Subjective and Objective Pain Assessment in Persons with Alzheimer’s Disease and Related Dementias: Comparisons Among Self-Report of Pain, Observer-Rated Pain Assessment, and Functional Near-Infrared Spectroscopy

Pain assessment in older adults with Alzheimer’s disease and related dementias (ADRD) is challenging due to memory and judgment impairment and limited ability to report pain verbally. There is growing interest in neuroimaging technology to measure pain at the neural level, such as functional near-infrared spectroscopy (fNIRS), for monitoring cerebral hemodynamic changes. The purpose of this study was to determine whether fNIRS is a reliable objective pain measure for older adults with early-stage ADRD. We compared clinical pain scores from two subjective pain measures—self-report (Numerical Rating Scale [NRS]) and caregiver’s observational report (Mobilization-Observation-Behavior-Intensity-Dementia-2 [MOBID-2])—and objective pain-related cortical response (fNIRS). In 40 older adults (mean 73 years [SD = 7.87], 90% White, 72.5% women) with early-stage ADRD, there was a significantly moderate to strong positive correlation between (a) self-reports and caregiver observations (r =.605, p <.05), (b) NRS and fNIRS measures for channels covering left frontal superior medial (r =.552, p <.05) and right frontal superior orbital (r =.553, p <.05) areas, and (c) MOBID-2 and fNIRS covering right frontal superior orbital (r =.568, p <.05) and frontal middle right region, r =.496, p <.05. Results indicated that fNIRS can be used as a supplement to subjective pain measures for older adults with early-stage ADRD in healthcare settings. Research is needed to test validity of fNIRS as complementary to subjective measures of pain assessment for early-stage ADRD. This trial was registered at www.clinicaltrials.gov (NCT04457973). Funded by National Institutes of Health (R15NR018050).