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Table 3 Estimated coefficient (beta) and 95% confidence intervals (95% CI) of HOMA-IR in US adults during 2015–2016 for each quartile increase in blood cobalt levels stratified by different covariates

From: Sex differences in the link between blood cobalt concentrations and insulin resistance in adults without diabetes

HOMA-IR Quartile 1 Quartile 2 Quartile 3 Quartile 4 P for trend
All 0.038 (− 0.009, 0.084) 0.045 (− 0.004, 0.094) 0.03 (− 0.036, 0.061) Reference 0.095
Age (years)
 < 60 0.073 (0.007, 0.139) 0.056 (− 0.013, 0.125) 0.022 (− 0.048, 0.093) Reference 0.016
 ≥ 60 − 0.017 (− 0.083, 0.049) 0.030 (− 0.041, 0.101) − 0.006 (− 0.073, 0.061) Reference 0.696
Gender
 Male 0.020 (− 0.056, 0.096) 0.032 (− 0.049, 0.113) 0.061 (− 0.024, 0.146) Reference 0.732
 Female 0.062 (0.001, 0.123) 0.061 (− 0.003, 0.126) − 0.016 (− 0.074, 0.043) Reference 0.037
Ethnicity
 Mexican American 0.047 (− 0.063, 0.158) − 0.026 (− 0.143, 0.091) − 0.030 (− 0.145, 0.086) Reference 0.779
 Other Hispanic 0.062 (− 0.064, 0.188) 0.082 (− 0.040, 0.204) 0.057 (− 0.071, 0.185) Reference 0.853
 Non-Hispanic White 0.017 (− 0.053, 0.087) 0.050 (− 0.026, 0.125) − 0.005 (− 0.074, 0.065) Reference 0.279
 Non-Hispanic Black 0.071 (− 0.050, 0.192) 0.083 (− 0.045, 0.211) 0.055 (− 0.087, 0.198) Reference 0.146
 Other race—including multiracial 0.049 (− 0.089, 0.187) 0.040 (− 0.110, 0.191) 0.021 (− 0.119, 0.160) Reference 0.372
PIR
 < 1 − 0.035 (− 0.145, 0.075) − 0.004 (− 0.119, 0.112) − 0.023 (− 0.127, 0.082) Reference 0.452
 ≥ 1 0.055 (0.004, 0.106) 0.057 (0.003, 0.112) 0.020 (− 0.035, 0.074) Reference 0.015
Alcohol use
 Yes 0.032 (− 0.024, 0.089) 0.064 (0.003, 0.124) 0.038 (− 0.023, 0.099) Reference 0.094
 No 0.076 (− 0.007, 0.158) 0.016 (− 0.068, 0.101) − 0.019 (− 0.099, 0.061) Reference 0.382
BMI (kg/m2)
 < 25 0.090 (− 0.003, 0.183) 0.080 (− 0.018, 0.178) 0.097 (0.008, 0.186) Reference 0.175
 25–30 0.014 (− 0.058, 0.085) 0.063 (− 0.010, 0.135) 0.021 (− 0.053, 0.095) Reference 0.177
 > 30 0.029 (− 0.049, 0.107) 0.011 (− 0.075, 0.097) − 0.059 (− 0.145, 0.028) Reference 0.610
Education level
 Less than 9th grade 0.127 (− 0.004, 0.257) 0.041 (− 0.093, 0.174) 0.056 (− 0.074, 0.186) Reference 0.205
 9th–11th grade 0.102 (− 0.048, 0.252) 0.163 (− 0.001, 0.326) 0.129 (− 0.024, 0.283) Reference 0.117
 High school graduate/GED or equivalent 0.041 (− 0.065, 0.148) 0.013 (− 0.094, 0.120) 0.029 (− 0.076, 0.135) Reference 0.710
 Some college or AA degree 0.039 (− 0.046, 0.123) 0.073 (− 0.023, 0.168) − 0.006 (− 0.097, 0.084) Reference 0.386
 College graduate or above − 0.019 (− 0.099, 0.060) 0.017 (− 0.067, 0.101) − 0.027 (− 0.116, 0.061) Reference 0.718
  1. Model was adjusted for age, gender, race, BMI, PIR, alcohol use, and education level.
  2. HOMA-IR homeostatic model assessment of insulin resistance, BMI body mass index, PIR poverty index ratio
  3. Cobalt (μg/L), quartile 1: < 0.11; quartile 2: 0.11–0.13; quartile 3: 0.13–0.17; quartile 4: > 0.17