Indicators of mortality risk in ageing horses

Clinical care for patients with limited life expectancy often requires adjustments, prioritizing immediate benefits over long-term outcomes, as the relevance of future complications diminishes. This study identifies indicators of mortality risk in horses with chronic orthopaedic conditions to enhance individualized care and welfare. Over 3 years, 123 chronically lame horses and 6 healthy control horses at an animal sanctuary underwent regular (every 3 months) comprehensive health assessments and activity monitoring using wearable sensors. Data collected included body condition scores, musculoskeletal pain scores, lameness evaluations, and time budgets for eating, resting, and activity. Of the 123 chronically lame horses, 31 horses died (n = 31/123, 25.2%), with 10 succumbing to acute decompensation of their chronic condition (DAC, n = 10/123, 8.1%), while 21 were euthanized due to intractable pain or progressively deteriorating health and function (DCC, n = 21/123, 17.1%). Statistical modelling using death as outcome measure revealed body condition, pain scores, and time budget data to be strongly associated with equine mortality. Notably, low body condition score and reduced eating time predicted mortality in DAC horses, aligning with human studies linking weight loss to frailty and increased mortality risk. Additionally, depression-like behaviours were prevalent in DAC horses, mirroring the link between depression and mortality in humans. While pain scores were elevated in all deceased horses, weight loss was specific to DAC, suggesting multifactorial influences beyond pain. These findings provide a foundation for developing equine-specific tools to predict outcomes and guide clinical and end-of-life decisions, enabling individualized treatment to enhance the welfare and quality of life for aging horses. These insights may also offer valuable information for human medicine, particularly for at-risk groups such as individuals with cognitive impairments who may struggle to communicate their symptoms.