Association between the Urine Cotinine Level and Blood Pressure in Korean Adults with Secondhand Smoke Exposure: Korea National Health and Nutritional Examination Survey 2016–2018

BACKGROUND: Similar to smoking, exposure to secondhand smoke is a risk factor for developing hypertension and cardiovascular diseases; however, there is no standardized method for measuring smoke exposure. Measuring urine cotinine levels is one possible means for determining the degree of exposure to secondhand smoke. This study investigated the association between urinary cotinine levels and blood pressure in Korean adults exposed to secondhand smoke. METHODS: Data from the Korea National Health and Nutrition Examination Survey conducted between 2016 and 2018 were used. A total of 9,273 participants aged ≥19 years self-reported as current non-smokers, which was cotinine- verified. A complex sample general linear model regression analysis was performed to analyze the association between urine cotinine and blood pressure. A P-value of <0.05 was considered statistically significant. RESULTS: Corrected urine cotinine levels were positively associated with systolic and diastolic blood pressure in female participants (P<0.001 and P=0.040, respectively). Furthermore, a 10-fold increase in the corrected urine cotinine level of those in contact with secondhand smoke was independently associated with 2.085 mm Hg and 0.575 mm Hg increases in systolic and diastolic blood pressure, respectively. However, there was no association between systolic and diastolic blood pressure in male participants (P=0.226 and P=0.256, respectively). CONCLUSION: Urinary cotinine levels were positively associated with increased blood pressure in females exposed to secondhand smoke. Therefore, urinary cotinine may be used as an indicator to quantify and monitor the effects of blood pressure elevation in females exposed to secondhand smoke.