Cohort Profile Update: The Intergenerational Childhood Adversity and Lifetime Morbidity (I-CALM) study, an extension of the Mater-University of Queensland Study of Pregnancy (MUSP)

Child maltreatment (CM) is a global public health crisis with severe, enduring consequences, but the intergenerational impacts remain poorly researched. The Mater-University of Queensland Study of Pregnancy (MUSP) began in 1981, collecting data on 6753 pregnant women (Generation 1) and their 7223 babies (Generation 2). In 2000, CM cases related to MUSP Generation 2 were linked to their records. The Intergenerational Childhood Adversity and Lifetime Morbidity (I-CALM) study aims to understand the associations between maternal experiences of CM, and health outcomes and service use in the next generation (Generation 3). I-CALM includes 1696 women (Generation 2) who gave birth to 3296 children (Generation 3) between 2008 and 2024. The average age of Generation 3 as of 30 June 2024 was 10.6 ± 4.1 years. I-CALM includes diverse health outcomes and service use measures from perinatal, inpatient, emergency, and community mental health datasets. Contact Dr Claudia Bull ([email protected]) regarding opportunities for collaboration. The Mater-University of Queensland Study of Pregnancy (MUSP) study commenced as a 3- to 5-year longitudinal cohort study of 6753 pregnant women (Generation 1) birthing at the Mater Hospital in Brisbane, Australia, between 1981 and 1983 [1]. It also sought to follow up the 7223 babies (Generation 2) born to these women at 6 month postpartum [1]. MUSP has since evolved into one of Australia’s longest-running longitudinal birth cohort studies [2], with completed follow-up studies at 5, 14, 21, 27, 30, and 40 years [3]. In 2000, notified and substantiated child maltreatment (CM) cases reported to the Queensland Department of Families, Seniors, Disability Services and Child Safety were confidentially linked to Generation 2 records [4]. Notified instances of CM occur when contact has been made to an authorised department by people or other bodies alleging child abuse or neglect, child maltreatment, or harm to a child [5]. Substantiated instances of CM occurred when a notification was investigated and concluded that there was reasonable cause to believe the child had been, was being, or was likely to be abused, neglected, or otherwise harmed [5]. In 2023, the MUSP-Childhood Adversity and Lifetime Morbidity (MUSP-CALM) study was conceived, which linked public and private hospital admissions data, emergency department (ED) presentations data, and community mental health data to Generation 2, alongside their CM records. By linking to administrative health data, the MUSP-CALM study was able to increase the MUSP Generation 2 cohort size from 2900 participants (40.0%) at the 30-year follow-up (based on self-reported data) to 6087 participants (84.3%), significantly reducing the attrition rates (Figure 1). The loss to follow-up at 30 years was attributed largely to the fact that Generation 2 had entered a busy phase of life (28–30 years old with work and childcare commitments) [3]. The requirement for early-morning fasting blood glucose collection at the 30-year follow-up study may also have deterred participants, as it posed a practical inconvenience [3]. Those lost to follow-up were more likely to be younger, less educated, unmarried, receiving welfare benefits, not own a house, smoke, and be born in a non-English-speaking country [6]. Thus, the MUSP-CALM linkage also allowed a comprehensive examination of the consequences of CM on health outcomes and health service use up to 40 years of age [7–14]. MUSP, MUSP-CALM, and I-CALM cohort composition at each phase of data collection. The Intergenerational Childhood Adversity and Lifetime Morbidity (I-CALM) study was designed to explore the intergenerational consequences of CM by confidentially linking the administrative health records of Generation 3 to women in the MUSP Generation 2 cohort. Recent Australian research indicates that nearly two-thirds of Australian adults self-report experiencing abuse or neglect before the age of 18 years [15]. Self-reported CM data from the MUSP cohort collected at 30-year follow-up by using the Childhood Trauma Questionnaire Short-Form (CTQ-SF) revealed that 24.5% self-reported experiencing any type of CM [16], with 17.9% reporting physical abuse, 24.5% reporting emotional abuse, 40.8% reporting neglect, and 11.1% reporting sexual abuse [11]. Notified and substantiated CM cases in the MUSP cohort indicate a more conservative estimate. Approximately 11% of children experience at least one notified CM incident and 7.1% experience at least one substantiated CM incident [9]. These estimates more closely align with data from the Australian Institute of Health and Welfare, which indicate that, in 2022–23, 1 in 32 Australian children came into