REPRODUCTIVE CORRELATES OF BONE MASS IN ELDERLY WOMEN

Results from previous studies of reproductive factors and bone density have been conflicting; some demonstrate a beneficial effect, but othe rs show a detrimental effect on bone density. The present study invest igates the association of parity, lactation, and menstruation with rad ial bone density in 2230 white women, 65 years of age and older. Bone density was assessed by single-photon absorptiometry. Linear multiple regression was utilized to determine if reproductive factors were asso ciated with radial bone density. The number of births, duration of men strual bleeding, age at menarche, and years menstruating were signific ant independent predictors of postmenopausal bone density of the radiu s. A 1.4% increase in distal radius bone density was observed with eac h additional birth. Women who began menstruation at age 9 had 6.3% hig her bone density than women who began at age 16. Women who menstruated for 3 days during each menstrual cycle had 2.8% less distal radius bo ne density than women who bled for 7 days. Each decade of menstruation was associated with a 2% greater distal radius bone density. No diffe rence in bone density was demonstrated for women who breast-fed and wo men who did not. Length of the menstrual cycle, amount of menstrual fl ow, and irregularity of the menstrual cycle were not significantly ass ociated with radial bone mineral density. In conclusion, pregnancy and menstruation are associated with postmenopausal bone density of the r adius.