Elderly cohort study subjects unable to return for follow-up have lower bone mass than those who can return

Longitudinal studies of osteoporosis in older persons may underestimate bon e loss because of a lack of follow-up measurements on subjects too frail to return. The authors addressed this possible bias as part of the population -based Framingham Study; in 1996-1997, they used quantitative ultrasound to assess the bone status of elderly subjects regardless of their ability to return to the clinic. Broadband ultrasound attenuation (BUA) and speed of s ound of the calcaneus (heel) were measured in 433 subjects at the Framingha m, Massachusetts, clinic and in 167 subjects at their homes or nursing home s. All ultrasound parameters were measured with intramachine coefficients o f variation of <6.0%. The mean BUA for those subjects evaluated at the clin ic was higher than for those measured at home (9.2% higher for men, p = 0.0 81; 8.6% higher for women, p = 0.034). After adjustment for age and weight, the differences in BUA were no longer significant. Among the elderly subje cts participating in this longitudinal cohort study, those who were unable to return for follow-up were older, weighed less, and had a lower BUA than those who did return, suggesting that longitudinal studies of changes in bo ne mass with aging may underestimate the true population values.