contact with the child protection system (∼3.1%) and 121, 000 children (21 per 1000) were the subject of an investigation (2.1%) [17]. While the prevalence of CM remains a topic of debate [18], its financial burden in Australia is nonetheless considerable, exceeding $5 billion annually [19]. Moreover, the lifetime health and social consequences are substantial [14]. The MUSP and MUSP-CALM studies have reported that individuals who experienced one or more forms of CM were significantly more likely to experience negative long-term educational and employment outcomes in young adulthood [20, 21]; poorer psychological and mental health outcomes, including suicidal ideation and behaviour, anxiety, depression, post-traumatic stress disorder (PTSD), psychosis, delinquency, attention-deficit/hyperactivity disorder, and aggressive behaviour [22–27]; greater susceptibility to intimate partner violence and harassment [22–25]; alcohol and other substance-use disorders and addiction [7, 8, 28–30]; young pregnancy [31]; pregnancy miscarriage [31]; greater risk of obesity [32]; and poorer sleep quality [33]. There is a body of evidence to support the theory of intergenerational CM transmission [34–36]. That being, maltreatment begets maltreatment, whether that is in a homotypic pattern of transmission (i.e. an emotionally abused woman is more likely to have a child who experiences emotional abuse) or a heterotypic pattern of transmission (i.e. an emotionally abused woman is more likely to have a child who experiences physical abuse) [37]. Yet there remains a critical knowledge gap regarding the intergenerational consequences of CM in terms of health outcomes and patterns of health service use. As such, I-CALM employed a similar data linkage methodology as MUSP-CALM to anonymously identify members of the Generation 3 cohort. Based on the number of Generation 2 cohort members who had linkable administrative health data in 2024, we identified women who had given birth in Queensland and subsequently identified the babies born to these women (Generation 3). The following research question will be addressed through the I-CALM study: Are maternal experiences of CM associated with health outcomes and health service use in the next generation? We hypothesise that maternal experiences of CM will be strongly associated with poorer health outcomes in Generation 3, as well as increased health service use. We also hypothesise that maternal mental illness will be strongly associated with poorer health outcomes in Generation 3, as well as increased health service use. This study was registered as a retrospective observational study with the Australian New Zealand Clinical Trials Registry (registration number: ACTRN12624001423505). Human Research Ethics Committee (HREC) approval was obtained from the Metro South HREC (reference number: HREC/2024/QMS/107240) and the University of Queensland HREC (project number: 2024/HE002338). To identify the I-CALM Generation 2 and 3 cohorts, MUSP Generation 2 identifiers (limited to name and date of birth) were supplied by the MUSP data custodian to the Queensland Statistical Services Branch (SSB, Figure 2). The SSB subsequently identified and matched relevant Generation 3 records via the Queensland Perinatal Data Collection (QPDC) by using a Master Linkage File (MLF). Matching records by using an MLF is highly accurate and involves deterministic matching as opposed to probabilistic matching (i.e. a review of all possible matches is undertaken rather than using matching thresholds) [38]. A quality assurance process involving a manual review of any ‘grey areas’ identified was also undertaken by an independent member of the data linkage team [38]. A data linkage report was subsequently provided to the research team describing the linkage methodology employed, the constituents of Generations 2 and 3, and the linked Generation 3 data. Flow diagram of the I-CALM data linkage between the MUSP, the QPDC, the Queensland Hospital Admitted Patient Data Collection (QHAPDC), the Emergency Data Collection (EDC), and the Consumer Integrated Mental Health and Addiction (CIMHA) datasets. Figure 1 illustrates how the I-CALM Generation 2 and 3 cohorts were derived and how they relate to the MUSP and MUSP-CALM studies. Of the 5380 members (74.5%) of the Generation 2 cohort who had linkable data in 2024, 2552 (47.4%) were women and 1696 (66.5%) gave birth in the state of Queensland, Australia between 1 January 2008 and 30 June 2024. Table 1 shows that most women gave birth to their first child between the ages of 25 and 29 years (56.4%). There were 3296 babies born, representing Generation 3 of the I-CALM cohort. At the latest data extraction (30 June 2024), the mean age of the Generation 3 cohort was 10.6 years (SD = 4.1). Description of the I-CALM Generation 2 and 3 cohort sizes and ages. Description of the I-CALM Generation 