Paul C, Skegg D C, Spears G F, Kaldor J M
Br Med J (Clin Res Ed). 1986 Sep 20;293(6549):723-6. doi: 10.1136/bmj.293.6549.723.
In a population based case-control study 433 New Zealand women aged 25-54 with newly diagnosed breast cancer were compared with 897 women selected at random from the electoral rolls. The relative risk of breast cancer in women who had ever used oral contraceptives was 0.94 (95% confidence interval 0.70 to 1.25). The relative risk in women aged 25-34 at diagnosis was estimated to be 2.2 (95% confidence interval 0.47 to 9.9) and in older women less than 1. Analyses of risk by duration of use of oral contraceptives, age at first use, and time since first use showed no adverse effect of the pill. In particular, there was no increased risk in women who had used oral contraceptives before the age of 25 or before their first pregnancy, even for prolonged periods. Given the high prevalence of use in New Zealand, this study provides strong evidence against the hypothesis that use of oral contraceptives at young ages increases the risk of breast cancer.
在一项基于人群的病例对照研究中，将433名年龄在25至54岁之间、新诊断为乳腺癌的新西兰女性与从选民名册中随机选取的897名女性进行了比较。曾经使用过口服避孕药的女性患乳腺癌的相对风险为0.94（95%置信区间为0.70至1.25）。诊断时年龄在25至34岁之间的女性相对风险估计为2.2（95%置信区间为0.47至9.9），而年龄较大的女性相对风险小于1。按口服避孕药使用时长、首次使用年龄以及首次使用后的时间进行的风险分析显示，口服避孕药没有不良影响。特别是，在25岁之前或首次怀孕之前使用过口服避孕药的女性，即使使用时间较长，也没有增加风险。鉴于口服避孕药在新西兰的高使用率，这项研究提供了有力证据，反驳了年轻时使用口服避孕药会增加患乳腺癌风险这一假设。
