Search tips
Search criteria

Results 1-8 (8)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Vitamin D supplementation in pregnancy: A systematic review 
It is unclear whether the current evidence base allows definite conclusions to be made regarding the optimal maternal circulating concentration of 25(OH)-vitamin D during pregnancy, and how this might best be achieved. CRD42011001426.
Aim/ Research Questions
What are the clinical criteria for vitamin D deficiency in pregnant women?What adverse maternal and neonatal health outcomes are associated with low maternal circulating 25(OH)-vitamin D?Does maternal supplementation with vitamin D in pregnancy lead to an improvement in these outcomes (including assessment of compliance and effectiveness)?What is the optimal type (D2 or D3), dose, regimen and route for vitamin D supplementation in pregnancy?Is supplementation with vitamin D in pregnancy likely to be cost-effective?
We performed systematic review and where possible combined study results using meta-analysis to estimate the combined effect size.
Major electronic databases were searched up to June 2012 covering both published and grey literature. Bibliographies of selected papers were hand-searched for additional references. Relevant authors were contacted for any unpublished findings and additional data if necessary.
Inclusion and exclusion criteria
Pregnant women or pregnant women and their offspring.
Either assessment of vitamin D status (dietary intake, sunlight exposure, circulating 25(OH)-vitamin D concentration) or supplementation of participants with vitamin D or vitamin D containing food e.g. oily fish.
Offspring: Birth weight, birth length, head circumference, bone mass, anthropometry and body composition, risk of asthma and atopy, small for gestational dates, preterm birth, type 1 diabetes, low birth weight, serum calcium concentration, blood pressure and rickets. Mother: Preeclampsia, gestational diabetes, risk of caesarean section and bacterial vaginosis.
76 studies were included. There was considerable heterogeneity between the studies and for most outcomes there was conflicting evidence.
The evidence base was insufficient to reliably answer question 1 in relation to biochemical or disease outcomes.
For questions 2 and 3, modest positive relationships were identified between maternal 25(OH)-vitamin D and 1) offspring birth weight in meta-analysis of 3 observational studies using log-transformed 25(OH)-vitamin D concentrations after adjustment for potential confounding factors (pooled regression coefficient 5.63g/10% change maternal 25(OH)D, 95% CI 1.11,10.16), but not in those 4 studies using natural units, or across intervention studies; 2) offspring cord blood or postnatal calcium concentrations in a meta-analysis of 6 intervention studies (all found to be at high risk of bias; mean difference 0.05mmol/l, 95% CI 0.02, 0.05); and 3) offspring bone mass in observational studies judged to be of good quality, but which did not permit meta-analysis.
The evidence base was insufficient to reliably answer questions 4 and 5.
Study methodology varied widely in terms of study design, population used, vitamin D status assessment, exposure measured and outcome definition.
The evidence base is currently insufficient to support definite clinical recommendations regarding vitamin D supplementation in pregnancy. Although there is modest evidence to support a relationship between maternal 25(OH)-vitamin D status and offspring birth weight, bone mass and serum calcium concentrations, these findings were limited by their observational nature (birth weight, bone mass) or risk of bias and low quality (calcium concentrations). High quality randomised trials are now required.
PMCID: PMC4124722  PMID: 25025896
2.  A Dynamic Model of US Adolescents’ Smoking and Friendship Networks 
American Journal of Public Health  2012;102(6):e12-e18.
We investigated the associations between smoking and friend selection in the social networks of US adolescents.
We used a stochastic actor-based model to simultaneously test the effects of friendship networks on smoking and several ways that smoking can affect the friend selection process. Data are from 509 US high school students in the National Longitudinal Study of Adolescent Health, 1994–1996 (46.6% female, mean age at outset = 15.4 years).
Over time, adolescents’ smoking became more similar to their friends. Smoking also affected who adolescents selected as friends; adolescents were more likely to select friends whose smoking level was similar to their own, and smoking enhanced popularity such that smokers were more likely to be named as friends than were nonsmokers, after controlling for other friend selection processes.
Both friend selection and peer influence are associated with smoking frequency. Interventions to reduce adolescent smoking would benefit by focusing on selection and influence mechanisms.
PMCID: PMC3349762  PMID: 22515861
3.  MAVIDOS Maternal Vitamin D Osteoporosis Study: study protocol for a randomized controlled trial. The MAVIDOS Study Group 
Trials  2012;13:13.
MAVIDOS is a randomised, double-blind, placebo-controlled trial (ISRCTN82927713, registered 2008 Apr 11), funded by Arthritis Research UK, MRC, Bupa Foundation and NIHR.
