In the adult learning environment, nodding off in class happens occasionally. Before rushing to the teaching style as the culprit, we've found talking to the student about what s/he believes is causing the problem is very helpful. Much of the time we find it's not so much the need to use a different visual aid, but more so, the challenges outside of school that can cause sleep deprivation. Financial difficulties, arguing with spouse/children, caring for a sick child or aging parent, or simply having to work while attending school are common reasons for the inability to remain awake in a classroom environment. I do agree wholeheartedly it is vitally important to "mix it up" and ensure students are engaged in the material presentation whenever possible. But, to really get to the heart of at least some percentage of the root cause, a faculty member or administrator may have to dig deeper to find ways to assist in a grander sense.