Sex differences in the association between adiponectin and BMD, bone loss, and fractures: the Rancho Bernardo study

We evaluated sex differences in the prospective association between adiponectin with BMD, bone loss, and fractures. Adiponectin, an adipose-derived protein with insulin-sensitizing properties, is also expressed in bone-forming cells. Conflicting results and sex differences in the adiponectin-BMD association have been reported in cross-sectional studies. Serum adiponectin was measured in fasting blood samples obtained in 1984-1987 in 447 postmenopausal women (mean age: 76 yr) and 484 men (mean age: 75 yr). Four years later, BMD was measured at the midshaft radius by single photon absorptiometry and at the femoral neck, total hip, and lumbar spine by DXA. In 1992-1996, axial BMD was remeasured in 261 women and 264 men. Multivariable analysis adjusted for age, weight, calcium intake, type 2 diabetes, alcohol intake, and exercise. Among women, adiponectin was inversely associated with BMD at the femoral neck (beta = -0.002, p = 0.007), total hip (beta = -0.002, p = 0.009), lumbar spine (beta = -0.003, p = 0.008), and midshaft radius (beta = -0.002, p = 0.01) after 4.4 yr and at the femoral neck and total hip 8.6 yr later. Among men, adiponectin was inversely associated with BMD at the femoral neck, (beta = -0.002, p = 0.03), total hip (beta = -0.004, p < 0.001), and midshaft radius (beta = -0.003, p < 0.001) after 4.4 yr and at the hip 8.6 yr later. Adiponectin was not associated with 4-yr bone loss in either sex but was associated with vertebral fractures (adjusted OR: 1.13; 95% CI: 1.08-1.23; p = 0.009) among men only. Adiponectin was inversely associated with BMD; however, sex differences were observed by anatomical site and with regards to vertebral fractures.