Hip fracture prevalence in grandfathers is associated with reduced cortical cross-sectional bone area in their young adult grandsons.

CONTEXT Parent hip fracture prevalence is a known risk factor for osteoporosis. The role of hip fracture prevalence in grandparents on areal bone mineral density (aBMD) and bone size in their grandsons remains unknown. OBJECTIVE The objective of the study was to examine whether hip fracture prevalence in grandparents was associated with lower aBMD and reduced cortical bone size in their grandsons. DESIGN AND SETTING This was a population-based cohort study in Sweden. STUDY SUBJECTS Subjects included 1015 grandsons (18.9 +/- 0.6) (mean +/- sd) and 3688 grandparents. MAIN OUTCOME MEASURES aBMD, cortical bone size, volumetric bone mineral density and polar strength strain index of the cortex in the grandsons in relation to hip fracture prevalence in their grandparents were measured. RESULTS Grandsons of grandparents with hip fracture (n = 269) had lower aBMD at the total body, radius, and lumbar spine, but not at the hip, as well as reduced cortical cross-sectional area at the radius (P < 0.05) than grandsons of grandparents without hip fracture. Subgroup analysis demonstrated that grandsons of grandfathers with hip fracture (n = 99) had substantially lower aBMD at the lumbar spine (4.9%, P < 0.001) and total femur (4.1%, P = 0.003) and lower cortical cross-sectional area of the radius (4.1%, P < 0.001) and tibia (3.3%, P < 0.011). Adjusting bone variables for grandson age, weight, height, smoking, calcium intake, and physical activity and taking grandparent age at register entry, years in register, and grandparent sex into account strengthened or did not affect these associations. CONCLUSIONS Family history of a grandfather with hip fracture was associated with reduced aBMD and cortical bone size in 19-yr-old men, indicating that patient history of hip fracture in a grandfather could be of value when evaluating the risk of low bone mass in men.