Physical activity and sleep in Icelandic adolescents

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked FilesInngangur: Hreyfing og svefn eru mikilvægir áhrifaþættir heilsufars. Alþjóðlegar ráðleggingar mæla með því að börn og unglingar hreyfi sig að lágmarki 60 mínútur daglega af miðlungs eða mikilli ákefð og sofi í 8 til 10 klukkustundir á sólarhring. Tengsl hreyfingar og svefns meðal ungmenna eru ekki vel þekkt. Markmið rannsóknarinnar voru að meta: a) hversu hátt hlutfall 16 ára reykvískra ungmenna uppfyllir viðmið um hreyfingu og svefn, b) hvort tengsl séu milli hreyfingar og svefns og c) kynjamun á hreyfingu og svefni. Efniviður og aðferðir: Alls var 411 nemendum 10. bekkjar 6 grunnskóla í Reykjavík boðin þátttaka í rannsókninni vorið 2015. Gild gögn fengust frá 106 drengjum og 160 stúlkum. Hlutlægar og huglægar mælingar á hreyfingu og svefni voru gerðar með hröðunarmælum og spurningalistum. Niðurstöður: Um helmingur þátttakenda náði viðmiðum um hreyfingu samkvæmt niðurstöðum spurningalista. Þrátt fyrir að 51,9% teldu sig sofa nógu mikið náðu þó einungis 22,9% viðmiðum um ráðlagða svefnlengd samkvæmt hröðunarmælum. Engin tengsl fundust milli svefnlengdar og hreyfingar samkvæmt spurningalistum. Stúlkur hreyfðu sig marktækt meira en drengir á frídögum (p<0,01) samkvæmt hröðunarmælum en ekki var marktækur munur á meðaltali hreyfingar stúlkna og drengja yfir vikuna. Hvorki var marktækur kynjamunur á svefnlengd mældri með hröðunarmælum né spurningalista. Ályktun: Lífsstíll íslenskra ungmenna virðist ekki endurspegla viðmið opinberra aðila um daglega hreyfingu og svefn. Einungis 22,9% náðu viðmiðum um ráðlagðan svefntíma, og 11,3% uppfylltu bæði viðmið um hreyfingu og svefn.Introduction: Physical activity and sleep are major determinants of overall health. According to international recommendations, adolescents should engage in moderate to vigorous physical activity for at least 60 min each day and sleep eight to ten hours each night. The association between physical activity and sleep in adolescents is not well known. The aim of the study was to estimate a) the proportion of Icelandic adolescents that achieves recommended physical activity and sleep, b) if there is an association between physical activity and sleep patterns, and c) sex differences in physical activity and sleep. Material and methods: A total of 411 adolescents from the 10th grade in six schools in Reykjavik were invited to participate in a cross-sectional study in the spring of 2015. Valid data was obtained from 106 boys and 160 girls. Objective and subjective measures of physical activity and sleep were made by wrist-worn accelerometers and a questionnaire. Results: Almost half of the participants fulfilled the physical activity recommendations according to the questionnaire. Although 51.1% reported usually getting enough sleep, only 22.9% achieved the recommended sleep length according to objective assessment. No associations were observed between sleep and subjective physical activity. Girls had higher accelerometer-measured physical activity than boys on non-school days (p<0.01), but weekly averages were not different between sexes. Girls and boys did not differ in subjective or objective measures of sleep. Conclusion: The behavior of Icelandic adolescents does not reflect recommended amount of sleep and physical activity. Only 22.9% obtained the recommended sleep length and just 11.3% fulfilled recommendations of both sleep and physical activity.Ranní

Screen Time and Body Image in Icelandic Adolescents : Sex-Specific Cross-Sectional and Longitudinal Associations

Funding Information: Funding: This research was funded by The University of Iceland Research Fund, grant number. HI16120043, and the Icelandic Centre for research (RANNIS), grant number 152509-051. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Studies of adolescent body image and screen use are mostly limited to girls, and longitudinal data are scarce. We examined cross-sectional and longitudinal associations between these variables in mid-adolescent boys and girls. Data was collected when participants were at age 15 and 17, by questionnaire and objective measurements (n = 152 had complete data). Sex-specific linear regression was used to explore cross-sectional and longitudinal associations of self-reported screen use (total use, and time spent in gaming, TV/DVD/internet-based watching and internet use for communication) and body image, adjusting for vigorous physical activity, symptoms of depression, and body composition. Screen time was negatively associated with body image at both time points, although more strongly at age 15, and for girls only. Gaming and TV/DVD/internet watching was more strongly associated with body image than internet use for communication. Girls with above median screen time at both ages had 14% lower body image score at age 17 than girls with below median screen time at both time points. Our results suggest that screen use is likely to play a role in the development of body dissatisfaction among adolescent females. Limiting screen time may, therefore, help to mitigate body dissatisfaction in adolescent girls.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

Comparison of summer and winter objectively measured physical activity and sedentary behavior in older adults: Age, gene/environment susceptibility Reykjavik study

