. BACKGROUND
. Prevention of depression is a priority to reduce its global disease burden. Targeting specific risk factors, such as rumination, may improve prevention. Rumination-focused Cognitive Behavioral Therapy (RFCBT) was developed to specifically target depressive rumination.
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.
. OBJECTIVE
. The primary objective of this study was to test whether guided Web-based RFCBT (i-RFCBT) would prevent the incidence of major depression relative to usual care in UK university students. The secondary objective was to test the feasibility and estimated effect sizes of unguided i-RFCBT.
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. METHODS
. To address the primary objective, a phase III randomized controlled trial was designed and powered to compare high risk university students (N=235), selected with elevated worry/rumination, recruited via an open access website in response to circulars within universities and internet advertisements, randomized to receive either guided i-RFCBT (interactive Web-based RFCBT, supported by asynchronous written Web-based support from qualified therapists) or usual care control. To address the secondary objective, participants were also randomized to an adjunct arm of unguided (self-administered) i-RFCBT. The primary outcome was the onset of a major depressive episode over 15 months, assessed with structured diagnostic interviews at 3 (postintervention), 6, and 15 months post randomization, conducted by telephone, blind to the condition. Secondary outcomes of symptoms of depression and anxiety and levels of worry and rumination were self-assessed through questionnaires at baseline and the same follow-up intervals.
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. RESULTS
. Participants were randomized to guided i-RFCBT (n=82), unguided i-RFCBT (n=76), or usual care (n=77). Guided i-RFCBT reduced the risk of depression by 34% relative to usual care (hazard ratio [HR] 0.66, 95% CI 0.35 to 1.25; P=.20). Participants with higher levels of baseline stress benefited most from the intervention (HR 0.43, 95% CI 0.21 to 0.87; P=.02). Significant improvements in rumination, worry, and depressive symptoms were found in the short-to-medium term. of the 6 modules, guided participants completed a mean of 3.46 modules (SD 2.25), with 46% (38/82) being compliant (completing ≥4 modules). Similar effect sizes and compliance rates were found for unguided i-RFCBT.
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. CONCLUSIONS
. Guided i-RFCBT can reduce the onset of depression in high-risk young people reporting high levels of worry/rumination and stress. The feasibility study argues for formally testing unguided i-RFCBT for prevention: if the observed effect sizes are robustly replicated in a phase III trial, it has potential as a scalable prevention intervention.
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. CLINICALTRIAL
. ISRCTN Registry ISRCTN12683436; https://www.isrctn.com/ISRCTN12683436 (Archived by WebCite at http://www.webcitation.org/77fqycyBX)
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. INTERNATIONAL REGISTERED REPOR
. RR2-10.1186/s13063-015-1128-9
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Behavioural Activation (BA) is associated with a substantial evidence base for treatment of acute unipolar depression, and has promise as an easily disseminable psychological intervention for bipolar depression. Using a randomised multiple baseline case series design we examined the feasibility and acceptability of an adapted version of BA in a U.K. outpatient sample of 12 adults with acute bipolar depression. Participants were allocated at random to a 3–8 week wait period before being offered up to 20 sessions of BA. They completed outcome measures at intake, pre- and post-treatment and weekly symptom measures across the study period. Retention in therapy was high (11/12 participants completed the target minimum number of sessions), and all participants returning acceptability measures reported high levels of satisfaction with the intervention. No therapy-related serious adverse events were reported, nor were there exacerbations in manic symptoms that were judged to be a result of the intervention. The pattern of change on outcome measures is consistent with the potential for clinical benefit; six of the nine participants with a stable baseline showed clinically significant improvement on the primary outcome measure. The findings suggest adapted BA for bipolar depression is a feasible and acceptable approach that merits further investigation.