2 and 3 cohort sizes and ages. The data linkage for I-CALM provides new health outcomes and health service use measures for Generation 3 based on perinatal, admitted hospital, ED, and community mental health service data collections. It also provides new health outcomes and health service use measures for Generation 2 based on perinatal data collection. Sociodemographic measures for both Generations 2 and 3 are also provided. Table 2 describes these new measures. New health outcomes and service use measures enabled through data linkage for the I-CALM study. Generation 2: Previous number of pregnancies (including number in which the outcome was a live birth, stillbirtha, or abortion/miscarriage/ectopic pregnancy/hydatidiform mole) Parity (total number of live births) Presence of pre-existing medical conditions and other conditions arising during the current pregnancy (based on ICD-10-AM codes) Pregnancy-related complications arising in the period immediately preceding delivery (based on ICD-10-AM codes) Postnatal depression as captured by the EPDS Damage to the perineum (if any) and the extent, e.g. degree of laceration (based on ICD-10-AM codes) Generation 3: The manner in which labour started, e.g. spontaneous, induced, or nil due to caesarean section Presentation at birth, e.g. cephalic, vertex, or breech Complications during labour and delivery (based on ICD-10-AM codes) Gestational age at birth (in weeks) Weight at birth Plurality, e.g. singleton, twins APGAR score 1 and 5 minutes after birth Resuscitation required Presence of identified at of birth up to from birth (based on ICD-10-AM codes) Presence of or identified at of birth up to from birth (based on ICD-10-AM codes) Generation 2: of hospital of per hospital of during e.g. private of caesarean of number of for the current pregnancy the current pregnancy was the of and was or on the woman during or for and violence for use Generation 3: of for the birth in which the was e.g. caesarean to or Generation 2: (in 5-year at of birth at of birth during pregnancy as any and of Generation 2 during pregnancy as any and number of on a as any and of alcohol as any and at first of of and Generation 3: Generation 3 (based on ICD-10-AM mental and other disorders or disorders disorders related to use mental disorders and other disorders disorders to e.g. stress disorders e.g. and disorders disorders A disorders disorders Mental and disorders due to use of alcohol and for disorder disorders Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of or Mental and disorders due to use of Mental and disorders due to use of other including Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use and use of other use of or or other that not use of and for disorder for disorder disorders Mental of psychological e.g. disorders of and disorders Childhood e.g. and disorders of and e.g. emotional disorders of social disorders and suicidal ideation of hospital admissions of per to of in of as an admitted a of presentations of per of at of community Generation 2: Previous number of pregnancies (including number in which the outcome was a live birth, stillbirtha, or abortion/miscarriage/ectopic pregnancy/hydatidiform mole) Parity (total number of live births) Presence of pre-existing medical conditions and other conditions arising during the current pregnancy (based on ICD-10-AM codes) Pregnancy-related complications arising in the period immediately preceding delivery (based on ICD-10-AM codes) Postnatal depression as captured by the EPDS Damage to the perineum (if any) and the extent, e.g. degree of laceration (based on ICD-10-AM codes) Generation 3: The manner in which labour started, e.g. spontaneous, induced, or nil due to caesarean section Presentation at birth, e.g. cephalic, vertex, or breech Complications during labour and delivery (based on ICD-10-AM codes) Gestational age at birth (in weeks) Weight at birth Plurality, e.g. singleton, twins APGAR score 1 and 5 minutes after birth Resuscitation required Presence of identified at of birth up to from birth (based on ICD-10-AM codes) Presence of or identified at of birth up to from birth (based on ICD-10-AM codes) Generation 2: of hospital of per hospital of during e.g. private of caesarean of number of for the current pregnancy the current pregnancy was the of and was or on the woman during or for and violence for use Generation 3: of for the birth in which the was e.g. caesarean to or Generation 2: (in 5-year at of birth at of birth during pregnancy as any and of Generation 2 during pregnancy as any and number of on a as any and of alcohol as any and at first of of and Generation 3: Generation 3 (based on ICD-10-AM mental and other disorders or disorders disorders related to use mental disorders and other disorders disorders to e.g. stress disorders e.g. and disorders disorders A disorders disorders Mental and disorders