Periconceptional folic acid use and the prevalence of neural tube defects in The Netherlands

Population estimation using the multiple system estimator in the presence of continuous covariates

In the presence of continuous covariates, standard capture-recapture methods assume either that the registrations operate independently at the individual level or that the covariates can be stratified and log-linear models fitted, permitting the modelling of dependence between data sources. This article introduces an approach where direct dependence between registrations is modelled leaving the continuous covariates in their measurement scale. Simulations show that not accounting for possible dependence between registrations results in biased estimation of both the population size and standard error. The proposed method is applied to Dutch neural tube defect registration data.

Factors contributing to the success of folic acid public health campaigns

BACKGROUND

Studies in the 1990s have found that periconceptional dietary folate, supplementation of folic acid or supplemental multivitamins containing folic acid, help prevent neural tube defect (NTDs) if taken at the right time. This literature review assesses the extant folic acid public health campaigns literature and identifies some common variables used in folic acid consumption campaign evaluations.

METHODS

This review was part of a larger study that searched PUBMED, PsycINFO and Embase from 1976 to 2010 to identify articles related to the psychosocial and economic impact of NTDs (especially spina bifida) on patients and caregivers.

RESULTS

Awareness of folic acid levels prior to conception improved post-campaign from 6 to 41%. Knowledge about consumption and correct periconceptional use of folic acid also improved. However, in most studies more than 50% of women did not take folic acid as prescribed. Many factors were associated with or without taking folic acid post-campaign, including incomplete outreach, prior awareness and knowledge, closeness to pregnancy, demographics and other personal characteristics.

CONCLUSIONS

Sustained campaigning to maintain awareness about and promote periconceptional consumption of folic acid in order to reduce the incidence of NTDs is clearly needed. Additional initiatives could complement existing public health strategies.

A population-based case-control study of risk factors for neural tube defects in Shenyang, China

PURPOSE

To explore the risk factors for neural tube defects (NTD) in Shenyang, we carried out a population-based case-control study.

METHODS

We used chi-square test or Fisher's exact test to evaluate variations in the prevalence by selected covariates. Adjusted odds ratios and 95% confidence intervals were derived from univariate and multivariable conditional logistic models.

RESULTS

A history of maternal previous birth defect-affected pregnancy was a risk factor for NTDs (adjusted OR = 4.00, 95%CI = 1.29-12.45). Risks for NTDs were significantly associated with exposure to maternal factors during the periconceptional period such as a history of fever or cold (adjusted OR = 6.36, 95%CI = 3.24-12.52), use of analgesic and antipyretic drugs (adjusted OR = 4.94, 95%CI = 1.79-13.63), oral contraceptive use (adjusted OR 2.06, 95%CI 1.16, 3.68), and passive smoking (adjusted OR = 2.24, 95%CI = 1.04-4.81). Folic acid tablets use and fresh vegetable or fruit consumption ≥6 meals a week in periconception appeared to be protective factors (adjusted OR 0.33, 0.55, and 0.40, and 95%CI 0.13-0.44, 0.30-1.01, and 0.21-0.74, respectively). Differences in risk were found between the two most common phenotypes of NTD, anencephaly, and spina bifida.

CONCLUSIONS

This study suggests that a history of previous birth defect-affected pregnancy, a history of maternal fever or cold, use of analgesics, antipyretics, and oral contraceptives, exposure to passive smoking, folic acid use, and consumption of fresh vegetable and fruit may be associated with NTD risk.

Folic acid, methylation and neural tube closure in humans

This review provides a brief description of folate use and folic acid metabolism in relation to neural tube defect (NTD) risk. First, a meta-analysis of reduction in NTD recurrence and occurrence risk with periconceptional folic acid supplementation is presented. Second, an overview of the complex folate metabolism is given. Third, SNPs for genes involved in folate and homocysteine metabolism that have been studied in relation to NTD riskare discussed. Fourth, the questions whether folate receptor autoantibodies or hampered methylation are mechanisms underlying NTDs are briefly discussed.

Urinary tract infections in children with spina bifida: an inventory of 41 European centers

The introduction of clean intermittent catheterization (CIC) in 1972 and low-dose chemoprophylaxis (LDCP, antibiotic prophylaxis), anticholinergic medication and urological surgery in the mid-1980s has improved the long-term outcome of renal function in children with neurogenic bladder sphincter dysfunction (NBSD) due to spina bifida (SB). We have conducted a European survey of the protocols for diagnosing and treating urinary tract infections (UTIs) in these children, using a web-based questionnaire. The responses from 41 centers in 14 European countries confirm that although most centers have standardized protocols for treating UTIs, there is no consensus among European centers in terms of protocols for preventing, diagnosing and treating UTIs in children with NBSD and for CIC.

Analysing capture–recapture data when some variables of heterogeneous catchability are not collected or asked in all registrations

Registrations in epidemiological studies suffer from incompleteness, thus a general consensus is to use capture-recapture models. Lately, there has been a thrust to incorporate covariates which relate to the capture probabilities in order to improve the estimate of population size. Current approaches utilize covariates observed in all the pertinent registrations. In epidemiological applications, one often encounters capture-recapture data where some covariates are measured by some but not by all of the registrations under scrutiny. In this article, the usefulness of these types of covariates is evaluated and furthermore a methodology for analysing such capture-recapture data is presented. The methodology is illustrated by applying it to data on neural tube defects in the Netherlands.

The multiple-record systems estimator when registrations refer to different but overlapping populations

In multiple-record systems estimation it is usually assumed that all registration relate to the same population. In this paper, we develop a method which can be used when the registrations relate to different populations, in the sense that they cover, for example, different time periods or regions. We show that under certain conditions ignoring that the registrations relate to different populations results in correct estimates of population size. The EM algorithm is presented as a method that can be used for more general problems. The parametric bootstrap is used to construct a confidence interval. The proposed method is then applied to a data set with five registrations of neural tube defects, that cover different time periods.