The facial expression of pain in patients with dementia

The facial expression of pain has emerged as an important pain indicator in demented patients, who have difficulties in providing self-report ratings. In a few clinical studies an increase of facial responses to pain was observed in demented patients compared to healthy controls. However, it had to be shown that this increase can be verified when using experimental methods, which also allows for testing whether the facial responses in demented patients are still typical for pain. We investigated facial responses in 42 demented patients and 54 aged-matched healthy controls to mechanically induced pain of various intensities. The face of the subject was videotaped during pressure stimulation and was later analysed using the Facial Action Coding System. Besides facial responses we also assessed self-report ratings. Comparable to previous findings, we found that facial responses to noxious stimulation were significantly increased in demented patients compared to healthy controls. This increase was mainly due to an increase of pain-indicative facial responses in demented patients. Moreover, facial responses were closely related to the intensity of stimulation, especially in demented patients. Regarding self-report ratings, we found no significant group differences; however, the capacity to provide these self-report ratings was diminished in demented patients. The preserved pain typicalness of facial responses to noxious stimulation suggests that pain is reflected as validly in the facial responses of demented patients as it is in healthy individuals. Therefore, the facial expression of pain has the potential to serve as an alternative pain assessment tool in demented patients, even in patients who are verbally compromised.