Work ability in multiple sclerosis the impact of immunomodulating treatments and adjusted working conditions

Sammanfattning: Background Multiple sclerosis (MS) is a chronic inflammatory, demyelinating disease affecting the central nervous system (CNS) and is considered to be of autoimmune origin. The prevalence in Sweden is estimated to be about 1 in 500. The inflammation leads to demyelination as well as neurodegeneration and with time the patients often suffer from increasing neurological disability. The young age of onset makes MS one of the major causes of reduced ability to work in the Western society. Several factors in the disease affect the work ability. One important factor is ongoing inflammatory activity conferring risk to develop tissue damage and disability. Previous studies have indicated that fatigue, mobility and cognitive problems are the primary symptoms preventing individuals with MS to remain in employment. However, the possibility to adapt both tasks and the workplace, the possibility for sedentary work and flexible working hours also have great influence to keep the individual in employment.The purpose of the thesis was to investigate how factors in the disease, immunomodulating treatments and work requirements influence the ability to work and study in people with MS.Methods: A MS specific questionnaire was used in one retrospective and one prospective study to compare the work ability before and after start of the second-generation immunomodulating drug natalizumab. The number of working hours per week and the degree of sick leave before and after one year of treatment was calculated. The effect of disease-specific and workrelated factors on work ability was evaluated. The treatment effect on fatigue and walking ability was correlated to work ability. In addition, a healtheconomic calculation was performed to estimate the cost-benefit of the treatment. The degree of sickness absence was evaluated in a cross-sectional study of two MS-populations; one historical that never was exposed to immunomodulating drugs and the other consisted of individuals with MS that was diagnosed after the introduction of immunomodulating drugs. Furthermore, work ability was studied in two MS-populations, one southern and one northern cohort of Sweden, for the latter population more active immunomodulating treatment and work-promoting measures have been practiced. The data was collected using the instrument WAQ-MS. Results Paper I: After one year of treatment with natalizumab the average working hours per week had increased with 3.3 hours, corresponding to an economic value of 3216 euro per person per year. Paper II and III: After initiation of treatment with natalizumab, in an active phase of relapsing-remitting MS, the patients improved their working ability after one year from 31 % to 60 % (p<0.001) and reduced their sickness benefit correspondingly (p<0.001) in relation to their total employment rate. They also reported improved physical and cognitive ability in relation to their requirements. Short disease duration, younger age and lower Expanded Disability Status Scale (EDSS) grade at treatment onset predicted a positive effect on work ability and also improvement of walking ability correlated significantly with reduced sick leave. Paper IV: The proportion of individuals without any kind of sickness absence was higher in the MS population being exposed to disease modifying drugs compared to the unexposed population (66 % vs 38 %) (p<0.001). In addition, the proportion of patients with full-time sickness absence was higher in the unexposed compared to the exposed population (32 % vs 16 %) (p<0.001). The median EDSS was lower in the exposed compared to the unexposed MS population (p<0.001). Paper V: The proportion of MS patients who participated in the work force or studied was significantly higher in the northern cohort, where they had been exposed to more work promoting measures, compared with the southern cohort (p=0.022). MS patients in the northern cohort had significantly lower physical and cognitive requirements in their occupations, more adapted work conditions and could work more hours per week compared with the southern cohort. The EDSS level explained 12 % of the working ability in the northern cohort and 21 % in the southern cohort.Conclusion Our results indicate that patients in the inflammatory phase of the disease may retain their work ability several years after disease onset if they are subjected to effective anti-inflammatory treatment regimens from disease onset. Furthermore, work ability may be additionally improved by adjusted working conditions even in the progressive phase of the disease. It is obvious that these results have implications in a socioeconomic perspective as well as for the individual patients as improved quality of life due to retained work-life participation. Long-term follow-up of our data is required to determine whether these positive effects are durable over longer time-periods.