History of the Study
The Dunedin Multidisciplinary Health and Development Study (DMHDS) is an ongoing, longitudinal study of the health, development and well-being of a large sample of young New Zealanders. They were studied at birth (1972-73), followed up and assessed at the age of three, then every two years until the age of 15, then at ages 18 (1990-91), 21 (1993-94), 26 (1998-99), 32 (2003-2005), 38 (2010-2012). It is planned to next see the Study members at age 44, then again at age 50, and beyond.
There are three special features of the DMHDS that enables it to contribute new knowledge about health and development. First, the sample represents a cross-section of the Dunedin population. All children born at Dunedin's Queen Mary Hospital between 1 April 1972 and 31 March 1973 and still living in Otago at age three were eligible for membership of the Study sample. The children are therefore representative of Dunedin children born at that time, and mroe broadly, children born in the South Island of New Zealand. Second, very few members of the sample have been lost to follow-up over the years. For example, at the age 32 assessment, 96 per cent of the living cohort were followed up. Third, and perhaps the most valuable feature of the Study, has been its multidisciplinary focus. A comprehensive assessment of Study members has been carried out involving, as principal investigators, members of a wide range of key disciplines concerned with issues of human health and development. This has resulted in a large number of studies on a diverse range of health and development issues.
Background to the Study
In the 1960s and early 1970s, most obstetric and paediatric services in the developed world made important advances in the care of infants before, during and immediately after birth. New techniques were developed to identify and care for high risk pregnant mothers, new advances were used to manage the process of birth, and neonatal intensive care units with new technology became available to care for newborns whose start to life was complicated by such problems as low birth weight, preterm delivery, and breathing or other problems, such as jaundice. The aim of the new technology was to save infants' lives and to protect them.
As the new technology was introduced, infant mortality rates dropped. More infants who might previously have died, survived, including preterm and very low birth weight infants. While obstetricians and paediatricians were easily able to monitor the improvements in infant survival rates, they were unable to tell how those who had survived were doing in the longer term. Questions were raised about whether the new technology was decreasing the mortality rate but increasing the morbidity rate. Some believed that although more babies were surviving, more were suffering minor degrees of brain damage. For example, studies from Baltimore led to the promulgation of what became known as the 'theory of reproductive casualty'. Briefly, the theory stated that the perinatal events (events before, during and after birth) that caused infant death could, in less severe forms, cause varying degrees of damage to the brain from severe (e.g. causing mental retardation, cerebral palsy) to mild (e.g. causing learning difficulties, behaviour problems). Intense professional interest focused on the question of how well children who had experienced and survived various perinatal problems developed as they grew beyond infancy to childhood. In the late 1960s, the new medical technology became a feature of the work of Queen Mary Hospital, Dunedin's only obstetric hospital. Almost all (98 per cent) of Dunedin's infants were born at Queen Mary at that time and it was staffed mainly by obstetricians and paediatricians who were also members of the academic staff of the University of Otago Medical School. In addition to providing medical services applying the latest technology, medical staff were involved in a number of research projects that aimed to monitor and improve the quality of the services provided. It was one of these projects, conducted by the late Dr Patricia Buckfield, that led to the establishment of the Dunedin Multidisciplinary Health and Development Study.
Dr Buckfield, who at that time was a senior paediatrician specialising in neonatology, decided to study and record perinatal histories in the total newborn population of Dunedin over a period of time. This eventually involved studying all the births at Queen Mary Hospital from 1967 to 1973, and recording the obstetric, perinatal and neonatal histories of more than 12 000 babies and their mothers. The focus of these studies was the health of the newborn infant. Dr Buckfield and her colleagues were also interested in the longer-term development of the infants and wanted to find out whether particular perinatal problems (e.g. preterm delivery, low birth weight, birth hypoxia, hyperbilirubinaemia) might be associated with later problems. This led to the development of a successful proposal to the Medical Research Council of New Zealand for funding for a follow-up study of a sample of 250 four- and five-yearolds who had been born in 1968, half of whom had experienced perinatal problems and half whose start to life had been apparently normal. Phil A. Silva, and educational psychologist, was invited to design and carry out the developmental and psychological assessments of the sample for this study, which was a collaborative effort involving personnel from paediatrics, obstetrics and child psychology. The Children were administered numerous tests of psychological development, their behaviour was observed, they were weighed and measured, had their vision and hearing tested, and their neurological functioning assessed by paediatricians.
The early study, which was known as the Queen Mary Hospital Multidisciplinary Child Development Study, turned out to be a pilot study for what was to come later. It was found that certain perinatal problems were associated with small but significant disadvantages in later language development and intelligence. Publications also described other aspects of development and health, including the growth and vision of the children. The relative impact of external influences, including socio-economic status, parental characteristics and childhood experiences on the intelligence of the children was also reported.
