DEVELOPMENTAL FLUORIDE NEUROTOXICITY A SYSTEMATIC REVIEW AND META-ANALYSIS PDF

OBJECTIVE: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development. We also searched the China National Knowledge Infrastructure CNKI database, because many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups. Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies.

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Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development. We also searched the China National Knowledge Infrastructure CNKI database, because many studies on fluoride neurotoxicity have been published in Chinese journals only.

In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups.

Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking-water fluoride as the only exposure. Results: The standardized weighted mean difference in IQ score between exposed and reference populations was —0.

Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.

Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease.

Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment. Keywords: fluoride, intelligence, neurotoxicity A recent report from the National Research Council NRC concluded that adverse effects of high fluoride concentrations in drinking water may be of concern and that additional research is warranted.

Fluoride may cause neurotoxicity in laboratory animals, including effects on learning and memory Chioca et al. In many rural communities in China, populations with high exposure to fluoride in local drinking-water sources may reside in close proximity to populations without high exposure NRC Opportunities for epidemiological studies depend on the existence of comparable population groups exposed to different levels of fluoride from drinking water.

It is projected that all rural residents will have access to safe public drinking water by World Bank However, results of the published studies have not been widely disseminated. Four studies published in English Li XS et al.

Fluoride exposure to the developing brain, which is much more susceptible to injury caused by toxicants than is the mature brain, may possibly lead to permanent damage Grandjean and Landrigan In response to the recommendation of the NRC , the U.

EPA is reviewing the maximum amount of fluoride allowed in drinking water, which currently is set at 4. EPA To summarize the available literature, we performed a systematic review and meta-analysis of published studies on increased fluoride exposure in drinking water associated with neurodevelopmental delays.

We specifically targeted studies carried out in rural China that have not been widely disseminated, thus complementing the studies that have been included in previous reviews and risk assessment reports. Methods Search strategy. We searched records for — Our literature search identified 39 studies, among which 36 The latter showed that dose-related deficits were found, but the studies were excluded because our meta-analysis focused on studies with the high- and low-exposure groups only.

In addition, two studies were published twice, and the duplicates were excluded. Inclusion criteria and data extraction. Interpretations of statistical significance are based on an alpha level of 0. Information included for each study also included the first author, location of the study, year of publication, and numbers of participants in high-fluoride and low-fluoride areas.

We noted and recorded the information on age and sex of children, and parental education and income if available. Statistical analysis. A standardized weighted mean difference SMD was computed using both fixed-effects and random-effects models. The fixed-effects model uses the Mantel—Haenszel method assuming homogeneity among the studies, whereas the random-effects model uses the DerSimonian and Laird method, incorporating both a within-study and an additive between-studies component of variance when there is between-study heterogeneity Egger et al.

The estimate of the between-study variation is incorporated into both the SE of the estimate of the common effect and the weight of individual studies, which was calculated as the inverse sum of the within and between study variance. We evaluated heterogeneity among studies using the I2 statistic, which represents the percentage of total variation across all studies due to between-study heterogeneity Higgins and Thompson We evaluated the potential for publication bias using Begg and Egger tests and visual inspection of a Begg funnel plot Begg and Mazumdar ; Egger et al.

We also conducted independent meta-regressions to estimate the contribution of study characteristics mean age in years from the age range and year of publication in each study to heterogeneity among the studies. Another study Trivedi et al. Inclusion of this study in the meta-analysis resulted with a much smaller pooled random-effects SMD estimate and a much larger I2 —0.

Characteristics of the 27 studies included are shown in Table 1 An et al. Two of the studies included in the analysis were conducted in Iran Poureslami et al. Two cohorts were exposed to fluoride from coal burning Guo et al. Other intelligence measures included the Wechsler Intelligence tests 3 studies; An et al. Because each of the intelligence tests used is designed to measure general intelligence, we used data from all eligible studies to estimate the possible effects of fluoride exposure on general intelligence.

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Developmental fluoride neurotoxicity: an updated review

Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development. We also searched the China National Knowledge Infrastructure CNKI database, because many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups. Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking-water fluoride as the only exposure. Results: The standardized weighted mean difference in IQ score between exposed and reference populations was —0.

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Environ Health Perspect. Epub Jul Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Altern Ther Health Med.

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