Fig. 1
Two-piece piecewise regression and smooth curve-fitting for association between SUA and BMI stratified by gender. a The two-piece wise smooth curve for BMI-SUA association in women. When the BMI was smaller or equal than 21.3 kg/m2, there is a negative association between BMI and SUA. The regression coefficient β was − 2.70 (95% CI − 4.47, − 0.94). If BMI greater than 21.3 kg/m2, a significant positive association was found with a regression coefficient of 3.93 (95% CI 3.42, 4.43). b The two-piece wise smooth curve for BMI-SUA association in women. When BMI smaller or equal to 19.1 kg/m2, a negative BMI-SUA association was found with a regression coefficient of − 7.74 (95% CI − 14.7, − 0.75). When BMI greater than 19.1 kg/m2, a positive association was found, the coefficient was 5.10 (95% CI 4.44, 5.77). The two-piece wise models adjusted for age, current smoking status, current drinking status, occupational types, SBP, DBP, fasting blood sugar (log10 transformed), eGFR, LDL, triglyceride (log10 transformed), and total cholesterol