Pharmacoepidemiologic studies of infection among people with multiple sclerosis: Occurrence and effects of pharmacotherapy

Multiple sclerosis (MS) is a chronic condition in which the immune system damages the protective layer around axons in the brain and spinal cord. As a result of this damage and the use of medication with immunomodulatory effects, people with MS experience infections more often than the general population. Infections increase the burden of disease in MS. The main aim of this thesis is to further study this burden of infection, looking specifically at the effect of medication use and the treatment of infections if they do occur. Most studies in this thesis were conducted using data from routine clinical practice in the Netherlands and the United Kingdom. Important findings are that urinary tract infections are common and that their first treatment is less likely to be effective. People with MS experience recurrence of the infection more often and more often require a change in antibiotic therapy. Moreover, comprehensive analysis of the existing literature on infection while on medication to attenuate the underlying MS disease has yielded that this has been studied only sparsely, and that infections are not usually categorized by type of infection. This makes it more challenging to take such study findings into account in patient care. Ultimately, lowering the risk of infections is in the interest of people with MS not only because of the burden of the infection itself, but also because the infection can worsen the underlying MS disease.