Harris lines: a study of age-associated bias in counting and interpretation.

Harris lines are regularly used in paleopathology as indicators of episodic nonspecific stress, but the methodology for their use has not been clearly established. We studied radiographs of the distal shaft of the tibia in 82 immature and 49 mature subjects from a medieval burial site and compared the number of Harris lines and observer error according to age categories. We found statistically significant differences in both line counts and in observer error by age groups. In conclusion, studies of Harris lines must take into account age variation in order to be validated.