Importance of physical health and health-behaviors in adolescence for risk of dropout from secondary education in young adulthood: an 8-year prospective study

Education and health constitute two interlinked assets that are highly important to individuals. In Iceland, prevalence of dropout from secondary education poses a considerable problem. This 8-year prospective study assesses to what extent poor physical health and negative health-behaviors of Icelandic adolescents predict increased odds of dropout from secondary education. The sample included n = 201 Icelandic children who participated at age 15 (baseline) and again at age 23 (follow-up). Data included objective measurements of physical health and questionnaires assessing health-behaviors, education status, parental education, neighborhood characteristics, self-esteem, and depression. Independent t-tests and chi-square were used to assess differences in physical health and health-behaviors at follow-up stratified by education status. Ordinal regression models were conducted to assess whether physical health and health-behaviors at age 15 predicted increased odds of dropout from secondary education at age 23, independent of gender, parental education and psychological factors. At age 23, 78 % of girls and 71 % of boys had completed a secondary education. Completion of a secondary education was associated with significant health benefits, especially among women. Women without a secondary education had lower fitness, more somatic complaints, higher diastolic blood pressure, less sports participation, and poorer sleep, whilst men without a secondary education watched more television. In logistic regression models somatic complaints during adolescence were associated with 1.09 (95 % CI: 1.02-1.18) higher odds of dropout from secondary education in young adulthood, independent of covariates. Health-behaviors associated with higher dropout odds included smoking (3.67, 95 % CI: 1.50-9.00), alcohol drinking (2.57, 95 % CI: 1.15-5.75), and time spent watching television (1.27, 95 % CI:1.03-1.56), which were independent of most covariates. Finally, mother's higher education was strongly associated with significantly lower dropout odds (OR 0.54, 95 % CI: 0.34-0.88) independent of father's education and psychological factors, whilst high self-esteem was independently associated with lower dropout odds (OR 0.91, 95 % CI: 0.85-0.98). Completion of a secondary education yields substantial physical health benefits for young women, but not for men. Importantly, somatic complaints and negative health-behaviors among adolescent boys and girls adversely impact their educational outcomes later in life, and may have widespread consequences for their future prospects.Peer Reviewe

Physical activity of 9 and 15 year old Icelandic children - Public health objectives and relations of physical activity to gender, age, anthropometry and area of living

