Reliability and Validity of Pupillary Response During Dual-Task Balance in Parkinson Disease.

Reliability was tested only twice on the same day within two hours, so it does not show whether the measure is stable across days. People with Parkinson disease can have within-day fluctuations in thinking and movement, which same-day testing may not capture. The comparison measure, NASA-TLX, is self-reported and collected after each task, so it may reflect the end of the task rather than workload during the task. There is no accepted gold standard for cognitive workload, so the study could not confirm validity against a definitive measure. The main total-score validity result was null; the significant mental-demand finding came from a secondary subscale analysis. Healthy controls had more years of education than participants with Parkinson disease, which may affect cognitive task performance. The eyes-closed dual-task condition had lower consistency in healthy controls, and healthy controls showed a higher pupil response at retest. Participants with Parkinson disease were mild to moderate, tested on medication, and excluded if they had dementia, mild cognitive impairment, deep brain stimulation, unpredictable fluctuations, or other balance-affecting conditions.

All authors reported no conflicts of interest. The supplied text did not state a funding source.

Do not read this as proof that pupil-based measurement is a validated clinical test of overall cognitive workload or a tool to guide balance treatment. The total self-reported workload scores did not correlate with pupil-based scores, and the only significant link was a secondary analysis of the mental-demand subscale during eyes-closed dual-task balance.