Association Between Urinary Bisphenol A Concentration and Obesity Prevalence in Children and Adolescents

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Association Between Urinary Bisphenol A
Concentration and Obesity Prevalence in Children
and Adolescents

• Leonardo Trasande, MD, MPP
• Teresa Attina, MD, PhD, MPH
• Jan Blustein, MD, PhD

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Bisphenol A (BPA)
Discovered by Aleksandr Dianin, 1891

• Used to manufacture polycarbonate resin
• Found in canned food, polycarbonate bottled
  liquids and other consumer products
• Breakdown product of coatings intended to prevent
  metal corrosion in food and beverage containers
• Recently banned from baby bottles and sippy cups
  by US Food and Drug Administration
• Comprehensive, cross-sectional study of dust,
  indoor and outdoor air, and solid and liquid food
  in preschool age children suggested that dietary
  sources constitute 99 of BPA exposure

Schecter et al. Environ Sci Technol.
201044(24)9425-9430 Wilson et al. Environ Res.
Jan 2007103(1)9-20. Tavernise S. New York
Times, 17 July 2012 edition.
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BPA in humans

• Exposure is ubiquitous
• Studies suggest brief half-life (4-43 hours)
• But BPA also detected in fat
• Urinary levels of BPA do not decline rapidly with
  fasting time, suggesting accumulation in body
  tissues

Stahlhut et al. Environ Health Perspect.
2009117(5)784-789. Volkel et al.Chem Res
Toxicol. 200215(10)1281-1287. Fernandez et al.
Reprod Toxicol. Aug-Sep 200724(2)259-264.
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BPA and obesity

• Laboratory studies suggest that BPA disrupts
  multiple metabolic mechanisms,
• Occurs at exposure levels commonly seen in US
  population
• Urinary BPA concentration has been associated
  with
• Adult obesity
• Adult diabetes, cardiovascular diagnoses and
  abnormalities in liver function
• Increased frequency of later coronary artery
  disease in later life
• Differences in heart rate variability and blood
  pressure in elderly

Masuno et al. J Lipid Res. 200243(5)676-684 Saku
rai K et al. Br J Pharmacol. 2004141(2)209-214 C
arwile JL, Michels KB. Environ Res.
2011111(6)825-830 Lang al. JAMA.
2008300(11)1303-1310 Melzer et al. PLoS One.
20105(1)e8673 Melzer et al. Circulation.
2012125(12)1482-1490 Bae et al. Hypertension
201260786-793
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BPA and childhood obesity?

• Children are known to be uniquely vulnerable to
  environmental chemicals
• Yet no studies to date connecting environmental
  chemical exposures to obesity
• We examined associations of urinary BPA
  concentration with body mass in 6-19 year olds in
  NHANES 2003-8.
• NHANES is a federal survey of the nations
  health, conducted nationally through mobile
  testing sites.
• Sample was 2838 US children, representative of
  the US

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Quantifying BPA and body mass

• BPA
• Urinary concentrations from Centers for Disease
  Control and Prevention (CDC)s laboratories
• We transformed the concentrations in two ways
• Divided the sample into fourths based on BPA
  concentration (lowest to highest)
• Also looked at linear BPA concentration
  (expressed as the logarithm to normalize the
  distribution)
• Body mass
• Height and weight measured by CDCs trained staff
• We transformed these in two ways
• Standardized BMI (weight in kilograms divided by
  height in meters squared) for age and gender into
  Z-scores
• Classified overweight as at/above 85th percentile
  for age and gender (obese at/above 95th
  percentile)

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Other factors that were considered

• Simultaneously examined other factors associated
  with obesity
• Age group (6-11 and 12-19 years)
• Gender
• Racial/ethnic group
• Socioeconomic status
• Caregiver education
• Serum cotinine level (tobacco smoke exposure)
• Television watching
• Caloric intake
• Urinary dilution (creatinine)

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Key characteristics of the sample
34.1 overweight
17.8 obese

• Median BPA 2.8 ng/mL
• Caloric intake and television watching not
  associated with BPA, but BPA was associated with
  overweight and obesity

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Main (multivariable) results
Quartile (Percentile) Prevalence Odds Ratio BMI Z-score
1 (0-24) 10.3 Reference Reference
2 (25-49) 20.1 2.24 0.12
3 (50-74) 19.0 2.08 0.16
4 (75) 22.3 2.57 0.22
plt0.05 plt0.01 plt0.001
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Specificity of association

• We also examined chemically similar environmental
  phenols used in sunscreens and soaps
• Urinary concentrations of these similar phenols
  were not associated with obesity

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Race-specific effects

• Associations of BPA concentration with obesity
  (but not BMI Z-score) were isolated to whites,
  and were absent in Hispanics and Blacks.
• If obese whites have unique dietary behaviors
  that predispose them to increases in urinary BPA,
  then this could explain our results, though there
  is no evidence to support this.
• A difference in genetic or other predisposition
  is another plausible explanation.

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Caveats

• Reverse causation is possible
• Obese children ingest more foods that contain BPA
• Urinary BPA represents more recent exposure,
  rather than the chronic exposure that is more
  likely to lead to obesity
• BPA may disrupt metabolism earlier in life than
  in the childhood and adolescent years we studied

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Nonlinear association

• Consistent with biological activity of many
  hormones
• Duplicated in many studies
• Dr. Linda Birnbaum (NIEHS Director) has
  emphasized that regulatory policymakers should
  include information about non-linear
  associations, when they deliberate.

Vandenberg LN et al. Endocr Rev. Jun
201233(3)378-455. Birnbaum Environ Health
Perspect. Apr 2012120(4)A143-144.
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Summary

• First report of an association of an
  environmental chemical exposure with childhood
  obesity in a nationally representative sample
• Association evident when exposure and outcome are
  modeled in a number of different ways
• Adjusted prevalence of obesity of 22.3 (among
  children in the highest uBPA quartile, compared
  with a 10.3 prevalence among those in the lowest
  uBPA quartile.

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L Trasande and coauthors Association Between
Urinary Bisphenol A Concentration and Obesity
Prevalence in Children and Adolescents