Experiences of childhood trauma (abuse and neglect) are disproportionately higher in those with opioid use disorder (OUD). Childhood trauma may affect the reinforcing and rewarding properties of opioid drugs and responses to pain, potentially via developmental changes to the endogenous opioid system. This has been supported by preclinical research, yet this has not been investigated in non-addicted humans. Physically healthy participants with either a history of severe childhood trauma or no previous history of childhood trauma attended two sessions where they received either an intramuscular active dose of morphine (0.15 mg/kg) or a very low dose control (0.01 mg/kg) in a randomised, double-blind crossover design. Sessions were held 1 week apart. Participants' physical pain threshold and tolerance were measured pre- and post-drug administration using the cold water pressor test, alongside acute subjective and behavioural responses over 2.5 h. The trauma group reported liking the effects of morphine, feeling more euphoric and wanting more of the drug over the session, as well as feeling less nauseous, dizzy, and dislike of the effects of morphine compared to the non-trauma comparison group. Morphine increased pain threshold and tolerance, yet this did not differ between the groups. Childhood trauma may therefore sensitise individuals to the pleasurable and motivational effects of opioids and reduce sensitivity to the negative effects, providing compelling evidence for individual differences in opioid reward sensitivity. This may explain the link between childhood trauma and vulnerability to OUD, with consequent implications on interventions for OUD, the prescribing of opioids, and reducing stigmas surrounding OUD.

OBJECTIVE: to undertake meta-analysis and compare treatment effects estimated by the intention-to-treat (ITT) method and per-protocol (PP) method in randomized controlled trials (RCTs). PP excludes trial participants who are non-adherent to trial protocol in terms of eligibility, interventions, or outcome assessment. STUDY DESIGN AND SETTING: Five high impact journals were searched for all RCTs published between July 2017 to June 2019. Primary outcome was a pooled estimate that quantified the difference between the treatment effects estimated by the two methods. Results are presented as ratio of odds ratios (ROR). Meta-regression was used to explore the association between level of trial protocol non-adherence and treatment effect. Sensitivity analyses compared results with varying within-study correlations and across various study characteristics. RESULTS: Random-effects meta-analysis (N = 156) showed that PP estimates were on average 2% greater compared to the ITT estimates (ROR: 1.02, 95% CI: 1.00-1.04, P = 0.03). The divergence further increased with higher degree of protocol non-adherence. Sensitivity analyses reassured consistent results with various within-study correlations and across various study characteristics. CONCLUSION: There was evidence of larger treatment effect with PP compared to ITT analysis. PP analysis should not be used to assess the impact of protocol non-adherence in RCTs. Instead, in addition to ITT, investigators should consider randomization based casual method such as Complier Average Causal Effect (CACE).

BACKGROUND: We sought to evaluate the acceptability of a psychological therapy programme (Therapy for Inter-episode Mood Variability in Bipolar Disorder (ThrIVe-B)) for individuals with ongoing bipolar mood instability and the feasibility and acceptability of potential trial procedures. We also evaluated the performance of clinical and process outcome measures and the extent to which the programme potentially represents a safe and effective intervention. METHOD: We conducted an open (uncontrolled) trial in which 12 individuals with a bipolar spectrum diagnosis commenced the ThrIVe-B programme after completing baseline assessments. The programme comprised 16 group skills training sessions plus individual sessions and a supporting smartphone application. Follow-up assessments were at therapy end-point and 6 months post-treatment. RESULTS: Nine participants completed treatment. Ten provided end-of-treatment data; of these, nine were satisfied with treatment. Interviews with participants and clinicians indicated that the treatment was broadly feasible and acceptable, with suggestions for improvements to content, delivery and study procedures. Exploration of change in symptoms was consistent with the potential for the intervention to represent a safe and effective intervention. CONCLUSIONS: Conducting further evaluation of this approach in similar settings is likely to be feasible, whilst patient reports and the pattern of clinical change observed suggest this approach holds promise for this patient group. Future research should include more than one study site and a comparison arm to address additional uncertainties prior to a definitive trial. TRIAL REGISTRATION: Trial Registration: ClinicalTrials.gov NCT02637401; registered 22.12.15 (retrospectively registered).

