The association between urine cotinine level and hemoglobin and hematocrit levels: a cross-sectional study using the Korea National Health and Nutrition Examination Survey VIII (2019-2021)

Abstract

Smoking is a global health risk known to elevate hemoglobin (HB) levels through its effects on hematopoiesis. Urine cotinine, a metabolite strongly correlated with serum cotinine, serves as an effective biomarker for assessing smoking status. This study aimed to explore the relationship between urinary cotinine levels and both HB and hematocrit (HCT) levels in a Korean population. The study analyzed 4,454 healthy participants, categorized into three groups based on urine cotinine tertiles. Steiger's Z tests were used to assess correlations between HB, HCT levels, and urine cotinine. After adjusting for clinical variables, multiple linear regression was employed to evaluate the relationship between urine cotinine levels and HB/HCT. Receiver operating characteristic curves helped determine the cut-off values for urine cotinine in relation to HB and HCT levels. After adjusting for covariates, a positive correlation was found between urine cotinine and both HB and HCT levels. HB levels were 18% higher in the second tertile and 23% higher in the highest tertile than the lowest. Similarly, HCT levels increased by 44% in the second tertile and 50% in the highest tertile. The highest tertiles of HB and HCT had values of 504.650 and 202.950, respectively, with area under the curve values of 0.634 for HB and 0.616 for HCT. Conclusion: This study demonstrates a significant correlation between urine cotinine levels and elevated HB and HCT levels in a representative Korean population. Clinicians should consider urine cotinine levels when assessing anemia in smokers or individuals exposed to secondhand smoke. Further research is needed to validate these findings.