Study Reveals Prolonged Effectiveness of Early Intervention Program

Improvements in cognitive and behavioral development evident into adolescence

    • March 5, 2006

An 18-year follow-up study of the Infant Health and Development Program (IHDP), published in the March 2006 issue of Pediatrics, provides the best evidence to date of the sustained, positive effects of early educational intervention on children's long-term outcomes. This large, multi-site, randomized trial expands on earlier investigations—that were smaller and more limited in scope—to support the value of early intervention programs and the need to extend educational enrichment activities to a broader range of children. The IHDP intervention served lower- and higher-weight preterm infants, who tend to be at risk for serious health and developmental problems.

“These findings are very encouraging, and provide compelling and useful data for health care providers, policy makers, economists and parents with regard to the enduring benefits of early childhood interventions,” said principal investigator Marie C. McCormick, M.D., Sc.D., professor of maternal and child health at Harvard School of Public Health. “The sustainability of effects reinforces the importance of such programs, and the need to make these services available and accessible to at-risk infants early on—before problems arise—to maximize their impact.”

Adolescents in the intervention group were more likely to have higher achievement scores in math and reading and fewer risky behaviors (e.g., antisocial behavior, suicidal thoughts/attempts, smoking, alcohol or marijuana use) than the follow-up only group. The original 36-month intervention consisted of home visits every week for the first year of the child's life and every other week in the second and third year, along with daily center-based education beginning at 12 months (corrected for duration of gestation) and a support group for parents of participating children. The follow-up only group received frequent pediatric assessments and community services when needed during the intervention period. At age 18, 636 of the original 985 participants took part (65 percent, or 72 percent of those who were eligible having not died or refused at prior assessments). Earlier assessments were at 3, 5 and 8 years of age.

“This is the largest study ever to evaluate the effects of early development intervention for preterm infants, who we know to be at risk for all kinds of academic and behavioral problems,” explained Laura Leviton, Ph.D., senior program officer at the Robert Wood Johnson Foundation, which provided funding for this study. “Results indicate that high-quality early education services can greatly improve children's lives, giving them the best chance to achieve their full potential and become successful, healthy adults.”

While the present findings are strikingly parallel to those of earlier, smaller studies, the IHDP has important methodological strengths, which add credibility to the demonstrated long-term value of early educational interventions:

The program, which involves the largest number of preterm infants to date, was uniformly implemented and closely monitored at eight major birthing centers across the country.

  • This study was rigorously and carefully designed with strict randomization and masked assessments at major outcome points—previous studies predominantly involved healthy, low-income children often at a single site and with fewer participants overall.
  • The sample is heterogeneous with regard to health (especially neurodevelopmental status that might influence school outcomes) and socioeconomic status, which suggests that the results can be generalized.
  • Positive long-term effects observed for the heavier low birth weight babies (2,001-2,499 g) in the intervention group are highly comparable to normal birth weight babies. Hence, the study findings should translate to a larger infant population.
  • This is one of the few studies to assess and establish intervention effects into adolescence.

A variety of assessment instruments were selected and used to ensure continuity with previous measurement periods. Data were adjusted for cohort attrition and participant and control groups were comparable. The eight study sites were selected based on the institution's capacity to provide services and primarily reflect centers with large birthing populations. Participating centers were located in Little Rock, Ark., Boston, Mass., South Bronx, N.Y., Philadelphia, Pa., Dallas, Texas, Miami, Fla., Seattle, Wash., and New Haven, Conn.

"This study is an important contribution to the field of child development, and bolsters an impressive body of literature demonstrating the effectiveness of early interventions, shown to enhance educational achievement and social outcomes,” said Jim Heckman, Ph.D., Nobel Laureate and professor of economics at the University of Chicago. “Except for the lowest birth weight categories, there are lasting effects of the intervention on achievement and behavior.”

Direction for Future Research

The lack of observable benefits in the lighter low birth weight group (≤ 2,000 g) is of concern, and underscores the need for further research to identify educational, environmental or biological factors that may promote or impede sustained effects of early educational intervention. It is important to note, this group of high-risk babies did demonstrate positive effects at 3 years of age. The question of how to best support these high-risk infants, and extend the benefits of early education later into their lives, remains.

The age of assessment (18 years) may fall short in terms of being able to gauge important economic outcomes, such as higher educational attainment, occupational status and eventual income. The Abecedarian Project, which IHDP sought to replicate, reported sustained intervention advantages beyond 21 years of age, including the proportion of participants enrolled in a four-year college or university.

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