Longitudinal Functional Connectome in Pediatric Concussion: An Advancing Concussion Assessment in Pediatrics Study

Advanced magnetic resonance imaging (MRI) techniques indicate that concussion (i.e., mild traumatic brain injury) disrupts brain structure and function in children. However, the functional connectivity of brain regions within global and local networks (i.e., functional connectome) is poorly understood in pediatric concussion. This prospective, longitudinal study addressed this gap using data from the largest neuroimaging study of pediatric concussion to date to study the functional connectome longitudinally after concussion as compared with mild orthopedic injury (OI). Children and adolescents (n = 967) 8-16.99 years with concussion or mild OI were recruited from pediatric emergency departments within 48 h post-injury. Pre-injury and 1-month post-injury symptom ratings were used to classify concussion with or without persistent symptoms based on reliable change. Subjects completed a post-acute (2-33 days) and chronic (3 or 6 months via random assignment) MRI scan. Graph theory metrics were derived from 918 resting-state functional MRI scans in 585 children (386 concussion/199 OI). Linear mixed-effects modeling was performed to assess group differences over time, correcting for multiple comparisons. Relative to OI, the global clustering coefficient was reduced at 3 months post-injury in older children with concussion and in females with concussion and persistent symptoms. Time post-injury and sex moderated group differences in local (regional) network metrics of several brain regions, including degree centrality, efficiency, and clustering coefficient of the angular gyrus, calcarine fissure, cuneus, and inferior occipital, lingual, middle occipital, post-central, and superior occipital gyrus. Relative to OI, degree centrality and nodal efficiency were reduced post-acutely, and nodal efficiency and clustering coefficient were reduced chronically after concussion (i.e., at 3 and 6 months post-injury in females; at 6 months post-injury in males). Functional network alterations were more robust and widespread chronically as opposed to post-acutely after concussion, and varied by sex, age, and symptom recovery at 1-month post-injury. Local network segregation reductions emerged globally (across the whole brain network) in older children and in females with poor recovery chronically after concussion. Reduced functioning between neighboring regions could negatively disrupt specialized information processing. Local network metric alterations were demonstrated in several posterior regions that are involved in vision and attention after concussion relative to OI. This indicates that functioning of superior parietal and occipital regions could be particularly susceptibile to the effects of concussion. Moreover, those regional alterations were especially apparent at later time periods post-injury, emerging after post-concussive symptoms resolved in most and persisted up to 6 months post-injury, and differed by biological sex. This indicates that neurobiological changes continue to occur up to 6 months after pediatric concussion, although changes emerge earlier in females than in males. Changes could reflect neural compensation mechanisms.

Longitudinal Gray Matter Trajectories in Pediatric Mild Traumatic Brain Injury

BACKGROUND AND OBJECTIVES

This prospective, longitudinal cohort study examined trajectories of brain gray matter macrostructure after pediatric mild traumatic brain injury (mTBI).

METHODS

Children aged 8-16.99 years with mTBI or mild orthopedic injury (OI) were recruited from 5 pediatric emergency departments. Reliable change between preinjury and 1 month postinjury symptom ratings was used to classify mTBI with or without persistent symptoms. Children completed postacute (2-33 days) and/or chronic (3 or 6 months) postinjury T1-weighted MRI, from which macrostructural metrics were derived using automated segmentation. Linear mixed-effects models were used, with multiple comparisons correction.

