The life expectancy of an indoor cat varies based on his genetics, but is averaged to be 12 to 18 years. However, improvements in medicine, vaccinations and care have led indoor cats to live over 20 years, with the oldest reported cat living to age 28.
An outdoor cat usually dies earlier due to motor vehicle accidents or run-ins with other cats or dogs. He is also more likely to be infected or fall ill than an indoor cat.
To promote good health and longevity in an indoor cat, regular vaccinations, veterinary check-ups, a balanced diet and plenty of exercise are all crucial. Also be on the lookout for changes in behavior, litter box usage or grooming that indicate illness.
As a cat ages, he becomes less able to groom himself and is more likely to develop mats, odor and inflammation. He needs to be brushed and bathed by his owner to keep his coat and skin healthy. His claws need to be clipped more as they grow more brittle. Hearing and vision loss are very common. His risk of developing kidney failure, diabetes, arthritis, hyperthyroidism and other diseases increase as he ages. Dental disease is prevalent among older cats and may deter him from eating. Like some humans, elderly cats can start exhibiting signs of dementia and senility.