Oral contraceptive use in relation to age at menopause in the DOM cohort.
BACKGROUND
We investigated the hypothesis that long-term use of oral contraceptives (OCs), in particular high-dose OCs, could postpone age at menopause.


METHODS
Data was used from 8701 women who participated in a breast cancer screening programme in Utrecht (DOM-3 cohort), and who did not use hormone replacement therapy (HRT) or OCs in the 4 years prior to their last menses. Data on OC-use, menopausal status, age at menopause, year of birth, parity, smoking behaviour, socio-economic status, body mass index and age at menarche was available. Use of high-dose OCs has been defined in this study as OC-use before 1972. The data was analysed by means of linear regression and Cox's proportional hazards analysis. Women still menstruating, women with surgical menopause and women lost to follow-up were censored at their last known date of menstruation. Endpoint was the natural menopause (n = 4589).


RESULTS
The use of high-dose OCs advanced the onset of menopause by approximately 1.2 months for every year of OC-use compared with no OC-use. High-dose OC-use for > or = 3 years, adjusted for confounding variables, increased the risk of earlier menopause compared with no OC-use (adjusted hazard ratio 1.12; 95% CI 1.03--1.21). The use of lower dose OCs did not increase the risk of earlier menopause (adjusted hazard ratio 1.00; 95% CI 0.91--1.09).


CONCLUSIONS
These results are inconsistent with the hypothesis that long-term use of OCs could postpone the onset of menopause by inhibiting follicle depletion. Possible explanations are discussed.
de Vries
E
E
International Health Foundation, Utrecht, 3526 KS, The Netherlands.
den Tonkelaar
I
I
van Noord
P A
PA
van der Schouw
Y T
YT
te Velde
E R
ER
Peeters
P H
PH
D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D003276:Contraceptives, Oral / Q000008:administration & dosage / Q000009:adverse effects*; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D016014:Linear Models; D008572:Menarche; D008593:Menopause; D008875:Middle Aged; D009426:Netherlands; D010298:Parity; D016016:Proportional Hazards Models; D012907:Smoking; D012959:Socioeconomic Factors
D003276:Contraceptives, Oral