Amanda Langridge | The University of Western Australia (original) (raw)

Papers by Amanda Langridge

International journal of epidemiology, Apr 8, 2015

Research studies exploring the determinants of disease require sufficient statistical power to de... more Research studies exploring the determinants of disease require sufficient statistical power to detect meaningful effects. Sample size is often increased through centralized pooling of disparately located datasets, though ethical, privacy and data ownership issues can often hamper this process. Methods that facilitate the sharing of research data that are sympathetic with these issues and which allow flexible and detailed statistical analyses are therefore in critical need. We have created a software platform for the Virtual Pooling and Analysis of Research data (ViPAR), which employs free and open source methods to provide researchers with a web-based platform to analyse datasets housed in disparate locations. Database federation permits controlled access to remotely located datasets from a central location. The Secure Shell protocol allows data to be securely exchanged between devices over an insecure network. ViPAR combines these free technologies into a solution that facilitates ...

This report is the third in a series examining patterns and trends in mortality among Western Aus... more This report is the third in a series examining patterns and trends in mortality among Western Australian infants, children and young people, and covers the period 1980-2008.

Background: Few common traits separate the mothers of children with autism spectrum disorder (aut... more Background: Few common traits separate the mothers of children with autism spectrum disorder (autism) and intellectual disability (ID) from mothers in the general population. Objectives: * To review research on the pre-existing characteristics which differentiate mothers of children with autism and/or ID of unknown cause from each other and from mothers of children without these disabilities * To provide a source for research into the determinants of autism and/or ID, including the role of genetic and modifiable risk factors. Methods: The papers considered for this review resulted from a search of the Medline, Web of Knowledge, Scopus and Google scholar databases. Combinations of the search terms associated with autism and ID, the hypothesised aetiologies of autism and ID and terms associated with traits of mothers of children with autism and/or ID were used. Examples from each of the three groups are ‘autis*, pervasive development disorder* and intellectual disability’, immigra*, m...

BMJ open, 2011

The objective of this study was to compare international trends in pre-eclampsia rates and in ove... more The objective of this study was to compare international trends in pre-eclampsia rates and in overall pregnancy hypertension rates (including gestational hypertension, pre-eclampsia and eclampsia). Population data (from birth and/or hospital records) on all women giving birth were available from Australia (two states), Canada (Alberta), Denmark, Norway, Scotland, Sweden and the USA (Massachusetts) for a minimum of 6 years from 1997 to 2007. All countries used the 10th revision of the International Classification of Diseases, except Massachusetts which used the 9th revision. There were no major changes to the diagnostic criteria or methods of data collection in any country during the study period. Population characteristics as well as rates of pregnancy hypertension and pre-eclampsia were compared. Absolute rates varied across the populations as follows: pregnancy hypertension (3.6% to 9.1%), pre-eclampsia (1.4% to 4.0%) and early-onset pre-eclampsia (0.3% to 0.7%). Pregnancy hyperte...

Nutrition and Cancer, 2012

Childhood brain tumors (CBT) are the second most common childhood cancers, yet their etiology is ... more Childhood brain tumors (CBT) are the second most common childhood cancers, yet their etiology is largely unknown. We investigated whether maternal gestational intake of folate, vitamin B6 and B12 was associated with CBT risk in a nationwide case-control study conducted 2005-2010. Case children 0-14 years were recruited from all 10 Australian pediatric oncology centers. Control children were recruited by national random digit dialling, frequency matched to cases on age, sex and State of residence. Dietary intake was ascertained using food frequency questionnaires, and adjusted for total energy intake. Data from 293 case and 726 control mothers were analysed using unconditional logistic regression. The odds ratio (OR) for the highest versus lowest tertile of folate intake was 0.70 (95% CI: 0.48, 1.02). The ORs appeared lower in mothers who drank alcohol during pregnancy (OR 0.45, 95% CI: 0.22, 0.93), mothers who took folic acid (OR 0.67, 95% CI: 0.42, 1.06) or B6/B12 supplements (OR 0.51, 95% CI: 0.25, 1.06) and in children younger than 5 years (OR 0.50, 95% CI: 0.27, 0.93). These findings are consistent with folate's crucial role in maintenance of genomic integrity and DNA methylation. Dietary intake of B6 and B12 was not associated with risk of CBT.

