Vitamin D status of Icelandic children and its influence on bone accrual.

The importance of vitamin D for children's bone health has been well established, but the effects of less severe deficiency are not fully known. The main objective of this study was to assess the vitamin D status of Icelandic children at the age of 7, and again at 9 years of age, and the association of vitamin D status with bone mineral content and bone accrual over 2 years. We invited 321 children to participate in this study, and 267 (83 %) took part; 211 (79 %) underwent a DXA scan and 164 were again scanned 2 years later; 159 (60 %) vitamin D samples were measured and 119 (75 %) were measured again 2 years later. At age 7, 65 % of the children had vitamin D concentrations <50 nmol/l, and at age 9 this figure was 60 %. At age 7, 43 % of the children had insufficient amounts of vitamin D (37.5-50 nmol/l), and 22 % had a vitamin D deficiency (<37.5 nmol/l). In linear regression analysis, no association was found between vitamin D and bone mineral content. Furthermore, there was no significant difference in bone accrual over 2 years for the children with insufficient or deficient vitamin D at both ages, compared to those having more than 50 nmol/l at both time points. More than 60 % of Icelandic children have inadequate concentrations of vitamin D in serum repeatedly over a 2-year interval. However, vitamin D in the range did not have a significant effect on bone mineral content or accrual at ages 7 and 9.

The association of cardiorespiratory fitness to health independent of adiposity depends upon its expression.

BACKGROUND: The strong relation between cardiorespiratory fitness (CRF) and adiposity renders their independent associations to metabolic risk factors difficult to ascertain. AIM: To determine the associations of CRF and CRF relative to fat-free mass (CRFFFM) to total cholesterol, high-density lipoprotein, low-density lipoprotein, triglycerides, glucose, insulin and homeostasis model assessment (HOMA) and distinguish these relations from the association to adiposity. SUBJECTS AND METHODS: Anthropometrics, body fat percentage (%Fat) and fat-free mass (from dual energy X-ray absorptiometry) were measured in 127 (66 females) 17 and 23 year-olds. CRF from a maximal workload on a graded bicycle test and fasting blood samples were obtained. RESULTS: CRF was significantly related to total cholesterol, triglycerides, insulin and HOMA (r = -0.24 to -0.49, p < 0.03), as were all adiposity measures (r = 0.21-0.53, p < 0.05). Correcting CRF for %Fat rendered the relation to metabolic risk factors non-significant (p = 0.09-0.21); however, CRFFFM was significantly related to the metabolic risk factors (r = -0.25 to -0.32, p < 0.02). CONCLUSIONS: CRFFFM, where adiposity has been removed, is associated with metabolic risk factors, whereas CRF, which is related to adiposity, is not after adjustment for fatness. Previously, independent effects of CRF on health may have been underestimated by using an expression of CRF strongly related to the adiposity measures.

Insufficient autumn vitamin D intake and low vitamin D status in 7-year-old Icelandic children.

OBJECTIVE: The aim was to investigate autumn vitamin D intake and status in 7-year-old Icelanders, fitting BMI and cardiorespiratory fitness as predictors. DESIGN: Three-day food records and fasting blood samples were collected evenly from September to November, and cardiorespiratory fitness was measured with an ergometer bike. Food and nutrient intakes were calculated, and serum 25-hydroxyvitamin D (s-25(OH)D) and serum parathyroid hormone were analysed. Suboptimal vitamin D status was defined s-25(OH)D <50 nmol/l, and deficient status as s-25(OH)D <25 nmol/l. SETTING: School-based study in Reykjavik, Iceland in 2006. SUBJECTS: Of the 7-year-olds studied (n 265), 165 returned valid intake information (62 %), 158 gave blood samples (60 %) and 120 gave both (45 %). RESULTS: Recommended vitamin D intake (10 µg/d) was reached by 22·4 % of the children and 65·2 % had s-25(OH)D <50 nmol/l. Median s-25(OH)D was higher for children taking vitamin D supplements (49·2 nmol/l v. 43·2 nmol/l, respectively; P < 0·0 0 1). Median s-25(OH)D was lower in November (36·7 nmol/l) than in September (59·9 nmol/l; P < 0·001). The regression model showed that week of autumn accounted for 18·9 % of the variance in s-25(OH)D (P < 0·001), vitamin D intake 5·2 % (P < 0·004) and cardiorespiratory fitness 4·6 % (P < 0·005). CONCLUSIONS: A minority of children followed the vitamin D recommendations and 65 % had suboptimal vitamin D status during the autumn. Week of autumn was more strongly associated with vitamin D status than diet or cardiorespiratory fitness, which associated with vitamin D status to a similar extent. These results demonstrate the importance of sunlight exposure during summer to prevent suboptimal vitamin D status in young schoolchildren during autumn in northern countries. An increased effort is needed for enabling adherence to the vitamin D recommendations and increasing outdoor activities for sunlight exposure.

