Till Örebro universitet

Background: Multiple sclerosis is an autoimmune disease which leads to demyelination and subsequent damage of axons and neurons. Pain is known to commonly affect MS patients, however the clinical characteristics of this pain are not fully described. Prescribed pain medication identifies more severe and chronic pain and different drug types can be used to identify other pain characteristics.

Objectives: To assess whether MS patients in Sweden are at increased risk of receiving medication for pain relative to non-MS comparators. We aim to study overall pain, neuropathic pain, musculoskeletal pain and migraine.

Methods: This cohort study using data on 5,555 MS patients in Sweden individually matched to 5,555 non-MS Swedish residents on sex, year of birth and place of residence at the time of MS diagnosis. We used Cox PH models using date of entry or 1stJuly 2006 as the beginning of follow up, whichever occurred later, and end of study was date of death, date of prescription of a painkiller or December 31st 2014, whichever occurred first. Painkillers were identified through relevant ATC codes. For neuropathic pain, pregabalin, gabapentin, amitriptyline, capsaicin or nortriptyline were used for identification, and for migraine prescriptions of anti-migraine preparations were included in the outcome. Musculoskeletal pain was identified primarily through topical products for joint and muscular pain.

Results: Cox PH models showed MS patients to be at a 2.43 (CI 2.31–2.55) times increased risk of being prescribed any painkiller. The risk increased to 5.63 (CI 5.03–6.31) for neuropathic painkillers, however there was no significant difference for musculoskeletal painkillers (RR = 0.92 (CI 0.79–1.07)). MS patients were at a 1.28 (CI 1.10-1.50) times increased risk of being prescribed anti-migraine preparations. Restricting the data to MS patients showed that exposure to neuropathic painkillers was present in 32.8% of MS patients, and is associated with lower educational attainment and female sex.  

Conclusions: MS patients are at significantly increased risk of pain overall, with a particularly elevated risk for neuropathic pain. It seems that lower educational attainment and female sex are risk factors of neuropathic pain. However, the reason for this is not fully understood.*We would like to acknowledge the funding from the Science for Life - Astra Zeneca collaborative grant that supported this research