Fatigue and cognition: Pupillary responses to problem‐solving in early multiple sclerosis patients

Abstract

IntroductionIn early multiple sclerosis (MS) patients, cognitive changes and fatigue are frequent and troublesome symptoms, probably related to both structural and functional brain changes. Whether there is a common cause of these symptoms in MS is unknown. In theory, an altered regulation of central neuropeptides can lead to changes in regulation of autonomic function, cognitive difficulties, and fatigue. Direct measurements of central neuropeptides are difficult to perform, but measurements of the eye pupil can be used as a reliable proxy of function.MethodsThis study assesses pupil size during problem‐solving in early MS patients versus controls. A difference in pupil size to a cognitive challenge could signal altered activity within the autonomic system because of early functional brain changes associated with cognitive load. We recruited MS patients (mean disease duration: 2.6 years, N = 41) and age‐matched healthy controls (N = 43) without eye pathology. Neurological impairment, magnetic resonance imaging, visual evoked potentials, depression, and fatigue were assessed in all of the patients. In both groups, we assessed processing speed and retinal imaging. Pupil size was recorded with an eye‐tracker during playback of multiplication tasks.ResultsBoth groups performed well on the cognitive test. The groups showed similar pupillary responses with a mean of 0.55 mm dilation in patients and 0.54 mm dilation in controls for all the tasks collapsed together. However, controls (N = 9) with low cognitive scores (LCS) had an increased pupillary response to cognitive tasks, whereas LCS MS patients (N = 6) did not (p < .05). There was a tendency toward a smaller pupillary response in patients with fatigue.ConclusionsThis is the first study to investigate pupillary responses to cognitive tasks in MS patients. Our results suggest that MS‐related changes in cognition and fatigue may be associated with changes in arousal and the autonomic regulation of task‐related pupillary responses. This supports the theory of a link between cognition and fatigue in MS.

Pupil light reflex evoked by light-emitting diode and computer screen: Methodology and association with need for recovery in daily life

“…We furthermore observed that higher levels of need for recovery were associated with larger ACA, BPD and DV1 (SCREEN condition) values, suggesting larger PNS activation. This result is in line with the previous finding that people with higher levels of fatigue and need for recovery tend to show smaller pupil dilation during cognitive tasks, reflecting reduced PNS inhibition [ 51 , 74 ].…”

Functional–structural relationship in large‐scale brain networks of patients with end stage renal disease after kidney transplantation: A longitudinal study

“…Fourthly, the same scales were used to assess cognitive status in our follow‐up studies and learning effects could not be avoided. Last but not least, fatigue is found to be associated with cognition in many diseases such as post‐stroke and multiple sclerosis (de Rodez Benavent et al, ; Lagogianni, Thomas, & Lincoln, ), but we did not evaluate the fatigue in ESRD patients in our study. More efforts should be made to clarify the relationship between cognition and fatigue in the future study.…”

Association of Electronic Health Record Use With Physician Fatigue and Efficiency

“…The degree of pupillary constriction during a task is a validated biomarker for fatigue and alertness. 27,28 Research has consistently shown that during conditions of fatigue, baseline pupil diameters are smaller than normal. [29][30][31][32][33] Reduction in pupil size by 1 mm has been associated with signs of tiredness.…”