Oral contraceptives are a safe and acceptable form of contraception in perimenopausal women and may be effective in maintaining bone mass prior to menopause. Studies of the bone-sparing properties of oral contraceptives are difficult to interpret because of confounding variables, such as age, smoking, duration of use, exercise, menstrual function and endocrine diseases. Nevertheless, the results of many studies suggest that premenopausal use of oral contraceptives is associated with higher bone density than is nonuse. Long-term premenopausal oral contraceptive use allows women to enter menopause with bone density that is 2-3% higher than in nonusers. The optimal duration of use and dosage of estrogen and the clinical importance of this effect remain to be determined.
PIP: Confounding variables (e.g., age, smoking, duration of use, exercise, menstrual function, and endocrine diseases) make the interpretation of studies of bone-protective properties of oral contraceptives (OCs) difficult. A statistically significant effect of OC use among young, relatively healthY women may require many years. The literature shows that as women who used OCs during the premenopausal period enter menopause, their bone density is 2-3% higher than that of nonusers. We do not yet know the clinical significance of a 2-3% higher bone density, however. It may delay the time at which bone mineral density falls into the fracture-risk zone. Since osteoporosis and bone fractures and their associated morbidity and mortality have a significant economic impact on society, OC use and benefits may be warranted. We know already that OCs protect against osteoporosis in women with conditions that lower estrogen production: anorexia nervosa-induced amenorrhea, hypothalamic disease, excessive exercise, drug use, ovarian failure, hyperprolactinemia, and chromosomal disorders. The data suggest that long-term OC use (= or 8 years) provides the most protection against osteoporosis. The bone-protective properties of estrogen appear to be limited to doses of more than 25 mcg of ethinyl estradiol. Perhaps OCs could be promoted as a prophylactic against osteoporosis, especially during the later reproductive years. Research needs to determine the optimal duration of OC use, dosage of estrogen, and the clinical importance of the 2-3% higher bone density among OC users before clinicians promote OCs' noncontraceptive benefit of osteoporosis prevention among premenopausal and perimenopausal women.