OBJECTIVE: to undertake a methodological review of statistical methods used in randomized controlled trials (RCTs) for handling intervention nonadherence. STUDY DESIGN AND SETTING: Bibliographic databases were searched using predefined search terms. RESULTS: a substantive number of identified studies (56%) were excluded as they only used naive per protocol analysis for handling nonadherence. Our review included 58 articles published between 1991 and 2015. A total of 88 methodological applications were made by these studies. The two most used methods were complier average causal effect (56%) and instrumental variable (23%) predominantly with the use of maximum likelihood (ML) estimators. These alternative applications typically produced treatment effects greater than the intention-to-treat effect but as their standard errors were larger there was no statistical difference between the methods. CONCLUSION: a substantive proportion of RCTs rely on naive per protocol for handling nonadherence. Recent years have seen an increasing number of applications of more appropriate statistical methods, in particular complier average causal effect and instrumental variable methods. However, these later methods rely on strong underlying assumptions that may be vulnerable to violation. More empirical studies are needed that directly compare the usability and performance of different statistical methods for nonadherence in RCTs.

Objectives: This prospective study investigated anatomical and biomechanical risk factors for second and third metatarsal stress fractures in military recruits during training. Design: Prospective cohort study. Methods: Anatomical and biomechanical measures were taken for 1065 Royal Marines recruits at the start of training when injury-free. Data included passive range of ankle dorsi-flexion, dynamic peak ankle dorsi-flexion and plantar pressures during barefoot running. Separate univariate regression models were developed to identify differences between recruits who developed second (n = 7) or third (n = 14) metatarsal stress fracture and a cohort of recruits completing training with no injury (n = 150) (p < 0.05). A multinomial logistic regression model was developed to predict the risk of injury for the two sites compared with the no-injury group. Multinomial logistic regression results were back transformed from log scale and presented in Relative Risk Ratios (RRR) with 95% confidence intervals (CI). Results: Lower dynamic arch index (high arch) (RRR: 0.75, CI: 0.63–0.89, p < 0.01) and lower foot abduction (RRR: 0.87, CI: 0.80–0.96, p < 0.01) were identified as increasing risk for second metatarsal stress fracture, while younger age (RRR: 0.78, CI: 0.61–0.99, p < 0.05) and later peak pressure at the second metatarsal head area (RRR: 1.19, CI: 1.04–1.35, p < 0.01) were identified as risk factors for third metatarsal stress fracture. Conclusions: for second metatarsal stress fracture, aspects of foot type have been identified as influencing injury risk. For third metatarsal stress fracture, a delayed forefoot loading increases injury risk. Identification of these different injury mechanisms can inform development of interventions for treatment and prevention.

BACKGROUND: Prevention of depression is a priority to reduce its global disease burden. Targeting specific risk factors, such as rumination, may improve prevention. Rumination-focused Cognitive Behavioral Therapy (RFCBT) was developed to specifically target depressive rumination. OBJECTIVE: the primary objective of this study was to test whether guided Web-based RFCBT (i-RFCBT) would prevent the incidence of major depression relative to usual care in UK university students. The secondary objective was to test the feasibility and estimated effect sizes of unguided i-RFCBT. METHODS: to address the primary objective, a phase III randomized controlled trial was designed and powered to compare high risk university students (N=235), selected with elevated worry/rumination, recruited via an open access website in response to circulars within universities and internet advertisements, randomized to receive either guided i-RFCBT (interactive Web-based RFCBT, supported by asynchronous written Web-based support from qualified therapists) or usual care control. To address the secondary objective, participants were also randomized to an adjunct arm of unguided (self-administered) i-RFCBT. The primary outcome was the onset of a major depressive episode over 15 months, assessed with structured diagnostic interviews at 3 (postintervention), 6, and 15 months post randomization, conducted by telephone, blind to the condition. Secondary outcomes of symptoms of depression and anxiety and levels of worry and rumination were self-assessed through questionnaires at baseline and the same follow-up intervals. RESULTS: Participants were randomized to guided i-RFCBT (n=82), unguided i-RFCBT (n=76), or usual care (n=77). Guided i-RFCBT reduced the risk of depression by 34% relative to usual care (hazard ratio [HR] 0.66, 95% CI 0.35 to 1.25; P=.20). Participants with higher levels of baseline stress benefited most from the intervention (HR 0.43, 95% CI 0.21 to 0.87; P=.02). Significant improvements in rumination, worry, and depressive symptoms were found in the short-to-medium term. of the 6 modules, guided participants completed a mean of 3.46 modules (SD 2.25), with 46% (38/82) being compliant (completing ≥4 modules). Similar effect sizes and compliance rates were found for unguided i-RFCBT. CONCLUSIONS: Guided i-RFCBT can reduce the onset of depression in high-risk young people reporting high levels of worry/rumination and stress. The feasibility study argues for formally testing unguided i-RFCBT for prevention: if the observed effect sizes are robustly replicated in a phase III trial, it has potential as a scalable prevention intervention. TRIAL REGISTRATION: ISRCTN Registry ISRCTN12683436; https://www.isrctn.com/ISRCTN12683436 (Archived by WebCite at http://www.webcitation.org/77fqycyBX). INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.1186/s13063-015-1128-9.

