# Multimorbidity and animal models

## TL;DR

Multimorbidity, the presence of multiple chronic conditions, is a complex health issue that needs better animal models to understand and improve patient outcomes.

## Contribution

The paper proposes strategic directions for improving animal models of multimorbidity through cross-species validation and standardized protocols.

## Key findings

- Current animal models do not fully capture the complexity of human multimorbidity.
- A cross-species validation framework can help improve model accuracy and translatability.
- Advanced non-animal models and standardized protocols are needed for better research outcomes.

## Abstract

Multimorbidity—the co‐occurrence of more than two chronic conditions in the same individual—is associated with premature death, diminished function, reduced quality of life, and increased societal burden. This complex state involves dynamic interactions across multiple conditions, organ systems, and physiological pathways; yet research progress remains constrained by inadequate animal models that recapitulate human complexity. This review summarizes the predominant patterns of multimorbidity and evaluates current animal models spanning invertebrates, rodents, and large mammals. While no single model fully captures the multifaceted nature of human multimorbidity, we propose several strategic directions to address existing limitations: implementing a cross‐species validation framework (from simple organisms to rodents to large mammals), standardizing protocols integrating multimodal risk factors, developing advanced non‐animal models, and enhancing ethical oversight. Advancing multimorbidity models is crucial for decoding disease interactions and accelerating translation of research findings into improved patients outcomes.

Multimorbidity, defined as the coexistence of ≥2 chronic conditions, is associated with aging, genetics, and environmental factors. Animal models in multimorbidity research span three tiers: simple organisms for initial screening → rodents for mechanistic analysis → large mammals for clinical prediction.