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UCo and BMI in boys after adjustment for confounding factors (beta=−0.14, p<0.001) (Table 3). The VIF did not demonstrate a multicollinearity problem among the predictor variables (VIF<2.0). In addi-tion, the statistical analysis failed to indicate any significant relationship between the BMI and the urine levels of the other trace element (Table 4).CharacteristicsaLog UCoAge (months)Height (cm)Weight (kg)BMI (kg/m2)Birthweight (g)Average sleep duration (hour)Father’s BMIMother’s BMIParental smoking　Yes　No　Unknown (%)Annual household income (10000 yen)　0-299　300-599　600-999　1000+　UnknownFather’s education　High school or less　2-year college　4-year university　Graduate university　UnknownMother’s education　High school or less　2-year college　4-year university　Graduate university　Unknowna Data presented as mean ± SD or number (percentage)b Comparison between boys and girlsStudent’s t-test was used for continuous variables, Fisher’s exact probability test was used for categorical variables, Mann-Whitney’s U-test was used for ordinal scaleTable 2　Comparison of continuous and categorical variables between boys and girlsTotal (n=1542)−0.295±0.317145.6±3.6150.1±7.040.4±7.517.9±2.43032.2±408.28.8±0.723.6±3.221.0±2.7460 (29.8)1006 (65.2)76 (4.9)69 (4.5)349 (22.6)577 (37.4)528 (34.2)19 (1.2)262 (17.0)218 (14.1)821 (53.2)176 (11.4)65 (4.2)248 (16.1)687 (44.6)544 (35.3)54 (3.5)9 (0.6)Boys (n=860)−0.308±0.323145.6±3.5149.8±7.440.2±7.717.8±2.43061.6±411.98.8±0.723.4±3.220.9±2.7256 (29.8)552 (64.2)52 (6.0)42 (4.9)205 (23.8)304 (35.3)295 (34.3)14 (1.6)136 (15.8)129 (15.0)450 (52.3)98 (11.4)47 (5.5)140 (16.3)402 (46.7)284 (33.0)28 (3.3)6 (0.7)This study’s findings showed that increasing UCo levels were associated with a decrease in BMI in boys. This association was confirmed after adjustment for several covariates, including genetic, behavioral, and environmental factors, in the multi-variate analysis. Similarly, many previous studies Girls (n=682)−0.279±0.308145.5±3.7150.4±6.540.8±7.117.9±2.42995.2±400.88.8±0.723.7±3.221.1±2.8204 (29.9)454 (66.6)24 (3.5)27 (4.0)144 (21.1)273 (40.0)233 (34.2)5 (0.7)126 (18.5)89 (13.0)371 (54.4)78 (11.4)18 (2.6)108 (15.8)285 (41.8)260 (38.1)26 (3.8)3 (0.4)p-valueb0.0750.7450.0920.1180.2430.0020.3570.0680.4480.8210.3830.8110.075255Discussion