Incidence of fast bone losers and factors affecting changes in bone mineral density: A cohort study in a rural Japanese community

Abstract

The present study was conducted to determine the incidence of fast bone losers in the general population of a rural Japanese community and factors affecting changes in bone mineral density (BMD). In Miyama village, Wakayama Prefecture, a cohort of 1543 inhabitants aged 40–79 years (716 men and 827 women) was established on the basis of resident registration as of the end of December 1988, and a selfadministered questionnaire survey was performed. Fifty men and 50 women in each of four age strata between 40 and 79 years, totaling 400 participants, were selected randomly. In 1990, an initial examination measuring lumbar BMD by dualenergy X-ray absorptiometry was undertaken on these participants. As a follow-up study, BMD was again measured in the same participants in 1993. Those who showed a decrease in lumbar BMD of at least 3% per year were regarded as fast bone losers, and the incidence of these losers was determined. Factors affecting annual changes in BMD were investigated by multiple regression analysis. The results showed annual changes in 355 (170 men and 185 women) of the participants at the time of the initial examination. The rates of change in BMD in men in their 40s, 50s, 60s, and 70s were −0.53%, −0.40%, −1.07%, and −1.53%, respectively, and those in women in their 40s, 50s, 60s, and 70s were −1.53%, −4.35%, −2.26% and −2.36% in turn. The incidence of fast bone losers was 2.4% (4/170) in men and 9.7% (18/185) in women. As to the results of multiple regression analysis, partial regression coefficients for the rate of change in lumbar BMD were significant for the following items: history of tranquilizer use and Jikei's grading in both sexes; frequency of milk consumption in men; height and body weight at the initial measurement, and frequency of small fish consumption in women. Partial regression coefficients for menopause and the postmenopausal period were also significant in women.