due to use of alcohol and for disorder disorders Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of or Mental and disorders due to use of Mental and disorders due to use of other including Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use and use of other use of or or other that not use of and for disorder for disorder disorders Mental of psychological e.g. disorders of and disorders Childhood e.g. and disorders of and e.g. emotional disorders of social disorders and suicidal ideation of hospital admissions of per to of in of as an admitted a of presentations of per of at of community A is as a birth that not and was APGAR = and = of = = body = Integrated Mental Health = Emergency Data EPDS = Postnatal ICD-10-AM = Statistical of and Health Australian = = mental = = Queensland Hospital Admitted Patient Data = = for New health outcomes and service use measures enabled through data linkage for the I-CALM study. Generation 2: Previous number of pregnancies (including number in which the outcome was a live birth, stillbirtha, or abortion/miscarriage/ectopic pregnancy/hydatidiform mole) Parity (total number of live births) Presence of pre-existing medical conditions and other conditions arising during the current pregnancy (based on ICD-10-AM codes) Pregnancy-related complications arising in the period immediately preceding delivery (based on ICD-10-AM codes) Postnatal depression as captured by the EPDS Damage to the perineum (if any) and the extent, e.g. degree of laceration (based on ICD-10-AM codes) Generation 3: The manner in which labour started, e.g. spontaneous, induced, or nil due to caesarean section Presentation at birth, e.g. cephalic, vertex, or breech Complications during labour and delivery (based on ICD-10-AM codes) Gestational age at birth (in weeks) Weight at birth Plurality, e.g. singleton, twins APGAR score 1 and 5 minutes after birth Resuscitation required Presence of identified at of birth up to from birth (based on ICD-10-AM codes) Presence of or identified at of birth up to from birth (based on ICD-10-AM codes) Generation 2: of hospital of per hospital of during e.g. private of caesarean of number of for the current pregnancy the current pregnancy was the of and was or on the woman during or for and violence for use Generation 3: of for the birth in which the was e.g. caesarean to or Generation 2: (in 5-year at of birth at of birth during pregnancy as any and of Generation 2 during pregnancy as any and number of on a as any and of alcohol as any and at first of of and Generation 3: Generation 3 (based on ICD-10-AM mental and other disorders or disorders disorders related to use mental disorders and other disorders disorders to e.g. stress disorders e.g. and disorders disorders A disorders disorders Mental and disorders due to use of alcohol and for disorder disorders Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of or Mental and disorders due to use of Mental and disorders due to use of other including Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use and use of other use of or or other that not use of and for disorder for disorder disorders Mental of psychological e.g. disorders of and disorders Childhood e.g. and disorders of and e.g. emotional disorders of social disorders and suicidal ideation of hospital admissions of per to of in of as an admitted a of presentations of per of at of community Generation 2: Previous number of pregnancies (including number in which the outcome was a live birth, stillbirtha, or abortion/miscarriage/ectopic pregnancy/hydatidiform mole) Parity (total number of live births) Presence of pre-existing medical conditions and other conditions arising during the current pregnancy (based on ICD-10-AM codes) Pregnancy-related complications arising in the period immediately preceding delivery (based on ICD-10-AM codes) Postnatal depression as captured by the EPDS Damage to the perineum (if any) and the extent, e.g. degree of laceration (based on ICD-10-AM codes) Generation 3: The manner in which labour started, e.g. spontaneous, induced, or nil due to caesarean section Presentation at birth, e.g. cephalic, vertex, or breech Complications during labour and delivery (based on ICD-10-AM codes) Gestational age at birth (in weeks) Weight at birth Plurality, e.g. singleton, twins APGAR score 1 and 5 minutes after birth Resuscitation required Presence of identified at of birth up to from birth (based on ICD-10-AM codes) Presence of or identified at of birth up to from birth (based on ICD-10-AM codes) Generation 2: of hospital of per hospital of during e.g. private of caesarean of number of for the current pregnancy the current pregnancy was the of and was or on the woman during or for and violence for use Generation 3: of for the birth in which the was e.g. caesarean to or Generation 2: (in 5-year at of birth at of birth during pregnancy as any and of