Stefan A. Jackowski

Effect of maturational timing on bone mineral content accrual from childhood to adulthood: evidence from 15 years of longitudinal data.

A higher bone mass may reduce the risk of osteoporosis and fractures. The role of maturational timing for optimizing bone mass is controversial due to the lack of prospective evidence from childhood to adulthood. The purpose of this study was to examine the long term relationship between the onset of maturation and bone mineral content (BMC) development. Two hundred thirty individuals (109 males and 121 females) from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were classified into maturity groups based on age of peak height velocity. BMC was serially assessed using dual energy X-ray absorptiometry (DXA). Multilevel models were constructed to examine the independent development of BMC by maturity group. When age, body size, and body composition were controlled early maturing females had on average 3-4%, 62.2 ± 16.8g (p<0.05), more total body BMC than their average maturing peers by 20 years of age. In contrast, late maturing females had 50.7 ± 15.6g less total body BMC. No maturational effects were found at either the lumbar spine or femoral neck (p>0.05) in females. There were no significant differences in BMC development at any site among male maturational groups (p>0.05). In this group of healthy participants, there appears to be a sex-dependent effect on the relationship between maturational timing and total body BMC development. Early, average and late maturing males displayed similar BMC development. Late maturing females had compromised BMC accrual compared to their early and average maturing peers.

Oxidation levels of North American over-the-counter n -3 (omega-3) supplements and the influence of supplement formulation and delivery form on evaluating oxidative safety

The aim of the present study was to evaluate the oxidation status of North American n-3 (omega-3) PUFA nutritional supplements commercially available in Canada and evaluate the influence of product formulation and delivery form on oxidative safety. A total of 171 North American over-the-counter n-3 PUFA nutritional supplements were analysed for oxidation safety. Primary and secondary oxidation and total oxidation (TOTOX) were determined using the American Oil Chemists’ Society (AOCS) procedures. Comparisons between supplements’ final forms, oil source and n-3 PUFA concentration quartiles, as measures of product formulations and delivery forms, were compared using ANOVA. Of the products successfully tested, 50 % exceeded the voluntary recommended levels for markers of oxidation. Another 18 % of products were approaching the limits with 1–3 years before expiration. Encapsulated products without flavour additives had significantly lower secondary and TOTOX levels than bulk oils and flavoured products (P < 0·05). Childrens products had significantly higher primary, secondary and TOTOX levels compared with all other products (P < 0·05). Markers of oxidation did not differ between oil sources (P > 0·05), with the exception of krill oil products having higher secondary oxidation levels than plant-based products (P > 0·05). Markers of oxidation did not differ between n-3 PUFA supplement concentration quartiles. Consumers may be at risk of exposure to higher levels of oxidative products. New regulatory mandates need to be introduced to ensure that all n-3 PUFA products, used as nutritional supplements, regardless of their formulation or delivery form, can be tested for oxidative safety and compliance.

The timing of BMD and geometric adaptation at the proximal femur from childhood to early adulthood in males and females: A longitudinal study

During adolescence, the peak velocity in bone mass accretion preceded the peak velocity of estimated geometry at the hip. Whether this pattern continues into adulthood when maximum values are achieved remains unknown. The purpose of this study was (1) to identify the ages at which peak values of areal BMD (aBMD), cross‐sectional area (CSA), and section modulus (Z) occur, (2) to determine the percent of adult peak attained during adolescence, and (3) to determine the relationship between body composition and the timing of the adult peak values.

Structural Strength Development at the Proximal Femur in 4- to 10-Year-Old Precompetitive Gymnasts: A 4-Year Longitudinal Hip Structural Analysis Study

