EAL

FL: Fluoride Exposure in the US (2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To compare the estimates of fluoride levels in municipal drinking water from two sources:

The US Centers for Disease Control 1992 water Fluoridation Census
Source documents from state and local sources.

Inclusion Criteria:

Secondary study to a study of osteo-sarcoma and fluoride exposure. Inclusion criteria not described in this paper.

Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment

Subjects recruited from tertiary care hospitals located in urban areas (not described).

Design

Authors describe the study as case control, but this is inaccurate. The primary study was case control, but this study is a cross sectional design that compares two methods of estimating fluoride content in municipal drinking water.

Note: Actual fluoride levels in residences was not measured by the authors.

Blinding used

None

Intervention

None

Statistical Analysis

Kendall's tau was used to measure level of agreement between the two sources. Confidence interval is reported, but a priori alpha is not given.

Data Collection Summary:

Timing of Measurements

The dates of individual interviews is not specified. However, individuals were asked to provide a list of residences in which they had lived and where they currently resided. So, depending on the age of the respondent (not provided), the dates of exposure in particular residences. Authors obtained information on the fluoridation status of the particular communities at the time of the individual's residence.

Dependent Variables

Fluoridation levels based on three types of public water systems:
- Natural water systems (no adjustment of fluoride levels)
- Adjusted systems (fluoride level manipulated by water provider (up or down) to be within the optimal range (0.7-1.2ppm depending on temperature)
- Consecutive systems (municipal water purchased from one of the above systems)
Fluoride measured in terms of
- Natural fluoride level
- Year fluoride adjustment commenced
- Target fluoride level of adjustment.

Independent Variables

Community

Control Variables

None

Description of Actual Data Sample:

Initial N: Interviews of 471 individuals, resulting in 824 communities and 1,264 municipal water systems. Municipalities that switched to or from fluoridation over time were split into separate records providing 1,325 fluoride records
Final N:
- CDC Fluoride Census: 653 (49%) of fluoride records
- Source documents: 1318 (99%) of fluoride records
Age: Not applicable
Ethnicity: Not applicable
Other relevant demographics: Not applicable
Anthropometrics: Not applicable
Location: US (information from 43 states).

Summary of Results:

Availability of Estimates

While the CDC Fluoridation Census had information on only 49% of the municipal water sources, information was available from 99% of the municipal water sources from local and state source documents.

Level of Agreement

For municipalities for which there was both CDC and source document information, there was a high level of agreement (tau=0.85; 95% CI=0.79-0.90)
Fluoride level was divided up into four categories: 0-0.3ppm, >0.3-<0.7ppm, 0.7-1.2ppm, >1.2ppm. The two sources were in agreement in 96% of cases regarding the level of fluoride
Of the 667 municipalities missing from the CDC Fluoridation Census, 21% (143) of the municipalities had fluoride levels between 0.7 and 1.5ppm according to source documents. 62 percent had fluoride estimates less than or equal to 0.3ppm.
Only two municipalities missing source documentation had information from the CDC Fluoridation census. These had estimates of 2.2 and 2.5ppm.

Author Conclusion:

"The most striking finding was that we were able to estimate fluoride levels for nearly all of the records using source documentation, compared to fewer than half using only the CDC publication. For records where we found fluoride estimates using both methods, the correlation of the estimates was strong and concordance was very high when the fluoride estimates were categorized into four groups."

"It might be tempting to assume that the fluoride level is low if it does not appear in the CDC Fluoridation Census. However, using source documentation we found great variability in the range of fluoride levels for these residences; only 62 percent of these estimates were less than or equal to 0.3ppm and fully 21 percent were at least 0.7ppm."

Funding Source:

Government:

National Research Service Award grant

Reviewer Comments:

Strengths

National sample

Weaknesses

Process of source documentation was ad hoc (no a priori method for identifying source documents)
Not a random sample of individuals (individuals recruited for the purposes of another study) and not evenly distributed geographically
Water levels of fluoride not measured
Mis-statement of design.

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)	N/A
	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)	N/A

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?	No
2.	Was the selection of study subjects/patients free from bias?		No
	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?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
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?	N/A
	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?	No
	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.)	No
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		No
	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.)	No
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	No
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	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?		No
	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?	No
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
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?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	???
	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)?	N/A
	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