Table 2 Association between BMI (kg/m²) and lumbar bone mineral density (g/cm²)

BMI (kg/m²)

0.005 (0.004, 0.006) < 0.001

0.004 (0.003, 0.006) < 0.001

0.006 (0.003, 0.008) < 0.001

BMI categories

 Q1 (30.0–31.8 kg/m²)

Reference

Reference

Reference

 Q2 (31.9–34.2 kg/m²)

− 0.007 (− 0.026, 0.011) 0.437

− 0.009 (− 0.027, 0.010) 0.362

− 0.003 (− 0.023, 0.017) 0.774

 Q3 (34.3–38.4 kg/m²)

0.003 (− 0.017, 0.022) 0.793

− 0.002 (− 0.021, 0.017) 0.829

− 0.007 (− 0.029, 0.016) 0.568

 Q4 (38.5–65.8 kg/m²)

0.054 (0.035, 0.073) < 0.001

0.049 (0.030, 0.068) < 0.001

0.034 (0.002, 0.066) 0.038

Subgroup analysis stratified by sex

 Men

0.008 (0.005, 0.010) < 0.001

0.007 (0.005, 0.009) < 0.001

0.013 (0.008, 0.018) < 0.001

 Women

0.003 (0.002, 0.004) < 0.001

0.003 (0.002, 0.004) < 0.001

0.003 (0.000, 0.006) 0.044

Subgroup analysis stratified by race/ethnicity

 Non-hispanic white

0.005 (0.003, 0.007) < 0.001

0.005 (0.003, 0.007) < 0.001

0.006 (0.001, 0.010) 0.013

 Non-hispanic black

0.003 (0.001, 0.005) 0.004

0.004 (0.001, 0.006) 0.003

0.008 (0.003, 0.013) 0.002

 Mexican American

0.005 (0.002, 0.008) < 0.001

0.005 (0.002, 0.008) < 0.001

0.006 (0.000, 0.012) 0.037

 Other race/ethnicity

0.002 (− 0.001, 0.004) 0.171

0.003 (− 0.000, 0.005) 0.056

0.001 (− 0.004, 0.007) 0.598

Subgroup analysis stratified by age

 40–49 years

0.005 (0.004, 0.007) < 0.001

0.004 (0.002, 0.006) < 0.001

0.008 (0.004, 0.011) < 0.001

 50–59 years

0.004 (0.002, 0.006) < 0.001

0.005 (0.003, 0.006) < 0.001

0.004 (0.001, 0.008) 0.021