The relationship between sociodemographic variables and pregnancy loss in a rural area of Bangladesh

This study examines the relationship between eight sociodemographic variables and the risk of pregnancy loss in a rural area of Bangladesh. The risks of spontaneous miscarriage and stillbirth were significantly associated with maternal age, pregnancy order and previous pregnancy wastage.     

A prospective cohort study of pregnancy risk factors and birth outcomes in Aboriginal women

Background

Aboriginal women have been identified as having poorer pregnancy outcomes than other Canadian women, but information on risk factors and outcomes has been acquired mostly from retrospective databases. We compared prenatal risk factors and birth outcomes of First Nations and Métis women with those of other participants in a prospective study.

Methods

During the 12-month period from July 1994 to June 1995, we invited expectant mothers in all obstetric practices affiliated with a single teaching hospital in Edmonton to participate. Women were recruited at their first prenatal visit and followed through delivery. Sociodemographic and clinical data were obtained by means of a patient questionnaire, and microbiological data were collected at 3 points during gestation: in the first and second trimesters and during labour. Our primary outcomes of interest were low birth weight (birth weight less than 2500 g), prematurity (birth at less than 37 weeks'' gestation) and macrosomia (birth weight greater than 4000 g).

Results

Of the 2047 women consecutively enrolled, 1811 completed the study through delivery. Aboriginal women accounted for 70 (3.9%) of the subjects who completed the study (45 First Nations women and 25 Métis women). Known risk factors for adverse pregnancy outcome were more common among Aboriginal than among non-Aboriginal women, including previous premature infant (21% v. 11%), smoking during the current pregnancy (41% v. 13%), presence of bacterial vaginosis in midgestation (33% v. 13%) and poor nutrition as measured by meal consumption. Although Aboriginal women were less likely than non-Aboriginal women to have babies of low birth weight (odds ratio [OR] 1.46, 95% confidence interval [CI] 0.52–4.15) or who were born prematurely (OR 1.45, 95% CI 0.57–3.72) and more likely to have babies with macrosomia (OR 2.04, 95% CI 1.03–4.03), these differences were lower and statistically nonsignificant after adjustment for smoking, cervicovaginal infection and income (adjusted OR for low birth weight 0.85, 95% CI 0.19–3.78; for prematurity 0.90, 95% CI 0.21–3.89; and for macrosomia 2.12, 95% CI 0.84-5.36).

Interpretation

After adjustment for potential confounding factors, we found no statistically significant relation between Aboriginal status and birth outcome.It is generally recognized that Aboriginal women experience poorer birth outcomes than other North American women, including higher rates of stillbirth,¹ low-birth-weight infants^1,2,3 and prematurity.^2,3 Although significant efforts have been made to reduce Aboriginal infant mortality rates, these rates remain higher than for other infants in both Canada⁴ and the United States.⁵ Little is known about the reasons for differences in birth outcomes, although social, economic, medical and prenatal care factors have been suggested. Recent publications, based on retrospective analyses of large databases, have confirmed disparities in birth outcomes between Aboriginal and all other groups,^3,6,7 but there is a paucity of prospective data. In addition, although the term “Aboriginal” refers to a heterogeneous population comprising First Nations people, Métis and Inuit, there are few comparisons between specific Aboriginal groups or of Aboriginal groups with the general population.We report here the results of a prospective study in a general obstetric population, comparing birth outcomes and known pregnancy risk factors of Aboriginal women with those of non-Aboriginal Canadian women. In addition to well-recognized socioeconomic and reproductive risk factors, we investigated the prevalence of maternal cervicovaginal infections, which have been increasingly linked to prematurity.^8,9     

Associations between manganese exposure and multiple immunological parameters in manganese-exposed workers healthy cohort

