Having a cat upstairs can indeed have some impact on the downstairs neighbors. These include:
1. Cats running, jumping, or being active at night can generate noise, especially on hardwood floors, where the noise can be more noticeable and disturb the rest of downstairs residents.
2: If the upstairs cat owner does not clean the litter box in time, or if the cat's excrement is not disposed of properly, it may produce an odor, causing discomfort to the downstairs residents.

3. If the cats upstairs are not adequately supervised, they may enter the downstairs area through windows or balconies, posing a safety hazard to the residents downstairs.
Therefore, for the sake of harmonious neighborly relations, pet owners should take appropriate measures to reduce these impacts.