AIM: Residual β-cell function is present at the time of diagnosis with Type 1 diabetes. Preserving this β-cell function reduces complications. We hypothesized that exercise preserves β-cell function in Type 1 diabetes and undertook a pilot trial to address the key uncertainties in designing a definitive trial to test this hypothesis. METHODS: a randomized controlled pilot trial in adults aged 16-60 years diagnosed with Type 1 diabetes within the previous 3 months was undertaken. Participants were assigned to control (usual care) or intervention (exercise consultation every month), in a 1 : 1 ratio for 12 months. The primary outcomes were recruitment rate, drop out, exercise adherence [weeks with ≥ 150 min of self-reported moderate to vigorous physical activity (MVPA)], and exercise uptake in the control group. The secondary outcomes were differences in insulin sensitivity and rate of loss of β-cell function between intervention and control at 6 and 12 months. RESULTS: of 507 individuals who were approached, 58 (28 control, 30 intervention) entered the study and 41 completed it. Participants were largely white European males, BMI 24.8 ± 3.8 kg/m2 , HbA1c 75 ± 25 mmol/mol (9 ± 2%). Mean level of objectively measured MVPA increased in the intervention group (mean 243 to 273 min/week) and 61% of intervention participants reached the target of ≥ 150 min/week of self-reported MVPA on at least 42 weeks of the year. Physical activity levels fell slightly in the control group (mean 277 to 235 min of MVPA/week). There was exploratory evidence that intervention group became more insulin sensitive and required less insulin. However, the rate of loss of β-cell function appeared similar between the groups, although the change in insulin sensitivity may have affected this. CONCLUSION: We show that it is possible to recruit and randomize people with newly diagnosed Type 1 diabetes to a trial of an exercise intervention, and increase and maintain their exercise levels for 12 months. Future trials need to incorporate measures of greater adherence to exercise training targets, and include more appropriate measures of β-cell function. (Clinical Trials Registry No; ISRCTN91388505).

AIMS: Reference laboratories advise immediate separation and freezing of samples for the assay of proinsulin, which limit its practicability for smaller centres. Following the demonstration that insulin and C-peptide are stable in EDTA at room temperature for at least 24hours, we undertook simple stability studies to establish whether the same might apply to proinsulin. METHODS: Venous blood samples were drawn from six adult women, some fasting, some not, aliquoted and assayed immediately and after storage at either 4°C or ambient temperature for periods from 2h to 24h. RESULTS: There was no significant variation or difference with storage time or storage condition in either individual or group analysis. CONCLUSION: Proinsulin appears to be stable at room temperature in EDTA for at least 24h. Immediate separation and storage on ice of samples for proinsulin assay is not necessary, which will simplify sample transport, particularly for multicentre trials.