BackgroundManganese (Mn) ions play a crucial role in the immune response. The immunotoxicity of Mn is rarely reported compared with the neurotoxicity of Mn.ObjectivesThe purpose of this study was to investigate the associations between chronic Mn exposure and immunological parameters in occupational Mn-exposed workers.MethodsA total of 538 workers were selected from the follow-up of manganese-exposed workers healthy cohort (MEWHC) in 2017. We divided the workers into the low-exposure group and the high-exposure group by the cutoff of the manganese-time weighted average (Mn-TWA) setting at 0.15 mg/m³. We examined serum immunological parameters by the immunoturbidimetric method and leukocyte counts and ratios in blood routine. Then we used the generalized linear model analyses and spline analyses to explore the associations between external exposure of Mn and multiple immunological parameters adjusted for variables. Based on the epidemiological analyses, we used Elisa (enzyme-linked immune sorbent assay) to detect plasma complement C3 of Mn-exposed rats.ResultsIn male workers, the mean value of complement C3 was 1.20 ± 0.16 g/L in the high-exposure group, which was significantly lower as compared to the low-exposure group (1.25 ± 0.18 g/L, P = 0.023). The generalize linear models’ analyses showed that complement C3 value had a significantly negative association with external exposure of Mn included adjustment for variables (β = -0.04, P = 0.035). Moreover, in male rats, the high-exposure group also had a lower level of complement C3 compared with the low-exposure group (P < 0.001). None significant association was observed in immunological parameters among female workers and rats (all P > 0.05).ConclusionsMn exposure from inhalable dust was associated with decreased complement C3 among occupationally Mn-exposed male individuals but not in female workers, which was further confirmed by the rat model. Further research into the possible mechanism of C3 reduction is needed in the future.     

Neurocognitive outcomes in Malawian children exposed to malaria during pregnancy: An observational birth cohort study

BackgroundAnnually 125 million pregnancies are at risk of malaria infection. However, the impact of exposure to malaria in pregnancy on neurodevelopment in children is not well understood. We hypothesized that malaria in pregnancy and associated maternal immune activation result in neurodevelopmental delay in exposed offspring.Methods and findingsBetween April 2014 and April 2015, we followed 421 Malawian mother–baby dyads (median [IQR] maternal age: 21 [19, 28] years) who were previously enrolled (median [IQR] gestational age at enrollment: 19.7 [17.9, 22.1] weeks) in a randomized controlled malaria prevention trial with 5 or 6 scheduled assessments of antenatal malaria infection by PCR. Children were evaluated at 12, 18, and/or 24 months of age with cognitive tests previously validated in Malawi: the Malawi Developmental Assessment Tool (MDAT) and the MacArthur–Bates Communicative Development Inventories (MCAB-CDI). We assessed the impact of antenatal malaria (n [%] positive: 240 [57.3]), placental malaria (n [%] positive: 112 [29.6]), and maternal immune activation on neurocognitive development in children. Linear mixed-effects analysis showed that children exposed to antenatal malaria between 33 and 37 weeks gestation had delayed language development across the 2-year follow-up, as measured by MCAB-CDI (adjusted beta estimate [95% CI], −7.53 [−13.04, −2.02], p = 0.008). Maternal immune activation, characterized by increased maternal sTNFRII concentration, between 33 and 37 weeks was associated with lower MCAB-CDI language score (adjusted beta estimate [95% CI], −8.57 [−13.09, −4.06], p < 0.001). Main limitations of this study include a relatively short length of follow-up and a potential for residual confounding that is characteristic of observational studies.ConclusionsThis mother–baby cohort presents evidence of a relationship between malaria in pregnancy and neurodevelopmental delay in offspring. Malaria in pregnancy may be a modifiable risk factor for neurodevelopmental injury independent of birth weight or prematurity. Successful interventions to prevent malaria during pregnancy may reduce the risk of neurocognitive delay in children.

Andrea Weckman and co-workers study associations between children’s neurodevelopmental outcomes and malaria in pregnancy.     

Correlation between subsequent lengths of postpartum amenorrhoea in a prospective study of breast-feeding women in rural Bangladesh.

The relationship between subsequent lengths of lactational amenorrhoea for individual women in a prospective study of breast-feeding women in Bangladesh was studied. The data indicate that previous length of amenorrhoea has significant predictive value for the subsequent length of amenorrhoea. Information on previous experience with lactational amenorrhoea should be therefore incorporated into guidelines for the introduction of family planning during lactation.     