Generation 2 during pregnancy as any and number of on a as any and of alcohol as any and at first of of and Generation 3: Generation 3 (based on ICD-10-AM mental and other disorders or disorders disorders related to use mental disorders and other disorders disorders to e.g. stress disorders e.g. and disorders disorders A disorders disorders Mental and disorders due to use of alcohol and for disorder disorders Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of or Mental and disorders due to use of Mental and disorders due to use of other including Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use of Mental and disorders due to use and use of other use of or or other that not use of and for disorder for disorder disorders Mental of psychological e.g. disorders of and disorders Childhood e.g. and disorders of and e.g. emotional disorders of social disorders and suicidal ideation of hospital admissions of per to of in of as an admitted a of presentations of per of at of community A is as a birth that not and was APGAR = and = of = = body = Integrated Mental Health = Emergency Data EPDS = Postnatal ICD-10-AM = Statistical of and Health Australian = = mental = = Queensland Hospital Admitted Patient Data = = for The I-CALM data linkage was completed in January Table 3 provides all Generation 3 cohort members were admitted to hospital at least between 1 January 2008 and 30 June 2024. to an at least and of the Generation 3 cohort community mental health for Generation 3 health service use and Generation 2 experiences of = records have data Generation 3 cohort members have at least one for the birth CM = Child = = Emergency = Mental for Generation 3 health service use and Generation 2 experiences of = records have data Generation 3 cohort members have at least one for the birth CM = Child = = Emergency = Mental experiences of CM will be critical to research Approximately of women in the Generation 2 cohort had any of notified CM during and physical abuse were the most of the Generation 2 cohort had any of substantiated CM during Substantiated emotional abuse and physical abuse were the most of the Generation 2 cohort self-reported any of to CM by using the Self-reported sexual abuse, emotional neglect, and emotional abuse were the most The of the I-CALM study in the linkage between the MUSP Generation 2 records and administrative health data to identify Generation 3 cohort This linkage has the of a with health outcomes and health service use the health outcomes and health service use data of a diverse with which we research Moreover, both and and self-reported of CM data are for Generation This to a more comprehensive of intergenerational CM transmission consequences, which to of CM data when to support public health A of I-CALM is that Generation 2 women who gave birth in Queensland between 1 January 2008 and 30 June 2024, the of the Generation 3 cohort. There were 5380 Generation 2 cohort members at the follow-up who had linkable administrative health data and were (Figure 1). members of Generation 2 who may have had children were to be as are in the Moreover, Generation 2 women gave birth of Queensland, they not have been as the is a administrative There are also partner data for women in Generation 2, which is are likely to have to the health and of Generation 3 of I-CALM is the in data the While and health service use data are for Generations 2 and 3 through administrative health data data are for Generation This to intergenerational and may of or social with other is This may any number of including the of research on of to support a research and by with This will with one or more of the I-CALM The I-CALM data are not of the data are by the MUSP and the linked administrative health data are by Queensland to these data is for on an Health and have to the data. who to the data will be required to the and Health contact Dr Claudia Bull via ([email protected]) more the I-CALM data. of the MUSP including each follow-up and data be at in these data are to contact via ([email approval for study was obtained from the Metro South Research Ethics Committee (reference number: HREC/2024/QMS/107240) and the University of Queensland Human Research Ethics Committee (project number: 2024/HE002338). This research was in with the in the of The the Statistical and Linkage of the Queensland Health for linking the in and the MUSP I-CALM data and obtained approval for the data and the data a in with and for that was subsequently to all data and the first of the and is for its provided critical on the This work was by the Metro South Research to and the administrative health data be approval from relevant data and the of Research and of Queensland Contact for Queensland Health be at MUSP data are from a on reasonable Contact be at were in collecting data, or or in the

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