Dipstick proteinuria and cancer incidence: a nationwide population-based study

Background: The association between proteinuria and malignancy has been frequently reported, but the issue is matter of controversy. Thus, in order to shed light on the association, we evaluated proteinuria as a risk factor for malignancy using the dataset from the Korean National Health Insurance System (NHIS). Methods: The subjects had undergone a medical examination in 2009 (index year) among the entire Korean adult population. From a pool of 10,505,818 participants, we excluded subjects who were younger than 19 years (15,327), had a previous diagnosis of cancer (152,095), had missing data for at least one variable (544,508), and were diagnosed with cancer within 1 year from the index year (79,501). Proteinuria was examined by a single dipstick urinalysis. Results: A total of 9,714,387 subjects were included in this study and tracked until December 31, 2017. The participants were divided into three groups; no (95.2%), trace (2.3%), and overt (2.5%) proteinuria. Over the duration of this study, we observed that overt proteinuria was associated with an increased risk of cancer development (all cancers) (adjusted HR 1.154, 95% CI 1.134–1.173) and the long-term risk of cancer incidence increased proportionally according to the changes in proteinuria over a four-year period. Limitations: Our study population consisted of Korean adults. Therefore, the results of this study may not be generalized to other ethnicities. Conclusions: We found a significant relationship between proteinuria and the risk of overall and site-specific cancer development. Further studies are needed to find an explanation of these findings.