RESULTS

Groups (N = 623; 407 mTBI/216 OI; 59% male; age mean = 12.03, SD = 2.38 years) did not differ in total brain, white, or gray matter volumes or regional subcortical gray matter volumes. However, time postinjury, age at injury, and biological sex-moderated differences among symptom groups in cortical thickness of the angular gyrus, basal forebrain, calcarine cortex, gyrus rectus, medial and posterior orbital gyrus, and the subcallosal area all corrected p < 0.05. Gray matter macrostructural metrics did not differ between groups postacutely. However, cortical thinning emerged chronically after mTBI relative to OI in the angular gyrus in older children (d [95% confidence interval] = -0.61 [-1.15 to -0.08]); and in the basal forebrain (-0.47 [-0.94 to -0.01]), subcallosal area (-0.55 [-1.01 to -0.08]), and the posterior orbital gyrus (-0.55 [-1.02 to -0.08]) in females. Cortical thinning was demonstrated for frontal and occipital regions 3 months postinjury in males with mTBI with persistent symptoms vs without persistent symptoms (-0.80 [-1.55 to -0.05] to -0.83 [-1.56 to -0.10]) and 6 months postinjury in females and younger children with mTBI with persistent symptoms relative to mTBI without persistent symptoms and OI (-1.42 [-2.29 to -0.45] to -0.91 [-1.81 to -0.01]).

DISCUSSION

These findings signal little diagnostic and prognostic utility of postacute gray matter macrostructure in pediatric mTBI. However, mTBI altered the typical course of cortical gray matter thinning up to 6 months postinjury, even after symptoms typically abate in most children. Collapsing across symptom status obscured the neurobiological heterogeneity of discrete clinical outcomes after pediatric mTBI. The results illustrate the need to examine neurobiology in relation to clinical outcomes and within a neurodevelopmental framework.

Altered longitudinal structural connectome in paediatric mild traumatic brain injury: an Advancing Concussion Assessment in Paediatrics study

Advanced diffusion-weighted imaging techniques have increased understanding of the neuropathology of paediatric mild traumatic brain injury (i.e. concussion). Most studies have examined discrete white-matter pathways, which may not capture the characteristically subtle, diffuse and heterogenous effects of paediatric concussion on brain microstructure. This study compared the structural connectome of children with concussion to those with mild orthopaedic injury to determine whether network metrics and their trajectories across time post-injury differentiate paediatric concussion from mild traumatic injury more generally. Data were drawn from of a large study of outcomes in paediatric concussion. Children aged 8-16.99 years were recruited from five paediatric emergency departments within 48 h of sustaining a concussion (n = 360; 56% male) or mild orthopaedic injury (n = 196; 62% male). A reliable change score was used to classify children with concussion into two groups: concussion with or without persistent symptoms. Children completed 3 T MRI at post-acute (2-33 days) and/or chronic (3 or 6 months, via random assignment) post-injury follow-ups. Diffusion-weighted images were used to calculate the diffusion tensor, conduct deterministic whole-brain fibre tractography and compute connectivity matrices in native (diffusion) space for 90 supratentorial regions. Weighted adjacency matrices were constructed using average fractional anisotropy and used to calculate global and local (regional) graph theory metrics. Linear mixed effects modelling was performed to compare groups, correcting for multiple comparisons. Groups did not differ in global network metrics. However, the clustering coefficient, betweenness centrality and efficiency of the insula, cingulate, parietal, occipital and subcortical regions differed among groups, with differences moderated by time (days) post-injury, biological sex and age at time of injury. Post-acute differences were minimal, whereas more robust alterations emerged at 3 and especially 6 months in children with concussion with persistent symptoms, albeit differently by sex and age. In the largest neuroimaging study to date, post-acute regional network metrics distinguished concussion from mild orthopaedic injury and predicted symptom recovery 1-month post-injury. Regional network parameters alterations were more robust and widespread at chronic timepoints than post-acutely after concussion. Results suggest that increased regional and local subnetwork segregation (modularity) and inefficiency occurs across time after concussion, emerging after post-concussive symptom resolve in most children. These differences persist up to 6 months after concussion, especially in children who showed persistent symptoms. While prognostic, the small to modest effect size of group differences and the moderating effects of sex likely would preclude effective clinical application in individual patients.

Physical activity levels, pulmonary function, and MRI in children born extremely preterm: A comparison between children with and without bronchopulmonary dysplasia

INTRODUCTION

Children with a history of bronchopulmonary dysplasia (BPD) may have lower physical activity levels, but evidence to date is mixed. This study compared physical activity levels between children born extremely preterm with and without history of BPD, and examined their associations with pulmonary magnetic resonance imaging (MRI) and pulmonary function test (PFT) indices.