Journal of Autism and Developmental Disorders, 2013

The International Collaboration for Autism Registry Epidemiology (iCARE) is the first multination... more The International Collaboration for Autism Registry Epidemiology (iCARE) is the first multinational research consortium

Journal of Epidemiology & Community Health, 2010

Background There has been widespread international concern about declining fertility rates and th... more Background There has been widespread international concern about declining fertility rates and the long-term negative consequences particularly for industrialised countries with ageing populations. In an attempt to boost fertility rates, the Australian Government introduced a maternity payment known as the Baby Bonus. However, major concerns have been raised that such monetary incentives would attract teenagers and socially disadvantaged groups. Methods Population-level data and generalised linear models were used to examine general fertility rates between 1995 and 2006 by socioeconomic group, maternal age group, Aboriginality and location in Western Australia prior to and following the introduction of the Baby Bonus in July 2004. Results After a steady decline in general fertility rates between 1995 and 2004, rates increased significantly from 52.2 births per 1000 women, aged between 15 and 49 years, in 2004 to 58.6 births per 1000 women in 2006. While there was an overall increase in general fertility rates after adjusting for maternal sociodemographic characteristics, there were no significant differences among maternal age groups (p¼0.98), between Aboriginal and non-Aboriginal women(p¼0.80), maternal residential locations (p¼0.98) or socioeconomic groups (p¼0.68). The greatest increase in births were among women residing in the highest socioeconomic areas who had the lowest general fertility rate in 2004 (21.5 births per 1000 women) but the highest in 2006 (38.1 births per 1000 women). Conclusions Findings suggest that for countries with similar social, economic and political climates to Australia, a monetary incentive may provide a satisfactory solution to declining general fertility rates.

xii Background xii Aims xii Methods xiii Results xiii Conclusions xiv Acknowledgements xv Table of

BMJ open, 2013

To use propensity score methods to create similar groups of women delivering in public and privat... more To use propensity score methods to create similar groups of women delivering in public and private hospitals and determine any differences in mode of delivery and neonatal outcomes between the matched groups. Population-based, retrospective cohort study. Public and private hospitals in Western Australia. Included were 93 802 public and 66 479 private singleton, term deliveries during 1998-2008, from which 32 757 public patients were matched with 32 757 private patients on the propensity score of maternal characteristics. Neonatal outcomes were compared in the propensity score-matched cohorts using conditional logistic regression, adjusted for antenatal risk factors and mode of delivery. Outcomes included Apgar score <7 at 5 min, neonatal resuscitation (endotracheal intubation or external cardiac massage) and admission to a neonatal special care unit. No significant differences in maternal characteristics were found between the propensity score-matched groups. Private patients wer...

PLoS ONE, 2013

As well as being highly comorbid conditions, autism spectrum disorders (ASD) and intellectual dis... more As well as being highly comorbid conditions, autism spectrum disorders (ASD) and intellectual disability (ID) share a number of clinically-relevant phenomena. This raises questions about similarities and overlap in diagnosis and aetiological pathways that may exist for both conditions. To examine maternal conditions and perinatal factors for children diagnosed with an ASD, with or without ID, and children with ID of unknown cause, compared with unaffected children. The study population comprised all live singleton births in Western Australia (WA) between January 1984 and December 1999 (N = 383,153). Univariate and multivariate multinomial logistic regression models were applied using a blocked modelling approach to assess the effect of maternal conditions, sociodemographic factors, labour and delivery characteristics and neonatal outcomes. In univariate analyses mild-moderate ID was associated with pregnancy hypertension, asthma, urinary tract infection, some types of ante-partum haemorrhage, any type of preterm birth, elective C-sections, breech presentation, poor fetal growth and need for resuscitation at birth, with all factors showing an increased risk. Severe ID was positively associated with poor fetal growth and need for resuscitation, as well as any labour or delivery complication. In the multivariate analysis no maternal conditions or perinatal factors were associated with an increased risk of ASD without ID. However, pregnancy hypertension and small head circumference were associated with a reduced risk (OR = 0.64, 95% CI: 0.43, 0.94; OR = 0.58, 95% CI: 0.34, 0.96, respectively). For ASD with ID, threatened abortion before 20 weeks gestation and poor fetal growth were associated with an increased risk. Findings show that indicators of a poor intrauterine environment are associated with an elevated risk of ID, while for ASD, and particularly ASD without ID, the associations are much weaker. As such, these findings highlight the importance of accounting for the absence or presence of ID when examining ASD, if we are to improve our understanding of the causal pathways associated with these conditions.