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn Skoða/Opna(view/open)Objective: The main objective of the study was to assess to what degree nine and fifteen year old Icelandic children followed the national physical activity (PA) guidelines for children set forth by the Icelandic Public Health Institute, which recommend no less than 60 minutes of moderate-to-vigorous physical activity a day (MVPA). Material and methods: The study was conducted between September 2003 and January 2004 at eighteen randomly selected schools in the capital area of Reykjavik and towns and rural areas in the northeast. All nine years old (N=662) and fifteen years old (N=661) students were offered to participate. Half of the children were randomly chosen to partake in the PA part of the study where 176 nine-year-old and 162 fifteen-year-old children yielded usable data. We measured participants' height, weight and skinfold thickness and their PA by ActiGraph™ with respect to moderate-to-vigorous intensity (defined as counts >3400 cpm) and average volume. Results: Only 5% of 9-year-old and 9% of 15 year-old students followed the recommended PA guidelines of at least 60 minutes a day of MVPA. MVPA was positively associated with sex (being a boy) and age, but negatively associated with skinfold thickness. Those living in the capital area of Reykjavik rather than in smaller towns and rural areas were likelier to accrue more minutes of MVPA per day. Conclusion: The results highlight the importance of developing PA interventions targeting children of school age. It is important to research and evaluate different ways as to how these interventions should best be conducted. Key words: physical activity, children, body composition, accelerometers. Correspondence: Kristjan Thor Magnusson, [email protected]: Megintilgangur þessarar rannsóknar var að rannsaka í hvaða mæli 9 og 15 ára börn og unglingar á Íslandi uppfylltu nýlegar hreyfiráðleggingar Lýðheilsustöðvar. Efniviður og aðferðir: Rannsóknin var gerð á tímabilinu september 2003 til janúar 2004 í 18 skólum á höfuðborgarsvæðinu og í þéttbýliskjörnum og dreifbýli á Norðausturlandi sem valdir voru af handahófi. Öllum 9 ára (N=662) og 15 ára (N=661) nemendum skólanna var boðin þátttaka. Helmingur hvors árgangs var valinn, einnig af handahófi, í hreyfihluta rannsóknarinnar og skiluðu 176 9 ára og 162 15 ára nothæfum gögnum. Þátttakendur voru hæðar- og þyngdarmældir og þykkt húðfellinga mæld á fjórum stöðum. Ákefð og tímalengd hreyfingar var mæld með hröðunarmælum (ActiGraph™). Aðalútkomubreyta rannsóknarinnar, fjöldi mínúta yfir 3400 slög/mín á dag, miðaðist við neðri mörk hreyfingar af meðalerfiðri ákefð. Niðurstöður: Samkvæmt hröðunarmælum uppfylltu 5% úrtaks 9 ára barna hreyfiráðleggingar varðandi meðalerfiða og erfiða ákefð dag hvern, en tæp 9% 15 ára unglinga. Aukin hreyfing af þessari ákefð var frekar tengd strákum en stelpum, því að vera 15 ára frekar en 9 ára, að vera með minni þykkt húðfellinga en meiri, auk þess að búa á höfuðborgarsvæðinu frekar en í bæ eða strjálbýli á Norðausturlandi. Ályktanir: Niðurstöðurnar benda til þess að íhlutunar sé þörf til þess að auka meðalerfiða og erfiða hreyfingu barna á skólaaldri. Mikilvægt er að rannsaka hvaða leiðir séu færar í þeim efnum, meðal annars í samvinnu við heimili, skóla, íþróttahreyfinguna og sveitarfélög

Fatness but Not Fitness Relative to the Fat-Free Mass Is Related to C-Reactive Protein in 18 Year-Old Adolescents

Introduction The interaction between fatness, fitness, and C-reactive protein (CRP) in adolescents is not well characterized but may be important to prevent low grade inflammation. The purpose of this study was to assess the relationship between adiposity, different expressions of fitness, and CRP in late adolescence using direct measures of fitness and fatness. Methods Anthropometric measurements were taken on 245 eighteen-year-old participants (116 girls). Fasting CRP, glucose, and insulin were measured and homeostatic model assess- ment (HOMA) calculated. Body composition was estimated via dual energy X-ray absorpti- ometry. Fitness was assessed with maximal oxygen uptake (VO2max) during a treadmill test and also expressed relative to the fat-free mass (VO2maxFFM). Results Prevalence of overweight/obesity based on body mass index (BMI) was 20.7% and 25.6% among girls and boys, respectively (p = 0.407), but 42.5% and 58.1% when based on body fat percentage (%fat, p = 0.015). Higher proportion of boys (81.3%) than girls (54.5%) were highly fit (p0.05). VO2maxFFM was unrelated to CRP with (r = -0.07 to -0.11, p>0.05) or without (r = -0.10, p = 0.142) adjustment for adiposity. Additional adjustment for HOMA did not change any of the relationships, although the coefficients were attenuated. Conclusions Fatness has a greater association with CRP than fitness in late adolescence. However, VO2maxFFM, which is truly independent of adiposity, is unrelated to CRP, indicating that the effects of fitness might be mediated via the fatness component embedded in fitness expressed relative to body mass.Ministry of Education Sports Fund, University of Iceland Research FundPeer Reviewe

Prevalence of sport injuries, sport participation and drop out due to injury in young adults

