Cats and dogs are living longer, thanks to better medicine and nutrition, and you are likely seeing more senior and geriatric or end-of-life pets in your practice as a result. The science of gerontology is young in veterinary medicine, but one of the aspects that is becoming important in assessing and caring for older animals is the newly emerging concept of frailty.
Frailty is defined as a state of increased vulnerability in multiple ways that can lead to adverse health outcomes. In humans, for instance, people who are frail may have such signs as weakness, exhaustion, a slow gait, poor balance, and cognitive impairment. They are at increased risk for falls, broken bones, disability, hospitalization, and death.
Gerontologists can assess human patient risk using a frailty index (FI), which is an indicator of how well a person will rally after a catastrophic event, such as a broken hip and subsequent surgery. Veterinarians are seeking to develop a similar instrument for dogs and cats, which could help them better inform clients about a pet’s condition, prognosis and options, whether they need surgery or are facing a serious illness.
“We see a lot of the weak and wobbly, as we call them,” says Sheilah Robertson, BVMS, PhD, DACVAA, DECVAA, DACAW, DECAWBM (WSEL), FRCVS. In her end-of-life practice as medical director for Lap of Love, Dr. Robertson sees patients with decreased function reserve, or immunosenescence. They are less resilient, therefore less able to combat the stressors of daily life, making them more vulnerable to adverse medical outcomes. “If they lose fluids or bleed or they’re stressed or exposed to infection, they have less of a reserve to call on,” she says.
Development of a frailty instrument would be an opportunity to talk to clients about quality of life in an objective way, says Dana Varble, DVM, CAE, chief veterinary officer for Veterinary Meeting & Expo. Further, this can help track patient condition using a more objective scale: Is it changing? Is it getting worse? How has the animal’s lifestyle changed? Sometimes the love and connection between pets and people can cloud how clients are seeing their animals age and the progression of their condition.
“We’re looking at quality of life in a more holistic sense,” Dr. Varble says. “It used to be ‘If they’re eating, they must be happy,’ but we know that’s not true. Some dogs will eat regardless of the disease process, whether or not they’re in pain, and other pets don’t eat because it’s Tuesday and they didn’t feel like it. We know we need a more holistic score than just a few parameters.”
How a frailty scale might work
Research is being done to assess frailty in older dogs and develop frailty scoring for both cats and dogs. The senior care guidelines1 issued in 2021 by the American Association of Feline Practitioners (AAFP) note, as with human frailty scales, a cat or dog FI should be able to identify frail subjects, supported by a biologic causative theory, and reliably predict adverse clinical outcomes and patient response to therapy and stressors.
According to the guidelines, a “frailty prevention model” would have three levels of intervention: primary, with the goal of minimizing risk factors and disease onset; secondary, delaying progression of disease; and tertiary, reducing or limiting impairment. For senior cats, the focus is on the third level.
“With improved identification of frailty, we can establish corrective actions, physiologically and psychologically,” the guidelines state. “With increased awareness and recognition, predictive factors can be identified.”
A study for cats,2 conducted by Tony Buffington, DVM, PhD, DACVN, is underway to create such metrics.
On the canine side, an Italian study3 looked at 401 dogs of various breeds with a mean age of 8.64 and a range of two to 19 years. Researchers calculated a frailty index using a checklist of 33 health deficits (found in Annex 1 of the study). They also recorded information including age, sex, breed, weight, body condition score, diet, and vaccination status. The FI showed moderate accuracy in prediction of short-term mortality, according to study results.
An earlier French study4 evaluated 116 guide dogs with a median age of nine years and an age range of five to 13 years, using a score sheet assessing 38 items over 13 body systems: cutaneous, digestive, respiratory, cardiovascular, urinary, genital, ocular, musculoskeletal, neurologic, oral cavity, general condition, behavior and oncological status. One of their findings was poor mobility and low physical activity were significantly associated with time to death.
A Texas A&M study,5 in partnership with the Dog Aging Project (DAP), and published last June, reviewed frailty instruments in human medicine, sought to define frailty, and dug into the potential components and applications of a frailty index in dogs—or FIDo. Unlike human frailty evaluations, however, assessments for companion animals rely heavily on owner-reported information. That means a frailty instrument should be low-tech and low-cost, says the study’s lead author, Rachel L. Melvin, DVM. Clients should be able to complete it in less than 15 minutes with no need for expensive diagnostics. Whatever method is used to evaluate frailty, some common conditions can signal it.
