Neutrophil to Lymphocyte Ratio (NLR) in captive chimpanzees (Pan troglodytes): The effects of sex, age, and rearing

Abstract

0In humans, neutrophil to lymphocyte ratio (NLR) has been used as a clinical tool in diagnosis 3 1 and/or prognosis of a variety of cancers and medical conditions, as well as in measuring 3 2 physiological stress over time. Given the close phylogenetic relationship and physical similarities 3 3 between humans and apes, NLR may similarly be a useful diagnostic tool in assessing 3 4chimpanzee health. Only one study has examined NLR in apes, reporting that NLR increased 3 5 with age and was affected by body-mass index and sex. In the current study, we examined 3 6 changes in NLR data from longitudinal health records for 443 chimpanzees in two captive 3 7 chimpanzee populations. Using these data, we analyzed intra-individual changes and inter-3 8 individual differences in NLR as a function of age, rearing history, and sex. Contrary to previous 3 9 studies in humans and the one previous study in chimpanzees, NLR values did not change over a 4 0 10-year timespan within individual chimpanzees. However, cross-sectional comparisons revealed 4 1 a significant quadratic relationship between age and NLR with the highest values during mid-life 4 2 (20-30 years of age) and the lowest values in younger and older individuals. Additionally, males 4 3 and mother-reared individuals had higher NLR than females and nursery-reared chimpanzees, 4 4respectively. Lastly, males and those with higher NLR values died at younger ages. These 4 5 findings may suggest that NLR can be used a predictor of longevity in chimpanzees. However, 4 6given the complexities of these relationships, more research is needed to determine the utility of 4 7 NLR as a diagnostic health tool for use in chimpanzees. 4 8