Breastfed children are more intelligent, according to the latest findings of a joint University of Queensland–Mater Hospital longitudinal study.
The study of breastfeeding’s impact on the cognitive development of almost 4000 Brisbane-born children was conducted as part of the 21-year-old Mater–University of Queensland Study of Pregnancy – Australia’s largest longitudinal study tracking mothers and their children.
It is the first known Australian study of the relationship between breastfeeding and children’s cognitive development to be adjusted for a wide range of biological and psychosocial factors.
These included: marital status; whether or not parents were born in an English-speaking country; maternal education level; degree to which the mother had played with the child, talked to the child, taught the child and encouraged the child’s interests; maternal cigarette-smoking; and maternal anxiety and depression.
Researchers tested 3880, five-year-old children with a surrogate IQ questionnaire after earlier establishing breastfeeding patterns when the same group of children was aged just six-months-old.
At this time, mothers were asked to categorise the period they had breastfed as either: never breastfed; less than three weeks; three weeks to less than seven weeks; seven weeks to less than four months; four months to less than six months; or still breastfeeding at six months.
The surrogate IQ test given to the children, known as the Peabody Picture Vocabulary Test Revised (PPVT-R), is a standardised test of language among young children.
The researchers, led by Associate Professor Michael O’Callaghan (joint appointment with Mater Children’s Hospital and UQ’s School of Paediatrics and Child Health) and Dr Pat Quinn (Mater Children’s Hospital), found increased PPVT-R scores with increased durations of breastfeeding.
The collaborative research project also involved Professor Jake Najman from UQ’s Schools of Social Science and Population Health, Professor Gail Williams of the School of Population Health, Dr William Bor of the School of Psychiatry and Dr Margaret Andersen of the School of Medicine.
In particular, after adjustment for other factors, the average test result for those children breastfed for six months or more was 8.2 points higher for females and 5.8 points higher for males when compared with those who were never breastfed.
Professor Najman said the study’s findings could be explained by psychological influences such as a stronger attachment being facilitated between mother and child through the act of breastfeeding, thereby encouraging cognitive development.
Another possibility was that sensory stimulation, integral to brain development, was increased through being held and fed from the mother’s body, he said. “An infant’s brain grows fastest in the first year of life, with the brain increasing in size by around 35 percent in the 12 months following birth,” Professor Najman said.
He said a second factor could be a unique, nutritional component of breast milk, possibly a lipid, essential for optimal brain development.
“In addition to the other known benefits of breastfeeding, this study supports the need to encourage breastfeeding of infants wherever possible,” Professor Najman said.
FACT SHEET: The Mater–University of Queensland Study of Pregnancy
• The Mater–University of Queensland Study of Pregnancy (MUSP) is Australia’s largest longitudinal study tracking mothers and their children and has been in progress for the past 21 years.
• A total of 8556 women attending their first antenatal visit at the Mater Mothers’ Hospital between 1981 and 1984 were enrolled in the MUSP project. After stillbirths, neonatal or infant deaths, multiple births, adoptions and those delivered at other centres were excluded, 7661 singleton children remained in the study after birth.
• Data were collected at enrolment, shortly after birth then at six months, five years and 14 years after delivery by questionnaire and included social features of the family and psychological characteristics of the mother.
• Biological measures of the pregnancy, birth and delivery were recorded by obstetric staff associated with the project at or shortly after birth.
• At five years, a questionnaire relating to the health and wellbeing of mother and child was completed by 5360 mothers who could be contacted.
• Because of a lack of funding in the later part of the study and practical issues such as distance, only 3867 children were able to attend for a clinical assessment at the five-year follow-up including administration of the Peabody Picture Vocabulary Test Revised (PPVT-R).
• Recent National Health and Medical Research Council (NHMRC) grants worth $1.1 million will enable 21-year follow-ups of both the mothers and the children to be conducted over the next three years.
• The study has so far achieved a creditable retention rate of up to 70 percent of participants – attributed to recognition by members that they are part of a very special group. The researchers’ past experience has shown that the participants located agree to continue with the study because they are familiar with it and recognise the value of their contributions.
• The collaborative research project involves a range of people and disciplines including Professor Najman in the Schools of Social Science and Population Health and other UQ colleagues including Dr William Bor (School of Psychiatry), Dr Michael O`Callaghan (School of Paediatrics and Child Health) and Professor Gail Williams (School of Population Health) – all of whom have worked together for many years on these issues. Dr Kathy Ahern (School of Social Science) joined the project as an Associate Investigator in 2001, in preparation for the current follow-up.
• The youth grant component of this recent funding boost, totalling almost $700,000, will enable researchers to study the mental and physical well-being of the 21-year-olds.
– With growing mental health problems and obesity in young people, this sample of more than 7000 young Australians represents a unique
opportunity for researchers to study the factors contributing to these
problems.
– Available evidence suggests 20–25 percent of young people
have experienced a major mental health problem and more than 10
percent are obese, with a substantially higher proportion being
overweight.
• The mothers’ grant component of the recent NHMRC funding, totalling more than $420,000, will enable researchers to study the health of women in mid-life when health problems associated with biological and social transitions such as menopause are major concerns.
– National estimates indicate that 15–20 percent of middle-aged women
have experienced mental illness in the past year.
– This study will examine the mother’s mental health symptoms over a
21-year period, and assess the association between her early mental
health, the child’s health and her current health status.
– The longitudinal nature of the study will permit greater understanding of how women’s health changes over time and the factors associated
with these changes.
– It represents the first large-scale study of factors influencing women’s
health transition through menopause.
Media: For more information, contact Professor Jake Najman (telephone 07 3365 5180), Jan King or Shirley Glaister at UQ Communications (telephone 07 3365 1120 or 07 3365 2339 or mobile 0413 601 248) or Kelly Quinlan at the MUSP (telephone 07 3840 8522).