Potential signs of frailty
Phenotypical (such as weight loss, weakness, slowness), physiological (for example, ataxia), and psychological factors (cognitive or social function deficits) can all contribute to identification of frailty.
Unintended weight loss and the accompanying loss of muscle mass, or sarcopenia, is common in aged animals. Muscle condition is important as mammals age, and monitoring this can help to assess the progress of deterioration. Sarcopenia occurs in all mammals as they age. However, the degree is variable depending on lifestyle—active or inactive—and other things, such as good-quality nutrition. Intervention to slow its progress is based on exercise and nutrition. Dr. Robertson recommends recording not only body condition score, but also muscle condition score, starting with a patient’s first visit. The World Small Animal Veterinary Association (WSAVA) has tools on its website for assessing both body6 and muscle7 condition.
Weight loss is particularly common in aging cats. In a January 2024 EveryCat Health Foundation webinar on the role of diet in feline kidney disease, Dottie Laflamme, DVM, PhD, DACVN, raised the question of whether maintaining weight and lean body mass can delay morbidity and mortality. She noted based on at least one study,8 by Carolyn J. Cupp, DVM, MS, the answer is yes. Dr. Cupp followed 90 senior cats through the natural end of their life and found preservation of body weight, lean body mass and body fat all helped to prolong their survival during the course of the study.
Mobility is a good measure of physical function. In humans and rodents, slower walking speeds have been shown to be predictive of worse postoperative outcomes, morbidity, and mortality. The DAP FIDo may include times to traverse a measured distance on- and off leash over a flat surface. Owners should be able to perform low-tech assessments of their dogs’ speed with minimal training and obtain accurate measurements.
In cats, mobility changes include jumping patterns, house-soiling, changes in sleeping locations, and increased sleeping time. The double whammy of joint disease and muscle weakness can play a role in all of those.
Strength is another metric. In humans, grip strength is measured, but since pets lack opposable thumbs, an alternative suggested by the Texas A&M researchers might be a timed stair ascent, a routine and accessible activity for many dogs.
Finally, cognitive function may be evaluated. While the relationship between frailty and mild cognitive impairment is not completely understood, the ability to perform simple tasks, such as recalling the location of a food item after delays may give insight into a pet’s level of frailty. The assessment would be performed at home by the client through an interactive online survey. Clients might also answer such questions, such as, “How often does your dog stare blankly at the walls or floor?” or “Compared with six months ago, does your dog have difficulty finding food dropped on the floor?” The answers could help to detect early, mild changes in cognitive performance.
While chronological age cannot be reversed, frailty may be manageable.
“The first step is being able to detect frailty,” Dr. Melvin says. “Once we can detect it, then we can intervene. We’re in the young stages of introducing this into veterinary medicine, but our ultimate hope is that it can be reversed as it is in humans or at least managed to
some degree.”
Kim Campbell Thornton has been writing about dogs, cats, wildlife, and marine life since 1985, and is a recipient of multiple awards for her articles and books from the Cat Writers Association, Dog Writers Association of America, and American Society of Journalists and Authors.
References
- https://catvets.com/guidelines/practice-guidelines/senior-care-guidelines
- https://everycat.org/grant/w20-044-development-and-initial-validation-of-a-frailty-scale-for-domestic-cats/
- Banzato, T, Franzo, G, Di Maggio, R, Nicoletto, E, Burti, S, Cesari, M, Canevelli, M. A Frailty Index based on clinical data to quantify mortality risk in dogs. Scientific Reports 9 16749 (2019).
- Hua, J, Hoummady, S, Muller, C, Pouchelon, J-L, Blondot, M, Gilbert, C, Desquilbet, L. Assessment of frailty in aged dogs. AJVR, Vol. 77, No. 12, December 2016.
- Melvin, RL, Ruple, A, Pearson, EB, Olby, NJ, Fitzpatrick, AL, Creevy, K. “A review of frailty instruments in human medicine and proposal of a frailty instrument for dogs.” Front. Vet. Sci., 27 June 2023.
- https://wsava.org/wp-content/uploads/2020/01/WSAVA-Nutrition-Assessment-Guidelines-2011-JSAP.pdf
- https://wsava.org/wp-content/uploads/2020/01/Muscle-Condition-Score-Chart-for-Cats.pdf
- Cupp, CJ, Jean-Phillipe, C, Kerr, WW, Patil, AR, Perez-Camargo, G. Effect of Nutritional Interventions on Longevity of Senior Cats. Intern J Appl Res Vet Med. Vol. 5, No. 7, 2007.