Triggers

For issues specific to caring for someone with dementia.
Following on a bit from Norrms post I wonder if my own mums decline started very quietly and slowly when my father died.
Is there any research at all on possible triggers? Does anyone think there could be any kind of link between life changing events and some kind of changes in the brain?
Vicky
Vicky, my Great Nan's decline started in 1986 when she lost her husband of 55 years and it was a rapid onset. Also my Nan had a great shock which seemed to trigger the onset of dementia. I don't know of any studies though.