Summary Bone mass achievement predicts later fracture risk. This population-based study describes bone mineral density levels (BMD) and associated factors in Norwegian adolescents. Compared with international reference ranges, BMD levels appear higher and physical activity levels are positively associated with BMD.Purpose Norway has one of the highest reported incidences of osteoporotic fractures. Maximization of peak bone mass may prevent later fractures. This population-based study compared BMD levels of Norwegian adolescents with international reference ranges and explored associated factors.Methods All first year upper secondary school students, aged 15-19 years in the Tromsø region were invited to the Fit Futures study in 2010-2011. Over 90% of the invited participants attended, 508 girls and 530 boys. BMD was measured at total hip, femoral neck and total body by dual x-ray absorptiometry.Lifestyle variables were collected by self-administered questionnaires and interviews. All analyses were performed sex stratified, using linear regression models.Results In girls mean BMD (SD) was 1.060 (0.124), 1.066 (0.123) and 1.142 (0.077) g/cm² at the total hip, femoral neck and total body respectively. In boys corresponding values were 1.116 (0.147), 1.103 (0.150) and 1.182 (0.097), with significant higher values than the Lunar pediatric reference at 16 years of age In girls, height and self-reported intensive physical activity of more than four hours a week and early sexual maturation were positively associated with BMD at both femoral sites (p<0.047). Among boys age, height, body mass index, physical activity and alcohol intake were positively (p<0.038), whereas early stages of sexual maturation and smoking was negatively (p<0.047) related to BMD.Conclusions Despite the heavy fracture burden, Norwegian adolescents´ BMD levels are higher than agematched Caucasians. Physical activity is associated with 1 SD increased BMD levels in those involved in competition or hard training.

ObjectivesLow levels of physical activity may have considerable negative effects on bone health in adolescence, and increasing screen time in place of sporting activity during growth is worrying. This study explored the associations between self-reported screen time at weekends and bone mineral density (BMD).DesignIn 2010/2011, 1038 (93%) of the region’s first-year upper-secondary school students (15–18 years) attended the Tromsø Study, Fit Futures 1 (FF1). A follow-up survey (FF2) took place in 2012/2013. BMD at total hip, femoral neck and total body was measured as g/cm² by dual X-ray absorptiometry (GE Lunar prodigy). Lifestyle variables were self-reported, including questions on hours per day spent in front of television/computer during weekends and hours spent on leisure time physical activities. Complete data sets for 388/312 girls and 359/231 boys at FF1/FF2, respectively, were used in analyses. Sex stratified multiple regression analyses were performed.ResultsMany adolescents balanced 2–4 h screen time with moderate or high physical activity levels. Screen time was positively related to body mass index (BMI) in boys (p=0.002), who spent more time in front of the computer than girls did (p<0.001). In boys, screen time was adversely associated with BMDFF1 at all sites, and these associations remained robust to adjustments for age, puberty, height, BMI, physical activity, vitamin D levels, smoking, alcohol, calcium and carbonated drink consumption (p<0.05). Screen time was also negatively associated with total hip BMDFF2 (p=0.031). In contrast, girls who spent 4–6 h in front of the computer had higher BMD than the reference (<2 h).ConclusionsIn Norwegian boys, time spent on screen-based sedentary activity was negatively associated with BMD levels; this relationship persisted 2 years later. Such negative associations were not present among girls. Whether this surprising result is explained by biological differences remains unclear.

The overall incidence of fractures in childhood in Northern Norway corresponds with other reports from Scandinavia, although the proportion of fractures in girls is higher than in other studies. Both sexes seem especially vulnerable at stages related to sexual maturation. Whether this reflects bone vulnerability or other changes related to puberty requires further investigation.