BACKGROUND: Diabetes is closely linked to obesity, and obesity rates climb during adolescence for reasons that are not clear. Energy efficiency is important to obesity, and we describe a temporary but substantial fall in absolute energy expenditure, compatible with improved energy efficiency, during the rapid growth phase of puberty. METHODS: in a longitudinal cohort study lasting 10 years, we measured voluntary energy expenditure as physical activity (PA) by accelerometry, involuntary energy expenditure as resting energy expenditure (REE) by oxygen consumption, body mass index (BMI) and body composition by dual energy X-ray absorptiometry annually on 10 occasions from 7 to 16 years in the 347 children of the EarlyBird study. We used mixed effects modelling to analyse the trends in REE and their relationship to BMI, lean mass (LM), fat mass (FM), age, PA and pubertal stage. RESULTS: Relative REE and total PA fell during puberty, as previously described, but the longitudinal data and narrow age-range of the cohort (s.d.±4m) revealed for the first time a substantial fall in absolute REE during the period of maximum growth. The fall became clearer still when adjusted for FM and LM. The fall could not be explained by fasting insulin, adiponectin, leptin, luteinising hormone or follicle stimulating hormone. CONCLUSIONS: There appears to be a temporary but substantial reduction in energy expenditure during puberty, which is unrelated to changes in body composition. If it means higher energy efficiency, the fall in REE could be advantageous in an evolutionary context to delivering the extra energy needed for pubertal growth, but unfavourable to weight gain in a contemporary environment.

Background: Tibial stress fractures cause a significant burden to Royal Marines recruits. No prospective running gait analyses have previously been performed in military settings.
Aim: We aimed to identify biomechanical gait factors and anthropometric variables associated with increased risk of TSF.
Methods: 1065 Royal Marines recruits were assessed in week-2 of training. Bilateral plantar pressure and 3D lower limb kinematics were obtained for barefoot running at 3.6 m.s-1, providing dynamic arch index, peak heel pressure and lower limb joint angles. Age, bimalleolar breadth, calf girth, passive hip internal/external range of motion and body mass index (BMI) were also recorded. Ten recruits who sustained a TSF during training were compared with 120 recruits who completed training injury-free using a binary logistic regression model to identify injury risk factors.
Results: Four variables significantly (p

BACKGROUND: Depression is a global health challenge. Although there are effective psychological and pharmaceutical interventions, our best treatments achieve remission rates less than 1/3 and limited sustained recovery. Underpinning this efficacy gap is limited understanding of how complex psychological interventions for depression work. Recent reviews have argued that the active ingredients of therapy need to be identified so that therapy can be made briefer, more potent, and to improve scalability. This in turn requires the use of rigorous study designs that test the presence or absence of individual therapeutic elements, rather than standard comparative randomised controlled trials. One such approach is the Multiphase Optimization Strategy, which uses efficient experimentation such as factorial designs to identify active factors in complex interventions. This approach has been successfully applied to behavioural health but not yet to mental health interventions. METHODS/DESIGN: a Phase III randomised, single-blind balanced fractional factorial trial, based in England and conducted on the internet, randomized at the level of the patient, will investigate the active ingredients of internet cognitive-behavioural therapy (CBT) for depression. Adults with depression (operationalized as PHQ-9 score ≥ 10), recruited directly from the internet and from an UK National Health Service Improving Access to Psychological Therapies service, will be randomized across seven experimental factors, each reflecting the presence versus absence of specific treatment components (activity scheduling, functional analysis, thought challenging, relaxation, concreteness training, absorption, self-compassion training) using a 32-condition balanced fractional factorial design (2IV7-2). The primary outcome is symptoms of depression (PHQ-9) at 12 weeks. Secondary outcomes include symptoms of anxiety and process measures related to hypothesized mechanisms. DISCUSSION: Better understanding of the active ingredients of efficacious therapies, such as CBT, is necessary in order to improve and further disseminate these interventions. This study is the first application of a component selection experiment to psychological interventions in depression and will enable us to determine the main effect of each treatment component and its relative efficacy, and cast light on underlying mechanisms, so that we can systematically enhance internet CBT. TRIAL REGISTRATION: Current Controlled Trials ISRCTN24117387. Registered 26 August 2014.

