経口避妊薬を長期に服用しても死亡率と関連しない


 経口避妊薬を長期に服用している喫煙者は死亡率が高い(10年以内なら大丈夫)という報告があるが(Lancet 1977:727-31.)、経口避妊薬の服用期間と死亡率には関連性は見られなかったという報告。



経口避妊薬と死亡率:コホート研究
Mortality among contraceptive pill users: cohort evidence from Royal College of General Practitioners’ Oral Contraception Study
BMJ 2010;340:c927

全文が読めます
http://www.bmj.com/cgi/content/full/340/mar11_1/c927


 経口避妊薬を服用してる女性と、1度も服用したことがない女性の死亡率の比較。一般開業医、国民医療サービスに登録をしている患者の1968年以降の前向きコホート研究。連合王国での1400名の医師を対象に、46,112名の女性を39年間調査し、経口避妊薬を378 006名が非服用者で、819 175 名が服用経験者だった。第一のアウトカムは、全死亡率と原因別の死亡率。
 結果、非服用者のうち1,747名が死亡、服用経験者は2,864名死亡。非服用者の方が、有意に全死亡率が低かった(adjusted relative risk 0.88, 95% confidence interval 0.82 to 0.93)。癌による死亡率も、すべての癌において、非服用者の方が死亡率が低かった。
 しかし、全死亡率と、経口避妊薬の投与期間には関連性は見られなかった。


メモ)
・がんも含めたリスクとベネフィットのバランスは、不明

Objective To see if the mortality risk among women who have used oral contraceptives differs from that of never users.
Design Prospective cohort study started in 1968 with mortality data supplied by participating general practitioners, National Health Service central registries, or both.

Setting 1400 general practices throughout the United Kingdom.

Participants 46 112 women observed for up to 39 years, resulting in 378 006 woman years of observation among never users of oral contraception and 819 175 among ever users.

Main outcome measures Directly standardised adjusted relative risks between never and ever users for all cause and cause specific mortality.

Results 1747 deaths occurred in never users of oral contraception and 2864 in ever users. Compared with never users, ever users of oral contraception had a significantly lower rate of death from any cause (adjusted relative risk 0.88, 95% confidence interval 0.82 to 0.93). They also had significantly lower rates of death from all cancers; large bowel/rectum, uterine body, and ovarian cancer; main gynaecological cancers combined; all circulatory disease; ischaemic heart disease; and all other diseases. They had higher rates of violent deaths. No association between overall mortality and duration of oral contraceptive use was observed, although some disease specific relations were apparent. An increased relative risk of death from any cause between ever users and never users was observed in women aged under 45 years who had stopped using oral contraceptives 5-9 years previously but not in those with more distant use. The estimated absolute reduction in all cause mortality among ever users of oral contraception was 52 per 100 000 woman years.

Conclusion Oral contraception was not associated with an increased long term risk of death in this large UK cohort; indeed, a net benefit was apparent. The balance of risks and benefits, however, may vary globally, depending on patterns of oral contraception usage and background risk of disease.


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