What conditions can increase my cat's risk of a reaction under anesthesia?

Obesity's a big one in our cats. Many of our indoor cats are overweight, and so that's an increased risk for them. It's harder to breathe, harder to recover, and they take longer to recover. So that's a big one. Other ones would be age is not necessarily a disease, but we know that they can handle things differently. And the older the pet, the more likely it is that another illness is going on, like kidney disease or thyroid disease in our cats.