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenInngangur:Þátttaka í íþróttum og líkamsrækt hefur farið vaxandi undanfarna áratugi og íþróttameiðsli því orðin algengari. Tilgangur rannsóknarinnar var að meta algengi íþróttameiðsla og brottfall vegna þeirra. Að auki var tilgangurinn að skoða hvort íþróttameiðsli hefðu tengsl við kyn, aldur, þrek, holdafar og iðkun sem var meiri en 6 klukkustundir á viku, miðað við 6 klukkustundir eða minna. Efniviður og aðferðir: Rannsóknin var þversniðsrannsókn á 457 ungmennum, 17 og 23 ára. Hæð, þyngd, líkamsfita, fitulaus mjúkvefjamassi, beinmassi og þrek (W/kg) voru mæld en spurningalisti notaður til þess að meta þátttöku í íþróttum og líkamsrækt, algengi íþróttameiðsla og brottfall. Niðurstöður: Fjögurhundruð og fjörutíu (96%) höfðu einhvern tímann stundað íþróttir með íþróttafélagi en 277 (63%) voru hætt, fleiri (p=0,058) í hópi stúlkna (67,6%) en drengja (58,8%). Þrjátíu og sjö (8,4%) hættu vegna íþróttameiðsla. Af þeim sem æfðu með íþróttafélagi síðastliðna 12 mánuði voru 51% sem þurftu læknisfræðilega aðstoð einu sinni eða oftar vegna íþróttameiðsla. Þeir sem æfðu meira en 6 klukkustundir á viku höfðu fimmfalt hærra líkindahlutfall þess að hafa leitað læknisfræðilegrar aðstoðar (OR = 5,30; 95% CI: 3,00-9,42) en þeir sem æfðu 6 klukkustundir eða minna. Ályktun: Íþróttameiðsli eru talsvert vandamál sem geta valdið brottfalli úr íþróttum. Áhættuþætti íþróttameiðsla þarf að rannsaka betur svo hægt verði að efla forvarnir og tryggja þjálfun sem byggir á gagnreyndum aðferðum.Introduction: Sport participation has increased during the past few decades, with accompanying rise in sport injuries. The purpose of this study was to assess the prevalence of sport injuries, and drop-out due to them along with possible risk factors (hours of sports participation, sex, age, aerobic fitness and body composition). Material and methods: A retrospective, cross-sectional design was used and the 457 participants were 17 and 23 years old. Height, weight, body fat, lean soft tissue, bone mass, and aerobic fitness (W/kg) were measured. Participation in sports and physical training, and the prevalence of sport injuries and drop-out were estimated using questionnaires. Results: Four hundred and forty participants (96%) had at some time point participated in organized sports, but 277 (63%) were no longer practicing, more commonly (p=0.058) among girls (67.6%) than boys (58.8%). Thirty-seven (8.4%) dropped-out due to sport injuries. Of those participating in organized sports for the past 12 months, 51% required medical assistance at least once because of sport injuries. Multiple regression analysis revealed 5-fold increased risk for requiring medical assistance among those practicing more than 6 hours per week compared to those who practiced 6 hours or less (OR = 5.30, 95% CI: 3.00 to 9.42). Conclusion: Youth sport injuries are a significant problem that can cause drop-out from participation in sport. More research is needed to better understand the impact of risk factors in order to promote prevention and ensure evidence-based training.Rannís, Lýðheilsusjóður, Embætti landlæknis, Íþróttasjóður Mennta- og menningarmálaráðuneytis, Rannsóknarsjóður HÍ, Hjartavernd, Landsbankinn, Síminn, Icepharma, Bílaleigu Akureyrar

Physical activity and its relation to metabolic and cardiovascular risk factors among three professions

