Bone mineral density in immigrants from southern China to Denmark. A cross-sectional study

Immigration from Japan to USA has been shown to increase bone mineral density (BMD) and body fat in women. The effects of immigration between other geographical areas on bone mass and body composition are largely unknown, especially in men. In the present study, we measured bone mass and body composition by dual energy X-ray absorptiometry (Hologic QDR-2000) in 73 healthy premenopausal women (age 35 +/- 8 years) and 69 men (age 40 +/- 12 years) who had immigrated from southern China to Denmark 2 months to 36 years ago. The BMD measurements (Total BMD, trunk BMD and leg BMD) were related positively to years since immigration (YSI) (R2 = 0.10-0.16, p < 0.05) in premenopausal women, but not in men. Fat distribution was related mainly to age in both premenopausal women and men (R2 = 0.16-0.26, p < 0.05). For comparison, we included 51 white, Danish premenopausal women (age 36 +/- 6 years). Chinese premenopausal women with a YSI below or equal to 12 years (N = 38) had significantly lower total and regional BMD (trunk, legs, arms) (p < 0.05), while women with a YSI above 12 years (N = 35) had significantly lower BMD in the legs only (p < 0.05) when compared to the Danish premenopausal women. After correction for age weight and height, Chinese premenopausal women with a YSI below or equal to 12 years still had significantly lower BMD in all regions (4-7%, p < 0.05), whereas no differences in BMD were found between Chinese premenopausal women with a YSI above 12 years compared with Danish premenopausal women. In conclusion, Chinese premenopausal women who immigrated to Denmark more than 12 years ago have a similar BMD to that of Danish premenopausal women. In the group who immigrated less than 12 years ago, a significantly lower BMD was found.