Perhaps the most important contribution of the first study was the experience it provided in conducting follow-up studies of young children. It was also particularly helpful in the field of early child developmental and psychological assessment. At that time (the early 1970s), many developmental psychologists believed that it was possible to assess very distinct aspects of cognitive functioning and that these assessments could provide an indication of which part of the brain might have been damaged by particular events such as those occurring near the time of birth. Others, however, believed that results of tests of cognitive functioning were highly correlated and reflected more general functioning. The early DMHDS involved the administration of 36 different measures of cognitive functioning to 225 four- and five-year-olds. The properties of these measures were studied by factor analysing the correlations among them. These analyses indicated that the 36 measures were highly inter-correlated and were tapping only two broad aspects of cognitive functioning, designated as 'verbal' and 'nonverbal' ability. This finding and other information gained helped to determine the selection of tests and measures that would later be used in the DMHDS. The most striking finding from the early study, however, was unexpected. The examination and assessment of the four- and then five-year-olds, and an interview with their parents, revealed that a relatively large percentage of the children had problems. These included problems of development (e.g. language and/or motor delays), behaviour problems (e.g. being very difficult to manage), hearing problems, vision problems and other health problems. It was also found that a considerable number of children had experienced injuries, some of which left them with long-lasting disabilities (e.g. as a result of burns). Many of the problems detected were quite serious, causing distress to the children and their parents, and likely to affect the children's schooling and longer-term development. Despite this, many of the problems had not previously been detected or addressed by the existing services.
The DMHDS was designed to investigate broader questions of child health and development, but was not originally conceived as a long-term study (nobody originally involved would have guessed that the children would be followed into adulthood!). The original idea was simply to locate a one-year birth cohort who had been studied at birth by Dr Buckfield and to invite them to return for an assessment at age three. The aims were to study the nature and prevalence of some developmental and health problems in three-year-olds, and some of the factors associated with those problems (e.g. some perinatal, family and experiential factors).
The resources for the Study were scarce. The Founding Director, Dr Phil A. Silva, was assisted by a part-time secretary, a group of volunteers from the university staff and five young medical doctors whose family commitments meant that they chose not to work full-time. Several dozen volunteers from the community assisted with locating the Study members, carrying out clerical and data processing work, looking after the children and parents, and doing some of the interviewing. Small donations and assistance from various sources helped stretch the limited resources, and accommodation was found in the old (condemned) Presbyterian manse and Sunday school halls at Knox Church. There were no funds to pay the modest rent at first; later it was paid by the National Children's Health Research Foundation.
A one-year birth cohort was selected for the Study. Those born in the first three months of 1972 were used as a trial sample, with the birth cohort comprising all those born between 1 April 1972 and 31 March 1973. The one-year birth cohort was selected because it was expected to yield a sample of about 1000 children. This number was similar to that included in the Newcastle-upon-Tyne Thousand Families Study, UK, and was considered large enough to allow study of groups of children with the more common disorders. For example, a disorder with a 3 per cent prevalence rate should result in about 30 children with that disorder in the sample. Another consideration in selecting the sample size was the limited number of personnel and scarce resources available to carry out the Study. During 1975 and the first month of their third birthday, this involved carrying out a range of assessments on the children. The descriptive results were written up and presented to the Medical Research Council in 1976 in an extensive, unpublished report entitled “A Thousand Dunedin Three Year Olds”.
In 1977, the Medical Research Council awarded the first of three five-year research programme grants to allow the Study members to be assessed every two years to age 15, then again at age 18. In 1990, the Medical Research Council was disbanded and the Health Research Council of New Zealand established in its place. The new Council allowed the continuation of the previous Medical Research Council grant to the end of 1991, then extended it to the end of 1992. A series of new project grants was then awarded to extend the Study for five years from 1993. These grants, plus funding from the Accident Rehabilitation Compensation and Insurance Corporation of New Zealand (ACC) and the United States National Institutes for Mental Health, enabled the Study to continue.
Over the years, grants have also been received from a variety of other funding bodies including the Departments of Education and Health, the Asthma Foundation of New Zealand, the Otago Medical Research Foundation, the New Zealand Cancer Society, the National Children's Health Research Foundation, the Deafness Research Foundation, the Foundation for the Newborn, the IYC Telethon Trust, the Child and Youth Development Trust, the Alcoholic Liquor Advisory Council, the National Heart Foundation, the Neurological Foundation, the J.R. McKenzie Trust Board and IBM (New Zealand) Ltd.
Most recently, funding has been received by the Health Research Council of New Zealand, the US National Institutes for Mental Health, the US National Institute for Dental and Craniofacial Health, the US National Institute of Child Health and Human Development, the US National Institute on Aging, and the UK Medical Research Council.
[The majority of this material has been extracted from Silva & Stanton, 1996, From Child to Adult: The Dunedin Multidisciplinary Health & Development Study, Oxford University Press.]