Background: Mothers often do not realize when their child is overweight. We aimed to compare mothers' perceptions of children's weight before and during puberty, and to explore factors at 7 years predicting recognition of overweight at 16 years. Methods: Mothers of 237 children (136 boys) from the EarlyBird study estimated their own weight category and that of their child aged 7 years and 16 years. The children estimated their own weight category at 16 years. Annual measures: body mass index standard deviation score (BMIsds), per cent fat, physical activity. Pubertal development assessed by age at peak height velocity (APHV). Maternal measures: BMI, education, socio-economic status. Results: at 7 years 21% of girls and 16% of boys were overweight or obese, rising to 27% and 22% respectively at 16 years. The accuracy of the mother's perception of her child's weight category improved from 44% at 7 years to 74% at 16 years, but they were less able to judge overweight in sons than daughters. The mothers' level of concern about overweight was greater for girls than boys, and increased for girls (52% mothers of overweight/obese girls were worried at 7 years, 62% at 16 years), but remained static in the boys (42% vs. 39%). Over 80% of the youngsters realized when they were overweight, but 25% normal-weight girls also classed themselves as overweight. Only BMI predicted a mother's ability to correctly perceive her child's weight. Neither her awareness, nor concern, about the child's weight at 7 years had any impact on the trajectory of the child's BMI from 7 years to 16 years. Conclusions: Parents are central to any successful weight reduction programme in their children, but will not engage while they remain ignorant of the problem. Crucially, any concern mothers may have about their child's excess weight at 7 years appears to have no impact on subsequent weight change.

BACKGROUND: Mothers often do not realize when their child is overweight. We aimed to compare mothers' perceptions of children's weight before and during puberty, and to explore factors at 7 years predicting recognition of overweight at 16 years. METHODS: Mothers of 237 children (136 boys) from the EarlyBird study estimated their own weight category and that of their child aged 7 years and 16 years. The children estimated their own weight category at 16 years. Annual measures: body mass index standard deviation score (BMIsds), per cent fat, physical activity. Pubertal development assessed by age at peak height velocity (APHV). MATERNAL MEASURES: BMI, education, socio-economic status. RESULTS: at 7 years 21% of girls and 16% of boys were overweight or obese, rising to 27% and 22% respectively at 16 years. The accuracy of the mother's perception of her child's weight category improved from 44% at 7 years to 74% at 16 years, but they were less able to judge overweight in sons than daughters. The mothers' level of concern about overweight was greater for girls than boys, and increased for girls (52% mothers of overweight/obese girls were worried at 7 years, 62% at 16 years), but remained static in the boys (42% vs. 39%). Over 80% of the youngsters realized when they were overweight, but 25% normal-weight girls also classed themselves as overweight. Only BMI predicted a mother's ability to correctly perceive her child's weight. Neither her awareness, nor concern, about the child's weight at 7 years had any impact on the trajectory of the child's BMI from 7 years to 16 years. CONCLUSIONS: Parents are central to any successful weight reduction programme in their children, but will not engage while they remain ignorant of the problem. Crucially, any concern mothers may have about their child's excess weight at 7 years appears to have no impact on subsequent weight change.