Efst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinni nngangur: Þó jákvæð áhrif hreyfingar á áhættuþætti efnaskipta-, hjarta- og æðasjúkdóma séu vel þekkt, hafa þau lítið verið skoðuð hér á landi með hlutlægum mælingum. Tilgangur rannsóknarinnar var að athuga mun á hreyfingu og áhættuþáttum efnaskipta-, hjarta- og æðasjúkdóma þriggja starfsstétta: verkafólks, skrifstofufólks og bænda. Efniviður og aðferðir: Þátttakendur (73 karlar, 89 konur) komu úr Þingeyjarsýslu og undirgengust mælingar á hæð, þyngd, líkamsþyngdar - stuðli og líkamssamsetningu með húðfellingamælingum. Hreyfimælar voru notaðir til þess að mæla heildarhreyfingu auk þess tíma sem fólk varði í meðalerfiða hreyfingu. Blóðþrýstingur var tekinn og í fastandi blóðsýni var mælt heildarkólesteról, kólesteról í lágþéttnifituprótíni og háþéttni - fituprótíni, þríglýseríð, blóðsykur, insúlín og H o MA ( homeostatic model assessment ). n iðurstöður: Verkakarlar og karlbændur hreyfðu sig meira en skrifstofu - karlar (p<0,01) en enginn munur fannst meðal kvennanna. Kvenbændur vörðu hins vegar marktækt færri mínútum í meðalerfiða hreyfingu en hinar starfsstéttirnar (p<0,05). Lágt hlutfall (18,4%) þátttakenda náði að upp - fylla ráðleggingar Embættis landlæknis um daglega hreyfingu og enginn skrifstofukarlanna. Bændur höfðu lægri þríglýseríð (p=0,01) og blóðsykur (p<0,01) en hinar starfsstéttirnar og voru einnig með meiri fitulausan massa (p<0,03). Kólesteról í háþéttnifituprótíni var einnig hæst á meðal bænda, þá verkafólks en lægst meðal skrifstofufólks (p<0,02). Heildar - hreyfing hafði marktæk tengsl við mun fleiri áhættuþætti efnaskipta-, hjarta- og æðasjúkdóma heldur en tími sem varið var í meðalerfiða hreyfingu. Ályktun: Bændur hafa almennt ákjósanlegustu gildin fyrir áhættuþætti efnaskipta-, hjarta- og æðasjúkdóma í blóði og er hreyfing þeirra og meiri fitulaus massi líklegur hluti af skýringunni. Þó er hreyfing bændanna ekki mikil og einungis tæplega fimmtungur allra þátttakenda ná ráðlagðri daglegri hreyfingu. Heildarhreyfing virðist vera mikilvægari en tími í meðal - erfiðri hreyfingu fyrir jákvæð gildi áhættuþátta efnaskiptasjúkdóma200 LÆKNA blaðið 2015/101 RANNSÓKN Hlutfall þátttakenda með of hátt heildarkólesteról og LDL-kól - esteról var nokkuð hátt í þessari rannsókn. Hins vegar breytast þessir þættir minna við hreyfingu heldur en HDL-kólesteról eða þríglýseríðin. 30 Gildi HDL-kólesteróls voru hins vegar há hjá öllum hópum (og hlutfallslega fáir þátttakendur með lágt HDL-kólest - eról) sem eykur eðlilega heildarkólesterólið. Rannsóknir sem byggja á safngreiningum ( meta-analysis ) hafa sýnt að hreyfing geti lækkað slag- og hlébilsþrýsting um 3-3,8/2-2,4 mmHg 9 og meiri lækkanir hafa sést meðal aldraðra. 14 Okkar niður - stöður um lægri blóðþrýsting meðal karlbænda eru í samræmi við þessar rannsóknir. Kvennamegin voru verkakonur hins vegar almennt með hærri blóðþrýsting en hinar starfsstéttirnar. Verka - konurnar voru ekki frábrugðnar hinum starfsstéttunum varðandi hreyfingu og eru því ástæðurnar fyrir hækkuðum blóðþrýstingi hjá þeim óljósar. Niðurstöður þessarar rannsóknar sýndu að heildarhreyfing hafði marktæka neikvæða fylgni (jákvæða fyrir HDL-kólesteról) við alla áhættuþætti efnaskipta-, hjarta- og æðasjúkdóma sem mældir voru, nema heildarkólesteról, LDL-kólesteról og insúlín. Tími í meðalerfiðri hreyfingu tengdist hins vegar einungis BMI, mittismáli og hlutfalli líkamsfitu en ekki þeim áhættuþáttum sem mældir voru í blóði. Hugsanlega hefur heildarorkueyðslan fremur en ákefð áhrif á blóðþrýsting, -fitu og -sykursstjórn. Þessar niður - stöður benda í það minnsta til þess að heildarhreyfingin skipti meira máli fyrir fleiri áhættuþætti efnaskipta,- hjarta- og æðasjúk - dóma en erfiði hreyfingarinnar og eru í samræmi við fyrri rann - sóknir. 