In Iceland, there is a large variation in daylight between summer and winter. The aim of the study was to identify how this large variation influences physical activity (PA) and sedentary behavior (SB). Free living PA was measured by a waist-worn accelerometer for one week during waking hours in 138 community-dwelling older adults (61.1% women, 80.3 ± 4.9 years) during summer and winter months. In general, SB occupied about 75% of the registered wear-time and was highly correlated with age (β = 0.36). Although the differences were small, more time was spent during the summer in all PA categories, except for the moderate-to-vigorous PA (MVPA), and SB was reduced. More lifestyle PA (LSPA) was accumulated in ≥5-min bouts during summer than winter, especially among highly active participants. This information could be important for policy makers and health professionals working with older adults. Accounting for seasonal difference is necessary in analyzing SB and PA data. View Full-TextThis study has been funded by NIA contract N01-AG-1-2100, the NIA Intramural Research Program, Hjartavernd (the Icelandic Heart Association), and the Althingi (the Icelandic Parliament). This work was also supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0940903 and by the National Institutes of Health Intramural Research Program, grant number: Z01 DK071013 and Z01 DK071014 to Robert J. Brychta and Kong Y. Chen. The researchers are indebted to the participants for their willingness to participate in the study.Peer Reviewe

Association of Sedentary Time with Mortality Independent of Moderate to Vigorous Physical Activity

BACKGROUND: Sedentary behavior has emerged as a novel health risk factor independent of moderate to vigorous physical activity (MVPA). Previous studies have shown self-reported sedentary time to be associated with mortality; however, no studies have investigated the effect of objectively measured sedentary time on mortality independent of MVPA. The objective our study was to examine the association between objectively measured sedentary time and all-cause mortality. METHODS: 7-day accelerometry data of 1906 participants aged 50 and over from the U.S. nationally representative National Health and Nutrition Examination Survey (NHANES) 2003-2004 were analyzed. All-cause mortality was assessed from the date of examination through December 31, 2006. RESULTS: Over an average follow-up of 2.8 years, there were 145 deaths reported. In a model adjusted for sociodemographic factors, lifestyle factors, multiple morbidities, mobility limitation, and MVPA, participants in third quartile (hazard ratio (HR):4.05; 95%CI:1.55-10.60) and fourth quartile (HR:5.94; 95%CI: 2.49-14.15) of having higher percent sedentary time had a significantly increased risk of death compared to those in the lowest quartile. CONCLUSIONS: Our study suggests that sedentary behavior is a risk factor for mortality independent of MVPA. Further investigation, including studies with longer follow-up, is needed to address the health consequences of sedentary behavior

Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity

© 2015 Elsevier Inc. Dietary carbohydrate restriction has been purported to cause endocrine adaptations that promote body fat loss more than dietary fat restriction. We selectively restricted dietary carbohydrate versus fat for 6 days following a 5-day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Subjects received both isocaloric diets in random order during each of two inpatient stays. Body fat loss was calculated as the difference between daily fat intake and net fat oxidation measured while residing in a metabolic chamber. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002). Mathematical model simulations agreed with these data, but predicted that the body acts to minimize body fat differences with prolonged isocaloric diets varying in carbohydrate and fat

Acute mountain sickness.

Acute mountain sickness (AMS) is a clinical syndrome occurring in otherwise healthy normal individuals who ascend rapidly to high altitude. Symptoms develop over a period ofa few hours or days. The usual symptoms include headache, anorexia, nausea, vomiting, lethargy, unsteadiness of gait, undue dyspnoea on moderate exertion and interrupted sleep. AMS is unrelated to physical fitness, sex or age except that young children over two years of age are unduly susceptible. One of the striking features ofAMS is the wide variation in individual susceptibility which is to some extent consistent. Some subjects never experience symptoms at any altitude while others have repeated attacks on ascending to quite modest altitudes. Rapid ascent to altitudes of 2500 to 3000m will produce symptoms in some subjects while after ascent over 23 days to 5000m most subjects will be affected, some to a marked degree. In general, the more rapid the ascent, the higher the altitude reached and the greater the physical exertion involved, the more severe AMS will be. Ifthe subjects stay at the altitude reached there is a tendency for acclimatization to occur and symptoms to remit over 1-7 days

Comparing ActiGraph equations for estimating energy expenditure in older adults

Accurate estimation of energy expenditure (EE) from accelerometer outputs remains a challenge in older adults. The aim of this study was to validate different ActiGraph (AG) equations for predicting EE in older adults. Forty older adults (age\ua0=\ua077.4\ua0±\ua08.1\ua0yrs) completed a set of household/gardening activities in their residence, while wearing an AG at the hip (GT3X+) and a portable calorimeter (MetaMax 3B - criterion). Predicted EEs from AG were calculated using five equations (Freedson, refined Crouter, Sasaki and Santos-Lozano (vertical-axis, vectormagnitude)). Accuracy of equations was assessed using root-mean-square error (RMSE) and mean bias. The Sasaki equation showed the lowest RMSE for all activities (0.47 METs) and across physical activity intensities (PAIs) (range 0.18-0.48 METs). The Freedson and Santos-Lozano equations tended to overestimate EE for sedentary activities (range: 0.48 to 0.97 METs), while EEs for moderate-to-vigorous activities (MVPA) were underestimated (range: -1.02 to -0.64 METs). The refined Crouter and Sasaki equations showed no systematic bias, but they respectively overestimated and underestimated EE across PAIs. In conclusion, none of the equations was completely accurate for predicting EE across the range of PAIs. However, the refined Crouter and Sasaki equations showed better overall accuracy and precision when compared with the other methods