METHODS

This multicentre cross-sectional study included children aged 7-9 years born extremely preterm, with and without BPD. Children wore a pedometer for 1 week, then completed the Physical Activity Questionnaire (PAQ), pulmonary MRI, and PFT. Spearman correlations and multivariable linear regression modeling were performed.

RESULTS

Of 45 children, 28 had a history of moderate-severe BPD. There were no differences in any physical activity outcomes by BPD status. Higher average daily step count and higher average daily moderate-to-vigorous physical activity (MVPA) were each correlated with greater forced vital capacity (r = 0.41 and 0.58), greater MRI lung proton density at full expiration (r = 0.42 and 0.49), and lower lung clearance index (r = -0.50 and -0.41). After adjusting for MRI total proton density and BPD status, a 5% increase in forced expiratory volume at 1 s was associated with 738 (95% CI: 208, 1268) more steps per day and 0.1 (0.0, 0.2) more hours of MVPA, respectively.

CONCLUSION

School-aged children born extremely preterm have similar physical activity levels to their peers, regardless of history of BPD. MRI and PFT measures suggestive of gas trapping and/or airflow obstruction are associated with lower physical activity levels.

Cardiometabolic dysregulation and cognitive decline: potential role of depressive symptoms

Background

Previous studies have examined associations of cardiometabolic factors with depression and cognition separately.

Aims

To determine if depressive symptoms mediate the association between cardiometabolic factors and cognitive decline in two community studies.

Methods

Data for the analyses were drawn from the Rotterdam Study, the Netherlands (n = 2940), the Whitehall II study, UK (n = 4469) and the Canadian Longitudinal Study on Aging, Canada (n = 13,720).

Results

Mediation analyses suggested a direct association between cardiometabolic factors and cognitive decline and an indirect association through depression: poorer cardiometabolic status at time 1 was associated with a higher level of depressive symptoms at time 2 (standardised regression coefficient 0.07 and 0.06, respectively), which, in turn, was associated with greater cognitive decline between time 2 and time 3 (standardised regression coefficient of -0.15 and -0.41, respectively).

Conclusions

Evidence from three independent cohort studies suggest an association between cardiometabolic dysregulation and cognitive decline and that depressive symptoms tend to precede this decline.

Key messages

• Cardiometabolic dysregulation and depression might increase cognitive decline.

• The association between cardiometabolic dysregulation and cognitive decline might be mediated by depression.

Depression, diabetes and change in cognitive functioning: results from the Canadian Longitudinal study on Aging

Background

Individuals who ultimately receive a diagnosis of dementia typically have an observable accelerated cognitive decline (ACD) many years prior to diagnosis. Depression in combination with diabetes is an emerging risk factor that is associated with cognitive problems. Using data from the Canadian Longitudinal Study on Aging, the objective of the present study was to investigate the longitudinal association between depression, diabetes, and cognitive decline in an elderly cohort.

Methods

Baseline and follow-up data from a population-based study in Canada were used. The sample consisted of 18161 adults between 45 and 85 years of age without diabetes. Cognitive functioning was assessed at baseline and after 4 years using six measures: the Rey Auditory Verbal Learning Test (RAVLT), the Mental Alternation Test (MAT), the Animal Fluency Test (AF), the Controlled Oral Word Association Test (COWAT), the Stroop Test, and the Prospective Memory Test. Depression was assessed using the CES-D10. Regression analysis was conducted to evaluate interactions between depression, diabetes and cognitive decline.

Results

The mean age of participants was 61 years. Participants with a comorbidity of depression and diabetes had an accelerated cognitive decline (g-factor) compared to those with depression without diabetes and those with diabetes without depression (regression coefficients ß=-0.145 (0.036), ß=-0.076 (0.011), and ß=-0.053 (0.021), respectively).

Conclusions

This study suggests that depression and diabetes might increase the risk of cognitive decline in a synergistic way.