Background/objective:The prevalence of childhood obesity continues to rise in most countries, but the exposures responsible remain unclear. The shape of the body mass index (BMI) distribution curve defines how a population responds, and can be described by its three parameters-skew (L), median (M) and variance (S). We used LMS analysis to explore differences in the BMI trajectories of contemporary UK children with those of 25 years ago, and to draw inferences on the exposures responsible.Subjects/methods:We applied Cole's LMS method to compare the BMI trajectories of 307 UK children (EarlyBird cohort) measured annually from 5-16 years (2000-2012) with those of the BMI data set used to construct the UK 1990 growth centiles, and used group-based trajectory modelling (GBTM) to establish whether categorical trajectories emerged.Results:Gender-specific birth weights were normally distributed and similar between both data sets. The skew and variance established by 5 years in the 1990 children remained stable during the remainder of their childhood, but the pattern was different for children 25 years on. The skew at 5 years among the EarlyBird children was greatly exaggerated, and involved selectively the offspring of obese parents, but returned to 1990 levels by puberty. As the skew diminished, so the variance in BMI rose sharply. The median BMI of the EarlyBird children differed little from that of 1990 before puberty, but diverged from it as the variance rose. GBTM uncovered four groups with distinct trajectories, which were related to parental obesity.Conclusions:There appear to be two distinct environmental interactions with body mass among contemporary children, the one operating selectively according to parental BMI during early childhood, the second more generally in puberty.

BACKGROUND/OBJECTIVE: the prevalence of childhood obesity continues to rise in most countries, but the exposures responsible remain unclear. The shape of the body mass index (BMI) distribution curve defines how a population responds, and can be described by its three parameters-skew (L), median (M) and variance (S). We used LMS analysis to explore differences in the BMI trajectories of contemporary UK children with those of 25 years ago, and to draw inferences on the exposures responsible. SUBJECTS/METHODS: We applied Cole's LMS method to compare the BMI trajectories of 307 UK children (EarlyBird cohort) measured annually from 5-16 years (2000-2012) with those of the BMI data set used to construct the UK 1990 growth centiles, and used group-based trajectory modelling (GBTM) to establish whether categorical trajectories emerged. RESULTS: Gender-specific birth weights were normally distributed and similar between both data sets. The skew and variance established by 5 years in the 1990 children remained stable during the remainder of their childhood, but the pattern was different for children 25 years on. The skew at 5 years among the EarlyBird children was greatly exaggerated, and involved selectively the offspring of obese parents, but returned to 1990 levels by puberty. As the skew diminished, so the variance in BMI rose sharply. The median BMI of the EarlyBird children differed little from that of 1990 before puberty, but diverged from it as the variance rose. GBTM uncovered four groups with distinct trajectories, which were related to parental obesity. CONCLUSIONS: There appear to be two distinct environmental interactions with body mass among contemporary children, the one operating selectively according to parental BMI during early childhood, the second more generally in puberty.

AIMS/HYPOTHESIS: the aim of this work was to test whether the mid-adolescent peak in insulin resistance (IR) and trends in other metabolic markers are influenced by long-term exposure to physical activity. METHODS: Physical activity (7 day ActiGraph accelerometry), HOMA-IR and other metabolic markers (glucose, fasting insulin, HbA1c, lipids and BP) were measured annually from age 9 years to 16 years in 300 children (151 boys) from the EarlyBird study in Plymouth, UK. The activity level of each child was characterised, with 95% reliability, by averaging their eight annual physical activity measures. Age-related trends in IR and metabolic health were analysed by multi-level modelling, with physical activity as the exposure measure (categorical and continuous) and body fat percentage (assessed by dual-energy X-ray absorptiometry) and pubertal status (according to age at peak height velocity and Tanner stage) as covariates. RESULTS: the peak in IR at age 12-13 years was 17% lower (p < 0.001) in the more active adolescents independently of body fat percentage and pubertal status. However, this difference diminished progressively over the next 3 years and had disappeared completely by the age of 16 years (e.g. difference was -14% at 14 years, -8% at 15 years and +1% at 16 years; 'physical activity × age(2), interaction, p < 0.01). Triacylglycerol levels in girls (-9.7%, p = 0.05) and diastolic blood pressure in boys (-1.20 mmHg, p = 0.03) tended to be lower throughout adolescence in the more active group. CONCLUSIONS/INTERPRETATION: Our finding that physical activity attenuates IR during mid-adolescence may be clinically important. It remains to be established whether the temporary attenuation in IR during this period has implications for the development of diabetes in adolescence and for future metabolic health generally.