Age of mother and pregnancy outcome in the 1981 Arkansas birth cohort

Higher levels of obstetric risk observed among teenage mothers seem to be an artifact of lower socioeconomic status and inferior access to health care rather than biological immaturity. In a study of matched Arkansas birth-infant death records for 1978, the proxy variables for health access (month care started and number of visits) have the strongest association with each of the dependent variables. The indicators of social status (education, race, and marital status) have a weaker association, and there is virtually no age effect observable once the affects of socioeconomic status and health access have been controlled for. A series of stepwise regression analyses shows that the multiple partial for health access indicators and mortality is 0.036, while the same coefficients for social status indicators and age are 0.001 and 0.006, respectively. Similar results are obtained using the other dependent variables. Health consequences of adolescent pregnancy usually include higher rates of malnutrition and prematurity and lower birth weight. It seems that the elevated morbidity and mortality among newborns delivered by teenagers are not a result of biologic factors. After the effects of lower status and health care access have been removed, the apparent biological disadvantages attributed to teenagers disappear, and, in the case of mortality and birth weight, are replaced by a slight advantage. This advantage is observed through the use of statisitical controls and will not be observed in the population at large unless there are changes in the policies governing access to contraception, abortion, and health care by adolescents, especially those at the youngest ages.     

Regulation of birthweight by placenta-derived miRNAs: evidence from an arsenic-exposed birth cohort in Bangladesh

Altered expression of microRNAs (miRNAs) is implicated in fetal growth. However, the mechanisms by which placenta-derived miRNAs regulate birthweight are not well understood. In Phase 1, we compared the expression of 754 miRNAs in the placenta of mothers from two extreme birthweight groups (0.8–2.2 kg vs. 3.3–3.9 kg, n = 77 each) selected from an arsenic-exposed Bangladeshi birth cohort (n = 1,141). We identified 49 miRNAs associated with the extreme birthweight groups and/or gestational age in Phase 1, which were further analyzed in Phase 2 among 364 randomly selected mother-infant pairs. Gestational age was determined by ultrasound. Causal mediation analysis was used to estimate the effect of miRNAs on birthweight considering gestational age a mediator, adjusting for core blood arsenic and other risk factors. miR-1290, miR-195, and let-7g showed significant inverse associations with gestational age, while miR-328 showed significant positive association [false discovery rate (FDR) <0.05]. Via changing gestational age, miR-1290, miR-195, and miR-27a showed significant inverse associations with birthweight, while miR-328 and miR-324-5p showed significant positive associations (FDR <0.05). The effect of miRNAs on birthweight varied by gestational age (for miR-1290, miR-195, miR-328) and in utero arsenic exposure (for miR-1290): stronger effect was observed among infants delivered early in gestation or exposed to higher concentrations of arsenic in cord blood. Gene enrichment analysis with in silico predicted targets identified cell proliferation, inflammation, apoptosis, insulin, and IGF family signaling cascades associated with these miRNAs. Future studies are warranted to replicate these findings and assess these miRNAs as early biomarkers of fetal growth.     

Adipose tissue fatty acid patterns and changes in anthropometry: a cohort study

Introduction

Diets rich in n-3 long chain polyunsaturated fatty acids (LC-PUFA), but low in n-6 LC-PUFA and 18:1 trans-fatty acids (TFA), may lower the risk of overweight and obesity. These fatty acids have often been investigated individually. We explored associations between global patterns in adipose tissue fatty acids and changes in anthropometry.

Methods

34 fatty acid species from adipose tissue biopsies were determined in a random sample of 1100 men and women from a Danish cohort study. We used sex-specific principal component analysis and multiple linear regression to investigate the associations of adipose tissue fatty acid patterns with changes in weight, waist circumference (WC), and WC controlled for changes in body mass index (WC_BMI), adjusting for confounders.

Results

7 principal components were extracted for each sex, explaining 77.6% and 78.3% of fatty acid variation in men and women, respectively. Fatty acid patterns with high levels of TFA tended to be positively associated with changes in weight and WC for both sexes. Patterns with high levels of n-6 LC-PUFA tended to be negatively associated with changes in weight and WC in men, and positively associated in women. Associations with patterns with high levels of n-3 LC-PUFA were dependent on the context of the rest of the fatty acid pattern.

Conclusions

Adipose tissue fatty acid patterns with high levels of TFA may be linked to weight gain, but patterns with high n-3 LC-PUFA did not appear to be linked to weight loss. Associations depended on characteristics of the rest of the pattern.     