Systemic inflammation and the risk of depression in people with type 2 diabetes

Background

Depression is a common co-morbidity in diabetes. The mechanisms underlying the association between depression and diabetes are poorly understood. Although risk factors, such as poor lifestyle behaviours, obesity, and stress have been identified, emerging evidence suggests that systemic inflammation may play an important role in the pathogenesis and recurrence of depression in people with diabetes. The aim of the present study was to evaluate if the inflammatory marker C-reactive protein (CRP) is associated with an increased risk of major depression episodes in people with type 2 diabetes.

Methods

A prospective, community-based study was conducted in Quebec, Canada. Individuals were recruited from the CARTaGENE (CaG) cohort, a population-based survey of Quebec residents aged 40 to 69 years. Our sample included 719 individuals with type 2 diabetes and 1423 individuals without diabetes. Individuals were assessed at baseline and 5 years after baseline. Major depression disorders were assessed using a clinical interview (CIDI). Inflammatory markers were assessed from blood samples. Elevated CRP levels were defined as ≥ 3 mg/L.

Results

Participants with both diabetes and elevated CRP levels had the highest risk of major depressive episodes (adjusted OR = 1.90, 95% CI 1.45, 2.50), compared to those without diabetes and without elevated CRP levels. The risk of major depressive episodes in individuals with diabetes without elevated CRP episodes was lower (adjusted OR = 1.21, 95% CI 0.85, 1.73) and similar to the risk of those without diabetes and elevated CRP levels (adjusted OR = 1.15, 95% CI 0.94, 1.39).

Discussion

The study highlights the interaction between diabetes, inflammatory makers, and depression in a community sample. Early identification, monitoring, and management of elevated inflammation levels might be an important depression prevention strategy in people with type 2 diabetes.

Childhood trauma, depression, and the risk of incident prediabetes in young adults: findings from the Lifelines Cohort Study

Background

Childhood trauma and depression have been shown to increase the risk of type 2 diabetes. However, many studies have focused on middle-age and older adults, with less known on the role of these variables in early glucose dysregulation. The goal of the study was to examine childhood trauma, depression, and their interactions, as risk factors for the onset of prediabetes in young adults.

Methods

Data were from the Dutch Lifelines Cohort Study. N = 8,650 adults (61% female) between 18-35 years without prediabetes/diabetes at baseline (2007-2014) were included. Childhood trauma was assessed using the Childhood Trauma Questionnaire. Depression was assessed using the Mini International Neuropsychiatric Interview. Prediabetes at follow-up (2014-2017) was considered by haemoglobin A1c levels between 5.7%-6.4%. Logistic regressions examined associations between depression and childhood trauma with the risk of incident prediabetes. Odds ratios (OR) and 95% confidence intervals (CI) for unadjusted analyses and analyses adjusted for age, sex, education, ethnicity, body mass index, smoking, and alcohol use (reduced adjusted sample size; n = 7,186) are presented.

Results

244 participants (2.8%) developed prediabetes. In univariate analyses, childhood trauma (OR = 1.02, CI = 1.01-1.03, p=.006) and depression (OR = 2.08, CI = 1.01-4.29, p=.048) predicted incident prediabetes. When childhood trauma subscales were examined, only sexual abuse significantly predicted incident prediabetes. In adjusted analyses, only childhood trauma, specifically sexual abuse, significantly predicted incident prediabetes (OR = 1.06, CI = 1.01-1.12, p=.021). No multiplicative interaction between depression and childhood trauma was found.

Conclusions

Young adults who have experienced childhood trauma, particularly sexual abuse, may be at risk of glucose dysregulation in early adulthood. Early targeted preventive care may help attenuate or halt glucose dysregulation and the development of type 2 diabetes.

