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Table 5 Covariates of CYP1A2 activity based on maximum R and stepwise regression: premenopausal women

From: Cytochrome P450 1A2 (CYP1A2) activity and risk factors for breast cancer: a cross-sectional study

Variable β (SE) F P Quartiles (mean [95% confidence interval]) P for trend
  Model R2 = 0.42    Q1 Q2 Q3 Q4  
Current smoker?
No (n = 121) 5.35 (4.76–6.03)1 19.48 <0.0001      
Yes (n = 21) 7.69 (6.41–9.23)        
SHBG2 0.07 (0.02) 14.21 0.0002 5.23 (4.39–6.22) 6.33 (5.34–7.50) 7.25 (6.11–8.60) 7.06 (6.08–8.21) 0.0004
Total cholesterol (mmol/day)3 -0.77 (0.21) 14.02 0.0003 7.02 (5.75–8.58) 6.39 (5.42–7.54) 6.40 (5.42–7.55) 5.55 (4.66–6.60) 0.04
Insulin (pmol/l)3 0.21 (0.08) 7.24 0.008 5.66 (4.82–6.65) 5.69 (4.75–6.82) 6.63 (5.64–7.78) 7.61 (6.41–9.05) 0.001
Caffeine intake (mg/day)2 0.019 (0.007) 7.59 0.007 5.70 (4.82–6.75) 6.28 (5.31–7.42) 6.59 (5.51–7.87) 7.17 (6.15–8.35) 0.006
Age (years) 0.014 (0.006) 5.00 0.03 5.84 (4.93–6.93) 6.11 (5.11–7.30) 6.63 (5.71–7.70) 6.98 (5.84–8.34) 0.02
Triglycerides (mmol/day)3 0.14 (0.07) 4.18 0.04 6.12 (5.14–7.28) 6.27 (5.35–7.36) 6.34 (5.38–7.48) 7.13 (5.81–8.74) 0.24
BMI -0.37 (0.18) 4.51 0.04 7.65 (6.49–9.02) 6.25 (5.38–7.27) 5.91 (5.00–6.98) 6.53 (5.41–7.89) 0.01
HDL (mmol/day) -0.20 (0.14) 2.20 0.14 7.23 (6.11–8.56) 6.20 (5.29–7.27) 6.82 (5.80–8.03) 5.63 (4.77–6.65) 0.05
  1. A total of 142 premenopausal women were studied. Model has been adjusted for ethnicity. Potential predictors of cytochrome P450 1A2 (CYP1A2) activity included in the stepwise and maximum R regression models were: age, number of livebirths, age at menarche, smoking status, body mass index (BMI), waist–hip ratio (WHR), caffeine intake, alcohol intake, dietary cholesterol, total carbohydrate intake, total fat intake, protein intake, total blood cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, dehydroepiandrosterone sulphate (DHEAS), total estradiol, sex hormone binding globulin (SHBG), progesterone, follicle stimulating hormone (FSH), growth hormone, insulin-like growth factor (IGF)-1, and IGF binding protein (IGFBP)-3. 1Least square means (95% confidence interval) reported for smokers and nonsmokers. Quartile least square means (95% confidence interval) provided for variables associated with CYP1A2 activity (P ≤ 0.15). 2Square root transformed. 3Natural log transformed. SE, standard error.
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