And, potentially, mental health - though the variance between people is huge. While my grandfather (mother's side) was mentally as sharp as he'd ever been when he died at 92 and my 94 year old grandmother (father's side) still plays bridge several times a week and has a fantastic memory for everything related to the family, it's also all too easy to find people who have been afflicted with dementia and alzheimer's from their 70s and 80s.
Mental health in that sense is physical health - age-related mental decline is caused failure in the physical processes of the brain. E.g. loss of blood vessel integrity, buildup of aggregates, diminished stem cell activity in response to rising cellular damage, etc.
