Interpersonal and temporal variability of urinary cotinine in elderly subjects

Area of Science:

• Environmental Health
• Biomarkers
• Gerontology

Background:

• Urinary cotinine is a common biomarker for tobacco smoke exposure.
• Its validity for estimating long-term exposure, especially in elderly populations, requires further evaluation.

Purpose of the Study:

• To assess the efficacy of a single urinary cotinine measurement for estimating long-term smoking exposure.
• To analyze the reliability of this biomarker in an elderly cohort.

Main Methods:

• Utilized a cohort of elderly subjects with multiple urinary cotinine measurements over eight weeks.
• Employed a mixed-effects model to analyze interpersonal and temporal variability.
• Compared exposure group classifications using single versus multiple measurements.

Main Results:

• Interpersonal variability in urinary cotinine levels exceeded temporal variability.
• Population averages for long-term exposure were consistent across single measurements.
• Classification of high/low exposure groups showed similar distributions with single or multiple measurements.
• Misclassification rates were 9.3% and 5.6% at 20 and 100 μg/g creatinine cut-offs, respectively, using single measurements.

Conclusions:

• Urinary cotinine is a valuable biomarker for characterizing tobacco smoke exposure.
• A single measurement may accurately represent long-term exposure in populations, despite potential individual misclassification.
• The consistency of population averages supports the use of single measurements for monitoring long-term exposure.