BackgroundOptimization of the genetic potential for bone accrual in early life may prevent future fractures. Possible modification factors include lifestyle factors such as nutrition and physical activity. Measured levels of bone mineral density (BMD) and bone mass content (BMC) are indicators of bone strength, and are correlated with fracture risk. This study explored the impact of self-reported physical activity frequencies and intensity on BMD and BMC in Norwegian adolescents.MethodsIn 2010–2011 school students in two North-Norwegian municipalities were invited to a health survey, the Fit Future study. 508 girls and 530 boys aged 15–18 years attended. BMD and BMC were measured by dual X-ray absorptiometry. Physical activity and other lifestyle-factors were reported by questionnaires and clinical interviews. Statistical analyses were performed sex stratified, using ANOVA for comparison of means and linear regression models adjusting for factors known to affect bone.ResultsApproximately 2/3 of girls and boys reported themselves as physically active outside school hours. Active participants had a significantly higher BMD and BMC at all sites (p < 0.001), except for BMC total body in girls, compared to inactive participants. In multiple linear regression analyses, increased physical activity measured as days a week, categorized into seldom, moderate and highly, was positively associated with BMD (g/cm2) at all sites in girls. Girls reporting themselves as highly active had BMD levels 0.093 g/cm2, 0.090 g/cm2 and 0.046 g/cm2 higher (p < 0.001) than their more seldom active peers at femoral neck, total hip and total body respectively. Corresponding values for boys were 0.125 g/cm2, 0.133 g/cm2 and 0.66 g/cm2. BMC measures showed similar trends at femoral neck and total hip.ConclusionsIncreased level of physical activity is associated with higher BMD and BMC levels in adolescents. For both sexes high activity frequency seems to be essential, whilst boys reporting quite hard intensity has an additional impact. The differential effects of physical activity on bone strength in adolescence have clinical implications, especially in preventive strategies.

Summary Background Fat and fat‐free masses and fat distribution are related to cardiometabolic risk. Objectives: to explore how birth weight, childhood body mass index (BMI) and BMI gain were related to adolescent body composition and central obesity. Methods In a population‐based longitudinal study, body composition was measured by dual‐energy X‐ray absorptiometry in 907 Norwegian adolescents (48% girls). Associations between birth weight, BMI categories, and BMI gain were evaluated by fitting linear mixed models and conditional growth models with fat mass index (FMI, kg/m2), fat‐free mass index (FFMI, kg/m2) standard deviation scores (SDS), and central obesity at 15 to 20 years, as well as change in FMI SDS and FFMI SDS between ages 15 to 17 and 18 to 20 as outcomes. Results Birth weight was associated with FFMI in adolescence. Greater BMI gain in childhood, conditioned on prior body size, was associated with higher FMI, FFMI, and central overweight/obesity with the strongest associations seen at age 6 to 16.5 years: FMI SDS: β = 0.67, 95% CI (0.63‐0.71), FFMI SDS: 0.46 (0.39, 0.52), in girls, FMI SDS: 0.80 (0.75, 0.86), FFMI SDS: 0.49 (0.43, 0.55), in boys. Conclusions Compared with birth and early childhood, high BMI and greater BMI gain at later ages are strong predictors of higher fat mass and central overweight/obesity at 15 to 20 years of age.

RA patients showed immediate positive effects with regard to disease activity, physical function, and symptoms during a 4-week rehabilitation programme. The effects on disease activity and symptoms were larger and better maintained at least 3 months after rehabilitation in a warm rather than in a cold climate.

Patients with ankylosing spondylitis benefit from a 4-week rehabilitation programme in Norway, but even more so from a similar programme in a Mediterranean setting.

SummaryAreal bone mineral density (aBMD) predicts future fracture risk. This study explores the development of aBMD and associated factors in Norwegian adolescents. Our results indicate a high degree of tracking of aBMD levels in adolescence. Anthropometric measures and lifestyle factors were associated with deviation from tracking.PurposeNorway has one of the highest reported incidences of hip fractures. Maximization of peak bone mass may reduce future fracture risk. The main aims of this study were to describe changes in bone mineral levels over 2 years in Norwegian adolescents aged 15–17 years at baseline, to examine the degree of tracking of aBMD during this period, and to identify baseline predictors associated with positive deviation from tracking.MethodsIn 2010–2011, all first year upper secondary school students in Tromsø were invited to the Fit Futures study and 1038 adolescents (93%) attended. We measured femoral neck (FN), total hip (TH), and total body (TB) aBMD as g/cm2 by DXA. Two years later, in 2012–2013, we invited all participants to a follow-up survey, providing 688 repeated measures of aBMD.ResultsaBMD increased significantly (p < 0.05) at all skeletal sites in both sexes. Mean annual percentage increase for FN, TH, and TB was 0.3, 0.5, and 0.8 in girls and 1.5, 1.0, and 2.0 in boys, respectively (p < 0.05). There was a high degree of tracking of aBMD levels over 2 years. In girls, several lifestyle factors predicted a positive deviation from tracking, whereas anthropometric measures appeared influential in boys. Baseline z-score was associated with lower odds of upwards drift in both sexes.ConclusionsOur results support previous findings on aBMD development in adolescence and indicate strong tracking over 2 years of follow-up. Baseline anthropometry and lifestyle factors appeared to alter tracking, but not consistently across sex and skeletal sites.