A four-year-old cat is roughly equivalent to a 32-year-old human, placing them in the early middle-age stage of life. It's important to note that being middle-aged doesn't mean a cat is old. This is a key point to remember when evaluating your cat's well-being. 
The common rule of thumb is that after the age of two, each year for a cat is approximately equivalent to four human years. Therefore, a four-year-old cat is about 32 in human years, signifying they are entering middle age. However, factors such as breed and living conditions can affect this, making this just an approximate comparison. If you notice that your cat's activity levels are decreasing compared to previous years, it’s crucial to adjust their diet to prevent obesity and reduce the risk of age-related illnesses. This middle-aged period is a good time to reassess your cat's needs and adjust their care accordingly.
How to Tell if Your Cat is Getting Older
1. Increased Sleepiness and Sensitivity to Cold
Cats are known for sleeping a lot, spending roughly two-thirds of their day asleep. However, as cats enter their senior years, their sleeping time tends to increase even more. If your cat is sleeping for most of the day and frequently seeks out warm places, such as under blankets or in sunbeams, it's likely a sign of aging. This increased desire to stay warm and sleep for longer periods are typical in senior cats. Keep an eye on these changes in your cat's habits.
2. Decreased Appetite
Generally, cats are known for their eagerness to eat, especially when it comes to their favorite foods. If you notice a significant decrease in your cat's appetite or they’re no longer finishing their meals, this can be another indicator of aging. A loss of interest in food, even for typically enjoyed treats, is a notable change and can signal that your cat is entering its senior years. It's a good idea to consult a vet if you observe these kinds of appetite changes, as they could also indicate a health issue that needs to be addressed.