Associations between prenatal physical activity,birth weight,and DNA methylation at genomically imprinted domains in a multiethnic newborn cohort

Birth weight is a commonly used indicator of the fetal environment and a predictor of future health outcomes. While the etiology of birth weight extremes is likely multifactorial, epidemiologic data suggest that prenatal physical activity (PA) may play an important role. The mechanisms underlying this association remain unresolved, although epigenetics has been proposed. This study aimed to estimate associations between prenatal PA, birth weight, and newborn DNA methylation levels at differentially methylated regions (DMRs) regulating 4 imprinted genes known to be important in fetal development. Study participants (N = 1281) were enrolled as part of the Newborn Epigenetics Study. Prenatal PA was ascertained using the Pregnancy Physical Activity Questionnaire, and birth weight data obtained from hospital records. Among 484 term mother-infant pairs, imprinted gene methylation levels were measured at DMRs using bisulfite pyrosequencing. Generalized linear and logistic regression models were used to estimate associations. After adjusting for preterm birth and race/ethnicity, we found that infants born to mothers in the highest quartile of total non-sedentary time had lower birth weight compared to infants of mothers in the lowest quartile (β = −81.16, SE = 42.02, P = 0.05). These associations appeared strongest among male infants (β = −125.40, SE = 58.10, P = 0.03). Methylation at the PLAGL1 DMR was related to total non-sedentary time (P < 0.05). Our findings confirm that prenatal PA is associated with reduced birth weight, and is the first study to support a role for imprinted gene plasticity in these associations. Larger studies are required.     

Changes of oxidative stress parameters in diabetic pregnancy

BACKGROUND: The molecular aetiology of disturbed embryogenesis and other unfavourable outcomes in offspring of diabetic mothers is not fully understood. Experimental studies have suggested an involvement of radical oxygen species (ROS) in the teratological process. THE AIM OF OUR STUDY: To investigate if maternal diabetes in humans is capable of inducing alterations in vascular oxidative stress parameters and whether such changes are associated with disturbances in foetal development. METHODS: Seventy patients with pre-gestational diabetes (PGDM) were chosen for the study: 29 (41.4%) belonged to class B according to White, 15 (21.4%) to class C, 8 (11.4%) to class D, 3 (4.3%) to class F, 3 to class R and 12 (17.1%) to class F/R. In 20 (28.6%) patients from this group an unfavourable outcome was noted. All patients were subjected to intensive insulin therapy. Glycaemia was estimated by daily self-monitoring, and diurnal glucose profiles and glycated haemoglobin (HbA1c) concentrations were measured monthly. Oxidative stress was evaluated as changed superoxide dismutase, catalase and glutathione peroxidase activities as well as of malondialdehyde (MDA) and peroxides concentrations in maternal erythrocytes and blood serum. RESULTS: Prior to conception, the mean glycaemia in the group that had a planned pregnancy was 6.6mmol/l and HBA1c was 9.35%. Throughout the course of pregnancy, these parameters were maintained at a level of 6.7 mmol/l and 7.85%, respectively. The activity of all antioxidative enzymes was lower before than during pregnancy, and so was the concentration of MDA. The MDA concentrations were higher in patients with elevated glycaemia and with an unfavourable outcome. The investigated ROS, the glycaemia level, as well as the concentration of HBA1c did not show any significant differences between pregnancies with and without vascular complications. Patients with a favourable perinatal outcome presented a higher activity of antioxidant enzymes, than those with unfavourable outcome, throughout the whole course of pregnancy. The appearance of unfavourable perinatal outcomes in relation to parameters of oxidative stress was assessed by logistic regression. Both SOD and GPX activities, as well as peroxides' concentration, showed significant correlations (p < 0.005) with foetal complications. However, after mean glucose levels in the studied group were included into these analyses, this relationship was only evident with SOD and GPX activity (p < 0.0016). CONCLUSION: Oxidative stress is one of several important factors contributing to unfavourable outcome of human diabetic pregnancy.     

