Table 4.
CYP1A2 activity and risk factors for breast cancer: postmenopausal women
| Variable | β (SE) | F | P | Quartiles (mean CMR [95% confidence interval]) | P for trend | |||
| Q1 | Q2 | Q3 | Q4 | |||||
| Age (years) | -0.012 (0.006) | 4.51 | 0.04 | 7.17 (6.18–8.32) | 6.42 (5.60–7.37) | 6.69 (5.72–7.82) | 5.93 (5.07–6.94) | 0.02 |
| Age at first birth (years)2 | 0.02 (0.15) | 0.03 | 0.87 | |||||
| Age at menarche (years) | -0.03 (0.02) | 3.97 | 0.05 | 6.75 (5.91–7.72) | 6.96 (5.90–8.20) | 6.69 (5.60–7.98) | 5.75 (4.92–6.73) | 0.04 |
| Age at menopause (years) | -0.004 (0.006) | 0.33 | 0.57 | |||||
| BMI (kg/m2)2 | -0.45 (0.14) | 0.10 | 0.75 | |||||
| WHR | -0.96 (0.42) | 5.19 | 0.02 | 6.69 (5.67–7.91) | 6.83 (5.79–8.05) | 6.39 (5.49–7.43) | 6.04 (5.17–7.05) | 0.17 |
| Caffeine (mg/day)1 | -0.003 (0.006) | 0.23 | 0.64 | |||||
| Alcohol (kcal/day)2 | -0.02 (0.02) | 1.26 | 0.26 | |||||
| Cholesterol (mg/day)2 | 0.02 (0.06) | 0.08 | 0.78 | |||||
| Total energy (kcal/day)1 | 0.003 (0.005) | 0.42 | 0.52 | |||||
| Carbohydrate (g/day)1 | 0.01 (0.01) | 0.32 | 0.57 | |||||
| Fat intake (g/day)1 | 0.02 (0.02) | 1.03 | 0.31 | |||||
| Protein intake (g/day)2 | 0.04 (0.09) | 0.20 | 0.66 | |||||
| Total estradiol (pmol/l)3 | -0.26 (0.42) | 0.40 | 0.53 | |||||
| Free estradiol (%)2 | -0.03 (0.01) | 5.11 | 0.03 | 7.04 (6.03–8.22) | 7.07 (6.04–8.27) | 5.86 (5.05–6.80) | 5.96 (4.97–7.15) | 0.01 |
| SHBG (nmol/l)4 | 0.03 (0.02) | 1.80 | 0.18 | 5.96 (4.98–7.14) | 5.69 (4.88–6.63) | 6.98 (5.91–8.24) | 6.55 (5.55–7.72) | 0.08 |
| Progesterone, (nmol/l)2 | -0.02 (0.05) | 0.23 | 0.63 | |||||
| FSH (IU/l)2 | 0.06 (0.07) | 0.60 | 0.44 | |||||
| GH (μg/l)5 | 0.02 (0.02) | 0.57 | 0.45 | |||||
| IGF-1 (ng/ml)6 | 0.85 (0.33) | 6.68 | 0.01 | 6.30 (5.30–7.48) | 6.49 (5.50–7.65) | 6.42 (5.43–7.60) | 7.46 (6.27–8.89) | 0.13 |
| IGFBP-3 (mg/l)7 | -0.66 (0.23) | 8.32 | 0.005 | 8.04 (6.82–9.48) | 6.27 (5.29–7.44) | 6.40 (5.46–7.51) | 6.01 (5.11–7.07) | 0.003 |
| Insulin (pmol/l)2 | -0.01 (0.08) | 0.01 | 0.92 | |||||
| Total cholesterol (mmol/l)2 | -0.35 (0.18) | 3.70 | 0.06 | 6.98 (5.97–8.16) | 6.88 (5.90–8.04) | 6.40 (5.46–7.51) | 6.13 (5.28–7.11) | 0.05 |
| LDL-cholesterol (mmol/l)2 | -0.13 (0.13) | 1.00 | 0.32 | |||||
| HDL-cholesterol (mmol/l)2 | -0.16 (0.12) | 1.82 | 0.18 | 5.77 (5.02–6.63) | 5.53 (4.83–6.34) | 5.63 (4.89–6.48) | 4.85 (4.17–5.66) | 0.08 |
| Triglycerides (mmol/l)2 | -0.12 (0.06) | 3.37 | 0.07 | 6.94 (5.90–8.16) | 6.68 (5.75–7.75) | 6.52 (5.52–7.70) | 6.15 (5.24–7.20) | 0.15 |
A total of 149 postmenopausal women were studied (n = 114 for age at first birth; n = 139 for age at menopause; n = 126 for total estradiol and sex hormone binding globulin [SHBG]; n = 147 for free estradiol; and n = 134 for growth hormone [GH], insulin-like growth factor [IGF]-1, and IGF binding protein [IGFBP]-3). Cytochrome P450 1A2 (CYP1A2) activity is log transformed and modeled as the dependent variable for all models. Models are adjusted for age, smoking status, body mass index (BMI), waist–hip ratio (WHR), and ethnicity. BMI models do not adjust for BMI and WHR models do not adjust for WHR. Quartile means (95% confidence interval) are provided for variables associated with CYP1A2 activity (P ≤ 0.20). 1Square root transformed. 2Log transformed. 3Power transformation used, in which y = (1 - 1/sqrt [estradiol + 0.5]) × 2; models adjusted for SHBG. 4Square root transformed; models adjusted for total estradiol levels. 5Log transformed; analyses adjusted for IGF-1 and IGFBP-3. 6Square root transformed; analyses adjusted for growth hormone and IGFBP-3. 7Square root transformed; analyses adjusted for GH and IGF-1. CMR, caffeine metabolic ratio; FSH, follicle-stimulating hormone; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SE, standard error.