his a icle can be ound a
h ps://doi.o g/10.1016/j.jadoheal h.2020.03.013.
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