Dementia - does your job protect you?

One of the biggest fears for many of us is this possibility of developing the insidious disease of dementia. My paternal aunt had the illness and her last years were those of confusion, which was sad for her and us. So can the profession or work that you do protect you? Researchers at Heriot-Watt University Edinburgh have suggested a correlation, but this is as we know isn't a causal explanation. A cohort of some 1,000 Scottish citizens aged 70 year old have been tested at regular intervals as part of this longitudinal study. The researchers have suggested that the legal profession, teaching and computer science all demanding of a high IQ may protect? Notwithstanding this caveat this is an area of research that is being further pursued. In addition moreover they are going onto consider a possible link, if there is one between doing work that is less intellectually demanding and the onset of dementia?
I think a more interesting area or research would be to consider whether there is or not a correlation between chronic depression and dementia. I'm not talking about an acute episode but ongoing and protracted depression over time. Endogenous and not reactive depression. My opinion is that there is such a connection as the serotonin is depressed in the brain and important mood stimulant. Furthermore there is much over prescribing of anti-depressants where the talking cure would be more efficacious and cheaper over time.