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Principal component analysis and discrimination of variables associated with pre- and post-natal exposure to mercury
Rejane C Marques1, José V E Bernardi, José G Dórea
1Fundação Universidade Federal de Rondônia, Porto Velho, RO, Brazil.
Insights
Principal component analysis (PCA) explored neurodevelopment in exclusively breastfed infants, examining mercury (Hg) exposure and vaccination timing. PCA identified key factors influencing infant development and highlighted potential exposure risk variables for neurodevelopmental schedules.
Area of Science:
- Environmental Health
- Neuroscience
- Pediatrics
Background:
- Mercury (Hg) exposure, including from Thimerosal-containing vaccines (TCV), is a concern for infant neurodevelopment.
- Understanding the interplay between prenatal/postnatal Hg exposure and infant development is crucial.
Purpose of the Study:
- To analyze variables related to neurodevelopment, prenatal Hg exposure, and postnatal Hg exposure in exclusively breastfed infants.
- To identify relationships between birth weight, vaccination schedules, and neurodevelopmental outcomes using Principal Component Analysis (PCA).
Main Methods:
- Principal Component Analysis (PCA), a multivariate statistical method, was applied to a dataset of 82 exclusively breastfed infants.
- Variables included prenatal Hg levels (placenta, blood, hair) and postnatal Hg exposure (TCV), alongside neurodevelopmental assessments (Gesell scores) and birth weight.
Main Results:
- PCA identified a two-factor solution explaining 92% of the variance.
- The first component (57% variance) linked birth weight and initial vaccine doses (Hepatitis B, DTP).
- The second component (35% variance) represented a neurodevelopmental gradient (Gesell scores).
Conclusions:
- Infant development (birth weight) and the timing of TCV immunization are important considerations in epidemiological studies.
- PCA effectively differentiates between early and late TCV exposures in relation to infant neurodevelopmental schedules.
- While the benefits of immunization are undisputed, further research is needed to confirm links between Thimerosal-Hg exposure and infant neurodevelopmental disorders, though PCA offers a method for identifying potential exposure risk variables.
Abstract:
The variance of variables associated with neurodevelopment at 180 days, pre-natal variables (Hg in placenta, blood and hair) and post-natal Hg exposure (including Thimerosal-containing vaccines, TCV) were examined in 82 exclusively breastfed infants using principal component analysis (PCA). This multivariate method was applied to identify hierarchy and sets of interrelated variables. The PCA yielded a two-factor solution, explaining 92% of variance and summarizing most of the relevant information in the dataset matrix: the first component represented birth weight and vaccine (first doses of Hepatitis B and DTP) variability and explained 57% of variance; the second component represented a gradient of neurodevelopment (Gesell scores) and explained 35% of variance. The third component explained only 3% of the remaining 8% variance. Beside CNS priming by breastfeeding, infant development (birth weight) and time of immunization with TCV should be considered in epidemiological studies. PCA can classify sets of variables related to vaccination and neuromotor development schedules, clearly discriminating between earlier and later TCV exposures of exclusively breastfed infants. In conclusion, the incommensurable concept of the chance of toxic risk caused by TCV-EtHg exposure against the proven benefit of immunization is in no way disputed here. However, infant neurodevelopmental (ND) disorders linked to Thimerosal-Hg stands in need of proof, but PCA points to the possibility of identifying exposure risk variables associated with ND schedules.
