A psychophysical investigation of the facial action coding system as an index of pain variability among older adults with and without Alzheimer's disease

Objective. Reflexive responses to pain such as facial reactions become increasingly important for pain assessment among patients with Alzheimer's disease (AD) because self-report capabilities diminish as cognitive abilities decline. Our goal was to study facial expressions of pain in patients with and without AD. Design. We employed a quasi-experimental design and used the Facial Action Coding System (FACS) to assess reflexive facial responses to noxious stimuli of varied intensity. Two different modalities of stimulation (mechanical and electrical) were employed. Results. The FACS identified differences in facial expression as a function of level of discomforting stimulation. As expected, there were no significant differences based on disease status (AD vs control group). Conclusions. This is the first study to discriminate among FACS measures collected during innocuous and graded levels of precisely measured painful stimuli in seniors with (mild) dementia and in healthy control group participants. We conclude that, as hypothesized, FACS can be used for the assessment of evoked pain, regardless of the presence of AD.