Gymnastics, a high‐impact weight‐bearing physical activity, has been shown to be highly osteogenic. Previously in this cohort, bone mass development (bone mineral content accrual [BMC]) was shown to be positively associated with low‐level (recreational) gymnastics exposure (1 to 2 hours per week); however, BMC is only one single component of bone strength. Bone strength is influenced not only by bone mineralization but also bone geometry, bone architecture, and the imposing loads on the bone. The aim of this study was to investigate whether low‐level gymnastics training influenced the estimated structural geometry development at the proximal femur. A total of 165 children (92 gymnasts and 73 non‐gymnasts) between the ages of 4 and 6 years were recruited into this study and assessed annually for 4 years. During the 4 years, 64 gymnasts withdrew from the sport and were reclassified as ex‐gymnasts. A dual‐energy X‐ray absorptiometry (DXA) image of each childs hip was obtained. Values of cross‐sectional area (CSA), section modulus (Z), and cortical thickness (CT) at the narrow neck (NN), intertrochanter (IT), and shaft (S) were estimated using the hip structural analysis (HSA) program. Multilevel random‐effects models were constructed and used to develop bone structural strength development trajectories (estimate ± SEE). Once the confounders of body size and lifestyle were controlled, it was found that gymnasts had 6% greater NN CSA than non‐gymnasts controls (0.09 ± 0.03 cm2, p < 0.05), 7% greater NN Z (0.04 ± 0.01 cm3, p < 0.05), 5% greater IT CSA (0.11 ± 0.04 cm3, p < 0.05), 6% greater IT Z (0.07 ± 0.03 cm3, p < 0.05), and 3% greater S CSA (0.06 ± 0.03 cm3, p < 0.05). These results suggest that early exposure to low‐level gymnastics participation confers benefits related to geometric and bone architecture properties during childhood and, if maintained, may improve bone health in adolescence and adulthood.

Adolescent Physical Activity and Bone Strength at the Proximal Femurin Adulthood.

INTRODUCTION Physical activity (PA) enhances bone structural strength at the proximal femur in adolescence, but whether these benefits are maintained into early adulthood remains unknown. The purpose of this study was to investigate whether males and females, described as active, average, and inactive during adolescence, display differences in structural strength at the proximal femur in early adulthood (20-30 yr). METHODS One hundred four participants (55 males and 49 females) from the Pediatric Bone Mineral Accrual Study (PBMAS) were categorized into adolescent PA groupings (inactive, average, and active) using the Physical Activity Questionnaire for Adolescents. Cross-sectional area and section modulus (Z) at the narrow neck, intertrochanter, and femoral shaft (S) sites of the proximal femur were assessed using hip structural analysis in young adulthood from femoral neck dual-energy x-ray absorptiometry scans. Group differences were assessed using ANCOVA, controlling for adult height (Ht), adult weight (Wt), adolescent bone geometry, sex, percentage adult total body lean tissue (LTM%), and adult PA levels. RESULTS Active adolescents had significantly greater adjusted bone geometric measures at all sites than their inactive classified peers during adolescence (P < 0.05). In adulthood, when adjusted for Ht, Wt, adolescent bone geometry, sex, LTM%, and adult PA levels, adolescent participants categorized as active had significantly greater adjusted adult bone geometric measures at the proximal femur than adult participants who were classified as inactive during adolescence (P < 0.05). CONCLUSIONS Skeletal advantages associated with adolescence activity appear to confer greater geometric bone structural strength at the proximal femur in young adulthood.

Tracking of aerobic fitness from adolescence to mid-adulthood

Abstract Background: Although adults’ aerobic fitness is known to be correlated with cardiovascular disease risk, the longitudinal relationship with adolescent aerobic fitness is poorly described. Aim: To longitudinally investigate the relationship between aerobic fitness during adolescence and adulthood. Subjects and methods: Participants (207 boys, 149 girls) aged 7–17 years performed annual measures of VO2peak. In adulthood (40 and 50 years), 78 individuals (59 males and 18 females) were reassessed. Serial height measurements were used to estimate age at peak height velocity (APHV). During adolescence, VO2peak was measured via a treadmill test to voluntary exhaustion; adult VO2peak was assessed using submaximal predictive tests. Correlations were tested using Spearman’s rho. ANCOVA was used to assess adult VO2peak group differences based off APHV VO2peak groupings (low, average or high). Results: When sexes were pooled, moderate tracking existed from 2 years prior to APHV to APHV and APHV to 2 years after APHV (0.46, p < 0.001 and 0.35, p < 0.01, respectively). Correlations between APHV and adult values were low when sexes were pooled (p < 0.05). Comparisons of aggregated sexes revealed the low adolescent VO2peak group had lower values in adulthood relative to other groups (p < 0.05). Conclusion: Aerobic fitness has a low tracking between APHV and adulthood.