Osteoporosis is a major public health problem as a result of associated fragility fractures. Skeletal strength increases from birth to a peak in early adulthood. This peak predicts osteoporosis risk in later life. Vitamin D insufficiency in pregnancy is common (31% in a recent Southampton cohort) and predicts reduced bone mass in the offspring. In this study we aim to test whether offspring of mothers supplemented with vitamin D in pregnancy have higher bone mass at birth than those whose mothers were not supplemented.
Women have their vitamin D status assessed after ultrasound scanning in the twelfth week of pregnancy at 3 trial centres (Southampton, Sheffield, Oxford). Women with circulating 25(OH)-vitamin D levels 25-100 nmol/l are randomised in a double-blind design to either oral vitamin D supplement (1000 IU cholecalciferol/day, n = 477) or placebo at 14 weeks (n = 477). Questionnaire data include parity, sunlight exposure, dietary information, and cigarette and alcohol consumption. At 19 and 34 weeks maternal anthropometry is assessed and blood samples taken to measure 25(OH)-vitamin D, PTH and biochemistry. At delivery venous umbilical cord blood is collected, together with umbilical cord and placental tissue. The babies undergo DXA assessment of bone mass within the first 14 days after birth, with the primary outcome being whole body bone mineral content adjusted for gestational age and age. Children are then followed up with yearly assessment of health, diet, physical activity and anthropometric measures, with repeat assessment of bone mass by DXA at age 4 years.
As far as we are aware, this randomised trial is one of the first ever tests of the early life origins hypothesis in human participants and has the potential to inform public health policy regarding vitamin D supplementation in pregnancy. It will also provide a valuable resource in which to study the influence of maternal vitamin D status on other childhood outcomes such as glucose tolerance, blood pressure, cardiovascular function, IQ and immunology.
PMCID: PMC3395865  PMID: 22314083
Vitamin D; cholecalciferol; supplementation; trial; osteoporosis; DXA; pregnancy; neonate
4.  Neural mechanisms of ageing and cognitive decline 
Nature  2010;464(7288):529-535.
During the past century, treatments for the diseases of youth and middle age have helped raise life expectancy significantly. However, cognitive decline has emerged as one of the greatest health threats of old age, with nearly 50% of adults over the age of 85 afflicted with Alzheimer’s disease. Developing therapeutic interventions for such conditions demands a greater understanding of the processes underlying normal and pathological brain ageing. Recent advances in the biology of ageing in model organisms, together with molecular and systems-level studies of the brain, are beginning to shed light on these mechanisms and their potential roles in cognitive decline.
PMCID: PMC2927852  PMID: 20336135
5.  Association Between Bone Mass and Fractures in Children: A Prospective Cohort Study 
This is the first prospective cohort study of the association between bone mass and fracture risk in childhood. A total of 6213 children 9.9 years of age were followed for 24 months. Results showed an 89% increased risk of fracture per SD decrease in size-adjusted BMC.
Although previous case-control studies have reported that fracture risk in childhood is inversely related to bone mass, this has not been confirmed in prospective studies. Additionally, it remains unclear which constituent(s) of bone mass underlie this association. We carried out a prospective cohort study to examine the relationship between DXA measures in children 9.9 years of age and risk of fracture over the following 2 years.
Materials and Methods
Total body DXA scan results obtained at 9.9 years of age were linked to reported fractures over the following 2 years in children from a large birth cohort in southwest England. DXA measures consisted of total body less head (TBLH) BMD, bone area, and BMC, and results of subregional analysis of the humerus. Analyses were adjusted for age, sex, ethnicity, and social position.
Complete data were available on 6213 children. There was a weak inverse relationship between BMD at 9.9 years and subsequent fracture risk (OR per SD decrease = 1.12; 95% CI, 1.02–1.25). In analyses examining the relationship between fracture risk and volumetric BMD, fracture risk was inversely related to BMC adjusted for bone area, height, and weight (OR = 1.89; 95% CI, 1.18–3.04) and to estimated volumetric BMD of the humerus (OR = 1.29; 95% CI, 1.14–1.45). Fracture risk was unrelated to both TBLH and humeral bone area. However, in analyses of the relationship between fracture risk and bone size relative to body size, an inverse association was observed between fracture risk and TBLH area adjusted for height and weight (OR = 1.51; 95% CI, 1.17–1.95).
Fracture risk in childhood is related to volumetric BMD, reflecting an influence of determinants of volumetric BMD such as cortical thickness on skeletal fragility. Although bone size per se was not related to fracture risk, we found that children who fracture tend to have a smaller skeleton relative to their overall body size.
PMCID: PMC2742714  PMID: 16939408
population studies; bone densitometry; clinical/pediatrics; fractures; epidemiology
6.  Doctors and managers 
BMJ : British Medical Journal  2003;326(7400):1214.
PMCID: PMC1126074  PMID: 12775639

Results 1-8 (8)