8,31 Hins vegar ber að halda því til haga að heildarhreyfing og erfiði hennar tengjast sterkum böndum enda hefur erfiði hreyf - ingarinnar áhrif á þá heildarhreyfingu sem viðkomandi nær. Helsti styrkleiki þessarar rannsóknar er sá að þetta er ein fyrsta íslenska rannsóknin sem fjallar um samband hreyfingar og áhættuþátta efnaskipta-, hjarta- og æðasjúkdóma hjá miðaldra Íslendingum. Að auki gera hreyfimælarnir okkur kleift að meta á hlutlægan hátt hversu hátt hlutfall þátttakenda uppfyllir ráð - leggingar um daglega hreyfingu. Veikleiki rannsóknarinnar felst fyrst og fremst í því að þátttakendur voru ekki mjög margir, fjöldi þeirra í hverri starfsstétt var mismunandi og kynjahlutfallið var aðeins frábrugðið á milli stétta. Einnig má benda á að gögnin eru 10 ára gömul en það rýrir hins vegar ekki mikilvægi þeirra. Ályktun Niðurstöðurnar benda almennt til þess að hjá þessum þremur starfsstéttum sem rannsakaðar voru hafi bændur ákjósanlegustu gildin fyrir áhættuþætti efnaskipta-, hjarta- og æðasjúkdóma í blóði og er hreyfing bændanna og meiri FFM líklegur hluti af skýringunni. Athygli vekur að enginn skrifstofukarl nær ráðlegg - ingum Embættis landlæknis um daglega hreyfingu og almennt hreyfa starfsstéttirnar sig lítið þar sem einungis tæplega fimmt - ungur þátttakenda nær áðurnefndum ráðleggingum. Heildar - hreyfing virðist hafa jákvæðari tengsl við fleiri áhættuþætti efna - skipta-, hjarta- og æðasjúkdóma en erfiði hreyfingarinnar og því mætti velta því upp hvort hreyfiráðleggingar ættu að byggjast á heildarhreyfingu fremur en erfiði hennar. Þakkir Fyrst ber að þakka öllum þátttakendum rannsóknarinnar. Einnig ber að þakka starfsfólki Heilsugæslunnar á Húsavík. Þórarni Sveinssyni prófessor er þakkað fyrir hjálp í úrvinnslu hreyfimæla - gagnanna. Að lokum á Eric Richter, annar leiðbeinenda Barkar, þakkir skildar vegna hjálpar hans við verkefnið. EN g LISH SUMMA r Y i ntroduction: The relation between objectively measured physical activity (PA) and metabolic and cardiovascular risk factors has not been studied in Iceland. This study aimed to investigate PA and metabolic and cardiovascular risk factors among three professions: manual laborers, office workers, and farmers. Material and methods: The participants (73 males, 89 females) under - went anthropometric measurements. Total PA and time spent in mod - erate-to-vigorous PA (MVPA) was assessed with activity monitors. Blood pressure was measured and fasting blood samples analyzed for total cholesterol, low- and high-density lipoprotein cholesterol, triglycerides, glucose, insulin and homeostatic model assessment. Results: Male manual laborers and farmers were more physically active than office workers (p<0.01), but no difference was found among females. Nevertheless, female farmers spent less time in MVPA than other professions (p<0.05). Low proportion (18.4%) of all participants and none of the male office workers met the guidelines of the Directo - rate of Health for daily PA. Farmers had lower levels of triglycerides (p=0.01) and glucose (p<0.01), and greater fat-free mass (p<0.03) than other professions. They also had the highest levels of high-density lipoprotein cholesterol, followed by manual laborers, and then office workers (p<0.02). Total PA was significantly related to a greater number of metabolic risk factors than time spent in MVPA. Conclusion: Farmers have the most favorable metabolic and cardiovas - cular risk factors in the blood and their PA and fat-free mass are a likely explanation. Regardless, their PA is low, and only one-fifth of all participants meet the guidelines for daily PA. Total PA appears more important for the metabolic and cardiovascular risk factors than time spent in MVPA

