Effect of Treatment with Natalizumab on Ability to Work in People with Multiple Sclerosis Productivity Gain Based on Direct Measurement of Work Capacity before and after 1 Year of Treatment

Background: Sweden is a high endemic region for multiple sclerosis (MS), a neurologic disorder characterized by repeated inflammatory episodes affecting the CNS. The disease has its peak age of onset at approximately 30 years and affects women twice as often as men. The young age of onset makes MS one of the major causes of reduced capacity to work due to neurologic disease in Western society. Natalizumab (Tysabri(R)) is among the new generation of biologic drugs for the treatment of MS. Clinical studies have demonstrated that natalizumab is an effective treatment for preventing relapses and inflammatory activity. Objective: The aim of the study was to estimate the monetary value of treatment with natalizumab on the ability to work in patients with MS in Sweden, based on a direct measurement of weekly hours worked before and after 1 year of treatment with natalizumab. Methods: A sample of patients, consisting of all patients who had started treatment with natalizumab during the period June 2007 May 2008, was identified through the Swedish Multiple Sclerosis Register (SMSreg). Data about sex, age, disease severity, and disease duration were collected from the register. Data about type of work and work capacity (number of hours worked per week) were collected retrospectively through a postal questionnaire. The average hours worked per week was estimated at baseline (2 weeks before treatment started) and at follow-up (50 weeks after treatment started), and the change was assigned an economic value using the human capital approach. Results: This study showed that after 50 weeks of treatment with natalizumab, people with MS increased their productivity by 3.3 hours per week on average (p<0.01), which corresponded to an economic value of 3216 per person per year (year 2007 values). A shorter duration of illness or being 25-35 years old was significantly associated with a greater productivity gain (p = 0.025 and p = 0.002, respectively). Conclusion: A shorter duration of illness and a lower age at the start of treatment were significantly associated with a greater productivity gain after 50 weeks of treatment with natalizumab, which indicates that it is more beneficial to initiate efficient therapy early in patients with MS.