Effects of grandmothers' smoking in pregnancy on birth weight: intergenerational cohort study

Objective To investigate the influences on birth weight of maternal smoking during pregnancy across generations.Design Intergenerational cohort study.Participants Members of the 1958 birth cohort and their offspring and mothers.Setting England, Scotland, and Wales.Main outcome measure Birth weight.Results Information on grandmothers'' smoking during pregnancy was available for 9028 singleton offspring of 4302 female cohort members. Assuming heritable transmission through the intergenerational association, grandmothers'' smoking was predicted to result in a 34 g reduction (95% confidence interval -41 g to -28 g) in the birth weight of grandchildren. Random effects models showed a negative association between grandmothers'' smoking and birth weight of grandchildren (β regression coefficient -24 g, -50 g to 3 g), but this effect was eliminated after adjustment for maternal smoking (0 g, -26 g to 26 g).No association was evident among the offspring of non-smoking mothers (n = 6105; 14 g, -17 g to 46 g), and after adjustment for maternal birth weight, adult height and body mass index, grandmothers'' smoking was positively associated with the birth weight of grandchildren (45 g, 10 g to 80 g).Conclusion Deficits in mothers'' birth weight attributable to their mother smoking was not evident in the grandchildren.     

Urogenital schistosomiasis during pregnancy is associated with low birth weight delivery: analysis of a prospective cohort of pregnant women and their offspring in Gabon

An estimated 40 million women of childbearing age suffer from schistosomiasis. Animal models indicate a deleterious effect of maternal schistosomiasis on pregnancy outcomes. To date there is a lack of epidemiological evidence evaluating schistosomiasis-related morbidity in pregnancy. This study was designed to describe the impact of urogenital schistosomiasis on pregnancy outcomes in a highly endemic region of central Africa. Pregnant women attending antenatal clinics in Fougamou and Lambaréné, Gabon, were consecutively screened for the presence of Schistosoma haematobium eggs in diurnal urine samples. Maternal and newborn characteristics assessed at delivery were compared between infected and uninfected mothers. The impact of maternal schistosomiasis on low birth weight and preterm delivery was assessed using logistic regression analysis. Urogenital schistosomiasis was diagnosed in 103 (9%) of 1115 pregnant women. Maternal age was inversely associated with the prevalence of urogenital schistosomiasis, with a higher burden amongst nulliparous women. Low birth weight was more common amongst infants of S. haematobium-infected mothers. This association was unaffected by controlling for demographic characteristics, gestational age and Plasmodium infection status (adjusted Odds Ratio 1.93; 95% confidence interval: 1.08–3.42). Other risk factors associated with low birth weight delivery were underweight mothers (adjusted Odds Ratio 2.34; 95% confidence interval: 1.12–4.92), peripheral or placental Plasmodium falciparum infection (adjusted Odds Ratio 2.04; 95% confidence interval: 1.18–3.53) and preterm birth (adjusted Odds Ratio 3.12; 95% confidence interval: 1.97–4.96). Preterm delivery was not associated with S. haematobium infection (adjusted Odds Ratio 1.07 95% confidence interval: 0.57–1.98). In conclusion, this study indicates that pregnant women with urogenital schistosomiasis are at an increased risk for low birth weight deliveries. Further studies evaluating targeted treatment and prevention programmes for urogenital schistosomiasis in pregnant women and their impact on delivery outcomes are warranted.     

Differentials of fertility between polygynous and monogamous marriages in rural Bangladesh

This paper discusses polygynous marriages in rural Bangladesh, using marital status and birth registration data from the Demographic Surveillance System (DSS) of the International Center for Diarrheal Disease Research, for the period 1975-79. Of all the marriages recorded during this period about 5% were polygynous. To identify the women polygynously married, 1974 census data of the DSS area were used. The difference in age at marriage between the polygynous groom and his subsequent wife was 15 years on average. The socioeconomic indicators studied were education, occupation and area of dwelling space. In general, these indicators between women in monogamous marriages were significantly higher than between the women in polygynous unions. During the period 1976-79, 863 polygynous marriages were recorded (4.9% of all marriages in the study area). Polygynous marriages were found to be less frequent among men with 2ndary and higher levels of education. The highest proportion of polygynous marriages occurred among husbands with no schooling or Koranic education. The general fertility rate of women in monogamous marriages was significantly higher than for women in polygynous marriages, overall and in all age groups except 20-24. During the period 1975-79, the mean number of liveborn children for monogamous women was higher than that of polygynous women.     