Time at home during the COVID-19 pandemic: a prospective examination of psychosocial health in people with and without type 2 diabetes using digital phenotyping

Introduction

Societal restrictions due to COVID-19 have had a profound effect on our ability to connect with one another and limited our personal mobility. There is evidence that loneliness, social isolation, and psychological distress increased during restrictions for people with diabetes. Fluctuating restrictions provide a unique opportunity to utilise continuous GPS data from personal smartphones (digital phenotypes) to explore the relationship between time-at-home and psychosocial health for people with diabetes. This study aims to (1) describe the digital phenotypes of time-at-home during varying societal COVID-19 restrictions for people with and without type 2 diabetes and (2) to explore associations between these digital phenotypes and loneliness, social support, and other psychosocial factors and compare for people with and without type 2 diabetes.

Methods

Data come from a longitudinal observational study in the Republic of Ireland that ran between March and August 2021. Participants are seventy-four adults (64.8% female; median age-group = 50-54) with (N = 40) and without (N = 34) diabetes. Continuous GPS data were recorded for 2 months through the Beiwe smartphone application. Loneliness (UCLA-3), social support (MSPSS), diabetes stigma (DSAS-2; diabetes cohort only) as well as other demographic, psychosocial, and lifestyle questionnaires were assessed at baseline, 1 month, and 2 months follow-up.

Analysis

GPS data are being processed. The GPS-derived features of time-at-home, overall movement, and location variance will be computed. Associations between these digital phenotypes and psychosocial factors will be explored and changes over time examined using multilevel modeling.

Conclusions

We expect this study to be the first to describe and compare the digital phenotypes of people with and without diabetes during varying societal COVID-19 restrictions, providing new insights into the effects of such policies on the psychosocial health of people with diabetes.

Symptoms of diabetes distress, depression, and anxiety in people with type 2 diabetes: identifying central and bridge symptoms using network analysis

Introduction

People with diabetes are vulnerable to diabetes-related distress and are more likely to experience depressive and anxiety symptoms than the general population. Diabetes distress, depressive, and anxiety symptoms also tend to commonly co-occur.

Objectives

This study aimed to apply network analysis to explore the associations between diabetes distress, depressive, and anxiety symptoms in a cohort of adults with type 2 diabetes.

Methods

Data were from the baseline (2011) assessment of the Evaluation of Diabetes Insulin Treatment (EDIT) study (N = 1,796; 49% female; mean age = 60, SD = 8) from Quebec, Canada. A first network using the 17 items of the diabetes distress scale (DDS-17) was estimated. A second network was estimated using the 17 items of the DDS-17, the 9 depressive items of the PHQ-9, and the 7 anxiety items of the GAD-7. Symptom centrality, network stability, and bridge symptoms were examined.

Results

Regimen-related and physician-related distress symptoms were amongst the most central (highly connected) in the diabetes distress network. Worrying too much (anxiety), Not feeling motivated to keep up diabetes self-management (diabetes distress), and Feeling like a failure (depression) were the most central symptoms in the combined network. Feeling like a failure (depression) was highly connected to diabetes distress symptoms, representing a potential bridge between diabetes distress and depression.

Conclusions

Identifying central and bridge symptoms may provide new insights into diabetes distress, depressive, and anxiety symptom maintenance and comorbidity in people with type 2 diabetes.

Disclosure

No significant relationships.

An investigation of depression and inflammation as potential mediators linking adverse childhood experiences with cognitive decline in adulthood: results from a prospective cohort study

Introduction

Adverse childhood experiences (ACEs) have been associated with numerous health consequences in adulthood including cognitive decline. However, the underlying mechanisms implicated remain unclear.

Objectives

In this study, depressive symptoms and systemic inflammation were investigated as potential independent mediators of the association between ACEs and cognitive decline.

Methods

Participants were adults aged 50+ from the English Longitudinal Study of Ageing (N = 3,029; 54.8% female). Measures included self-reported ACEs at wave 3 (2006-2007), C-reactive protein (CRP) and depressive symptoms at wave 4 (2008-2009), and cognitive function at waves 3 and 7 (2014-2015). Mediation analyses examined the direct associations between ACEs and cognitive function at wave 7 and the indirect associations via depressive symptoms and CRP at wave 4 and were conducted using ordinary least squares regression models with the SPSS PROCESS macro. In Step 1, models were adjusted for sociodemographic factors and baseline cognitive function. Models in Step 2 were additionally adjusted for obesity and health behaviours (n = 1,874).

