External Publications Using GUI Data

In  this  paper  we  make  use  of  the  first  and  second  waves  of  the 2008  and 1998  cohorts  of  the  Growing  Up  in  Ireland  study,  to  develop  a  multidimensional  and  dynamic  approach  to understanding the impact on families and children in Ireland of the Great Recession. Economic vulnerability is operationalised as involving a distinctive risk profile in relation to relative income, household  joblessness  and  economic  stress.  We  find  that  the  recession  was  associated  with  a  significant increase in levels of economic vulnerability and changing risk profiles involving a more prominent  role  for  economic  stress  for  both  the  2008  and  1998  cohorts.  The  factors  affecting  vulnerability outcomes were broadly similar for both cohorts. Persistent economic vulnerability was  significantly  associated  with  lone  parenthood,  particularly  for  those  with  more  than  one  child, lower levels of primary care giver (PCG) education and, to a lesser extent, younger age of PCG  at  child’s  birth,  number  of  children  and  a  parent  leaving  or  dying.  Similar  factors  were  associated  with  transient  vulnerability  in  the  first  wave  but  the  magnitude  of  the  effects  was significantly weaker particularly in relation to lone parenthood and level of education of the PCG. For entry into vulnerability the impact of these factors was again substantially weaker than for persistent and transient vulnerability indicating a significantly greater degree of socioeconomic heterogeneity among the group that became vulnerable during the recession. The findings raise policy and political problems that go beyond those associated with catering for groups that have tended to be characterized by high dependence on social welfare.

A poor quality diet may be a common risk factor for both obesity and dental problems such as caries. The aim of this paper is to use classification tree analysis (CTA) to identify predictors of dental problems in a nationally representative cohort of Irish pre-school children. CTA was used to classify variables and describe interactions between multiple variables including socio-demographics, dietary intake, health-related behaviour, body mass index (BMI) and a dental problem. Data were derived from the second (2010/2011) wave of the ‘Growing Up in Ireland’ study (GUI) infant cohort at 3 years, n = 9793. The prevalence of dental problems was 5.0% (n = 493). The CTA model showed a sensitivity of 67% and specificity of 58.5% and overall correctly classified 59% of children. Ethnicity was the most significant predictor of dental problems followed by longstanding illness or disability, mother’s BMI and household income. The highest prevalence of dental problems was among children who were obese or underweight with a longstanding illness and an overweight mother. Frequency of intake of some foods showed interactions with the target variable. Results from this research highlight the interconnectedness of weight status, dental problems and general health and reinforce the importance of adopting a common risk factor approach when dealing with prevention of these diseases.

Keywords: body mass index; diet; dental problem; classification tree

Using the first wave of the Growing Up in Ireland Survey of nine year old children we examine whether a teacher’s assessment of their pupil’s academic ability is influenced by the weight status of the child and/or the child’s mother. Multivariate regression analyses of the teacher’s assessment, controlling for the child’s actual test performance, their BMI, their mother’s BMI, other socio-demographic and teacher characteristics were undertaken. The study highlighted that child BMI was not a significant determinant but that children whose mother was obese were more likely to be rated as below average in reading and in maths compared to those whose mother was leaner, after adjusting for their measured ability. The potential for mother’s weight status to influence teachers’ assessments of their children’s perceived ability could have long term ramifications for educational outcomes and warrants further study.

This paper examines the relationship between maternal employment, childcare during infancy and the overweight status of pre-school children. Using data from the Infant Cohort of the Growing-Up in Ireland Survey, propensity score matching addresses the issue of potential selection bias, quantile regression allows the impact of both maternal employment and childcare to be examined throughout the weight distribution and multiple imputation is used to address the problem of missing data due to item non-response. The results suggest that both full-time and part-time maternal employment when a child is 9 months old increase the likelihood of being overweight at 3 years old, but only for children of mothers with higher levels of education. Informal childcare at 9 months also has harmful effects on child weight, but again only for children of more educated mothers. Quantile regression finds that the children most impacted by maternal employment are those at the upper percentiles of the weight distribution. When selection on observables is used to assess bias arising from selection on unobservables, maternal employment estimates are determined to be a lower bound, while informal childcare results could be attributed to selection bias. Overall findings are consistent with research from North America and the United Kingdom, and are in contrast to recent findings from the rest of Europe, suggesting the possible role of institutional factors.

