Testing lipid markers as predictors of all-cause morbidity, cardiac disease, and mortality risk in captive western lowland gorillas ( Gorilla gorilla gorilla)

Abstract

Great apes and humans develop many of the same health conditions, including cardiac disease as a leading cause of death. In humans, lipid markers are strong predictors of morbidity and mortality risk. To determine if they similarly predict risk in gorillas, we measured five serum lipid markers and calculated three lipoprotein ratios from zoo-housed western lowland gorillas (aged 6–52 years, $n=\mathrm{61}$ , subset with routine immobilizations only: $n=\mathrm{47}$ ): total cholesterol (TC), triglycerides (TGs), high-density lipoprotein (HDL), low-density lipoprotein (LDL), apolipoprotein A1 (apoA1), $\mathrm{TC}/\mathrm{HDL}$ , $\mathrm{LDL}/\mathrm{HDL}$ , and $\mathrm{TG}/\mathrm{HDL}$ . We examined each in relation to age and sex, then analyzed whether they predicted all-cause morbidity, cardiac disease, and mortality using generalized linear models (GLMs). Older age was significantly associated with higher TG, $\mathrm{TC}/\mathrm{HDL}$ , $\mathrm{LDL}/\mathrm{HDL}$ , and $\mathrm{TG}/\mathrm{HDL}$ , and lower HDL and apoA1. With all ages combined, compared to females, males had significantly lower TG, $\mathrm{TC}/\mathrm{HDL}$ , $\mathrm{LDL}/\mathrm{HDL}$ , and $\mathrm{TG}/\mathrm{HDL}$ , and higher HDL. Using GLMs, age, sex, and lower $\mathrm{LDL}/\mathrm{HDL}$ were significant predictors of all-cause morbidity; this is consistent with research demonstrating lower LDL in humans with arthritis, which was the second most prevalent condition in this sample. In contrast to humans, lipid markers were not better predictors of cardiac disease and mortality risk in gorillas, with cardiac disease best predicted by age and sex alone, and mortality risk only by age. Similar results were observed when multimodel inference was used as an alternative analysis strategy, suggesting it can be used in place of or in addition to traditional methods for predicting risk.