Is the oral contraceptive pill associated with fracture in later life? New evidence from the Royal College of General Practitioners Oral Contraception Study
Several studies, including an earlier analysis from the Royal College of General Practitioners (RCGP) Oral Contraception Study, have suggested that ever users of oral contraceptives have an increased risk of fracture when compared with never users. In this paper, we examined a subset of women in the RCGP study living in Scotland to determine whether this risk has persisted.
Study Design
A nested case-control study was carried out using data collected prospectively for the RCGP Oral Contraception Study. Cases were women with a first ever diagnosis of fracture (n=651), age-matched to two controls (n=1302). Adjustments were made for smoking, social class and parity.
Results
There was not a significant association between ever use of oral contraception and fracture (adjusted odds ratio 1.05, 95% confidence interval 0.86-1.29), compared with never users. Neither were significant associations found between fracture and smoking, social class and parity. The findings did not vary materially with age or type of fracture.
Conclusion
Ever use of oral contraception was not associated with fracture in this study.
oral contraceptive pill fracture risk later life, RCGP oral contraception study fracture nested case-control, oral contraceptive ever use bone fracture association, contraceptive pill bone density fracture postmenopausal women, Royal College General Practitioners oral contraception long-term outcomes, oral contraceptive fracture risk age-matched controls, hormonal contraception skeletal health fracture epidemiology, oral contraceptive osteoporosis fracture prospective cohort Scotland, combined oral contraceptive bone mineral density fracture risk, nested case-control study contraceptive use fracture outcome
PMID 21664509 21664509 DOI 10.1016/j.contraception.2010.11.019 10.1016/j.contraception.2010.11.019 Memon et al. 2011, Memon 2011
Cite this article
Memon, S., Iversen, L., & Hannaford, P. C. (2011). Is the oral contraceptive pill associated with fracture in later life? New evidence from the Royal College of General Practitioners Oral Contraception Study. Contraception, 84(1), 40-47. https://doi.org/10.1016/j.contraception.2010.11.019
Memon S, Iversen L, Hannaford PC. Is the oral contraceptive pill associated with fracture in later life? New evidence from the Royal College of General Practitioners Oral Contraception Study. Contraception. 2011;84(1):40-47. doi:10.1016/j.contraception.2010.11.019
Memon, S., et al. "Is the oral contraceptive pill associated with fracture in later life? New evidence from the Royal College of General Practitioners Oral Contraception Study." Contraception, vol. 84, no. 1, 2011, pp. 40-47.
Little is known on fracture risk in young women using oral contraceptives. Case-control study (64,548 cases, 193,641 controls). Overall, no major association with risk of fracture was present. Only in a few age groups a limited increase (OR 1.1-1.5) was seen in those using low average doses (less than one tablet per day - i.e., intermittent use). Neither 20 nor >or=30 mcg per day of ethinylestradiol was associated with risk of fractures, while changing from 20 to >or=30 mcg per day or vice versa was associated with a limited increase in fracture risk (OR 1.1-1.4) in some age groups. In general, use of oral contraceptives in young women did not seem to be associated with an increased risk of fractures. The isolated increase seen in some strata with low average doses may be linked to factors associated with discontinuation of oral contraceptives rather than pharmacological effects.
Prior studies have suggested that oral contraceptives (OCs) may be associated with an increased fracture risk. However, the previous studies have only performed a limited adjustment for other potential risk factors. Subjects and methodsAll women with a fracture (n=64,548) in the year 2000 in Denmark served as cases. For each case, three age-matched controls were randomly drawn from the general population (n=193,641). Exposure was use of OCs between January 1, 1996, and December 31, 2000. Adjustments were made for use of other drugs, pregnancy, prior fracture, other diseases and social variables. In the unadjusted analysis, use of OCs in low dose was associated with a small increase in overall fracture risk. However, upon adjustment, no increase in fracture risk could be demonstrated in any age or dose group. Oral contraceptives are not associated with an increase or a decrease in fracture risk. Any change in fracture risk may be due to confounders.
There is good evidence that estrogens and progestogens have an important effect on bone metabolism. This article explores the relationship between oral contraceptive (OC) use and fractures occurring at various sites among the 17,032 participants in the Oxford-Family Planning Association contraceptive study, which now includes information accumulated during 310,000 woman-years of observation between 1968 and 1994. In total, 1308 women suffered at least one fracture during the follow-up period, which was largely confined to premenopausal years. When all fractures were combined, there was a modest, but highly significant trend (p < 0.001) of increasing risk with total duration of oral contraceptive use. In addition, there was statistically significant heterogeneity (p < 0.01) when overall fracture rates were examined in relation to recency of oral contraceptive use during the premenopausal lifespan. The highest relative risk (1.3, 95% CI 1.1-1.5) was for current or recent oral contraceptive users; however, viewed as a whole, no clear pattern of risk was apparent. Examination of the data for individual fracture sites (including the lower end of the radius/ulna) did not provide any evidence of a protective effect of oral contraceptive use. These results are closely similar to those reported from the Royal College of General Practitioners Oral Contraception Study in 1993. Estrogens and progestogens have an important effect on bone metabolism. The present study explored the relationship between oral contraceptive (OC) use and bone fractures in the cohort of 17,032 English and Scottish participants in the Oxford-Family Planning Association contraceptive study (1968-94). The analysis was based on the calculation of woman-years of observation terminated by referral for fracture or release from follow-up due to death, emigration, or short-term pill users reaching age 45 years. A total of 1308 women experienced at least one fracture during 310,000 woman-years of observation and there was a significant (p 0.001) positive relationship between age and fracture risk. Most common were fractures of the radius/ulna, tarsal/metatarsal bones, and ankle. When all fractures were combined, there was a significant (p 0.001) increasing risk with total duration of OC use. Also observed was a significant (p 0.01) heterogeneity when overall fracture rates were examined in relation to recency of OC use during the premenopausal lifespan. The highest relative risk (1.3; 95% confidence interval, 1.1-1.5) was recorded among current or recent OC users. There was about a 20% increase in the overall risk of fracture in women who had used OCs at any time compared with never-users. Overall, however, no clear pattern of risk emerged. These results are similar to those reported in the 1993 Royal College of General Practitioners OC Study. It is assumed that the increased fracture risk in OC users results from life-style characteristics of such women rather than a direct effect of OCs on bone.
To test for the possible association of past oral contraceptive (OC) use and incident fracture after menopause.
A prospective cohort of 93,725 postmenopausal women.
Forty Women's Health Initiative (WHI) clinical centers across the United States. PATIENT(S): Ethnically diverse 93,725 volunteer postmenopausal women, 50 to 79 years old. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The main outcome was self-reported incident first fracture assessed prospectively by annual questionnaire. RESULT(S): The adjusted relative hazard (HR) for fracture among past OC users was 1.07 (95% CI, 1.01-1.15). Among women without any postmenopausal hormone treatment, past OC use for < or =5 years led to an HR of 1.15 (95% CI, 1.04-1.27) and for past OC use >5 years led to an HR of 1.09 (95% CI, 0.97-1.23) compared with never users. CONCLUSION(S): This study does not support the idea that past OC use protects against later fracture.