Results

Cumulative ACEs exposure was shown to positively predict later-life depressive symptoms, which in turn predicted cognitive decline. ACEs were also shown to positively predict systemic inflammation as measured by CRP. However, CRP did not mediate the association between ACEs and cognitive decline.

Conclusions

These findings suggest that ACEs are related to cognitive decline partly via depressive symptoms and corroborate prior research linking ACEs with adult systemic inflammation. Efforts towards screening for, preventing, and mitigating the effects of ACEs may therefore represent an important avenue for improving health outcomes in later life.

Disclosure

No significant relationships.

Trait-anger, hostility, and the risk of incident type 2 diabetes and diabetes-related complications: a systematic review of longitudinal studies

Introduction

There is a well-established association between anger, hostility, and an increased risk of cardiovascular disease. Emerging evidence also suggests associations between anger/hostility and type 2 diabetes (T2D), though evidence from longitudinal studies has not yet been synthesized.

Objectives

To systematically review findings from existing prospective cohort studies on trait anger/hostility and the risk of T2D and diabetes-related complications.

Methods

Electronic searches of MEDLINE (PubMed), PsychINFO, Web of Science, and CINAHL were performed for articles/abstracts published up to December 15, 2020. Peer-reviewed longitudinal studies conducted with adult samples, with effect estimates reported for trait anger or hostility and incident T2D or diabetes-related complications, were eligible for inclusion. Risk of bias/study quality was assessed. The review protocol was published a priori in PROSPERO (CRD42020216356) and was in keeping with PRISMA guidelines. Screening for eligibility, data extraction, and quality assessment was conducted by two independent reviewers.

Results

Four studies with a total of 155,146 participants met the inclusion criteria. A narrative synthesis of extracted data was conducted according to the Synthesis Without Meta-Analysis guidelines. While results were mixed, our synthesis suggested a positive association between high trait-anger/hostility and increased risk of incident T2D. No longitudinal studies were identified relating to anger/hostility and incident diabetes-related complications. Geographical locations of the study samples were limited to the USA and Japan.

Conclusions

Further research is needed to investigate whether trait-anger/hostility predicts incident type 2 diabetes after adjustments for potential confounding factors. Longitudinal studies are needed to investigate trait-anger/hostility and the risk of diabetes-related vascular complications.

Disclosure

No significant relationships.

Longitudinal white matter microstructural changes in pediatric mild traumatic brain injury: An A-CAP study

In the largest sample studied to date, white matter microstructural trajectories and their relation to persistent symptoms were examined after pediatric mild traumatic brain injury (mTBI). This prospective, longitudinal cohort study recruited children aged 8–16.99 years with mTBI or mild orthopedic injury (OI) from five pediatric emergency departments. Children's pre‐injury and 1‐month post‐injury symptom ratings were used to classify mTBI with or without persistent symptoms. Children completed diffusion‐weighted imaging at post‐acute (2–33 days post‐injury) and chronic (3 or 6 months via random assignment) post‐injury assessments. Mean diffusivity (MD) and fractional anisotropy (FA) were derived for 18 white matter tracts in 560 children (362 mTBI/198 OI), 407 with longitudinal data. Superior longitudinal fasciculus FA was higher in mTBI without persistent symptoms relative to OI, d (95% confidence interval) = 0.31 to 0.37 (0.02, 0.68), across time. In younger children, MD of the anterior thalamic radiations was higher in mTBI with persistent symptoms relative to both mTBI without persistent symptoms, 1.43 (0.59, 2.27), and OI, 1.94 (1.07, 2.81). MD of the arcuate fasciculus, −0.58 (−1.04, −0.11), and superior longitudinal fasciculus, −0.49 (−0.90, −0.09) was lower in mTBI without persistent symptoms relative to OI at 6 months post‐injury. White matter microstructural changes suggesting neuroinflammation and axonal swelling occurred chronically and continued 6 months post injury in children with mTBI, especially in younger children with persistent symptoms, relative to OI. White matter microstructure appears more organized in children without persistent symptoms, consistent with their better clinical outcomes.

