The Influence of Body Size on Adult Skeletal Age Estimation Methods

When human skeletal remains are found in prehistoric, historic, or forensic contexts, establishing age at death is an important step in reconstructing life histories, building demographic profiles, and identifying victims. Reliability for adult skeletal age estimations is generally lower than ideal, especially for individuals over the age of 40 years. A factor rarely considered in age estimation is that of body size; namely, how individuals of varying body sizes experience skeletal aging. This thesis explores the variables of BMI, stature, and body mass to quantify the influence of error from body size on adult skeletal age estimates. Eight age estimation methods were tested on 764 adult skeletons from the Hamann-Todd and William Bass Collections. These individuals were documented to have ranged in stature from 1.30m to 1.93m and body mass from 24.0kg to 99.8kg. Each age estimation method was evaluated separately. Analyses show that underweight individuals have the most error associated with their age estimations for all methods. All methods under-age underweight individuals by 5 to 15 years compared to average and obese individuals. The Kunos et al. method is the most reliable rib method, and the Lovejoy et al. and Suchey-Brooks methods are the most reliable pelvic methods. The İşcan et al. fourth rib method under-ages individuals by the highest degree compared to all other methods. The DiGangi et al. method is the most unreliable method with low accuracy (over twenty years) and high bias scores (under-aging individuals by almost 20 years). Body mass has a stronger influence on age estimation than stature. Studies have shown that body mass has a strong impact on bone resorption and remodelling rates, regardless of nutrition, and that tissue type (i.e. fat vs. muscle), physical activity, and mechanical loading influence bone remodelling. Skeletal remains of underweight individuals have fewer age markers while obese individuals show an increase in surface texture degeneration and osteophytic lipping. This is the first study to show that body size influences skeletal age estimation, and that age estimations are significantly different between weight-bearing and non-weight-bearing joints.Ph