FAMILY HISTORY OF OSTEOPOROSIS AND BONE-MINERAL DENSITY AT THE AXIAL SKELETON - THE RANCHO-BERNARDO STUDY

To determine whether a family history of osteoporosis identifies indiv iduals with low bone mineral density (BMD), we studied 1477 white elde rly (aged 60-89 years), noninstitutionalized ambulatory men (n = 600) and women (n = 877) from the Rancho Bernardo, California cohort. Famil y history data on biologic parents and full sisters were obtained by q uestionnaire. BMD of the lumbar spine and hip was measured using dual- energy x-ray absorptiometry. After adjustment for age, body mass index , history of cigarette smoking, thiazide use, and estrogen use, men an d women with a family history of osteoporosis had lower BMD than those with a negative family history. In men, a positive family history was associated with lower BMD at the hip (p = 0.01), whereas in women a s ignificant association was observed for the spine (p = 0.02). BMD decr eased in a stepwise fashion with an increasing number of family member s with a history of osteoporosis. Analysis of the effect of parental h istory of osteoporosis on BMD showed a significant relation between pa ternal (but not maternal) history and lumbar spine BMD in both sexes a nd a significant relation between maternal (but not paternal) history and hip BMD only in men. The relative risk of having categoric osteope nia was highest in those whose fathers had a history of osteoporosis ( RR 2.16, 95% CI = 1.38-3.37). A similar association was found for subj ects with fractures. These results were not explained by differential awareness of family history in individuals with known osteoporosis, be cause the prevalence of family history was unrelated to personal histo ry of osteoporosis in men and only weakly related in women. The positi ve predictive value of family history as an indicator of categorically defined low bone density was 22% in men and 24% in women, although in women this value increased to 33% when father's history alone was con sidered. The negative predictive value of overall family history was 6 5% in men and 81% in women. Overall, these data suggest that clinician s who ask patients about family history of osteoporosis should ask abo ut both parents.