senility (n.), senile (adj.)

https://doi.org/10.1351/goldbook.12069
Characteristics typically associated with old age, especially relating to memory loss and other mental impairment.
See also: dementia
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 904 [Terms] [Paper]