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

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.

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

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.

Less screen time and more physical activity is associated with more stable sleep patterns among Icelandic adolescents.

OBJECTIVES: Emerging evidence suggests that inconsistent sleep may affect physical and psychological health. Thus, it is important to identify modifiable determinants of sleep variability. Screen time and physical activity are both thought to affect sleep, but studies of their relationship to sleep variability using objective measures are lacking. We examined cross-sectional associations between these variables in mid-teen adolescents using objectively measured sleep and activity. METHODS: Wrist-worn accelerometers were used to measure one week of sleep and activity in 315 tenth grade students (mean age 15.8y) from six Reykjavík compulsory schools. Participants reported their daily hours of screen time. Regression analysis was used to explore associations of screen time and physical activity with variability in duration, quality, and timing of sleep, adjusting for DXA-measured body fat percentage, parental education, and physical activity or screen time. RESULTS: Screen time, especially game playing, was associated with variability in duration, timing, and quality of sleep, most strongly with variation in bedtime. Physical activity was inversely associated with variability in duration, timing, and quality of sleep, most strongly with variation in the number of awakenings. Boys had less stable sleep patterns and higher screen time than girls, and sex-specific associations of screen time with sleep variability parameters were significant for boys only. CONCLUSIONS: Less screen time and more physical activity were independently associated with less sleep variability among mid-teen adolescents. Our results indicate that encouraging youngsters toward an active lifestyle with limited screen use may be important to achieve more consistent sleep.

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 < .001), but reported bedtime was consistently earlier (>30 minutes, p < .001) and with wide inter-method confidence intervals (> ±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.

Less screen time and more frequent vigorous physical activity is associated with lower risk of reporting negative mental health symptoms among Icelandic adolescents.

OBJECTIVE: Few studies have explored the potential interrelated associations of screen time and physical activity with mental health in youth, particularly using objective methods. We examined cross-sectional associations of these variables among Icelandic adolescents, using objective and subjective measurements of physical activity. METHODS: Data were collected in the spring of 2015 from 315 tenth grade students (mean age 15.8 years) in six elementary schools in metropolitan Reykjavík, Iceland. Participants reported, via questionnaire, on demographics, weekly frequency of vigorous physical activity, daily hours of screen time and mental health status (symptoms of depression, anxiety and somatic complaints, self-esteem and life satisfaction). Total physical activity was measured over one week with wrist-worn accelerometers. Body composition was determined by DXA-scanning. Poisson regression analysis was used to explore independent and interactive associations of screen time and physical activity with mental health variables, adjusting for gender, body fat percentage and maternal education. RESULTS: Less screen time (below the group median of 5.3 h/day) and more frequent vigorous physical activity (≥4x/week) were each associated with reporting fewer symptoms of depression, anxiety, low self-esteem, and life dissatisfaction. No significant associations were observed between objectively measured physical activity and mental health outcomes. Interactive regression analysis showed that the group reporting both less screen time and more frequent vigorous physical activity had the lowest risk of reporting symptoms of depression, anxiety, low self-esteem, and life dissatisfaction. CONCLUSIONS: Reports of less screen time and more frequent vigorous physical activity were associated with lower risk of reporting mental health problems among Icelandic adolescents. Those who reported a combination of engaging in less screen time and more frequent vigorous physical activity had the lowest risk, suggesting a synergistic relationship between the two behaviors on mental health outcomes. Our results support guiding youth towards more active and less sedentary/screen-based lifestyle.

[Physical activity and sleep in Icelandic adolescents].

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.

Sleep deficiency on school days in Icelandic youth, as assessed by wrist accelerometry.

AIMS: The purpose of this study was to objectively measure, with wrist-worn actigraphy, free-living sleeping patterns in Icelandic adolescents, and to compare sleep duration, sleep quality and clock times between school days (SchD) and non-school days (NSchD) and the association between sleep and body mass index (BMI). METHODS: A cross-sectional study on 15.9-year-old (±0.3) adolescents from six schools in Reykjavík, Iceland, took place in the spring of 2015. Free-living sleep was measured on 301 subjects (122 boys and 179 girls) over seven days using wrist-worn actigraphy accelerometers. Total rest time (TRT), total sleep time (TST), sleep quality markers, and clock times for sleep were quantified and compared between SchD and NSchD and between the sexes, using paired and group t-tests as appropriate. Linear regression was used to assess the association between sleep parameters and BMI. RESULTS: On SchD, TST was 6.2 ± 0.7 h, with sleep efficiency (SLE) of 87.9 ± 4.4% for the group. On NSchD, TST increased to 7.3 ± 1.1 h (p < 0.001), although SLE decreased to 87.4 ± 4.7% (p < 0.05). On SchD and NSchD, 67% and 93% had bed times after midnight, respectively, and on SchD 10.7% met sleep recommendations (8 h/night). There was no association between BMI and average sleep parameters. CONCLUSION: The majority of Icelandic adolescents did not get the recommended number of hours of sleep, especially on SchD. While TST increased on NSchD, many participants still did not achieve the recommendations. These findings provide information on the sleep patterns of adolescents and may serve as reference for development of policies and interventions to promote better sleep practices.

Physical Activity from Early Adulthood and Risk of Prostate Cancer: A 24-Year Follow-Up Study among Icelandic Men.

Physical activity in adult life may reduce prostate cancer risk. Data are scarce on the role of activity during early adulthood, as well as combined recreational and occupational physical activity on prostate cancer risk and mortality. We undertook a prospective study of 8,221 Icelandic men (born 1907 to 1935) in the population-based Reykjavik Study. At enrollment, between 1967 and 1987, the men provided information on regular recreational physical activity since the age of 20 years as well as current occupational activity. Through linkage to nationwide cancer and mortality registers, the men were followed for prostate cancer diagnosis and mortality through 2009. We used Cox models to calculate the relative risk of prostate cancer by level of physical activity. During a mean follow-up of 24.8 years, 1,052 men were diagnosed with prostate cancer, of whom 349 had advanced disease (stage 3+ or prostate cancer death). Neither recreational nor occupational physical activity was, independently or combined, associated with overall or localized prostate cancer. Compared with physically inactive men, we observed a nonsignificant lower risk of advanced prostate cancer [HR, 0.67; 95% confidence interval (CI), 0.42-1.07] among men reporting both recreational and occupational physical activities (P value for interaction = 0.03). Awaiting confirmation in larger studies with detailed assessment of physical activity, our data suggest that extensive physical activity beginning in early adulthood may reduce the risk of advanced prostate cancer.

Barley as a green factory for the production of functional Flt3 ligand.

Biologically active recombinant human Flt3 ligand was expressed and isolated from transgenic barley seeds. Its expression is controlled by a tissue specific promoter that confines accumulation of the recombinant protein to the endosperm tissue of the seed. The recombinant Flt3 ligand variant expressed in the seeds contains an HQ-tag for affinity purification on immobilized metal ion affinity chromatography (IMAC) resin. The tagged protein was purified from seed extracts to near homogeneity using sequential chromatography on IMAC affinity resin and cation exchange resin. We also show that the recombinant Flt3 ligand protein undergoes posttranslational modifications: it is a glycoprotein containing alpha-1,3-fucose and alpha-1,2-xylose. The HQ-tagged Flt3 ligand variant exhibits comparable biological activity to commercial Flt3 ligand. This is the first report showing expression and accumulation of recombinant human growth factor in barley seeds with a yield of active protein similar to a bacterial expression system. The present results demonstrate that plant molecular farming is a viable approach for the bioproduction of human-derived growth factors.