This article explores the role that home-learning activities (HLAs) play in the relationship between social origin and cognitive development using an Irish birth cohort study, Growing Up in Ireland. Numerous studies using different measures of the home-learning environment (HLE) have shown that it has considerable influence on young children’s cognitive development, and that the HLE is often linked to social origin. We find a social gradient in vocabulary even at age 3 years, with the largest gaps for mothers’ education. Family income, mothers’ education, and social class are also associated with vocabulary independently, though these associations are reduced by adding all three measures simultaneously. The extent of HLAs helps explain a very small part of the education differences and none of the income or social class differences in vocabulary. We find some evidence that HLAs may be more salient for children from families with low income and lower social class backgrounds in terms of supporting vocabulary development, thereby compensating somewhat for disadvantage. HLAs also appear to encourage vocabulary development between age 3 and 5, and play a role in reducing the gap in vocabulary between high- and low-income children.

Background
There is growing concern around youth mental health. A population health approach to improve mental health must address, among other issues, economic insecurity, access to housing and education, harm reduction from substance use. As a universal public health intervention, increasing physical activity at a population level may have an important role in our approach. The aim of this study was to examine the longitudinal association between physical activity patterns between childhood and early adolescence and emotional-behavioural difficulties in later adolescence.

Methods
This study was based on data from the ′98 Child cohort of the Growing Up in Ireland Study. Participants were categorized according to physical activity levels at ages 9 and 13. Emotional-behavioural difficulties at age 17 were measured using the parent-reported Strengths and Difficulties Questionnaire. Logistic regression was used to examine the association between physical activity and emotional-behavioural outcomes.

Results
Among 4618 participants included in the regression model, those categorized as Inactive (n=1607) or Reducer (n=1662) were more than twice as likely to have emotional-behavioural difficulties at age 17 compared with those who were Active [adjusted odds ratio (AOR) 2.1, 95% CI 1.46–3.01, P<0.001; AOR 1.93, 95% CI 1.34–2.76, P<0.001, respectively]. Among those with emotional-behavioural difficulties at baseline (n=525), those categorized as Active had 2.3-fold reduced odds for emotional-behavioural problems at age 17 compared with those who were Inactive (AOR 0.43, 95% CI 0.23–0.78, P=0.006).

Conclusions
Increasing physical activity among adolescents is a safe and sustainable public health intervention associated with improved mental health.

Background
Physical activity (PA) can reduce young peoples’ risk of depressive symptoms. Associations between PA and depressive symptoms are often investigated over timeframes spanning minutes to weeks. Less is known about whether childhood/adolescent PA can predict depressive symptoms in early adulthood.

Methods
Using a nationally representative sample from Ireland, latent growth mixture modelling was performed to investigate the extent to which different PA trajectories existed from ages 9–17, whether gender, weight status, and socio-economic deprivation at age 9, predicted PA trajectories from ages 9–17, and whether trajectory class membership predicted depressive symptoms at age 20.

Results
A 4-class solution was the best fit to the data (AIC = 52 175.69; BIC = 52 302.69; ssaBIC = 52 245.49; entropy = 1.00). Classes were labelled according to their baseline PA and slope of their trajectory: ‘High-Decreasers’; ‘Moderate-Decreasers’; ‘Moderate-Stable’; and ‘Low-Increasers’. A negative linear association existed between activity trajectory and the likelihood class members were female, overweight or socioeconomically deprived at age 9. The most active class (High-Decreasers) were significantly less likely to report depressive symptoms at age 20 than other classes.

Conclusions
Multiple PA trajectories exist throughout childhood and adolescence although differences in PA levels reduced over time. The most/least active children continued to be the most/least active throughout adolescence. Those most active were least at risk of depressive symptoms in early adulthood. Being female, overweight or experiencing deprivation at age 9 were all risk factors for inactivity throughout adolescence. Findings have implications for public health and PA promotion in young people

