A 2009 article that hints the causation could be due to sleep, at least in mice: http://www.sciencemag.org/content/326/5955/1005 http://www.sciencemag.org/conte

A 2009 article that hints the causation could be due to sleep, at least in mice: http://www.sciencemag.org/content/326/5955/1005 http://www.sciencemag.org/content/326/5955/1005 (see also http://en.wikipedia.org/wiki/Beta_amyloid#Circadian_rhythm_of_amyloid_beta http://en.wikipedia.org/wiki/Beta_amyloid#Circadian_rhythm_o...).