As Alzheimer's disease progresses towards the later stages, the ability of the affected person to communicate becomes increasingly compromised. Caregivers can no longer ask "are you comfortable?" or, "are you in pain?" and get a reliable answer. A caregiver has to interpret what behavior means. Are shouts, screams, severe withdrawal, aggression, due to confusion, something else, or are they signs of pain?

The way in which we experience pain differs. Pain is a subjective experience. People...