Seasonal patterns in trace elements assessed in toenails

Area of Science:

• Environmental Health
• Biomarkers
• Epidemiology

Background:

• Seasonal patterns in biomarker measurements can introduce error in epidemiological studies.
• Research on the seasonality of metals and trace elements in toenail samples is limited.
• Accounting for seasonality can improve precision and reduce bias in exposure-health outcome models.

Purpose of the Study:

• To assess and describe seasonal patterns in toenail measurements of trace elements.
• To identify specific elements exhibiting seasonal trends in toenail concentrations.
• To inform adjustments in epidemiological models for enhanced accuracy.

Main Methods:

• Utilized toenail clippings from the Sister Study cohort.
• Employed trigonometric regression models to analyze seasonal patterns of 17 trace elements.
• Compared trigonometric models against constant models to evaluate seasonal effects.

Main Results:

• Significant seasonal trends were found for 11 elements, including iron, aluminum, arsenic, cadmium, and lead.
• Peak concentrations for these elements occurred around mid-August.
• Observed seasonal patterns were consistent across two independent subsamples analyzed in different laboratories.

Conclusions:

• Seasonal patterns in toenail trace elements necessitate adjustments in epidemiological models.
• Correcting for seasonality is important for accurate estimation of exposure-health associations.
• The underlying reasons for elevated summer toenail concentrations remain undetermined.