A longitudinal study of estrogen and calcium supplement use among Japanese women living in Hawaii

Estrogen and calcium supplements represent accepted treatments for the prevention of osteoporosis in the United States. The effectiveness of these treatments, however, will depend upon the extent that they are utilized, which may vary over time. We report a longitudinal study of estrogen and calcium use among a cohort of Japanese-American women living in Hawaii. Their mean age at the baseline examination in 1981 was 63.9 (age range 45 to 81). Between 1981 and 1992 the same women were repeatedly surveyed regarding their estrogen and calcium supplement use. During the decade of follow-up the prevalence of estrogen use doubled, with 25 to 30% of the women reporting estrogen use in the later years. The prevalence of calcium supplement use (500 mg/day or more) quadrupled over the same interval, with 20% of the women reporting calcium supplement use in the later years. The increases in estrogen and calcium supplement use derived from complex patterns of use. For estrogen, less than half of the users in 1981 were still using 5 years later; the number of women stopping estrogen, however, were more than replaced by new estrogen users. For calcium supplements, fewer than half of the women initiating use continued for as long as 5 years. Women beginning estrogen were younger, had more often used estrogen in the past, had a lower body mass index, had dietary calcium intakes of 400 mg/day or greater, and were more likely to have regularly used alcohol. Women initiating calcium supplements exhibited several of the same characteristics as women initiating estrogen use (younger age, past estrogen use, and regular alcohol use). The changes in use over the past decade may reduce the risk of osteoporotic fractures among our cohort. Benefits from the changes, however, could be limited by the inconsistent use by many of the cohort women. Also of concern are the weak associations observed between estrogen and calcium supplement use and bone mass measurements, which are strong indicators of fracture risk. It appears that treatment in our cohort has failed to reach many of the women with the greatest fracture risks.