"In a report published Wednesday in The BMJ, researchers say that among 1,796 people with Alzheimer’s disease and 7,184 controls, those who have used benzodiazepines showed a 51% higher risk of the neurodegenerative disorder. Among people who took the drugs more than 180 days, the risk escalated to about two-fold higher."
Of course as we all get older the body makes less melatonin and generally older people have a harder time to have quality sleep, and the article posted by North provided tantalizing ideas but no solid connection. Maybe also a chicken and egg thing.