Associations between quality of life, cognitive capacity of information processing and attention in patients with multiple sclerosis Foto: Peter Senko (2018)

Introduction

Multiple sclerosis (MS) is a chronic disease characterized by an unpredictable course. Damage occurring in this chronic illness primarily affects the central nervous system (CNS). It manifests as changes in the gray and white matter of the brain and spinal cord, leading to demyelination of axons and their subsequent damage. The most common initial symptoms include optic neuritis, paresthesias, motor problems of the upper and lower limbs, cerebellar disorders, vertigo, urinary and bowel disorders, sexual problems, fatigue, depression, pain, and cognitive disorders (Havrdová, 2002).

MS often starts to show symptoms early in adulthood, around age twenty, and affects more women than men, in a ratio of 2:1. Its etiology is still not fully understood, and there is still no medication that can successfully cure this disease. The course of this disease is highly individual (Dennison et al., 2009). In patients with MS, periods with symptom manifestations, called relapses, alternate with periods when these symptoms are absent (Murray, 2006).

This disease affects many areas of life, from sensory functions to social relationships. The physical limitations brought by MS are evident in everyday basic activities such as dressing, eating, bathing, or traveling. Fatigue, one of the most commonly reported symptoms of this disease, may also affect patients' hobbies or leisure activities (Edmonds et al., 2007). Changes in patients' ability to work due to a worsening health condition are particularly distressing for patients with a chronic disease. All these changes require psychological adaptation to the altered situation. Fear of losing independence, lack of understanding from loved ones, or changes in previous functioning generate questions and doubts about the patient’s psychological identity and negatively affect health-related quality of life in patients with MS (Edmonds et al., 2007; Nagyová, 2005). Quality of life is a multidimensional concept that includes both physical and mental components. In the case of MS, this concept is especially relevant, as the physical limitations that characterize this disease are closely linked to psychological and social functioning as well (Kircher and Lara, 2011).

Another area affected by an MS diagnosis is patients’ cognitive functioning. Research and clinical practice indicate that people with MS score lower than healthy populations on several neuropsychological tests (Scherder et al., 2017; Hanneghan et al., 2017). Patients with longer disease duration usually show more pronounced reductions in cognitive functioning compared to patients who have had the disease for a shorter period (Roy et al., 2017). These cognitive changes concern both information processing capacity and sustained and divided attention.

The aim of this paper is to gain insight into cognitive information processing, attention, and their association with physical and mental quality of life in patients with multiple sclerosis. We assumed that these two constructs would be related, and that this association could be useful in disease management aimed at improving the functional status of people with multiple sclerosis.

Methods Patients sample and study procedure The patient sample consisted of people diagnosed with multiple sclerosis who attended the Neurological Clinic of the Louis Pasteur University Hospital in Košice, covering the Eastern Slovak region. A total of 214 patients were invited, of whom 58 refused participation (24 men and 35 women), corresponding to 72.9% of participating respondents. Exclusion criteria were cognitive deficit (Mini-Mental State Examination score <24), pregnancy, and age below 18 years. Based on these criteria, one participant was excluded from the study. All patients provided written consent to participate in the study, which had been approved in advance by the ethics committee of UPJŠ LF. Data collection consisted of self-report scales provided to patients during their visit to the neurological clinic, cognitive-neurological tests administered by a trained psychologist, and neurological assessment of functional status through Kurtzke’s scale (Kurtzke, 1983).

Methodological procedures SF-36 Health-related quality of life was assessed by the SF-36 questionnaire (36-item Short-Form health survey) (Ware and Sherbourne, 1992). The SF-36 consists of eight scales, with four scales related to physical quality of life (physical functioning; physical roles; bodily pain; general health) and four related to mental quality of life (vitality; social functioning; emotional roles; mental health). The raw score of this scale is transformed into a 100-point scale, where 0 indicates very poor and 100 indicates optimal health-related quality of life.

Paced Auditory Serial Addition Test (PASAT) This auditory test, focused on serial addition of numbers at a regular pace, is a cognitive function test that evaluates speed and flexibility in auditory information processing, as well as mathematical ability. It was originally developed by Gronwall in 1977 to monitor rehabilitation in patients with mild head injuries (Gronwall, 1977). It was later adapted for use in patients with MS (Rao et al., 1989). PASAT is administered to patients using a CD player. Single-digit numbers are presented every 3 seconds in this test, and the patient’s task is to add each new number to the one presented immediately before it. The obtained score corresponds to the number of correct sums and can reach a maximum of 60 points, with higher scores indicating better cognitive functioning.