Associations between functional polymorphisms in antioxidant defense genes and urinary oxidative stress biomarkers in healthy, premenopausal women

Functional polymorphisms in endogenous antioxidant defense genes including manganese superoxide dismutase (MnSOD), catalase (CAT), and glutathione peroxidase (GPX-1) have been linked with risk of cancer at multiple sites. Although it is presumed that these germline variants impact disease risk by altering the host’s ability to detoxify mutagenic reactive oxygen species, very few studies have directly examined this hypothesis. Concentrations of 8-isoprostane F2α (8-iso-PGF2α) and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxoxdG)—sensitive indicators of lipid peroxidation and DNA oxidation, respectively—were measured in 24-h urine samples obtained from 93 healthy, premenopausal women participating in a dietary intervention trial. In addition, DNA was extracted from blood for genotyping of MnSOD Val16Ala, CAT-262 C > T, and GPX1 Pro198Leu genotypes by Taqman assay. Although geometric mean concentrations of 8-iso-PGF2_α and 8-oxoxdG varied across several study characteristics including race, education level, body mass index, and serum antioxidant levels, there was little evidence that these biomarkers differed across any of the examined genotypes. In summary, functional polymorphisms in endogenous antioxidant defense genes do not appear to be strongly associated with systemic oxidative stress levels in young, healthy women.     

Exposure to non-steroidal anti-inflammatory drugs during pregnancy and the risk of selected birth defects: a prospective cohort study

Background

Since use of non-steroidal anti-inflammatory drugs (NSAIDs) during pregnancy is common, small increases in the risk of birth defects may have significant implications for public health. Results of human studies on the teratogenic risks of NSAIDs are inconsistent. Therefore, we evaluated the risk of selected birth defects after prenatal exposure to prescribed and over-the-counter NSAIDs.

Methods and Findings

We used data on 69,929 women enrolled in the Norwegian Mother and Child Cohort Study between 1999 and 2006. Data on NSAID exposure were available from a self-administered questionnaire completed around gestational week 17. Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. Only birth defects suspected to be associated with NSAID exposure based upon proposed teratogenic mechanisms and previous studies were included in the multivariable logistic regression analyses. A total of 3,023 women used NSAIDs in gestational weeks 0–12 and 64,074 women did not report NSAID use in early pregnancy. No associations were observed between overall exposure to NSAIDs during pregnancy and the selected birth defects separately or as a group (adjusted odds ratio 0.7, 95% confidence interval 0.4–1.1). Associations between maternal use of specific types of NSAIDs and the selected birth defects were not found either, although an increased risk was seen for septal defects and exposure to multiple NSAIDs based on small numbers (2 exposed cases; crude odds ratio 3.9, 95% confidence interval 0.9–15.7).

Conclusions

Exposure to NSAIDs during the first 12 weeks of gestation does not seem to be associated with an increased risk of the selected birth defects. However, due to the small numbers of NSAID-exposed infants for the individual birth defect categories, increases in the risks of specific birth defects could not be excluded.     

Associations between chronotype,morbidity and mortality in the UK Biobank cohort

Later chronotype (i.e. evening preference) and later timing of sleep have been associated with greater morbidity, including higher rates of metabolic dysfunction and cardiovascular disease (CVD). However, no one has examined whether chronotype is associated with mortality risk to date. Our objective was to test the hypothesis that being an evening type is associated with increased mortality in a large cohort study, the UK Biobank. Our analysis included 433 268 adults aged 38–73 at the time of enrolment and an average 6.5-year follow-up. The primary exposure was chronotype, as assessed through a single self-reported question-defining participants as definite morning types, moderate morning types, moderate evening types or definite evening types. The primary outcomes were all-cause mortality and mortality due to CVD. Prevalent disease was also compared among the chronotype groups. Analyses were adjusted for age, sex, ethnicity, smoking, body mass index, sleep duration, socioeconomic status and comorbidities. Greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of all comorbidities. Comparing definite evening type to definite morning type, the associations were strongest for psychological disorders (OR 1.94, 95% CI 1.86–2.02, p = < 0.001), followed by diabetes (OR 1.30, 95% CI 1.24–1.36, p = < 0.001), neurological disorders (OR 1.25, 95% CI 1.20–1.30, p = < 0.001), gastrointestinal/abdominal disorders (OR 1.23, 95% CI 1.19–1.27, p = < 0.001) and respiratory disorders (OR 1.22, 95% CI 1.18–1.26, p = < 0.001). The total number of deaths was 10 534, out of which 2127 were due to CVD. Greater eveningness, based on chronotype as an ordinal variable, was associated with a small increased risk of all-cause mortality (HR 1.02, 95% CI 1.004–1.05, p = 0.017) and CVD mortality (HR 1.04, 95% CI 1.00–1.09, p = 0.06). Compared to definite morning types, definite evening types had significantly increased risk of all-cause mortality (HR 1.10, 95% CI 1.02–1.18, p = 0.012). This first report of increased mortality in evening types is consistent with previous reports of increased levels of cardiometabolic risk factors in this group. Mortality risk in evening types may be due to behavioural, psychological and physiological risk factors, many of which may be attributable to chronic misalignment between internal physiological timing and externally imposed timing of work and social activities. These findings suggest the need for researching possible interventions aimed at either modifying circadian rhythms in individuals or at allowing evening types greater working hour flexibility.     

