What causes dementia?

It's usually poor nutrition.

I am sorry for the loss of your grandmother to this horrible disease. May she rest in peace 🧡🧡

It may seem that way because of your experience. My dad was diagnosed with Hodgkin's Lymphoma and fought for years. Then one day he decided he had enough and stopped fighting. He passed away a few months later. There have been cases of people giving up and just letting themselves shut down.

"However, Dementia is caused by changes in the brain, including abnormal buildups of proteins known as amyloid plaques and tau tangles. Frontotemporal dementia, a rare form of dementia that tends to occur in people younger than 60. It is associated with abnormal amounts or forms of the proteins tau and TDP-43.

How to reduce your risk of Alzheimer's and other dementias:

Physical activity.
Eating healthily.
Don't smoke.
Drink less alcohol.
Stay mentally and socially active.
Take control of your health."

That's all from an article I googled. Take care of yourself 🧡

No idea what causes dementia but a fairly similar thing happened with my grandmother. One day she just kind of gave up on living, flat out said she was ready for the grave, and kind of wilted away like a dying flower. It was really disturbing. Just sat there, stopped talking, health failing, and it went on for years until she finally passed. Family tried everything imaginable to keep her engaged. She just threw in the towel.

We can land probes on comets but the human brain is still pretty much a mystery.

My great grandmother sat down in a rocking chair on the front porch, said "I've seen the Atlantic Ocean, and I've seen the Pacific Ocean. I guess I can rest now", laid her head against the back of the chair, fell asleep, and never woke up. It was like she just decided it was time to check out.

In Bruce Willis' case, it has recently been speculated that an injury that he sustained on the set of the film Tears of the Sun could likely be a contributing factor:
https://www.theguardian.com/film/2004/nov/24/news1

Bruce Willis is suing the makers of his 2003 action movie Tears of the Sun for injuries allegedly sustained on the set of the film.

Willis's lawsuit against Revolution Studios claims that he suffered "extreme mental, physical and emotional pain" after an on-set incident in October 2002 when he was struck on the forehead by a "projectile" during the detonation of pyrotechnics by the film's special effects unit.

The lawsuit did not further specify the nature of Willis' injuries, but accuses Revolution and its special effects foreman Joe Pancake of incompetence in maintaining his safety. The financial damages sought by the actor are not specified, but the suit does claim that Willis "was required to and did employ physicians and other medical personnel," and that he will incur more medical expenses in the future relating to the incident.

You're right that one of the causes of dementia is losing purpose in life. Maybe in Bruce's case he spent the last 30-40 years on TV and movie sets. The endless hours sitting around, the stress of having to constantly perform, along with lack of exercise and sleep is very toxic to the body. I also believe Bruce used to drink very regularly.

In short, it's very possible Bruce's lifestyle was the cause of his dementia.

Tell ya, when I want serious medical info, I come to a fucking movie message board to get it. That’s how much I really want to know.