Table 3.
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 history of benign breast disease (BBD) and body mass index (BMI)
| With BBD | Without BBD | BMI <25 kg/m | BMI ≥25 kg/m2 | |||||
|---|---|---|---|---|---|---|---|---|
| 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 | 97 | 1.00 [Reference] | 145 | 1.00 [Reference] | 119 | 1.00 [Reference] | 123 | 1.00 [Reference] |
| >68.0, ≤181.0 | 100 | 1.10 (0.83–1.46) | 112 | 0.76 (0.59–0.97) | 127 | 1.11 (0.87–1.43) | 85 | 0.69 (0.52–0.91) |
| >181.0, ≤352.2 | 110 | 1.23 (0.93–1.63) | 141 | 0.91 (0.72–1.15) | 142 | 1.20 (0.93–1.54) | 109 | 0.88 (0.68–1.15) |
| >352.2, ≤486.3 | 89 | 1.03 (0.77–1.39) | 156 | 1.00 (0.79–1.27) | 128 | 1.02 (0.79–1.32) | 117 | 1.03 (0.79–1.34) |
| >486.3 | 108 | 1.32 (0.99–1.76) | 130 | 0.84 (0.66–1.08) | 141 | 1.16 (0.90–1.50) | 97 | 0.87 (0.66–1.14) |
| P value for trend* | .10 | .71 | .43 | .85 | ||||
| Coffee | ||||||||
| Almost never | 116 | 1.00 [Reference] | 158 | 1.00 [Reference] | 146 | 1.00 [Reference] | 128 | 1.00 [Reference] |
| <1 cup/day | 61 | 0.99 (0.73–1.36) | 84 | 0.94 (0.72–1.22) | 75 | 0.95 (0.72–1.26) | 70 | 0.97 (0.73–1.30) |
| 1 cup/day | 79 | 1.18 (0.89–1.58) | 87 | 0.85 (0.66–1.11) | 99 | 1.06 (0.82–1.37) | 67 | 0.87 (0.65–1.18) |
| 2–3 cups/day | 159 | 1.08 (0.84–1.38) | 246 | 1.02 (0.83–1.25) | 219 | 0.99 (0.80–1.23) | 186 | 1.11 (0.88–1.39) |
| ≥4 cups/day | 89 | 1.35 (1.01–1.80) | 102 | 0.91 (0.71–1.18) | 115 | 1.13 (0.88–1.46) | 76 | 0.99 (0.74–1.32) |
| P value for trend* | .08 | .96 | .41 | .53 | ||||
| Decaffeinated coffee | ||||||||
| Almost never | 244 | 1.00 [Reference] | 385 | 1.00 [Reference] | 341 | 1.00 [Reference] | 288 | 1.00 [Reference] |
| <1 cup/day | 115 | 0.94 (0.75–1.17) | 160 | 1.04 (0.86–1.25) | 146 | 0.89 (0.73–1.09) | 129 | 1.11 (0.90–1.37) |
| 1 cup/day | 51 | 0.95 (0.70–1.29) | 43 | 0.67 (0.49–0.92) | 55 | 0.77 (0.58–1.03) | 39 | 0.83 (0.59–1.16) |
| ≥2 cups/day | 85 | 0.96 (0.74–1.23) | 84 | 0.90 (0.71–1.15) | 104 | 0.97 (0.77–1.21) | 65 | 0.87 (0.66–1.14) |
| P value for trend* | .78 | .16 | .76 | .15 | ||||
| Tea | ||||||||
| Almost never | 143 | 1.00 [Reference] | 245 | 1.00 [Reference] | 221 | 1.00 [Reference] | 167 | 1.00 [Reference] |
| <1 cup/day | 226 | 1.23 (1.00–1.52) | 272 | 0.90 (0.76–1.07) | 265 | 1.00 (0.84–1.20) | 233 | 1.04 (0.85–1.27) |
| 1 cup/day | 64 | 1.24 (0.92–1.67) | 66 | 0.74 (0.56–0.98) | 75 | 0.96 (0.74–1.25) | 55 | 0.86 (0.63–1.16) |
| ≥2 cups/day | 67 | 1.24 (0.92–1.66) | 88 | 0.92 (0.72–1.18) | 85 | 1.02 (0.79–1.31) | 70 | 1.05 (0.80–1.40) |
| P value for trend* | .37 | .51 | .93 | >.99 | ||||
*
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 history of benign breast disease
‡
Adjustments for variables in multivariable analysis in footnote to Table 2, except for body mass index