Smoking amplifies the risk of albuminuria in individuals with high sodium intake: the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2011 and 2014-2018.

BACKGROUND

Smoking and sodium intake (SI) have been evaluated as risk factors for kidney disease; however, the data are inconsistent. We assessed the association between SI and cotinine-verified smoking status and the risk of albuminuria.

METHODS

An observational study using the Korea National Health and Nutrition Examination Survey (2008-2011 and 2014- 2018) was performed. We included 37,410 adults with an estimated glomerular filtration rate of ≥60 mL/min/1.73 m2. The smoking status was assumed based on the urine cotinine/creatinine ratio (Ucot/Ucrea). SI was estimated from spot urine sodium using the Kawasaki formula.

RESULTS

Ucot/Ucrea levels were significantly higher in current smokers (920.22 ± 9.00 ng/mg) than in ex-smokers and nonsmokers (48.31 ± 2.47 and 23.84 ± 1.30 ng/mg) (p < 0.001). Ucot/Ucrea levels were significantly higher in second-hand smokers than in participants without a history of smoking (p < 0.001). Ucot/Ucrea levels were positively associated with SI (p for trend < 0.001). Smoking status was not associated with albuminuria. SI had a linear relationship with albuminuria (p < 0.001). In groups with the highest Ucot/Ucrea levels, the highest SI quartile indicated a significantly higher risk of albuminuria than that in the lowest quartile (risk ratio, 2.22; 95% confidence interval, 1.26-3.92; p = 0.006). The risk of albuminuria was not significant in groups with the lowest and middle tertile adjusted for multiple risk factors.

CONCLUSION

Smokers consume higher dietary sodium and dietary SI was positively related to the risk of albuminuria. Smoking is not associated with albuminuria as a single factor. The risk of albuminuria is the higher in participants with smoking and high SI.