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Original Investigation
October 29, 2018

Association of Prenatal Phthalate Exposure With Language Development in Early Childhood

Author Affiliations
  • 1Department of Health, Karlstad University, Karlstad, Sweden,
  • 2Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, New York
  • 3Laboratory Medicine, Lund University, Lund, Sweden
  • 4Department of Psychiatry, Mount Sinai School of Medicine, New York, New York
  • 5School of Medical Sciences, Örebro University School of Medical Sciences, Örebro, Sweden
  • 6Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, New York
  • 7Department of Pediatrics, University of Washington, Seattle
  • 8Department of Epidemiology, Rutgers School of Public Health, Piscataway, New Jersey
  • 9University of Minnesota, Minneapolis
  • 10Department of Psychiatry and Pediatrics, Center for Health and Community, University of California, San Francisco, San Francisco
JAMA Pediatr. Published online October 29, 2018. doi:10.1001/jamapediatrics.2018.3115
Key Points

Question  Is prenatal phthalate exposure associated with language development in children at 30 to 37 months of age?

Findings  In this cohort study of 2 independent studies that included a total of 1333 mother–child pairs, exposure to dibutyl phthalate and butyl benzyl phthalates during pregnancy was significantly associated with language delay in preschool-aged children.

Meaning  These findings suggest that additional examination of the association of phthalates with language delay is warranted.

Abstract

Importance  Prenatal exposure to phthalates has been associated with neurodevelopmental outcomes, but little is known about the association with language development.

Objective  To examine the association of prenatal phthalate exposure with language development in children in 2 population-based pregnancy cohort studies.

Design, Setting, and Participants  Data for this study were obtained from the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study conducted in prenatal clinics throughout Värmland county in Sweden and The Infant Development and the Environment Study (TIDES) conducted in 4 academic centers in the United States. Participants recruited into both studies were women in their first trimester of pregnancy who had literacy in Swedish (SELMA) or English or Spanish (TIDES). This study included mothers and their children from both the SELMA study (n = 963) and TIDES (n = 370) who had complete data on prenatal urinary phthalate metabolite levels, language delay, and modeled covariables. For SELMA, the data were collected from November 1, 2007, to June 30, 2013, and data analysis was conducted from November 1, 2016, to June 30, 2018. For TIDES, data collection began January 1, 2010, and ended March 29, 2016, and data analysis was performed from September 15, 2016, to June 30, 2018.

Main Outcomes and Measures  Mothers completed a language development questionnaire that asked the number of words their children could understand or use at a median of 30 months of age (SELMA) and 37 months of age (TIDES). The responses were categorized as fewer than 25, 25 to 50, and more than 50 words, with 50 words or fewer classified as language delay.

Results  In the SELMA study, 963 mothers, 455 (47.2%) girls, and 508 [52.8%] boys were included. In TIDES, 370 mothers, 185 (50.0%) girls, and 185 (50.0%) boys were included in this analysis. The prevalence of language delay was 10.0% in both SELMA (96 reported) and TIDES (37 reported), with higher rates of delay in boys than girls (SELMA: 69 [13.5%] vs 27 [6.0%]; TIDES: 12 [12.4%] vs 14 [7.6%]). In crude analyses, the metabolite levels of dibutyl phthalate and butyl benzyl phthalate were statistically significantly associated with language delay in both cohorts. In adjusted analyses, a doubling of prenatal exposure of dibutyl phthalate and butyl benzyl phthalate metabolites increased the odds ratio (OR) for language delay by approximately 25% to 40%, with statistically significant results in the SELMA study (dibutyl phthalate OR, 1.29 [95% CI, 1.03-1.63; P = .03]; butyl benzyl phthalate OR, 1.26 [95% CI, 1.07-1.49; P = .003]). A doubling of prenatal monoethyl phthalate exposure was associated with an approximately 15% increase in the OR for language delay in the SELMA study (OR, 1.14; 95% CI, 1.00-1.31; P = .05), but no such association was found in TIDES (OR, 0.98; 95% CI, 0.79-1.23).

Conclusions and Relevance  In findings from this study, prenatal exposure to dibutyl phthalate and butyl benzyl phthalate was statistically significantly associated with language delay in children in both the SELMA study and TIDES. These findings, along with the prevalence of prenatal exposure to phthalates, the importance of language development, and the inconsistent results from a 2017 Danish study, suggest that the association of phthalates with language delay may warrant further examination.

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