Orginal article
Cognitive Reserve and Symptom Experience in Multiple Sclerosis: A Buffer to Disability Progression Over Time?

Presented as a poster to the European Committee for Treatment and Research in Multiple Sclerosis, October 10–13, 2012, Lyons, France.
https://doi.org/10.1016/j.apmr.2013.05.009Get rights and content

Abstract

Objective

To investigate the possible buffering effect of cognitive reserve on symptom experience for multiple sclerosis (MS) disease course.

Design

Secondary analysis of longitudinal data from the North American Research Committee on MS Registry.

Setting

Registry study and web-based supplemental survey.

Participants

People with MS (N=859).

Interventions

Not applicable.

Main Outcome Measures

Two health outcome measures, the Symptom Inventory and the Performance Scales, were collected biannually over 1 and 6 years, respectively. Active and passive cognitive reserve was measured using the Stern Leisure Activities and the Sole-Padulles Childhood Enrichment tools, respectively. Linear regression, chi-square, multilevel random-effects modeling, and classification and regression tree modeling were used to compare cross-sectional means, disease course by cognitive reserve, longitudinal trajectories, and active cognitive reserve item endorsement by disability groups, respectively.

Results

Patients with high-active reserve had a lesser symptom burden than those with low-active reserve independent of passive reserve (P<.01). Cognitive reserve was associated with course of disease, such that high-active patients were overrepresented among relapsing-remitting patients, and underrepresented among patients with progressive disease (χ2=14.7, P<.03). Longitudinal modeling revealed a significant interaction of active reserve and time in mobility, fatigue, and overall disability in the whole sample (P<.05 in all comparisons). Among patients whose disability trajectories changed over time, active cognitive reserve was associated with less deterioration (P<.001). Passive cognitive reserve evidenced no effect in the longitudinal analyses. Active cognitive reserve scores across disability groups had a similar range but comprised different items, indicating that patients maintain active cognitive reserve with different activities as the disease progresses.

Conclusions

Our findings suggest that active cognitive reserve is a buffer for functional limitation across disability groupings. Cognitive reserve may provide an alternative lens for thinking about the disease course of MS, providing a longer “runway” until disability accrual through cortical remodeling. Loss of cognitive reserve may explain the onset of progressive disease in MS.

Section snippets

Sample and design

This project involved secondary analysis of longitudinal data from 859 people who provided data in a supplemental survey to the North American Research Committee on Multiple Sclerosis (NARCOMS) Registry. This self-report registry includes more than 36,000 individuals 18 years or older, reporting clinician-diagnosed MS. Participants are not paid to be part of NARCOMS, but rather volunteer to participate to expedite MS research. The registry supports a host of epidemiologic studies. The

MS health outcomes

Three disease-specific health outcome measures were selected on the basis of their documented reliability and validity, as well as their availability in this existing data set. They included (1) the Symptom Inventory disability-specific short forms, a 10-subscale measure of MS symptoms that focuses on discriminating levels of disability in mobility, use of assistive devices, hand function, vision, fatigue, cognition, bowel/bladder, spasticity, sensory, and vasomotor symptoms10, 11, 12; (2) the

Sample description

Table 1 shows the sample demographic characteristics. Participants in the study sample had a mean age of 54 years, and 74% of the participants were women, which is consistent with the sex distribution in MS.24 Less than half of the sample was employed, with a median annual household income between $50,000 and $100,000 in the whole sample.

A comparison of cognitive-reserve group differences (see table 1) suggests that the groups differed in terms of proportion of women (P<.03), mean age (P<.001),

Discussion

Our findings suggest that active cognitive reserve appears to be associated with a milder disease course based on cross-sectional and some longitudinal analyses. Patients with MS who have high-active cognitive reserve report a significantly lower symptom burden. Further, among those patients whose disability changed over time, the high-active reserve patients showed less deterioration (negative β coefficient) over time than those with low active reserve. Active reserve may thus be a buffer for

Conclusions

In summary, our findings support the idea that active cognitive reserve is a buffer against symptom burden and onset of progressive disease. Because of the above-mentioned study limitations, our study findings cannot confirm causal relationships but rather can generate hypotheses that must be tested and replicated in other MS samples. Future research should test the hypotheses generated by the present work. We believe that active cognitive reserve is something that individuals can be assisted

Suppliers

  • a.

    Stata Statistical Software, Release 12; StataCorp LP, 4905 Lakeway Dr, College Station, TX 77845.

  • b.

    The R Foundation for Statistical Computing, Vienna, Austria. Available at: http://www.r-project.org.

Acknowledgments

We thank Gary Cutter, PhD, Stacey Cofield, PhD, and Rita Bode, PhD, for data management services early in the project; and Ruth Ann Marrie, MD, PhD, and Robert Fox, MD, for helpful comments on an earlier draft of this manuscript.

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    Dr. Schwartz received research support from the National Multiple Sclerosis Society and the Foundation of the Consortium of Multiple Sclerosis Centers. Part of the data collected for this work was provided in the context of a Consortium of Multiple Sclerosis Centers/Global Multiple Sclerosis Registry Visiting Scientist Fellowship to Dr. Schwartz, which was supported through a Foundation of the Consortium of Multiple Sclerosis Centers grant from EMD Serono, Inc. Consortium of Multiple Sclerosis Centers/Global Multiple Sclerosis Registry is supported by the Consortium of Multiple Sclerosis Centers and its Foundation. Dr. Healy receives research support from Merck Serono S.A. Dr. Benedict receives Continuing Medical Education support from Teva and EMD Serono; research support from Shire, Accorda, and Biogen; consultancy or AdvBoard support from Bayer, Biogen, Novartis, Actelion, and MedImmune; and royalties from Psychological Assessment Resources, Inc. In the past 2 years, Dr. Vollmer has received honoraria for serving on scientific advisory boards, or as a consultant from Teva Neuroscience, Biogen Idec, Elan Pharmaceuticals, Hoffman LaRoche, Accelerated Cure Project, MedicalLogix, Xenoport, PRIME Education, Projects in Knowledge, Guidepoint Global, Esai Pharmaceuticals, Sanofi-Aventis, Novartis, Schering-Plough, Buffalo Neurological Institute, Consortium of Multiple Sclerosis Centers, Acorda Pharm, and research support from Acorda Therapeutics, Biogen Idec, Teva Neuroscience, Genzyme, Ono Pharmaceuticals, Eli Lilly, Novartis, Elan Pharmaceuticals, National Institutes of Health, Biosite, Daiichi Sankyo, Rocky Mountain Multiple Sclerosis Center, and Jansen Research & Development.

    No commercial party having a direct financial interest in the results of the research supporting this article has conferred or will confer a benefit on the authors or on any organization with which the authors are associated.

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