Gender Equivalence in the Prevalence of Nephrolithiasis among Adults Younger than 50 Years in the United States

Purpose: Although urolithiasis affects each gender, conventional teaching proposes that men are 3 times more likely to have stones. However, clinical practice refutes such a disparity, particularly among working age adults. Small studies have suggested an erosion of this gender gap. Therefore, we examined the relationship between gender and stone prevalence among American adults younger than 50 years. Materials and Methods: We analyzed the NHANES (National Health and Nutrition Examination Survey) 2007 to 2012 cohort. Weighted proportions and multivariate logistic regression of the cohort and pertinent subgroups were assessed to determine the prevalence and the odds of nephrolithiasis. Results: The cohort of 17,658 subjects, which was weighted to represent the American population of 218,828,951 adults, was 48.1% male. In our cohort of 8,888 adults weighted to represent 123,976,786 subjects younger than 50 years, which was 49.3% male and 50.7% female, there was no difference in stone prevalence (6.3% in males and 6.4% in females, p = 0.85). On unadjusted logistic regression of those younger than 50 years men were no more likely to report a stone history (OR 0.98, p = 0.85). Multivariate logistic regression adjusting for diabetes, obesity, ethnicity, age, and water, sodium and protein intake confirmed no difference in stone prevalence between the genders (OR 1.1, p = 0.51). Conclusions: Among adults of working and child rearing ages in the United States the much touted gender disparity in nephrolithiasis is not present. Prior assessments of gender based stone prevalence may have failed to specifically assess this economically critical demographic or there may in fact be an ongoing epidemiological change. Recognition that women are as likely as men to form stones in this cohort suggests the need to better elucidate the pathophysiology of stones in women.