Limited effects of a 2-year school-based physical activity intervention on body composition and cardiorespiratory fitness in 7-year-old children.

The aim of this study was to assess the effects of a 2-year cluster-randomized physical activity and dietary intervention program among 7-year-old (at baseline) elementary school participants on body composition and objectively measured cardiorespiratory fitness. Three pairs of schools were selected and matched, then randomly selected as either an intervention (n = 151) or control school (n = 170). None of the effect sizes of body composition were statistically significant. Children in the intervention group increased their fitness by an average of 0.37 z score units more than the controls (95% CI:-0.27 to 1.01, P = 0.18), representing an improvement of 0.286 W/kg. Boys had higher fitness (mean(diff) = 0.35 z scores, 95% CI: 0.13-0.58, P = 0.001) than girls, independent of study group, fitness z score at baseline and body mass index. Post hoc analysis showed that the intervention school with the highest fitness z score change was significantly different from two of the lowest control schools (mean(diff) = 0.83 z scores, 95% CI: 0.44-1.21, P < 0.0001 and mean(diff) = 0.70 z scores, 95% CI: 0.29-1.10, P = 0.01), but it was also significantly different from the lowest intervention school (mean(diff) = 0.59 z scores, 95% CI: 0.19-0.99, P = 0.05). The results of this intervention are inconclusive as regards to the effects on fitness, but the intervention did not have any statistically significant effect on body composition.

Assessment of a two-year school-based physical activity intervention among 7-9-year-old children.

BACKGROUND: Physical activity (PA) in children has declined in recent decades, highlighting the need for effective intervention programs for school-aged children. The main objective of this study was to assess to what extent PA during and after school hours changed among children who received a progressive two-year long intervention vs. that of children who only received general curriculum-based PA. METHODS: A cluster randomized intervention study was conducted and six elementary schools randomly assigned to serve as control- or intervention schools. All children attending second grade (mean age = 7.4 years - born in 1999) were invited to participate in the fall of 2006 (N = 320, 82% participated), again in 2007 (midpoint) and 2008 (end of intervention). The intervention consisted of multi-component PA-intervention during school hours and was conducted by teachers at each intervention school. PA was assessed by means of accelerometers and subjectively at the intervention schools via teachers' PA log-books. RESULTS: There was no difference in PA intensity (minutes of moderate-to-vigorous physical activity - min of MVPA) between the two study groups at baseline, but children in the intervention schools were more physically active at moderate-to-vigorous intensity compared to those in control schools after one year of intervention (mean difference of MVPAlog-minutes: 0.61, 95%CI: 0.02, 1.20, p = 0.04). Moreover, the model for minutes of MVPA during school hours, showed a significant three-way interaction between time at mid-point, group and gender (mean difference of MVPAlog-minutes: 1.06, 95%CI: 0.15, 1.97, p = .02), indicating a significantly greater increase among the boys in the intervention schools compared to girls. No difference in PA was detected between the study groups at the end of the study period after two years of intervention. CONCLUSIONS: The results suggest that the objective of increasing PA at school was met after one year of intervention, and it was more pronounced among boys. The lack of increase at the end of the study period suggested that any increase in PA during school may highly depend on both motivation and training of general teachers. Boys may respond better to PA interventions such as the one described in this study.

[Physical activity and its relation to metabolic and cardiovascular risk factors among three professions]. / Hreyfing þriggja starfsstétta og tengsl hennar við ahættuthætti efnaskiptasjúkdóma og hjarta- og æðasjúkdóma.

INTRODUCTION: 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) underwent anthropometric measurements. Total PA and time spent in moderate-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%lt;0.05). Low proportion (18.4%) of all participants and none of the male office workers met the guidelines of the Directorate 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 cardiovascular 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.

[Prevalence of sport injuries, sport participation and drop out due to injury in young adults]. / Algengi íþróttameiðsla, íþróttaþátttaka og brottfall vegna meiðsla hjá 17 og 23 ára ungmennum.

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.

[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]. / Líkamshreyfing 9 og 15 ára íslenskra barna í ljósi lýðheilsumarkmiða.

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.