Self-harm in adolescents and young adults (AYAs) is the result of a complex interaction of biological, psychiatric, psychological, social, and cultural risk factors. A lot of research has already been conducted to identify the risk factors for self-harm in AYAs. On the other hand, there has been less research conducted on the simultaneous effects of, and the interactions between, multiple risk factors for self-harm in heterogeneous AYA individuals. In this study, we conducted a latent class analysis (LCA) of three waves from the Growing Up in Ireland (GUI) longitudinal cohort study at ages 13, 17 and 20 to identify homogenous subgroups of AYA individuals who exhibit similar risk markers for self-harm at these three time points. Then, we evaluated the risk that these subgroups ever self-harmed by age 17, self-harmed at age 20, or were persistently self-harming across both time points. The most at-risk group appeared to be the individuals aged 17 who had been diagnosed with depression/anxiety. Compared to the low-risk-marker group, the ‘diagnosed with depression/anxiety’ group had a 30-fold risk of self-harm at age 17, and 32-fold risk of persistently self-harming by age 20. The ‘undiagnosed but high depression’ group at this time point was also at significant risk of self-harm. This research enables us to understand which risk markers tend to co-occur together and will help to identify high-risk groups for self-harm both clinically and in the community. An investigation of risk markers like this can potentially be used in the design of public health interventions to reduce the burden of self-harm, and indeed suicide, in young people.

Key messages

• We identified sub-groups of young people with a high-risk of self-harm and suicide from the general population.

• These identifiable sub-groups can inform intervention policies and strategies for prevention programmes both in clinical and non-clinical settings like schools.

Background
The COVID-19 pandemic has been dubbed the “biggest public health crisis since the Second World War”. In Ireland, schools were closed for 141 days, dramatically altering the day to day lives of children in Ireland. This research aimed to evaluate the overall wellbeing of schoolchildren in Ireland and capture the prevalence and factors contributing to poor mental health.

Methods
A cross-sectional study was performed based on data from the Growing Up in Ireland COVID-19 web survey of the ’08 Infant cohort. Mental Health Inventory-5 scores were used to assess children at risk of mental health disorders. Logistic regression examined associations between various demographic and psychosocial factors and risk of mental health disorders.

Results
This study included 2,867 primary caregiver- child dyads. Almost 25% of 12/13-year-olds were at risk of mental health disorders (MHDs). An adjusted logistic regression model found associations between being at higher risk of MHDs and factors such as reduced physical activity levels (OR 1.35, 95% CI 1.10-1.66), spending less time outdoors (OR 1.48, 95% CI 1.18-1.85), increased screen-time (OR 1.35, 95% CI 1.09-1.67) and increased arguments with PCGs (OR 3.44, 95% CI 2.78-4.27). Having a trusted adult confidante reduced the risk of MHD (OR 0.25, 95% CI 0.14-0.45).

Conclusions
The prevalence of 12/13-year olds at elevated risk of MHD was high, indicating an urgent need for enhancement of child and adolescent mental health services in Ireland. Physical activity, time outdoors and supportive relationships with primary caregivers were positively associated with reduced MHD risk.

Key messages

• Children were impacted by the COVID-19 restriction measures in a way that was disproportionate to their risk.
• To reduce the risk of poor mental health outcomes for a generation of “quarantweens” we need to place children front-andcentre of our response as we recover from COVID-19.

What does young adulthood look like for individuals who had mental health problems across childhood? Using the Growing Up in Ireland cohort (born in 1998 and studied from ages 9 to 20) we explored the association between mental health problems between ages 9 and 13, and subsequent poor outcomes in the same individuals at ages 17-20. We consider educational/economic outcomes, health service use, poor mental and physical health, social isolation, substance abuse, and subjective wellbeing in young adults. In a previous study that used latent class modelling, we identified four groups which captured mental health in a general population sample of children. Between ages 9 and 13, children could be grouped into: a low symptoms group (∼65%), an ‘externalising’ group with ADHD or conduct symptoms (∼20%), an ‘internalising’ group with depressive, anxiety or peer issues (∼10%), or a group showing many combined mental health symptoms (∼2%). All mental health problem groups had elevated odds across all 7 adverse outcomes in young adulthood. The 5 areas of young adult functioning most related to childhood mental health were: education/economics, subjective wellbeing, mental health, social isolation and substance abuse. Poor educational/economic outcomes were as likely as poor mental health (OR ∼ 2) in individuals with childhood psychopathology. The 3 childhood problem groups showed different risk profiles in young adulthood. For instance, the childhood internalising group had lower odds of substance abuse than all other groups, but had the highest odds of poor physical health by adulthood. Findings point to the need for a wider range of preventative supports for children and adolescents with a history of mental health problems, beyond just mental health support. These include interventions to improve physical health, treat substance abuse, reduce social isolation, and improve adverse educational and economic outcomes.

