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FL: Fluoride and the Brain (2010)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the association between use of silicofluoride treated water and blood lead concentrations.

Inclusion Criteria:

1990 Census data for communities of 15,000 to 75,000 which had at least 100 blood lead tests per community. Venous blood tests from the New York State Department of Children's Health, mostly 1994-1998. Community fluoridation status per the Center for Disease Control 1992 Fluoridation Census.

Exclusion Criteria:
  • Communities larger or smaller than inclusion criteria were excluded in order to avoid complications of extremely populated areas (i.e. New York City).
  • Capillary blood tests.
Description of Study Protocol:

Recruitment

Existing data from New York State Department of Children's Health and Center for Disease Control was reviewed.

Design

Venous blood level tests of children aged zero to six living in moderately-sized communities were compared based on community fluoridation status and other risk factors associated with high blood lead (old housing, poverty, unemployment, education, income and population density). 

Blinding used (if applicable)

 Not specified

Intervention (not applicable in cohort observational study)

Statistical Analysis   

  • Covariance assessment with logistic regression
  • Multivariate analysis and odds ratio assessment.
Data Collection Summary:

Timing of Measurements

1994 to 1998 

Dependent Variables

Blood lead concentrations

Independent Variables

Community fluoridation status (silicofluoride-treated or not): Determined from the CDC 1992 Fluoridation Census.

Control Variables

  • Age
  • Sex
  • Known risk factors for increased lead levels in blood:
    • Housing built before 1939
    • Children zero to five years living in poverty
    • Community unemployment rate
    • Parents with bachelors degree
    • Population density
    • Per capita income.
Description of Actual Data Sample:

Initial N

151,225

Attrition (final N)

151,225

Age

Zero to five years

Ethnicity

Included Black, Hispanic and White specified, others not specified

Other relevant demographics

  SiF Non-SiF
Communities, number studied 28 77
Mean population 34,778 25,627
Children zero to five (percentage of population) 8.5% 8%
Children zero to five (number) 2,960 2,046
VBL tests (total) 58,934 94,291
Capillary (total)  36,791  68,357
Blood (all lead tests, VBL + capillary)  95,725  162,648
Percentage VBL  61%  58%
Old housing (built before 1939)  49.4%  23.3%
Poverty  22.3%  8.5%
Community unemployment rate  3.5%  2.5%
Parents with bachelors degree  7.4%  9.3%
Population density  155  143
Total population  973,785  1,973,336
Per capita income  $14,698  $19,415

Anthropometrics

Not specified

Location

New York State, USA

 

Summary of Results:

Key Findings

  • There was a consistent significant association of Silicofluoride (SiF) treated community water and elevated blood lead
  • The highest likelihood of children (regardless of race or age) having venous blood lead (VBL) >10mcg/dL occurred when they were exposed to both SiF water and another known risk factor
    • In communities where SiF is used, the odds ratios of lead levels >10mcg/dL is doubled when subjects are exposed to five or more risk factors.

Table showing Odds Ratios for black children in SiF treated communities with high percentage of old housing and children poverty with venous blood lead (VBL) >10 mcg/dL

  n Odds Ratio CI P<
All ages 10,481 1.626 1.412, 1.873 0.0001
Less than two 4,076 1.729 1.354, 2.208 0.0001
2<4 3,900 1.736 1.396, 2.150 0.0001
4<7 2,505 1.277 0.959, 1.700 0.0949

 

Author Conclusion:
  • Over 91% of fluoridated water has been treated with sodium silicofluoride or fluosilicic acid
  • Extensive tests on animals exposed to sodium fluoride in their diets have never been replicated by exposure to commercial grades of sodium fluosilicate or fluosilicic acid
  • Officials responsible for water fluoridation appear to lack an understanding of fundamental chemical principles relating to the use of silicofluorides
  • Our findings indicate that SiF treated water probably exacerbates the risks of absorbing lead from other known environmental risk factors.
Funding Source:
Not-for-profit
Earhart Foundation
Other non-profit:
Reviewer Comments:

Strength

Large sample size

Weakness

Study not able to look at impact of Sodium Fluoride treated water potential impacts

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? Yes
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes