Perhaps not everyone's dementia sufferer displays this symptom, but thought I'd post it here for those that have seen it and are concerned by it. Dad is the only dementia sufferer I have seen that does it, but then I don't sit for an hour or more with other people. Myoclonus is the medical term for what Dad does and what your loved one may do, where their body suddenly gives one quick jerk, similar to what 'normal' people do when they are fallling asleep, except the dementia sufferer can do it any time of day. If your loved one is like Dad then this only occurs on a basis that is not too disruptive. It can occur more frequently though and cause problems with balance and grasping and eyesight.... See : http://www.myoclonus.com/ for more information. Be aware that is also the name for a disease, this does not mean that if your loved one does it that they have this disease too, it can be just a symptom of brain disorders in general.