The associations of exposure to combined hormonal contraceptive use on bone mineral content and areal bone mineral density accrual from adolescence to young adulthood: A longitudinal study

Background The association of long term combined hormone based contraceptives (CHC) use on bone mineral content (BMC) and areal bone mineral density (aBMD) development remains controversial, as it appears that the relationship may be age-dependent. The purpose of this study was to investigate the long-term associations of CHC exposure on the accrual of bone parameters from adolescence into young-adulthood. Methods 110 women (67 exposed to CHC) were drawn from the Pediatric Bone Mineral Accrual Study (PBMAS). Serial measures of total body (TB), lumbar spine (LS) and femoral neck (FN) BMC and aBMD were assessed by DXA (a total of 950 scans) and aligned by biological age (BA, years from peak height velocity [PHV]). Multilevel random effects models were constructed to assess the time dependent associations between annual CHC exposure and the development of bone parameters. Results After BA, height, lean tissue mass, fat mass, calcium and vitamin D intake, and physical activity were controlled, it was observed that those individuals exposed to CHC 6-years post PHV developed significantly less (−0.00986 ± 0.00422 g/cm2) TB aBMD than their non CHC exposed peers. Additionally, there were significant BA by CHC exposure interactions, where CHC exposure 6-years or more post PHV resulted in developing less TB BMC (−4.94 ± 2.41 g), LS BMC (−0.29 ± 0.11 g) and LS aBMD (−0.00307 ± 0.00109 g/cm2). One year after the attainment of PHV, CHC users were predicted to have 1.2% more TB BMC, 3.8% more LS BMC and 1.7% more LS aBMD than non-users. At 9-years post PHV the predicted differences showed that CHC users had 0.9% less TB BMC and 2.7% less LS BMC and 1.6% less LS BMD than those not exposed to CHC. Conclusions CHC may not hinder the development of BMC or aBMD during adolescence; however, exposure 6-years or more after PHV may be detrimental.

Maturational timing does not predict HSA estimated adult bone geometry at the proximal femur

Late maturational timing is documented to be detrimental to bone strength primarily at the distal radius. Studies at the proximal femur have focused on bone mass and the results remain controversial. The purpose of this study was to examine the long term relationship between the onset of maturation and the development of estimated cross sectional area (CSA) and section modulus (Z) at the proximal femur. Two hundred and twenty six individuals (108 males and 118 females) from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were classified into maturity groups based on age of attainment of peak height velocity. CSA and Z were serially assessed at the narrow neck (NN), intertrochanter (IT) and proximal shaft (S) sites using hip structural analysis (HSA). Multilevel models were constructed to examine the development of CSA and Z by maturity group. Cross sectional observations indicated that during adolescence, early maturing males had significantly greater CSA and Z than late maturing males at all sites of the proximal femur, while early maturing females had greater Z at the NN and S, and greater CSA at the NN, IT and S sites compared to late maturing females. When age, body size, body composition, physical activity and dietary intake were controlled no significant effects of maturational timing were found at the NN, IT or S regions (p>0.05) in either males or females. In this population of healthy individuals there appears to be no effect of the onset of maturation on estimated CSA and Z development at the proximal femur in both males and females. This may be a result of the proximal femurs loading environment. Future research is required to determine the role of loading on the relationship between maturational timing and bone structure and strength development at the proximal femur.

Adolescent Trajectories of Aerobic Fitness and Adiposity as Markers of Cardiometabolic Risk in Adulthood

Purpose The aim of this study was to investigate whether adolescent growth trajectories of aerobic fitness and adiposity were associated with mid-adulthood cardiometabolic risk (CMR). Methods Participants were drawn from the Saskatchewan Growth and Development Study (1963–1973). Adolescent growth trajectories for maximal aerobic capacity (absolute VO2 (AbsVO2)), skinfolds (SF), representing total body (Sum6SF) and central adiposity (TrunkSF), and body mass index (BMI) were determined from 7 to 17 years of age. In mid-adulthood (40 to 50 years of age), 61 individuals (23 females) returned for follow-ups. A CMR score was calculated to group participants as displaying either high or a low CMR. Multilevel hierarchical models were constructed, comparing the adolescent growth trajectories of AbsVO2, Sum6SF, TrunkSF, and BMI between CMR groupings. Results There were no significant differences in the adolescent development of AbsVO2, Sum6SF, TrunkSF, and BMI between adult CMR groupings (p > 0.05). Individuals with high CMR accrued 62% greater adjusted total body fat percentage from adolescence to adulthood (p=0.03). Conclusions Growth trajectories of adolescent aerobic fitness and adiposity do not appear to be associated with mid-adulthood CMR. Individuals should be encouraged to participate in behaviours that promote healthy aerobic fitness and adiposity levels throughout life to reduce lifelong CMR.