Background
Energy poverty, typified by cold homes and/or an inability to afford energy bills, presents risks to the mental health of occupants. Parents of young children may be especially susceptible to a mental health toll from energy poverty since they have a significant care obligation and spend much of their day at home.

Methods
Data from the Growing Up in Ireland study inform this longitudinal analysis.

Results
A 1.64 greater odds of maternal depression were estimated for households containing young children characterized by energy poverty [P = 0.000; 95% confidence interval (CI): 1.31–2.05]. For energy poor households with older children (9 years and above), the odds of maternal depression were also higher [odds ratio (OR) 1.74, P = 0.001; 95% CI: 1.27–2.39]. Fathers of young children had greater odds of depression in energy poor households (OR 1.59, P = 0.002; 95% CI: 1.19–2.12), though the deleterious effect on mental health was not statistically significant for fathers of older children.

Conclusions
Energy poverty increases the likelihood of depression in parents. These findings merit policy attention since a mental health burden is in itself important, and more widely, parental well-being can influence child development and outcomes.

Background
Psychotic experiences (PEs) are commonly reported in adolescence and are associated with a range of negative outcomes. Few targets for intervention for PEs have been identified. One potential target is self-concept: an individual’s beliefs about his/her personal attributes. Improvements in self-concept have been shown to reduce psychotic symptoms in patients with schizophrenia but no study has investigated the relationship between changes in self-concept and risk of PEs in the general population.

We aimed to investigate: (a) the relationship between child and adolescent self-concept and adolescent PEs; and (b) whether changes in self-concept between childhood and adolescence were associated with risk of adolescent PEs.

Method
Using data from age 9 and age 13 (n = 7,423) of the child cohort (Cohort’98) from the Growing Up in Ireland study we investigated the relationship between self-concept at age 9 and age 13 and PEs at age 13. PEs were measured using the Adolescent Psychotic Symptoms Screener and self-concept was measured using the Piers Harris-II. Using a stratified analysis, we investigated the relationship between change in self-concept between age 9 and age 13 and the risk of PEs at age 13. Additionally we investigated changes across the six self-concept subscales.

Results
Psychotic experiences were reported by 13% of participants at age 13. ‘Very low’ self-concept at age 9 was associated with an increased risk of PEs at age 13 (Adjusted-OR: 2.74, CI: 1.80–4.19), and ‘High’ self-concept at age 9 was associated with a decreased risk of PEs at age 13 (Adjusted-OR: 0.77, CI: 0.60–0.97). The stratified analysis indicated that improvements in self-concept reduced the odds of adolescent PEs and decline in self-concept increased the odds of adolescent PEs. This effect was noted across the majority of the self-concept subscales.

Conclusions
There is a strong relationship between self-concept and PEs. The antecedents of low self-concept may be a useful target for preventative psychiatry. Broad-spectrum interventions targeting self-concept in childhood may help to reduce the incidence of PEs in adolescence

Background
While it has been purported that excessive screen time can lead to behavioral problems, it has also been suggested that children with behavioral dysregulation receive more access to screens to manage problematic behavior. In this study, both temporally stable and longitudinal associations between screen time and externalizing and internalizing behaviors across childhood are examined to directly address this issue of directionality.

Methods
Data are from a prospective cohort of 10,172 Irish children, collected between 2010 and 2018 when children were ages 3, 5, 7, and 9. Children’s screen time (hours/day) and externalizing and internalizing behaviors (Strengths and Difficulties Questionnaire) were assessed via caregiver report. Random-intercepts cross-lagged panel models were used to estimate longitudinal bidirectional associations while controlling for temporally stable (i.e., ‘time-invariant’ or ‘trait-like’) differences between children.

Results
Temporally stable differences between children were observed for both screen time and behavior problems. Longitudinal trajectories for screen time lacked stability; however, and externalizing and internalizing behaviors stabilized increasingly during later childhood. Greater externalizing and internalizing behaviors at age 3 were directionally associated with increased screen time at age 5. Greater screen time at ages 3 and 5 was directionally associated with increased internalizing behaviors at ages 5 and 7, respectively. More screen time at age 7 was directionally associated with fewer internalizing behaviors at age 9. Screen time was not associated with later externalizing behaviors.