Advancing Concussion Assessment in Pediatrics (A-CAP): a prospective, concurrent cohort, longitudinal study of mild traumatic brain injury in children: protocol study

INTRODUCTION

Paediatric mild traumatic brain injury (mTBI) is a public health burden. Clinicians urgently need evidence-based guidance to manage mTBI, but gold standards for diagnosing and predicting the outcomes of mTBI are lacking. The objective of the Advancing Concussion Assessment in Pediatrics (A-CAP) study is to assess a broad pool of neurobiological and psychosocial markers to examine associations with postinjury outcomes in a large sample of children with either mTBI or orthopaedic injury (OI), with the goal of improving the diagnosis and prognostication of outcomes of paediatric mTBI.

METHODS AND ANALYSIS

A-CAP is a prospective, longitudinal cohort study of children aged 8.00-16.99 years with either mTBI or OI, recruited during acute emergency department (ED) visits at five sites from the Pediatric Emergency Research Canada network. Injury information is collected in the ED; follow-up assessments at 10 days and 3 and 6 months postinjury measure a variety of neurobiological and psychosocial markers, covariates/confounders and outcomes. Weekly postconcussive symptom ratings are obtained electronically. Recruitment began in September 2016 and will occur for approximately 24 months. Analyses will test the major hypotheses that neurobiological and psychosocial markers can: (1) differentiate mTBI from OI and (2) predict outcomes of mTBI. Models initially will focus within domains (eg, genes, imaging biomarkers, psychosocial markers), followed by multivariable modelling across domains. The planned sample size (700 mTBI, 300 OI) provides adequate statistical power and allows for internal cross-validation of some analyses.

ETHICS AND DISSEMINATION

The ethics boards at all participating institutions have approved the study and all participants and their parents will provide informed consent or assent. Dissemination will follow an integrated knowledge translation plan, with study findings presented at scientific conferences and in multiple manuscripts in peer-reviewed journals.

Genetic markers, bone mineral density, and serum osteocalcin levels

We evaluated five genetic markers for products that contribute to skeletal mineralization including the Sp1 polymorphism for type I collagen Ai (COLIA1), the vitamin D receptor (VDR) translation initiation site polymorphism, the promoter of the osteocalcin gene containing a C/T polymorphism, the estrogen receptor (ER) gene containing a TA repeat, and the polymorphic (AGC)n site in the androgen receptor. These markers were evaluated for their potential relationship with bone mineral density (BMD), measured by dual-energy X-ray densitometry, or its 3-year change. Additionally, potential associations of these genotypes and with baseline osteocalcin concentration or its 3-year change (assessed using radioimmunoassay) were evaluated. The study was conducted in 261 pre- and perimenopausal women of the Michigan Bone Health Study, a population-based longitudinal study of musculoskeletal characteristics and diseases. The polymorphic (AGC)n site in the androgen receptor showed a strong association with BMD of the femoral neck (FN) and lumbar spine and remained highly significant after adjusting for body mass index (BMI), oophorectomy/hysterectomy, oral contraceptive (OC) use and hormone replacement use (p < 0.001). The TA repeat at the 5' end of the ER gene was associated with total body calcium (p < 0.05) after adjusting for BMI, oophorectomy and hysterectomy, and OC use. The frequency of oophorectomy and hysterectomy within selected genotypes explained much of the statistically significant association of the ER genotypes with BMD of the FN and spine. There was no association of measures of BMD or bone turnover with the Sp1 polymorphism for COLIA1, the VDR translation initiation site polymorphism, or the C/T promoter polymorphism of the osteocalcin gene. These findings suggest that sex hormone genes may be important contributors to the variation in BMD among pre- and perimenopausal women.