The purpose of this study was to investigate the relevance of gender, age, and BMI (Body Mass Index) to changes in the urinary creatinine concentration in Korean adults. We recruited and surveyed 2,156 persons
20 years of age from 98 districts across the country, and collected urine samples for analyzing the creatinine concentration. Participants were 41.6% men and 58.4% women. In terms of age, the percentage of the population in their 20's and
60 years of age was relatively similar, with 13.6% and 17.8%, respectively, while the percentages in their 30's, 40's and 50's were also relatively similar, with 22.0%, 24.0%, and 22.6%, respectively. The proportion of participants in their 20's and 30's who were underweight (according to the BMI) was 25% and 19.2%, respectively, but only 6.2~6.4% of those
40 years of age were underweight. This showed that the underweight proportion in elder generations was less than that in younger generations. Meanwhile, the proportion who were overweight was 13.7%, 18.8%, 28.6%, 27.9%, 32.0% when the participants were in their 20's, 30's, 40's, 50's and
60 years of age, respectively (p<0.000). This showed that the overweight proportion increased along with increasing age. The overall urinary creatinine concentration was 10 mg/dl (arithmetic mean: AM), and 92.2 mg/dl (geometric mean: GM). The urinary creatinine concentration in men (132.6 mg/dl, AM) was significantly higher than that in women (93.3 mg/dl, AM (p<0.000)). Showing a similar trend in men and women, urinary creatinine concentrations were highest when the participants were in their 20's (135.6 mg/dl, AM), and tended to decrease with increasing age. Urinary creatinine concentrations in overweight and obese subjects (AM of 117.9 mg/dl and 118.0 mg/dl, respectively) were significantly higher than in other groups, and this trend was similar in men and women. In conclusion, we found that urinary concentrations were significantly affected by gender, age, and BMI, and that care should therefore be exercised when correcting urinary metabolites according to the urinary creatinine concentration.