Table 4.
Relative risks (RRs) and 95% confidence intervals (CIs) of breast cancer according to quintiles of caffeine and categories of coffee, decaffeinated coffee, and tea, by menopausal status and postmenopausal hormone use.
| Premenopausal women
|
Postmenopausal women
|
Postmenopausal hormone never users
|
Postmenopausal hormone current users
|
|||||
|---|---|---|---|---|---|---|---|---|
| No. of cases | RR (95% CI)† | No. of cases | RR (95% CI)† | No. of cases | RR (95% CI)‡ | No. of cases | RR (95% CI)‡ | |
| Caffeine, mg/day | ||||||||
| ≤68.0 | 52 | 1.00 [Reference] | 160 | 1.00 [Reference] | 34 | 1.00 [Reference] | 101 | 1.00 [Reference] |
| >68.0, ≤181.0 | 48 | 0.85 (0.58–1.27) | 130 | 0.86 (0.68–1.09) | 45 | 1.45 (0.92–2.29) | 76 | 0.76 (0.56–1.03) |
| >181.0, ≤352.2 | 67 | 1.18 (0.81–1.70) | 149 | 0.97 (0.77–1.22) | 44 | 1.33 (0.84–2.11) | 85 | 0.86 (0.64–1.15) |
| >352.2, ≤486.3 | 63 | 1.16 (0.80–1.69) | 150 | 0.93 (0.74–1.17) | 47 | 1.41 (0.90–2.23) | 84 | 0.81 (0.60–1.08) |
| >486.3 | 45 | 0.88 (0.58–1.33) | 153 | 1.01 (0.80–1.27) | 44 | 1.19 (0.75–1.89) | 93 | 1.10 (0.82–1.47) |
| P value for trend* | .97 | .66 | .78 | .34 | ||||
| Coffee | ||||||||
| Almost never | 67 | 1.00 [Reference] | 161 | 1.00 [Reference] | 38 | 1.00 [Reference] | 104 | 1.00 [Reference] |
| <1 cup/day | 31 | 0.89 (0.58–1.36) | 104 | 1.14 (0.89–1.46) | 21 | 0.89 (0.53–1.51) | 68 | 1.13 (0.83–1.54) |
| 1 cup/day | 39 | 1.07 (0.72–1.59) | 98 | 0.90 (0.70–1.16) | 36 | 1.15 (0.73–1.81) | 52 | 0.78 (0.56–1.09) |
| 2–3 cups/day | 100 | 1.10 (0.80–1.51) | 254 | 1.05 (0.86–1.28) | 80 | 1.26 (0.86–1.84) | 143 | 0.93 (0.72–1.20) |
| ≥4 cups/day | 38 | 0.97 (0.64–1.46) | 118 | 1.08 (0.85–1.38) | 34 | 1.01 (0.63–1.61) | 71 | 1.22 (0.89–1.66) |
| P value for trend* | .85 | .50 | .45 | .45 | ||||
| Decaffeinated coffee | ||||||||
| Almost never | 147 | 1.00 [Reference] | 383 | 1.00 [Reference] | 129 | 1.00 [Reference] | 204 | 1.00 [Reference] |
| <1 cup/day | 61 | 0.87 (0.64–1.18) | 176 | 1.06 (0.89–1.27) | 45 | 0.93 (0.66–1.31) | 114 | 1.22 (0.96–1.54) |
| 1 cup/day | 21 | 0.78 (0.49–1.24) | 64 | 0.86 (0.66–1.13) | 17 | 0.78 (0.47–1.31) | 40 | 0.92 (0.65–1.29) |
| ≥2 cups/day | 43 | 1.05 (0.75–1.49) | 104 | 0.92 (0.74–1.14) | 20 | 0.58 (0.36–0.93) | 71 | 1.13 (0.86–1.49) |
| P value for trend* | .74 | .26 | .02 | .75 | ||||
| Tea | ||||||||
| Almost never | 87 | 1.00 [Reference] | 244 | 1.00 [Reference] | 69 | 1.00 [Reference] | 140 | 1.00 [Reference] |
| <1 cup/day | 115 | 1.01 (0.76–1.34) | 319 | 1.07 (0.91–1.27) | 94 | 1.23 (0.90–1.69) | 187 | 1.01 (0.81–1.27) |
| 1 cup/day | 30 | 0.91 (0.60–1.38) | 78 | 0.91 (0.70–1.18) | 21 | 0.93 (0.57–1.53) | 50 | 0.95 (0.68–1.31) |
| ≥2 cups/day | 40 | 1.05 (0.72–1.53) | 89 | 1.02 (0.80–1.31) | 26 | 1.16 (0.74–1.84) | 54 | 1.03 (0.75–1.42) |
| P value for trend* | .88 | .76 | .93 | .93 | ||||
The test for trend was calculated using the median intake in each category as a continuous variable.
Adjustments for variables in multivariable analysis in footnote to Table 2, except for menopausal status. The variables of age at menopause, postmenopausal hormone use, prior hysterectomy, and prior bilateral oophorectomy were adjusted in multivariable models for postmenopausal women only.
Among postmenopausal women with adjustments for variables in multivariable analysis in footnote to Table 2, except for menopausal status and postmenopausal hormone use