Conclusions
Bidirectional associations between screen time and internalizing behaviors were observed for preschoolers. Directional associations between screen time and internalizing difficulties were observed across childhood. These findings can inform screen use guidelines and family media planning at different ages and stages of development.

The first 1000 days of life are a period of unique sensitivity and plasticity during which critical cognitive abilities are formed. Routine developmental screening tools aim to identify infants who would benefit from early intervention. While these tools have been validated for detecting children with more severe neurodevelopmental disorders, their ability to identify the larger proportion with below average cognitive function has not been sufficiently explored. The aim of this study was to examine the validity of the Ages and Stages Questionnaire (ASQ), for identifying children with later below average cognitive function.

The study population (n=8260) is formed from two national cohort studies, the Growing Up in Ireland (GUI) Infant cohort (n=7,444) and the Cork BASELINE cohort (n=816). The ASQ was completed at 8 months and 24-27 months respectively. Cognitive assessments were performed at age 5. Those scoring <1 standard deviation (SD) below the mean were categorised as below average cognitive function. Applying the currently used onward referral criterion (one fail in any domain) the sensitivity, specificity, positive and negative predictive values of the 8- and 24-27- month ASQ for detecting children with later below average cognitive function were calculated.

In the GUI cohort n=905 participants (12.5%) had scores <1SD below the mean on the Picture Similarities Scale. In the BASELINE cohort n=101 participants (13.4%) had an IQ <1SD below the cohort mean. Applying the currently used onward referral criterion (failing in any one domain in the ASQ), the sensitivity of the 8-month ASQ for detecting children scoring <1SD below the mean on the Picture Similarities Scale at age 5 was 16.4% (95% CI 14.0-19.0). The specificity was 92.0% (95% CI 91.3-92.6), with a positive predictive value (PPV) of 22.6% (95% CI 19.5-26.0) and a negative predictive value (NPV) of 88.5% (95% CI 87.7%-89.2%).

In the BASELINE cohort n=468 participants completed the 24-month ASQ and n=316 the 27-month ASQ. Applying the same onward referral criterion to the 24- and 27- month ASQ combined, the sensitivity for detecting those with an IQ <1SD below the cohort mean was 20.8% (95% CI 13.6-30.2) and the specificity was 91.1% (95% CI 88.6-93.2).

The ASQ has a low sensitivity for identifying children with below average cognitive function at age 5. The findings of this study suggest that if we are to intervene early in the developmental trajectory for children with below average cognitive function alternative methods of identifying high risk infants are needed.

Children with below average cognitive function represent a substantial yet under-researched population for whom academic and social demands, which increase in complexity year by year, pose significant challenge. Effects on emotional-behavioural development (EBD) are not well understood. The aim of this study was to compare trajectories of EBD for children with and without below average cognitive function. The underlying hypothesis was that trajectories of EBD would differ between groups, with divergence occurring as children are subject to increasingly complex cognitive demands.

Participants consist of 7,000 children and caregivers who completed the Growing Up in Ireland survey at age 3,5 and 9 years. Cognitive function was measured at age 3 using the Picture Similarities Scale. A t-score 1-2 standard deviations below the mean was categorised as below average cognitive function (n=767), and scores above this categorised as average cognitive function (n=6418). EBD was measured using the Strengths and Difficulties Questionnaire (SDQ) at age 3,5 and 9. Repeated measures ANOVA was used to examine the difference between the overall group means across the repeated measures of SDQ, the SDQ change over time, and the interaction between cognitive group and change over time. Further analysis of trajectories was performed using latent growth curve analysis.

Compared to those with average cognitive function, a significantly higher proportion of children with below average function were male (61.8% v 38.2%, χ2 (1, N=7134) = 42.07 p<0.001), born to a single parent family (22.4% v 14.7%, χ2 (1, N=7134) = 23.15 p<0.001), and had a parent who smoked (35.6% v 25.8%, χ2 (1, N=7134) = 33.23 p<0.001). Children with below average cognitive function had significantly higher mean total SDQ scores at all ages. Repeated measures ANOVA demonstrated a significant group-by-time interaction effect (F(2,7182)=4.649, p=0.010). The mean difference (MD) in SDQ between cognitive groups increased over time (MD Age 3:0.87, 95% confidence interval (CI) 0.53-1.21, Age 9 MD:1.49,95% CI 1.08-1.91). For those with average or above cognitive function the overall SDQ decreased between age 3-9 (MD: -0.49 95% CI -0.65—0.33). This decrease was not seen for those with below average function, who had a non-statistically significant increase in SDQ between age 3-9.