BACKGROUND: the regulation and role of SHBG in children are poorly defined. Here we investigated whether adiposity-related mechanisms regulate SHBG and whether SHBG levels are associated with the age of puberty. METHODS: Longitudinal modelling of annual physiological and endocrine measurements from age 5 to 15 years in a cohort of 347 Plymouth schoolchildren. RESULTS: SHBG levels were highest at age 5 years and then declined. Mean (SE) SHBG levels were higher in boys than girls at age 5 years [mean (SE) difference 7.68 (3.80) nmol/L; P =. 045] but lower in boys by age 15 years [difference 12.19 (3.4) nmol/L; P <. 001]. SHBG correlated inversely with adiposity [body mass index SD score (BMI SDS)], insulin, IGF-I, C-reactive protein (CRP), and leptin and positively with adiponectin but not with dehydroepiandrosterone sulphate, androstenedione, or T. In linear mixed models, five adiposity-related covariates (insulin, leptin, adiponectin, IGF-I, and CRP) all exerted significant main effects on SHBG (boys P =. 04 to <. 001; girls P =. 007 to <. 001). However, the further addition of BMI SDS rendered the effects of leptin, insulin, and adiponectin nonsignificant, whereas CRP and IGF-I remained significant. In separate models, the individual effects on SHBG of insulin, leptin, IGF-I, and adiponectin, but not CRP, were displaced by BMI SDS. Finally, in linear regression, BMI SDS little affected R(2) resulting from the five adiposity-related signals. Girls with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, tended to have earlier LH secretion, and earlier age at peak height velocity and menarche. In contrast, boys with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, but there were no relationships between SHBG and earlier onset of LH secretion or age at peak height velocity. CONCLUSIONS: Adiposity-related endocrine mechanisms and chronic inflammation were associated with the prepubertal decline of SHBG, and lower SHBG levels anticipated earlier puberty. These findings may be relevant to the occurrence of earlier puberty in recent decades.

BACKGROUND/OBJECTIVES: Body mass index (BMI) is reportedly gender assortative (mother-daughter, father-son) in contemporary children. We investigated the corresponding transmission of waist circumference (WC) and its implications. METHODS: We measured parental WC at baseline and WC, height, weight and para-umbilical skin-fold (USF) annually in their offspring from 5 to 15 years (n = 223 trios). Parents were deemed normal metabolic risk (NR) or high risk (HR) according to World Health Organization (WHO) cut-points for WC (mothers 80 cm, fathers 94 cm). The residual from WC adjusted for BMI (WC|BMI ) was used as a surrogate for excess intra-abdominal fat, and its association with insulin resistance (HOMA2-IR) was sought. RESULTS: WC and USF were both gender assortative, while WC|BMI was not. WC was greater by 1.62 cm (P 

A number of authors have identified multiple concurrent sexual partnerships by both men and women to lie at the root of the HIV/AIDS epidemic in sub-Saharan Africa. This study applies multilevel models to Demographic and Health Survey data collected during 2003-2008 in 20 sub-Saharan African countries to examine the influence of social and cultural context on involvement with multiple sexual partnerships in the region, above and beyond the effects of individual characteristics. The findings provide support for the ecological argument that health behaviours are shaped and determined by societal conditions, in addition to the effects of individual and household characteristics. Involvement with multiple sex partners is most prevalent in societies in which sexual norms are widely permissive and where polygyny is common. Individual autonomy is substantial and attitudes towards sexuality are more liberal among men and women who live in communities in which sexual norms are widely permissive. Men and women who are most likely to have multiple sex partners in the sub-Saharan region are those who initiated sexual activity earlier and those who have the individual attributes (e.g. young age, urban residence, education, media exposure and working for cash and away from home) that bring to them more rights and/or decision-making autonomy, but not necessarily more financial resources and economic security (mostly among women). On the other hand, involvement with multiple partners is determined by cultural norms (i.e. permissive sexual norms) and social change (i.e. mass education, expansion of cash employment). The findings suggest a number of opportunities for more effective policy and programmatic responses to curb the prevalence of multiple partnerships in sub-Saharan Africa.