Confirmation of the sex difference in continuing subperiosteal apposition.

A major sex difference in the rate of continuing bone expansion was confirmed for 5660 adult subjects of European ancestry. The five-decade gain in metacarpal midshaft area amounted to 8.4% in 3455 females and 2.8% in 2205 males. There was no systematic age effect on the length of the second metacarpal. Accordingly, both bone expansion and the marked sex difference in its magnitude may be attributed to sex-specific aspects of ageing much like the sex difference in endosteal surface loss. Continuing subperiosteal apposition during adult life is now a well-documented ageing phenomenon. First reported for the femur by Smith and Walker (‘64) and then for the rib section (Epker, Kelin and Frost, ’65), adult bone “expansion” has since been shown for the second metacarpal (Garn et al., ’67, ‘68) and for other tubular bones (Garn, ’70). A similar gain in outer bony dimensions has also been demonstrated for the skull (Israel, ’67, ’71). Apparently, continuing bone expansion is both absolutely and relatively greater for the female (cf. Garn et al., ’68; Garn, ’70). If this sex difference can be confirmed, it indicates that the sexes differ as systematically in adult subperiosteal gain as in adult endosteal loss, and hence in the pattern of adult remodeling at both bone surfaces. In the present study, we have made use of postero-anterior hand-wrist radiographs of a total of 5660 adult participants in the Ten-State Nutrition Survey of 1968-1970. There were 2205 males and 3455 females, all of European ancestry. Measurements of the total subperiosteal diameter (T) and medullary cavity width (M) of the second metacarpal at midshaft were made with the 0.05 mm readout Helios calipers. These two diameters were computer-converted into total subperiosteal area (0.785 T2) and medullary cavity area (0.785 M2) as described in Garn (‘70) and Garn, Poznanski and Nagy (‘71). The length of the second metacarpal (L) was also measured, as described. For uniformity with our several earlier publications on continuing metacarpal expansion, the total age range encompassed (25-84.9) was split into two three-decade groups, i.e., 25-54.9 and 55-84.9 with “midpoint” ages of 40 and 70 years, respectively (cf. Garn et al., ’67, ’68). In the present study there were not less than 858 subjects in any such three-decade age group. As shown in the first table (table l), there is clear evidence of an age-associated gain in total subperiosteal area (TA) at midshaft in both sexes. Comparing the two three-decade groupings, for each sex, the subperiosteal increase from midpoint age 40 to midpoint age 70 was 1.2 mm2 in males and 2.6 mm2 in females. Expressing these values on the basis of a five-decade period, apparent subperiosteal surface apposition amounted to 2.8% in males and 8.4% in females. These latter values are remarkably close to those previously observed for Central American and other populations where increases, expressed on a five-decade basis, equalled 2.9% for males and 8.6% for females, respectively (cf. Garn et al., ’68, table 2). Since the total period of continuing subperiosteal surface apposition considered in this study and encompassing the 377 AM. J. PHYS. ANTHROP., 36: 377-380 378 GARN, FRISANCHO, SANDUSKY A N D M c C A N N