Ethnic and sex differences in skeletal maturation among the Birth to Twenty cohort in South Africa

Aim To examine ethnic and sex differences in the pattern of skeletal maturity from adolescence to adulthood using a novel longitudinal analysis technique (SuperImposition by Translation And Rotation (SITAR)). Setting Johannesburg, South Africa. Participants 607 boys and girls of black as well as white ethnicity from the Birth to Twenty bone health study, assessed annually from 9 to 20 years of age. Outcome measure Bone maturity scores (Tanner–Whitehouse III radius, ulna, and short bones (TW3 RUS)) assessed longitudinally from hand-wrist radiographs were used to produce individual and mean growth curves of bone maturity and analysed by the SITAR method. Results The longitudinal analysis showed that black boys matured later by 7.0 SE 1.6 months (p<0.0001) but at the same rate as white boys, whereas black girls matured at the same age but at a faster rate than white girls (by 8.7% SE 2.6%, p=0.0007). The mean curves for bone maturity score consistently showed a midpubertal double kink, contrasting with the quadratic shape of the commonly used reference centile curves for bone maturity (TW3). Conclusions Skeletal maturity was reached 1.9 years earlier in girls than boys, and the pattern of maturation differed between the sexes. Within girls, there were no ethnic differences in the pattern or timing of skeletal maturity. Within boys, however, skeletal maturity was delayed by 7 months in black compared with white ethnicity. Skeletal maturation, therefore, varies differentially by sex and ethnicity. The delayed maturity of black boys, but not black girls, supports the hypothesis that boys have greater sensitivity to environmental constraints than girls

Life course associations of height, weight, fatness, grip strength, and all-cause mortality for high socioeconomic status Guatemalans

Objectives: The objective of this study was to investigate the association between physical growth in pre-adult life with five outcomes at age 64-76: weight, body mass index, estimated body fat percentage, hand grip strength and mortality. Methods: Super-Imposition by Translation and Rotation (SITAR) growth curves of 40,484 Guatemalan individuals aged 3-19 years were modelled for the parameters of size, timing and intensity (peak growth velocity, e.g. cm/year) of height, weight, body mass index, and grip strength. Associations between the SITAR parameters and old age outcomes were tested using linear and binary logistic regression for a follow-up sample of high socioeconomic status (SES) Guatemalans, of whom 50 were aged 64-76 years old at re-measurement and 45 died prior to the year 2017. Results: SITAR models explained 69-98% of the variance in each outcome, with height the most precise. Individuals in the follow-up sample who had a higher BMI before age 20 years had higher estimated body fat (B=1.4 CI -0.02-2.8) and BMI (B=1.2, CI 0.2-2.2) at the ages 64-76 years. Those who grew slower in height but faster in weight and BMI before age 20 years, had higher BMI and body fat later in life. Conclusions: These findings highlight the importance of a life course perspective on health and mortality risk. Childhood exposures leading to variation in pre-adult growth may be key to better understanding health and mortality risks in old age

A discussion of statistical methods to characterize early growth and its impact on bone mineral content later in childhood

Background Many statistical methods are available to model longitudinal growth data and relate derived summary measures to later outcomes. Aim To apply and compare commonly used methods to a realistic scenario including pre- and postnatal data, missing data and confounders. Subjects and methods Data were collected from 753 offspring in the Southampton Women’s Survey with measurements of bone mineral content (BMC) at age 6 years. Ultrasound measures included crown-rump length (11 weeks’ gestation) and femur length (19 and 34 weeks’ gestation); postnatally, infant length (birth, 6 and 12 months) and height (2 and 3 years) were measured. A residual growth model, two-stage multilevel linear spline model, joint multilevel linear spline model, SITAR and a growth mixture model were used to relate growth to 6-year BMC. Results Results from the residual growth, two-stage and joint multilevel linear spline models were most comparable: an increase in length at all ages was positively associated with BMC, the strongest association being with later growth. Both SITAR and the growth mixture model demonstrated that length was positively associated with BMC. Conclusions Similarities and differences in results from a variety of analytic strategies need to be understood in the context of each statistical methodology

Cost-effectiveness of a community-delivered multicomponent intervention compared with enhanced standard care of obese adolescents: cost-utility analysis alongside a randomised controlled trial (the HELP trial)

Objective To undertake a cost-utility analysis of a motivational multicomponent lifestyle-modification intervention in a community setting (the Healthy Eating Lifestyle Programme (HELP)) compared with enhanced standard care. Design Cost-utility analysis alongside a randomised controlled trial. Setting Community settings in Greater London, England. Participants 174 young people with obesity aged 12–19 years. Interventions Intervention participants received 12 one to-one sessions across 6months, addressing lifestyle behaviours and focusing on motivation to change and self esteem rather than weight change, delivered by trained graduate health workers in community settings. Control participants received a single 1-hour one-to-one nurse delivered session providing didactic weight-management advice. Main outcome measures Mean costs and quality adjusted life years (QALYs) per participant over a 1-year period using resource use data and utility values collected during the trial. Incremental cost-effectiveness ratio (ICER) was calculated and non-parametric bootstrapping was conducted to generate a cost-effectiveness acceptability curve (CEAC). Results Mean intervention costs per participant were £918 for HELP and £68 for enhanced standard care. There were no significant differences between the two groups in mean resource use per participant for any type of healthcare contact. Adjusted costs were significantly higher in the intervention group (mean incremental costs for HELP vs enhanced standard care £1003 (95% CI £837 to £1168)). There were no differences in adjusted QALYs between groups (mean QALYs gained 0.008 (95% CI −0.031 to 0.046)). The ICER of the HELP versus enhanced standard care was £120 630 per QALY gained. The CEAC shows that the probability that HELP was cost-effective relative to the enhanced standard care was 0.002 or 0.046, at a threshold of £20 000 or £30 000 per QALY gained. Conclusions We did not find evidence that HELP was more effective than a single educational session in improving quality of life in a sample of adolescents with obesity. HELP was associated with higher costs, mainly due to the extra costs of delivering the intervention and therefore is not cost-effective

Using Super-Imposition by Translation And Rotation (SITAR) to relate pubertal growth to bone health in later life: the Medical Research Council (MRC) National Survey of Health and Development

Background: To explore associations between pubertal growth and later bone health in a cohort with infrequent measurements, using another cohort with more frequent measurements to support the modelling, data from the MRC National Survey of Health and Development (2-26 years, 4901/30 004 subjects/measurements) and the Avon Longitudinal Study of Parents and Children (5-20 years) (10 896/74 120) were related to NSHD bone health outcomes at 60-64 years. Methods: NSHD data were analysed using SITAR growth curve analysis, either alone or jointly with ALSPAC data. Improved estimation of pubertal growth parameters of size, tempo and velocity was assessed by changes in model fit and correlations with contemporary measures of pubertal timing. Bone outcomes of radius (trabecular volumetric bone mineral density (vBMD) and diaphysis cross-sectional area (CSA)) were regressed on the SITAR parameters, adjusted for current body size. Results: The NSHD SITAR parameters were better estimated in conjunction with ALSPAC, i.e. more strongly correlated with pubertal timing. Trabecular vBMD was associated with early height tempo, while diaphysis CSA was related to weight size, early tempo and slow velocity, the bone outcomes being around 15% higher for the better versus worse growth pattern. Conclusions: By pooling NSHD and ALSPAC data, SITAR more accurately summarised pubertal growth and weight gain in NSHD, and in turn demonstrated notable associations between pubertal timing and later bone outcomes. These associations give insight into the importance of the pubertal period for future skeletal health and osteoporosis risk