Twinning rates in a rural area of Bangladesh

In this study we investigate the incidence of twin births over a period of 16 years in a rural area of Bangladesh using data from the Demographic Surveillance System of the International Centre for Diarrhoeal Disease Research. Over the study period twinning rates fluctuated between 7.8 and 11.2 per 1000 live births. The twinning rate was strongly correlated with maternal age; the rate for mothers over 35 years of age was about 3 times higher than for mothers younger than 20 years. The variation in twinning rate with maternal age is due to the variation in dizygotic twinning; the rate of monozygotic twinning is almost constant for all ages. Twinning rates were higher in the treatment area than in the comparison area after controlling for maternal age and parity. The rates were lower for monozygotic twinning and higher for dizygotic twinning in the treatment area than in the comparison area. Seasonality was observed for both twins and singletons, but the peak for twinning precedes that for singleton births by more than a month.     

Overweight and school performance among primary school children: the PIAMA birth cohort study

The aim of this study was to assess the association between overweight and school performance among primary school children prospectively and including a broad range of potential confounding factors. In addition it was investigated what factors mediate this association. For this purpose, data of 2,159 12-year-old children who participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study were used. Two indicators of school performance were parental reported when children were 12 years of age and included (i): the score on a standardized achievement test that Dutch children have to complete at the end of their primary education (Cito)-test and (ii): the teacher's advice regarding a child's potential performance level in secondary education. Children's height and weight were measured by a trained research assistant at the age of 8 and by their parents at the age of 12. Overweight was defined using age and gender specific cut-off points. Multivariate regression analyses were performed to assess the association between overweight and school performance. Besides, both confounder and mediation analyses were conducted. Results showed lower Cito-test scores and lower teacher's school-level advice among overweight children. These associations were no longer significant when adjusting for parental educational level, skipping breakfast, and screen time. This study found no independent association between overweight and school performance among primary school children. Results showed strong confounding by parental educational level.     

Application of a marriage model in rural Bangladesh

The standard marriage model is evaluated with respect to its applicability in Bangladesh, so that reliable and consistent estimates of mean marriage age for females in Bangladesh can be made. The standard marriage model proposes that a person enters the marriage market and waits until marriage occurs. The distribution of age at entry into the marriage market is generally normal. The delays until marriage occurs are modelled as negative exponential distributions. In a population where marriage is universal, the standard schedule of 1st marriage frequencies developed by Coale and McNeil is a close approximation to the convolution of a normal curve and several exponential distributions G(x), the cumulative probability of marriage at age x. Since the standard distribution of age at 1st marriage is closely approximated by the convolution of a normal curve and several negative exponential distributions, the age at entry to the marriage market for females, and whether this is normally distributed, should be examined. 1 cross-sectional study in Bangladesh concludes that onset of menarche determines entry into the marriage market. The proportion of ever married females by single year of age which is available from cross sectional demographic surveys can be fitted to the Coale-McNeil model. Marriages in the rural areas of Bangladesh seem to follow the pattern of entering the marriage market at puberty, then waiting until actual marriage takes place. This model of entries and delays can also be fitted to cross-sectional data from rural Bangladesh. The use of the Coale-McNeil marriage model in rural Bangladesh is appropriate for estimating the mean age of marriage.