Role of Longitudinal Change and Secular Trend in Age Differences in Male Body Dimensions

The smaller body size of the elderly is due in part to actual shrinkage over the lifespan (aging) and partly to earlier generations being physically smaller than recent ones (secular trend). To separate and quantify these two effects we examined 10-year multi-cohort longitudinal data on height, arm span and their component segments. Participants were 1212 males between the ages of 22 and 82 who were members of the Veterans Administration Normative Aging Study, Boston. Overall, there was 7.27 cm difference in height between the youngest and oldest age groups. Of this difference, 4.27 cm could be explained by aging changes, while 3.00 cm was due to secular trend. Although we hypothesized that aging change would predominate in the upper body, and secular trend would predominate in the lower body, both effects were found to be significant in both body halves. Arm span and its components also underwent longitudinal change, but again, a portion of the difference between younger and older men was attributable to secular trend. Evidence that the oldest cohort was larger in body size than preceding ones suggests the enhanced survival of larger men, although the possibility of sampling bias cannot be excluded.