Active smoking in urban households: An association between urinary cotinine metabolite level and serum eGFR concentration

INTRODUCTION Smoking stands as a primary contributor to preventable deaths globally and is linked to an increased risk of developing kidney failure and other diseases. A few studies have focused on the negative correlation between serum cotinine and estimated glomerular filtration rate (eGFR), indicating decreased kidney function. This study investigated the associations between urinary cotinine metabolite concentration and serum eGFR among active smokers in urban households. METHODS This was a cross-sectional study of active smokers in urban households' community Bangkok, Thailand from January to April 2023. The study involved 85 participants aged >= 18 years who were active smokers. Both urinary cotinine and serum eGFR concentrations were used as biomarkers. Independent sample t-tests were used to compare the urinary cotinine metabolite based on differences in the characteristic variable. We used multiple linear regression to test the association between cotinine metabolite and characteristics variables. Spearman's analysis was used to test the correlation between cotinine metabolite and eGFR concentration.
RESULTS The association between urinary cotinine metabolite and serum eGFR concentration decreased with increasing cotinine concentrations (r= -0.223, p=0.041), suggesting a decline in kidney function. However, this study found no significant difference between urinary cotinine metabolite and characteristic variables (p>0.05). Additionally, those who smoked for >= 10 years (117.40 +/- 89.80 ng/mL), smoked >= 10 cigarettes per day (117.40 +/- 89.80 ng/mL) and used conventional cigarettes (124.53 +/- 115.10 ng/mL). The results of the multiple linear regression models analysis indicated that those who were smokers for >= 10 years (beta=0.076; 95% CI: -31.575-59.715) and those who were smoked >= 10 cigarettes/day (beta=0.126; 95% CI: -65.636-18.150) were not associated with urinary cotinine metabolite level. CONCLUSIONS This study shows that the urinary cotinine metabolite level is associated with serum eGFR concentration among active smokers in urban households. The current study suggests that clinical identification and a prospective cohort study are needed before robust conclusions about how tobacco affects kidney efficiency.