What is the relevance of quality of life assessment for patients with attention impairment?

The use of self-reported outcomes in subjects with cognitive dysfunction is of particular concern [1]. The main argument against using self-reported quality of life (QoL) information from patients with cognitive dysfunction is that QoL instruments were not developed for use with cognitively impaired individuals. Some authors argue that cognitively impaired individuals suffering from multiple sclerosis (MS) are unable to produce valid QoL measures [2, 3], whereas other studies have suggested that cognitive decline in these patients does not compromise the reliability/validity of self-reported health measures [4‐7]. In these previous studies, the assessment of cognitive function focused on aspects of memory [5, 7] and executive functions [6].

Attention plays a role in cognitive processing and learning. Attention as a basic cognitive function represents an essential part of conscious perception and higher order cognitive functions and plays an important role in normal functioning. Attention is a broad term that is used to designate the processes that mediate the appropriate allocation of cognitive resources to relevant stimuli, such as objects, locations or moments. The limitation of this capacity may result from deficits in the automatic or controlled processing of information, as well as the incapacity to store and manipulate temporary information, the function known as working memory. In MS patients, cognitive performance is globally affected and impacts divided attention, focused attention, sustained attention, attentional flexibility, and response speed [8, 9]. Despite the high occurrence of working memory and attention disturbances in MS patients [10, 11], even during the early stages of the disease [12], no study has specifically examined the extent to which MS patients with attention dysfunction can validly self-report their QoL. Herein, we provide new evidence regarding the suitability of using self-reported QoL information in this impaired population. The aim of this study was to explore the construct validity, reliability and external validity of a MS-specific QoL instrument in MS subjects with or without attention impairment.

This study relied on a cross-sectional design and was performed in the neurology department of a public French academic teaching hospital (Marseille, France). The inclusion criteria were as follows: a MS diagnosis according to the McDonald criteria [13], age ≥ 18 years, any subtype of MS, outpatient status, no neurological disease (other than MS), no history of severe mental illness (except depressive disorder), no dementia (Mini Mental State Examination score < 24), no history of alcohol/drug abuse, and native French-speaking. The French Ethics Committee approved the study (Comité Consultatif de Protection des Personnes dans la Recherche Biomédicale, Marseille 2, France) and patients gave their written consent to participate. Sociodemographic (age, gender, marital status, education level, and occupational activity) and clinical (MS subtype and disease duration) data were recorded for each patient. MS disability was assessed using the Expanded Disability Status Scale (EDSS).

QoL was assessed using the French version of the Multiple Sclerosis International Quality of Life questionnaire (MusiQoL) and the Short Form 36 (SF36). The MusiQoL is a well-validated MS-specific questionnaire that describes the nine dimensions and yields a global index score: activity of daily living (ADL), psychological well-being (PWB), symptoms (SPT), relationships with friends (RFr), relationships with family (RFa), relationships with health care system (RHCS), sentimental and sexual life (SSL), coping (COP), and rejection (REJ). The SF36 is a generic questionnaire [14] describing eight subscales: physical function (PF), social function (SF), role physical (RP), role emotional (RE), mental health (MH), vitality (V), bodily pain (BP), and general health (GH). Two composite scores (physical and mental, PCS-SF36 and MCS-SF36) were also calculated.

Attention performance was measured using two tests: the French version of the Paced Auditory Serial Addition Test (PASAT) [15] and the attention/concentration subscale of the French version of the Wechsler Memory Scale (attention_WMS) [16]. The attention_WMS score was calculated using 3 subtests (mental control, digit span, and visual memory). By comparing with French normative values according to age group [16], a patient was considered cognitively impaired if their score was more than 1 standard deviation (SD) below the normative value. The PASAT score was generated using the PASAT-3 s version of the test (number of correct responses). By comparing with French normative values according to sex, age, and educational level [17], a patient was considered to be cognitively impaired if their PASAT score was more than 1 SD below the normative value.

A total of 124 patients participated in the study. The mean age was 45 years (SD 11), 71 (57,3%) of the patients were women, and 58 (47,2%) had more than 12 years of education. MS subtypes included 61 (49,2%) secondary progressive, 36 (29,0%) relapsing-remitting, 20 (16,1%) primary progressive, and 7 (5,6%) clinically isolated syndromes. The EDSS median was 4.75 (minimum 1.00, maximum 8.00), and the median disease duration was 9.86 years (minimum 0, maximum 31). After comparison to the French normative values, 75 non-impaired and 39 impaired individuals were identified based on the attention_WMS, and 32 non-impaired and 73 impaired individuals were identified based on the PASAT.

As reported in previous studies [4, 6, 7, 24], our results support the conclusion that cognitively impaired MS patients, as defined by attention dysfunction, reliably and consistently answer the MusiQoL questionnaire. The suitability indices of the impaired populations were close to those of the non-impaired populations, and they could be considered completely acceptable considering the small sample size of some of the defined populations. The assessment of QoL in MS patients could be more widely used without concern over the adequacy of this approach for cognitively impaired patients.

Some strengths and limitations of the current study should be considered:

i) Considering only one type of dysfunction may not have accurately reflected global cognitive functioning. It has been well documented that it is unusual to observe one deficit in isolation in clinical practice. However, there is little consensus on the definition of ‘global’ cognitive dysfunction [25]. Despite this limitation, the findings of the present study support the relevance of self-reported quality of life assessments for patients with cognitive disorders. Future studies should provide similar explorations in MS populations with cognitive dysfunction defined with other definitions integrating combination of different composites.

ii) We did not consider factors previously associated to cognitive performance, such as depression [26], fatigue [27], and MS medications [28]. However, the aim of this study was to provide evidence supporting the conclusion that cognitively impaired MS patients reliably answer a self-reported QoL questionnaire regardless of the presence or absence of other factors that could have influenced their performance.

iii) The suitability indices used to define satisfactory properties relied on debatable decision rules and non-standardized calculation methods. Analyses of sensitivity should be performed.

iv) Replication of these findings in larger groups of patients is required.

v) Similar studies should be performed in other populations suffering from cognitive impairment, such as severe mental illness and elderly individuals, to determine whether these findings are specific to patients with MS.