Osteoporosis and years since menopause

In Fukuoka Prefecture, in south-western Japan, a regional screening program for osteoporosis was conducted from 1994 to 1995. The screening level in the bone mineral density (BMD) at the distal non-dominant radius was equal to or less than two standard deviations below age-specific mean (≤ −2.0 SD). In 1177 examinees with natural menopause (mean age: 61.4, range: 42–88), 56 of those who were screened were subsequently radiologically confirmed by orthopedic specialists to have osteoporosis (case group). They were then compared with 802 normal BMD (≥ −1.0 SD) women (reference group) with their lifestyle and reproductive characteristics. The adjusted odds ratio (OR) and its 95% confidence interval (CI) were calculated using a logistic regression model. A significant increase in the ORs for osteoporosis based on the number of years since menopause was observed for 7–13 years since menopause (OR=2.3; 95% CI: 1.0–5.4) compared with <7 years, however, no increasing trend in risk was evident in 14+ years since menopause (OR=1.4; 95% CI: 0.4–5.1). Thus, the elevated risk continued up to around 10 years since menopause. These findings are consistent with previous studies that reported an alternation in the calcium metabolism and bone loss related to the length of time after menopause. Both the childhood and current milk consumption were also associated with a decreased risk: ORs were 0.4 (95% CI: 0.2–0.9) and 0.5 (95% CI: 0.3–1.0), respectively.