Harris lines revisited: prevalence, comorbidities, and possible etiologies

The occurrence of transverse radiopaque lines in long bones-Harris lines (HLs)-is correlated with episodes of temporary arrest of longitudinal growth and has been used as an indicator of health and nutritional status of modern and historical populations. However, the interpretation of HLs as a stress indicator remains debatable. The aim of this article is to evaluate the perspectives and the limitations of HLs analyses and to examine their reliability as a stress indicator.

The study was conducted on 241 tibiae from a medieval Swiss skeletal material and was carried out using a standardized, semiautomated HL detection and analysis tool developed by the authors. We compared four different age-at-formation estimation methods and analyzed the correlation of HL occurrence to life expectancy, mean-age-at-death, stature, tibia length, and metabolic disorders as expressed by linear enamel hypoplasia and hypothyroidism.

The evaluation of the age-at-formation estimation methods showed statistical significant differences. Therefore, a mathematical framework for the conversion between the methods has been developed. Remodeling had eliminated about half of the HLs formed during adolescence, and a further half of the remaining ones during early adulthood, whereas no association between the aforementioned conditions and HL prevalence could be determined. The peaks of high HL frequency among various populations were found to parallel normal growth spurts and growth hormone secretion.

We suggest a reconsideration of HLs as more of a result of normal growth and growth spurts, rather than a pure outcome of nutritional or pathologic stress.