The Postmortem Evaluation of Anatomical Thymic Parameters in the Context of Age, Cause of Death, Sex, and Body Mass Index in the Elderly Human Population

Abstract

The studies of thymic structure were performed predominantly in cohorts of younger individuals. Here, we established a cohort of body donors whose age at the time of death ranged from 57 to 103 to study the relationship between thymic structure and factors that, in the younger subjects, have shown to affect the organ’s anatomy, including the presence of the organ’s capsule, its weight, size of the left and right lobes, and a transverse diameter. We explored the relationships between these thymic parameters and the subjects’ age, sex, and cause of death (COD), asking how the thymus in the elderly differed from the organ’s macro-anatomy in a broader and younger human population, and whether age, sex, COD, and BMI could influence the thymic parameters in the elderly. Our analyses revealed that the thymic size but not thymic weight in the KYCOM cohort differed significantly from the younger individuals. The size of the thymus in males progressively decreased, but in females, the size of the right lobe increased. The encapsulated thymus was detected with a higher frequency in females than males. We found no associations between thymic parameters and the person’s COD, age, or sex. However, the person’s BMI was associated with thymic weight, suggesting that obesity may influence the aging of the immune system.