PASADENA, Calif., December 10, 2012 - Children who had in-utero exposure to ischemic-hypoxic conditions, situations during which the brain is deprived of oxygen, were significantly more likely to develop attention deficit hyperactivity disorder later in life as compared to unexposed children, according to a Kaiser Permanente study published in the journal Pediatrics. The findings suggest that events in pregnancy may contribute to the occurrence of ADHD over and above well-known familial and genetic influences of the disorder.
The population-based study examines the association between IHC and ADHD. Researchers examined the electronic health records of nearly 82,000 children ages 5 years old and found that prenatal exposure to IHC - especially birth asphyxia, neonatal respiratory distress syndrome, and preeclampsia - was associated with a 16 percent greater risk of developing ADHD. Specifically, exposure to birth asphyxia was associated with a 26 percent greater risk of developing ADHD, exposure to neonatal respiratory distress syndrome was associated with a 47 percent greater risk, and exposure to preeclampsia (high blood pressure during pregnancy) was associated with a 34 percent greater risk. The study also found that the increased risk of ADHD remained the same across all race and ethnicity groups.
"Previous studies have found that hypoxic injury during fetal development leads to significant structural and functional brain injuries in the offspring," said study lead author Darios Getahun, MD, PhD, of the Kaiser Permanente Southern California Department of Research & Evaluation. "However, this study suggests that the adverse effect of hypoxia and ischemia on prenatal brain development may lead to functional problems, including ADHD."
Researchers also found that the association between IHC and ADHD was strongest in preterm births and that deliveries that were breech, transverse (shoulder-first) or had cord complications were found to be associated with a 13 percent increased risk of ADHD. These associations were found to be the case even after controlling for gestational age and other potential risk factors.
"Our findings could have important clinical implications. They could help physicians identify newborns at-risk that could benefit from surveillance and early diagnosis, when treatment is more effective," said Getahun. "We suggest future research to focus on pre- and post-natal conditions and the associations with adverse outcomes, such as ADHD."
During critical periods of fetal organ development, IHC may result in a lack of oxygen and nutrient transport from the mother's blood to fetal circulation. The result may be compromised oxygen delivery to tissues and cerebrovascular complications. However, this study suggests that the adverse effect of hypoxia on prenatal brain development may lead to functional problems, including ADHD.
In 2005, the Centers for Disease Control and Prevention estimated the annual cost of ADHD-related illness in children under 18 years of age to be between $36 billion and $52.4 billion, making the condition a public health priority. In 2010, approximately 8.4 percent of children ages 3 to 17 had been diagnosed with ADHD. For about half the affected children, the disease persists into adulthood, according to CDC statistics. Symptoms of ADHD in children may include attention problems, acting without thinking, or an overly active temperament.
This study is part of Kaiser Permanente's ongoing research to understand the relationship between prenatal conditions and adverse medical outcomes. Earlier this year, Kaiser Permanente researchers found that in-utero exposure to relatively high magnetic field levels was associated with a 69 percent increased risk of being obese or overweight during childhood compared to lower in-utero magnetic field level exposure. And a Kaiser Permanente study conducted last year found exposure to selective serotonin reuptake inhibitors anti-depressants in early pregnancy may modestly increase the risk of autism spectrum disorders.
Kaiser Permanente can conduct transformational health research in part because it has the largest private patient-centered electronic health system in the world. The organization's electronic health record system, Kaiser Permanente HealthConnect®, securely connects 9 million people, 611 medical offices, and 37 hospitals, linking patients with their health care teams, their personal health information, and the latest medical knowledge. It also connects Kaiser Permanente's researcher scientists to one of the most extensive collections of longitudinal and medical data available, facilitating studies and important medical discoveries that shape the future of health and care delivery for patients and the medical community.
Other study authors included: George G. Rhoads, MD, MPH, and Kitaw Demissie, MD, PhD, of the UMDNJ School of Public Health Department of Epidemiology; Shou-En Lu, PhD, of the UMDNJ School of Public Health Department of Biostatistics; Michael J. Fassett, MD, of the Kaiser Permanente West Los Angeles Medical Center Department of Maternal-Fetal Medicine; Deborah A. Wing, MD, of the University of California, Irvine Department of Obstetrics-Gynecology; and Steven J. Jacobsen, MD, PhD, and Virginia P. Quinn, PhD, of the Kaiser Permanente Southern California Department of Research & Evaluation.
About the Kaiser Permanente Southern California Department of Research & Evaluation
The Department of Research & Evaluation (R & E) conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiology, health sciences and behavioral research as well as clinical trials. Areas of interest include diabetes and obesity, cancer, HIV/AIDS, cardiovascular disease, aging and cognition, pregnancy outcomes, women's and children's health, quality and safety, and pharmacoepidemiology. Located in Pasadena, Calif., the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general population. Visit www.kp.org/research.
About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We serve approximately 9 million members in 9 states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to www.kp.org/newscenter.