Widespread Multimorbidity in a Cohort of Aging, Radiation-exposed Rhesus Macaques

Delayed effects of acute radiation exposure (DEARE) and radiation late effects are a suite of conditions that become apparent months to years after initial exposure to radiation in both humans and non-human primates. Many of these disorders, including cardiac complications, insulin resistance, bone loss, hypertension, and others, are also more common among aging cohorts independent of radiation exposure. This study characterized disease incidence, age of onset, and multimorbidity for 20 common, chronic diseases in 226 irradiated and 51 control rhesus macaques (Macaca mulatta) from the Wake Forest Non-Human Primate Radiation Late Effects Cohort (RLEC) to identify the excess risk of chronic disease caused by radiation-induced tissue damage. Irradiated animals were exposed to 4.0-8.5 Gy of ionizing radiation (mean 6.17 ± 1.29 Gy) one year on average prior to joining the cohort. In addition to the acute impact of early-life irradiation, these animals have been aging postirradiation for up to 15 years (mean 5.2 ± 3.0 years). Lifespan is an average of 5.1 years shorter in irradiated animals and radiation is associated with significantly increased rates of periodontitis, cataracts, testicular atrophy, tumors, diabetes, and brain lesions. While most of these chronic diseases occur in non-irradiated macaques, irradiated animals have significantly earlier age of onset for periodontitis, cataracts, bone loss, being overweight, and arthritis. This accelerated onset leads to 2.9 ± 1.9 comorbid conditions among irradiated animals compared to 1.9 ± 1.2 diagnoses among controls by young adulthood (age 8) and 5.2 ± 2.4 compared to 3.4 ± 1.8 conditions by middle age (15 years). Subsets of these comorbid conditions cluster among animals with fibrosis-related disorders (diabetes, lung injury, liver disease, kidney disease, heart disease, and tumors) commonly diagnosed together independent of prevalence. A second cluster of comorbidities centers around bone loss and is associated with being underweight and female reproductive problems. While there are significant differences in disease burden between irradiated and control animals, there was no dose effect of radiation on lifespan, age to first diagnosis, or comorbidities and substantial heterogeneity across each of these measures. This underlying heterogeneity in response to radiation suggests the existence of a yet unidentified determinant of resilience.