Alice M. Wolf, DVM, Diplomate ACVIM (Internal Medicine), Diplomate ABVP (Feline)
Owners often ask us to compare "cat years" to human years. A figure that is commonly used is 7 cat years for each calendar year. However, this rule of thumb is not completely accurate. Feline development through puberty to young adulthood is accomplished over a period of about 18 to 24 months rather than 21 years as in humans. Thus, the cat's first calendar year is more like 16 human years and the cat's second calendar year is more like 5-7 human years (up to an equivalent age of 21 to 23 years in humans). After that, add about 4 years for each calendar year of cat life. Thus, an 8-year-old cat is like a 46 year old person. A ten-year-old cat would be 54, a 15-year-old cat 74, and a 20-year-old cat, 94 cat years of age. Experts differ as to when one would consider an aging cat to be "geriatric", but you can select your own cut-off based on this comparison to the equivalent age in humans.
MORBIDITY AND MORTALITY
The feline patient population is getting older as advances in animal health care and nutrition as well as lifestyle changes (more indoor only cats) have enhanced longevity. An AVMA survey in 1996 showed that animals over 6 years of age now comprise 47% of the average practice population. It is likely that this graying of our feline patient population will continue. The most common causes of death in aged cats include renal failure, cancer, and infectious disease.2 In contrast, the most frequent causes of death among old dogs are cardiac failure, cancer, and renal failure.
Common chronic diseases of aged cats include hyperthyroidism, inflammatory bowel disease, renal insufficiency, diabetes mellitus, degenerative joint disease, periodontal/dental disease, and feline immunodeficiency virus (FIV) infection.2-5 All of these recognized disease conditions provide opportunities for veterinary management that will improve the health of affected patients and improve the quality of life as well as quantity of life.
Each veterinarian and practice should develop a logical approach to evaluation of the geriatric cat so that abnormalities can be detected in an early, treatable stage. In addition to being consistent with the practice philosophy and appropriate health care objectives, each geriatric care program should be evaluated from the cat owner's perspective to be affordable, within the owner's ability to comply with recommendations, and consistent with the owner's philosophy of the level of care they want for their pet.6-8
Each clinician should decide if a thorough annual examination and evaluation is sufficient for an apparently healthy senior cat or if it would be best to recommend examination as frequently as every 4-6 months for such apparently healthy patients. Some feline practitioners recommend blood pressure evaluation as part of this routine examination. However, obtaining accurate blood pressure measurements in cats is often problematic. I do not believe that essential hypertension (hypertension without underlying disease such as renal insufficiency or hyperthyroidism) is sufficiently common in cats to warrant this additional patient stress and owner expense.9-12 For patients with chronic problems that are already receiving medical care, reevaluation should obviously be scheduled as indicated by the specific condition and the patient's response to management.
If you plan to include laboratory evaluation as part of the routine yearly healthy geriatric patient evaluation, the following are recommended:
Complete blood count
Serum biochemistry profile with electrolytes
Complete urinalysis (collected by cystocentesis because bacterial UTI, although uncommon in cats, is more likely in older patients)
Serum total T4 and/or free T4
A minimum alternative to this complete laboratory evaluation might include:
Urine specific gravity and dipstick chemistry evaluation
Packed cell volume and total protein
Blood urea nitrogen and creatinine
Alanine aminotransferase, serum alkaline phosphatase, gamma glutamyl transferase
Other tests should be considered for selected patients. Feline leukemia virus (FeLV) antigen and FIV antibody tests are always recommended for sick patients and should be considered for healthy animals that are outdoor or indoor/outdoor pets with possible exposure to these retroviruses. Fecal examination for parasites may be important for cats with outdoor exposure. Thoracic radiographs, and further cardiac evaluation (electrocardiography, echocardiography) may be recommended for cats with apparent pulmonary signs, or cardiac murmurs or arrhythmia.
AAFP GERIATRIC PRACTICE RECOMMENDATIONS
The American Association of Feline Practitioners (AAFP) has recently completed a major panel review documenting recommendations and suggestions for practitioners interested in improving the health maintenance and management of older feline patients. Most of this information is contained in the document above but is expanded in the AAFP document. Copies of this document have been published and are available from the AAFP/Academy of Feline Medicine.
References are available upon request.