Different cardiorespiratory fitness expressions based on the maximal cycle ergometer test show no effect on the relation of cardiorespiratory fitness to the academic achievement of nine-year-olds

The relationship between cardiorespiratory fitness and academic achievement has been inconclusive. The results may depend on how cardiorespiratory fitness is expressed. The aim of this study is to explore the impact of different cardiorespiratory fitness expression methods, measured by the maximal cycle ergometer test, on the relationship between cardiorespiratory fitness and academic achievement. A cross-sectional study consisting of 303 Icelandic 4th grade students (163 girls) was conducted. Cardiorespiratory fitness was assessed using a graded maximal cycle ergometer test and scores of standardized tests in Icelandic and math obtained from the Icelandic National Examination Institute. Cardiorespiratory fitness was measured as absolute power output in watts in a maximal progressive cycle ergometer test. To adjust for different body sizes, the power output was scaled to body weight, body height, body surface area, and allometrically expressed body weight. In addition, linear regression scaling was also used to adjust for different body sizes. No significant relationship was found between any of the cardiorespiratory fitness expressions and academic achievement, using both univariate and multivariate linear regression analyses. The use of different methods to express cardiorespiratory fitness does not significantly affect the association with the academic achievement of fourth grade students.The Icelandic Centre for Research (RANNIS) funded this study, along with the Ministry of Education, Science and Culture, and The Icelandic Primary Health Care Research Fund. The authors have no conflicts of interest.Peer Reviewe

Different cardiorespiratory fitness expressions based on the maximal cycle ergometer test show no effect on the relation of cardiorespiratory fitness to the academic achievement of nine-year-olds

The relationship between cardiorespiratory fitness and academic achievement has been inconclusive. The results may depend on how cardiorespiratory fitness is expressed. The aim of this study is to explore the impact of different cardiorespiratory fitness expression methods, measured by the maximal cycle ergometer test, on the relationship between cardiorespiratory fitness and academic achievement. A cross-sectional study consisting of 303 Icelandic 4th grade students (163 girls) was conducted. Cardiorespiratory fitness was assessed using a graded maximal cycle ergometer test and scores of standardized tests in Icelandic and math obtained from the Icelandic National Examination Institute. Cardiorespiratory fitness was measured as absolute power output in watts in a maximal progressive cycle ergometer test. To adjust for different body sizes, the power output was scaled to body weight, body height, body surface area, and allometrically expressed body weight. In addition, linear regression scaling was also used to adjust for different body sizes. No significant relationship was found between any of the cardiorespiratory fitness expressions and academic achievement, using both univariate and multivariate linear regression analyses. The use of different methods to express cardiorespiratory fitness does not significantly affect the association with the academic achievement of fourth grade students.The Icelandic Centre for Research (RANNIS) funded this study, along with the Ministry of Education, Science and Culture, and The Icelandic Primary Health Care Research Fund. The authors have no conflicts of interest.Peer Reviewe

Organized leisure-time sport participation and academic achievement in preadolescents

Publisher's version (útgefin grein)Aims: The aims of this study were to study the correlation between lifestyle-related factors, such as organized leisure-time sport participation (OLSP), cardiorespiratory fitness, and adiposity, and academic achievement among preadolescents. Methods: A cross-sectional study involving 248 nine-year-old school children was carried out. OLSP was self-reported with parental assistance, categorized as ≤ 1× a week, 2–3× a week, and ≥ 4× times a week or more. Academic achievement was estimated with results from standardized test scores in Icelandic and math. Cardiorespiratory fitness was estimated using a maximal cycle ergometer test. The sum of four skinfolds was used to estimate adiposity. Results: Tests of between-subjects effect indicated that OLSP significantly correlated with achievement in math only (F(2,235) = 3.81, p = 0.024). Further analysis showed that the two less active groups had significantly lower scores in math compared to the most active group with OLSP ≥ 4× times a week or more (2–3× times a week, unstandardized coefficient (b) = –4.08, 95% confidence interval (CI) [–7.09, –1.07]; ≤ 1× a week, b = −3.84, 95% CI [–7.59, –0.08]), independent of sex, age, maturity level (age to/from peak height velocity), family structure, and parental education. Neither cardiorespiratory fitness nor adiposity significantly correlated with academic achievements. Conclusions: The study’s result indicates that frequent (four times per week or more often) sport participation is not harmful but may be beneficial to learning. However, further intervention-based study of this topic is needed to determine if this relationship is causal.The Icelandic Centre for Research (RANNIS) funded this, along with the Ministry of Education, Science and Culture, and The Icelandic Primary Health Care Research FundPeer Reviewe

