Table 2. Correlation between OC use and breast cancer risk.
| Premenopausal women | Postmenopausal women | |||||||
| Case N (%) |
Control N (%) |
cORd (95% CI) |
aORe (95% CI) |
Case N (%) |
Control N (%) |
cORd (95% CI) |
aORf (95% CI) |
|
| OC use*a | ||||||||
| Never | 362 (80.8) | 414 (89.4) | 1 | 1 | 318 (91.9) | 323 (94.4) | 1 | 1 |
| Ever | 86 (19.2) | 49 (10.6) | 2.01 (1.38–2.93) | 2.06 (1.39–3.04) | 28 (8.1) | 19 (5.6) | 1.50 (0.82–2.74) | 1.41 (0.76–2.64) |
| Types of OC usea | ||||||||
| None | 362 (80.8) | 414 (89.4) | 1 | 1 | 318 (91.9) | 323 (94.4) | 1 | 1 |
| LOC/SOC | 46 (10.3) | 25 (5.4) | 2.10 (1.27–3.49) | 2.00 (1.19–3.36) | 21 (6.1) | 13 (3.5) | 1.78 (0.86–3.67) | 1.59 (0.70–3.58) |
| EOC | 40 (8.9) | 24 (5.2) | 1.91 (1.13–3.22) | 2.13 (1.24–3.66) | 7 (2.0) | 6 (1.8) | 1.19 (0.39–3.57) | 1.19 (0.34–4.10) |
| Time of LOC or SOC use, monthsb | ||||||||
| None | 402 (89.7) | 438 (94.6) | 1 | 1 | 325 (93.9) | 329 (96.2) | 1 | 1 |
| 1–6 | 24 (5.4) | 9 (1.9) | 2.91 (1.34–6.33) | 2.69 (1.22–5.94) | 10 (2.9) | 4 (1.2) | 2.53 (0.79–8.16) | 2.81 (0.73–10.76) |
| 7–12 | 11 (2.5) | 7 (1.5) | 1.71 (0.66–4.46) | 1.81 (0.69–4.75) | 4 (1.2) | 1 (0.3) | 4.05 (0.45–36.42) | 2.75 (0.22–34.59) |
| 13–39 | 4 (0.9) | 5 (1.1) | 0.87 (0.23–3.27) | 0.68 (0.17–2.76) | 3 (0.9) | 3 (0.9) | 1.01 (0.20–5.05) | 1.50 (0.27–8.17) |
| 39 | 7 (1.6) | 4 (0.9) | 1.91 (0.55–6.56) | 1.66 (0.47–5.84) | 4 (1.2) | 5 (1.5) | 0.81 (0.22–3.04) | 0.56 (0.11–2.80) |
| Number of times per year EOC was usedc | ||||||||
| None | 402 (89.7) | 434 (93.7) | 1 | 1 | 339 (98.0) | 335 (98.0) | 1 | 1 |
| ≤2 | 27 (6.0) | 19 (4.1) | 1.53 (0.84–2.80) | 1.62 (0.87–3.01) | 6 (1.7) | 5 (1.5) | 1.19 (0.36–3.92) | 1.19 (0.35–4.04) |
| 2 | 19 (4.2) | 10 (2.2) | 2.05 (0.94–4.46) | 2.45 (1.11–5.41) | 1 (0.3) | 2 (0.6) | 0.49 (0.05–5.48) | 0.69 (0.06–7.87) |
CI, confidence interval; EOC, an oral hormone drug used to practise contraception, and which was taken within 72 hours after unprotected sex or contraception failure; LOC, an oral hormone drug that inhibit ovulation and anti-implantation, and which was taken once a month; SOC, an oral hormone drug that inhibit ovulation and anti-implantation, and which was taken once a day.
*Subjects who have ever used OC in the past 10 years were defined as OC users.
aA total of 1,599 subjects.
bInclude subjects who only used LOC or SOC, and the total time of LOC or SOC use was categorized into quartile based on control distribution.
cInclude subjects who only used EOC as well as reported the frequency, and the number of times per year EOC was used was categorized based on median of control distribution.
dcOR: crude OR, it is an OR value estimated by unconditional logistic regression with non-confounders adjusted.
eaOR: adjusted OR, it is an OR value estimated by multivariate logistic regression with age, per capita annual income, and history of active smoking, passive smoking adjusted.
faOR: adjusted OR, it is an OR value estimated by multivariate logistic regression with age, per capita annual income, history of active smoking, alcohol drinking, and history of live birth adjusted.