Children with below average cognitive function experience higher and worsening mean SDQ scores throughout childhood. A scalable method of early identification of children at risk for below average cognitive function should be a research priority for public health, enabling early intervention for cognitive and adaptive outcomes.

This paper discusses the role of grandparents in informal childcare in Ireland. It considers how recent demographic change and government policy on childcare have the potential to place greater pressures on the provision of grandparent childcare. It illustrates research literature that has examined the prevalence and intensity of grandparent care, factors influencing such care, and the role and needs of grandparents in childcare. We argue that there are significant gaps in Irish research evidence about the extent of, role and needs of grandparents as childcarers and outline a data and research agenda that builds on previous research in this area.

Keywords
Childcare, Policy, Grandparents, Intergenerational

Reflecting the neglect of childhood disability in social stratification research, there is a notable dearth of research on the mechanisms underpinning disability differentials in educational outcomes. Drawing on rich longitudinal data collected at 9, 13 and 17 years as part of Ireland’s ‘Growing Up in Ireland’ study, we look at the impact of special educational needs (SEN) identification in primary school on upper secondary outcomes. A bioecological framework and the Process–Person–Context–Time model allow us to understand how interactions with family, teachers, friends and school—as proximal processes—relate to early school leaving and post-school planned pathways after accounting for personal and context characteristics. Overall, young people identified at age 9 as having SEN are at increased risk of early school leaving and are more likely to plan to attend further education and training, rather than higher education. However, after accounting for proximal processes and personal and context variables, students identified at age 9 as having SEN are no longer distinct in terms of secondary attainment and post-school planning. Instead, these young people are more likely to experience forms of vulnerability that are important in shaping these outcomes. These key educational outcomes are strongly shaped by family and school-related factors—both proximal processes and context characteristics—suggesting that efforts to support retention and pathway planning should be underpinned by an ecological understanding of young people’s trajectories and the cumulative disadvantages they face.

Key insights

What is the main issue that the paper addresses?

Using a bioecological framework and Growing Up in Ireland data, this paper explores early school leaving and post-school plans among young adults identified in primary school as having special educational needs (SEN). This is a key topic, as young people with SEN are at greater risk of early school leaving and less likely to attend higher education.

What are the main insights that the paper provides?

As a group, young people identified in primary school as having SEN are more likely to experience economic vulnerability and to attend schools with a socioeconomically vulnerable profile. After accounting for these and other key personal and contextual characteristics, childhood SEN status is no longer a significant factor in early school leaving or post-school plans.

Background
Orofacial clefts occur when the lips or the roof of the mouth do not fuse properly during the early weeks of pregnancy. There is strong evidence that periconceptional use of folic acid can prevent neural tube defects but its effect on oral clefts has generated debate.

Aim
To identify factors associated with suboptimal periconceptional use of folic acid and its potential effect on oral clefts.

Design and setting
The population-based infant cohort of the national Growing Up in Ireland study, which consists of 11 134 9-month-old infants.

Method
Data collection comprised questionnaires conducted by interviewers with parents in parents’ homes. Characteristics of mothers who did or did not take folic acid before and during pregnancy, as well as the effect of folic acid use on the prevalence of cleft lip and palate were recorded.

Results
The prevalence of cleft lip and palate was 1.98 (95% confidence interval [CI] = 1.31 to 2.99) per 1000 9-month-olds. The odds ratio for cleft lip was 4.36-fold higher (95% CI = 1.55 to 12.30, P = 0.005) for infants of mothers who did not take folic acid during the first 3 months of pregnancy, when compared with those who did have a folate intake during the first trimester. Folic acid use was suboptimal in 36.3% (95% CI = 35.4 to 37.2) of the sample.

Conclusion
These findings support the hypothesis that taking folic acid may partially prevent cleft lip and palate. They are particularly relevant for GPs, because they are usually the first port of call for women before and during early pregnancy.

Keywords
cleft lip, epidemiology, folic acid, general practice, infant