Expanded Disability Status Scale (EDSS) The Kurtzke Expanded Disability Status Scale (EDSS) is the most commonly used scale for assessing functional status in patients with MS. It evaluates the level of impairment in eight functional systems of the central nervous system, and the score for each system is compared with standards for patient mobility (Kurtzke, 1983). Scores on this scale range from 0.0 to 10.0, with higher scores indicating greater functional limitation.

Statistical analyses The first step of the statistical analysis was descriptive evaluation of the sample using frequencies and arithmetic means. We then used regression analysis to examine associations between physical and mental quality of life as dependent variables and cognitive information processing capacity as an independent variable. Age, sex, highest completed education level, disease duration, and EDSS served as control variables. Statistical analyses were performed in IBM SPSS 23.

The study sample consisted of 155 patients, of whom 117 were women (75.5%); mean age was 40.12±9.75 years, and mean disease duration was 7.54±5.74 years. Results of the descriptive analysis are shown in Table 1.

Table 2 describes correlations among the variables under study. Significant correlations were observed among age and disease duration, EDSS, PASAT, and physical quality of life (PCS). Other statistically significant correlations concerned particularly the relationship between functional disability measured by Kurtzke’s EDSS and physical quality of life, as well as with disease duration.

In the first regression model (Table 3) for PCS, age (β=-0.20, p≤0.05) and EDSS (β=-0.58, p≤0.05) were the only variables significantly associated with the dependent variable. In the model where MCS was the dependent variable, after including all variables in the analysis, a significant result was observed only for PASAT (β=0.23, p≤0.05). The final model explained 38% of the total variance of the dependent variable PCS, and in the MCS model the explained variance was 5%.

Discussion

The purpose of our study was to determine whether associations exist between physical and mental quality of life in patients with MS and cognitive information processing capacity and sustained attention measured by PASAT. Cognitive functioning changes in patients with MS involve several areas corresponding to functional changes in the central nervous system. Memory and attention in information processing are among the most commonly affected domains (Hanneghan et al., 2017), while attention is a key cognitive function involved in handling the PASAT test. The statistical analyses in this study did not find associations between physical quality of life and information-processing cognitive functions and attention, which is consistent with conclusions of other authors (Pavsic et al., 2015; Shawaryn et al., 2002), who did not observe cognitive improvements in pharmacological interventions, while they did observe improvements in motor functions. However, one cognitive function that appears to be at least partly modifiable by pharmacological interventions is attention (Kunkel et al., 2015). Variance in mental quality of life was explained at the 5% level by cognitive information processing capacity and sustained attention. Other researchers also highlight the role of education (Scarpazza et al., 2013) and its association with cognitive changes. A similar association was observed in our sample only before adding the PASAT variable to the analyses, but the potential may be used to improve mental quality of life, which shows an association with cognitive functions even when controlling for important clinical variables such as duration of MS and functional status measured by EDSS. An educational program aimed at improving cognitive functioning could have the potential to indirectly affect patients’ mental quality of life. Such a program should, in addition to supporting cognitive functioning, focus on coping strategies, mental health, social participation, prevention of social isolation, and other factors related to mental quality of life, thereby increasing the chance of improving MCS (Vasileiou et al., 2017; Costa et al., 2017; Mikula et al., 2014).

Among the limitations of this study, we include the cross-sectional character of the data, which cannot establish causality between variables, and a substantially higher proportion of women in the sample, which although consistent with the prevalence of MS in the population, also means that our results may describe the situation of women better than men with this disease.

Conclusion

The findings of this study could be used in creating an intervention program focused on mental quality of life in people with multiple sclerosis, targeting non-pharmacological interventions involving variables such as coping or social participation, which do not respond to pharmacological treatment but are key factors in mental quality of life, which is associated with cognitive information processing capacity and sustained attention.

This work was supported by the Research and Development Support Agency under contract no. APVV-15-0719 (50%) and the Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic and the Slovak Academy of Sciences under contract no. VEGA 1/0594/17 (50%).

Authors: Mgr. Pavol Mikula, PhD. Ústav sociálnej a behaviorálnej medicíny LF UPJŠ, Košice MUDr. Marianna Vitková, PhD. Neurologická klinika, LF UPJŠ, Košice doc. MUDr. Jarmila Szilasiová, PhD. Neurologická klinika, LF UPJŠ, Košice Mgr. Iveta Nagyová, PhD. Ústav sociálnej a behaviorálnej medicíny LF UPJŠ, Košice Bibliography

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