By applying a public health approach, researchers at three universities have discovered a key indicator for increased risk of mental retardation in the general population. The study assessed population-level risk factors by linking birth records of 12-14-year-old children in Florida with their respective public school records, over the course of a school year.
Using the rationale that high-prevalence risk factors can have a substantial impact at the population level, even if the risk to the individual is low, Derek Chapman, Assistant Professor of Epidemiology & Community Health at Virginia Commonwealth University, Keith Scott, Professor of Psychology, at the University of Miami, and Tina L. Stanton-Chapman, Assistant Professor of Curriculum Instruction and Special Education, at the University of Virginia, found that low maternal education resulted in the highest risk of intellectual disability to offspring compared with other factors such as maternal illness, delivery complications, gestational age at birth, and even very low birth weight.
Extremely low birth weight infants (<1000 grams or 2.2 lbs) were 9.1 times more likely to have a mild intellectual disability compared to normal birth weight infants (2500+g or 5.5 lbs), yet were only associated with 2.1% of cases in the population. Women with an education below the high school level were 8.9 times more likely to have a child with mild intellectual disability compared with women who had more than 12 years of education, but were associated with 50.9% of cases.
Significant socioeconomic effects were found across all levels of intellectual disabilities, with higher income and education dramatically attenuating risk associated with biologic factors such as low birth weight, indicating a range of opportunities for population-based prevention and early intervention services.
The study's corresponding author, Derek Chapman, explained, "This approach to the study of disabilities is critical because an exclusive focus on prevention via medical interventions ignores the tremendous impact we can have by addressing social factors for which low education is a marker. If infants born to women with a high school education or less had the same risk as those born to college-educated women, there would be a 75% reduction in mild intellectual disabilities. Although genetic and biologic factors clearly play a role, their risk can be attenuated and there is a greater potential impact by addressing social factors such as maternal stress, birth spacing, preconception care, the child-rearing environment, and access to early and comprehensive intervention for at-risk infants and children."
The authors speculate that in addition to direct genetic effects, prenatally, maternal education may impact cognitive development through awareness and avoidance by the mother of certain risk behaviors and access to early and comprehensive prenatal care. Likewise, the authors theorize that, postnatally, low maternal education can influence mental development of the child through poor nutrition choices by the mother, less cognitive stimulation in the home environment, less knowledge of and access to early intervention services, and increases in childhood injuries.
The results appear in the March 2008 issue of the American Journal of Mental Retardation ("Public Health Approach to the Study of Mental Retardation," by Derek A. Chapman, Keith G. Scott, and Tina L. Stanton-Chapman).
The above story is based on materials provided by American Association on Intellectual and Developmental Disabilities. Note: Materials may be edited for content and length.
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