Oral contraceptive use and bone mineral density in premenopausal women:  cross-sectional, population-based data from the Canadian Multicentre Osteoporosis  Study

Prior JC; Kirkland SA; Joseph L; Kreiger N; Murray TM; Hanley DA; Adachi JD; Vigna YM; Berger C; Blondeau L; Jackson SA; Tenenhouse A

Oral contraceptive use and bone mineral density in premenopausal women: cross-sectional, population-based data from the Canadian Multicentre Osteoporosis Study

Prior JC, Kirkland SA, Joseph L, Kreiger N, Murray TM, Hanley DA, Adachi JD, Vigna YM, Berger C, Blondeau L, Jackson SA, Tenenhouse A

Published October 16, 2001 CMAJ : Canadian Medical Association Journal = Journal De l'Association Medicale Canadienne, 165(8), 1023-1029

PMID 11699697 PMC PMC81536

RRM Academy Synopsis

Premenopausal women who used the pill had lower spine bone density

A national Canadian survey of 524 women aged 25 to 45 found women who had used oral contraceptives had lower spine and trochanter bone density than nonusers. Researchers measured bone density once.

Key Findings

Of 524 women (mean age 36.3 years), 454 (87%) had used oral contraceptives for 3 months or more, and 70 (13.4%) had not.
Mean duration of oral contraceptive use was 6.8 years (SD 4.8). Of the users, 90 were current users and 364 were past users.
Adjusted for age, BMI and height, spine bone density was 1.03 g/cm2 (SD 0.12) in users versus 1.07 g/cm2 (SD 0.12) in nonusers (95% CI of difference -0.07 to -0.001).
Trochanter bone density was 0.70 g/cm2 (SD 0.09) in users versus 0.72 g/cm2 (0.09) in nonusers. Femoral neck and Ward's area differences pointed the same way but were not statistically significant.
Bone density was not related to duration of use or to gynecological age at first use, and current and past users did not differ at any site.

Interpretation

The study drew a population-based national sample from 9 urban centers. Researchers measured bone density by DXA at a single time point, so the design is cross-sectional and reports an association. Users reported more alcohol and cigarette use, and results were adjusted for both. The authors wrote that it is possible unmeasured environmental or other variables accounted for the bone density differences. They reported that a 5-year prospective follow-up was under way.

RRM Context

Oral contraceptives are suppressive medications, and RRM evaluates the whole cycle. The authors tested whether ovulation changes after stopping the pill explained the lower bone density. Past and current users showed no difference at any site, so the data did not support that idea.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

Positive and negative effects on bone mineral density (BMD) have been described as a result of the premenopausal use of oral contraceptives (OCs); increased fracture rates have also been reported. This study assessed the relation between OC use and BMD in a population-based, 9-centre, national sample of women aged 25-45 years.

Methods

Premenopausal women who had been enrolled in the Canadian Multicentre Osteoporosis Study were classified as having ever been OC users (> or = 3 months) or as having never been OC users (0 to < 3 months). Data were obtained through extensive questionnaires and measuring of participants' weight, height and the BMD of lumbar vertebrae and the proximal femur.

Results

Of the sample of 524 women, whose mean age was 36.3 (standard deviation [SD] 5.9) years, 454 had used OCs; their mean age when they started using OCs was 19.8 (SD 3.5) years and the mean duration of use was 6.8 (SD 4.8) years. Women who had ever and those who had never used OCs showed no differences in age, age at menarche, parity, current calcium intake, exercise, body mass index (BMI), education, past irregular cycles or amenorrhea. OC users reported more alcohol and cigarette use and more use of medications to create regular cycles. Mean BMD values (adjusted for age, BMI and height) were 0.02-0.04 g/cm2 (that is, 2.3%-3.7%) lower in OC users, and were significantly lower in the spine and trochanter. The BMD of the spine in OC users was 1.03 (SD 0.12) g/cm2 versus 1.07 (SD 0.12) g/cm2 (95% confidence interval [CI] of difference -0.07 to -0.001) in those who had never used OCs. BMD was neither related to the duration of OC use nor to gynecological age at first use. Current and past users had similar BMD values.

Interpretation

National, population-based data show lower BMD values for the trochanter and spine in premenopausal women who have used OCs compared with those who have never used OCs.

Topics

Bone Health › Bone Mineral Density › Peak Bone Mass · Contraception › Oral Contraceptives › Metabolic Effects · Therapeutics › Hormonal Agents › Estrogen Preparations

Stuart A Jackson, Nancy Kreiger, Timothy M Murray, Jerilynn C Prior, Alan Tenenhouse

S Jackson, N Kreiger, Tim Murray, T Murray, J Prior, A Tenenhouse

PMID 11699697 11699697 Prior et al. 2001, Prior 2001

Keywords

Contraceptives, Oral

Oral contraceptive use and bone mineral density in premenopausal women: cross-sectional, population-based data from the Canadian Multicentre Osteoporosis Study

Premenopausal women who used the pill had lower spine bone density

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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Keywords