Less physical activity and more varied and disrupted sleep is associated with a less favorable metabolic profile in adolescents

Publisher's version (útgefin grein)Background: Sleep and physical activity are modifiable behaviors that play an important role in preventing overweight, obesity, and metabolic health problems. Studies of the association between concurrent objective measures of sleep, physical activity, and metabolic risk factors among adolescents are limited. Objective: The aim of the study was to examine the association between metabolic risk factors and objectively measured school day physical activity and sleep duration, quality, onset, and variability in adolescents. Materials and methods: We measured one school week of free-living sleep and physical activity with wrist actigraphy in 252 adolescents (146 girls), aged 15.8±0.3 years. Metabolic risk factors included body mass index, waist circumference, total body and trunk fat percentage, resting blood pressure, and fasting glucose and insulin levels. Multiple linear regression adjusted for sex, parental education, and day length was used to assess associations between metabolic risk factors and sleep and activity parameters. Results: On average, participants went to bed at 00:22±0.88 hours and slept 6.2±0.7 hours/night, with 0.83±0.36 hours of awakenings/night. However, night-to-night variability in sleep duration was considerable (mean ± interquartile range) 0.75±0.55 hours) and bedtime (0.64±0.53 hours) respectively. Neither average sleep duration nor mean bedtime was associated with any metabolic risk factors. However, greater night-to-night variability in sleep duration and bedtime was associated with higher total body and trunk fat percentage, and less physical activity was associated with higher trunk fat percentage and insulin levels. Conclusion: Greater nightly variation in sleep duration and in bedtime and less physical activity were associated with a less favorable metabolic profile in adolescents. These findings support the idea that, along with an adequate amount of physical activity, a regular sleep schedule is important for the metabolic health of adolescents.VR had financial support by The Icelandic Centre for Research (RANNIS) The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer Reviewe

Longitudinal Change in Adolescent Bedtimes Measured by Self-Report and Actigraphy

Introduction: Sleep is often quantified using self-report or actigraphy. Self-report is practical and less technically challenging, but prone to bias. We sought to determine whether these methods have comparable sensitivity to measure longitudinal changes in adolescent bedtimes. Methods: We measured one week of free-living sleep with wrist actigraphy and usual bedtime on school nights and non-school nights with self-report questionnaire in 144 students at 15 y and 17 y. Results: Self-reported and actigraphy-measured bedtimes were correlated with one another at 15 y and 17 y (p 30 minutes, p  ±106 minutes). Mean inter-method discrepancy did not differ on school nights at 15 y and 17 y but was greater at 17 y on non-school nights (p = .002). Inter-method discrepancy at 15 y was not correlated to that at 17 y. Mean change in self-reported school night bedtime from 15 y to 17 y did not differ from that by actigraphy, but self-reported bedtime changed less on non-school nights (p = .002). Two-year changes in self-reported bedtime did not correlate with changes measured by actigraphy. Conclusions: Although methods were correlated, consistently earlier self-reported bedtime suggests report-bias. More varied non-school night bedtimes challenge the accuracy of self-report and actigraphy, reducing sensitivity to change. On school nights, the methods did not differ in group-level sensitivity to changes in bedtime. However, lack of correlation between bedtime changes by each method suggests sensitivity to individual-level change was different. Methodological differences in sensitivity to individual- and group-level change should be considered in longitudinal studies of adolescent sleep patterns.Peer Reviewe