European Child & Adolescent Psychiatry, 2014

The objective of this study is to compare the time trend of reported diagnoses of autism spectrum... more The objective of this study is to compare the time trend of reported diagnoses of autism spectrum disorder (ASD), hyperkinetic disorder, Tourette's syndrome, and obsessive-compulsive disorder across four countries after standardizing the study period, diagnostic codes used to define the conditions and statistical analyses across countries. We use a population-based cohort, including all live-born children in Denmark, Finland, Sweden and Western Australia, from January 1, 1990, through December 31, 2007 and followed through December 31, 2011. The main outcome measure is age-specific prevalence of diagnoses reported to population-based registry systems in each country. We observe an increase in agespecific prevalence for reported diagnoses of all four disorders across birth-year cohorts in Denmark, Finland, Sweden, and (for ASD) Western Australia. Our results highlight the increase in the last 20 years in the number of children and families in contact with health care systems for diagnosis and services for an array of childhood neuropsychiatric disorders, a phenomenon not limited to ASD. Also, the age of diagnosis of the studied disorders was often much higher than what is known of the typical age of Electronic supplementary material The online version of this article (onset of symptoms, and we observe limited leveling off in the incidence rate with increasing age.

Recent Advances in Autism Spectrum Disorders - Volume I, 2013

PLoS ONE, 2012

Background: The Australian baby bonus maternity payment introduced in 2004 has been reported to h... more Background: The Australian baby bonus maternity payment introduced in 2004 has been reported to have successfully increased fertility rates in Australia. We aimed to investigate the influence of the baby bonus on maternal demographics and birth characteristics in Western Australia (WA).

Paediatric and Perinatal Epidemiology, 2010

Preterm birth is associated with a range of childhood morbidities and in industrialised societies... more Preterm birth is associated with a range of childhood morbidities and in industrialised societies is the primary cause of infant mortality. Social and racial inequalities in preterm birth have been reported in North America, UK, Europe and New Zealand. This study utilised population-level data to investigate social and racial inequalities in preterm birth among Aboriginal and non-Aboriginal infants in Western Australia. All live, singleton births between 1984 and 2006 (n = 567 468) were included, and multilevel multivariable logistic regression was used to investigate relative differences in preterm infants between socio-economic groups. Aboriginal and non-Aboriginal infants were analysed separately. The prevalence of preterm births increased from 7.1% in 1984-88 to 7.5% in 1999-2003, before decreasing to 7.2% in 2004-06. Inequalities in preterm births between Aboriginal and non-Aboriginal infants increased over time, with the percentage of preterm births being almost twofold higher for Aboriginal infants (14.8%), compared with non-Aboriginal infants (7.6%). A significant portion of the disparity between Aboriginal and non-Aboriginal infants is attributable to parental socio-economic and demographic characteristics, though the disparity continues to persist even after adjustment for these factors. While the overall rates of preterm birth in Western Australia have remained fairly static over the last two decades, the disparity between Aboriginal and non-Aboriginal infants has increased and is now similar to inequalities seen 20 years ago. These findings highlight a major public health issue that should be of great concern, given the short- and long-term morbidities and complications associated with preterm birth.

International Journal of Gynecology & Obstetrics, 2012

Objective: To determine whether common perinatal complications could explain variation in risk of... more Objective: To determine whether common perinatal complications could explain variation in risk of cesarean among foreign-born and Australian-born women in Western Australia (WA). Methods: Complication prevalence was calculated using the linked records of 208 982 confinements to non-indigenous women in WA between 1998 and 2006. Logistic regression was used to estimate differences in risk of elective cesarean and emergency cesarean compared with vaginal delivery for foreign-born women from different regions. Results:

Early Human Development, 2007