The epidemiology of multiple sclerosis in the Scottish Highlands: Prevalence, incidence and time to confirmed diagnosis and treatment initiation

Abstract

IntroductionAlthough multiple sclerosis (MS) is frequent in the northern hemisphere, there have not been recent epidemiological studies in the Scottish Highlands about MS. ObjectivesTo get updated data regarding MS prevalence, incidence and mortality in the Highlands. Time between symptom onset and MS diagnosis was also evaluated in incident MS cases and the pattern of use of disease-modifying therapies (DMTs) was analysed. MethodsStudy population was people with MS under the care of the Highland Health and Social Care Partnership. The catchment area included North area (Wick, Thurso, Brora, Invergordon), Center (Inverness, Aviemore, Nairn, Fort William), and West coast (Ullapool, Skye). Data were obtained from the MS database at Raigmore hospital (prevalence, midyear 2017) and the prospective hospital-register based study (diagnosis) that was carried out over a 12-month period, in 2016. The 2010 McDonald criteria for diagnosis of new MS cases were used. Crude prevalence and incidence and 95% confidence interval (CI) were calculated for the MS adult onset population, and data was standardised to the European standard population 2013; cause-specific mortality rate was analysed. Pattern of use of DMTs during the first year of diagnosis was also registered. Results745 patients were registered in the MS database. 75.4% (562 cases) were females, and female/male ratio was 3:1. Mean age of population was 54.1 ± 14.1 years (range: 15-95 years). Mean number of years since diagnosis was 8.5 ± 4.6 years. Estimated prevalence for the population aged 15 and older was 376 cases per 100,000 inhabitants (95% CI: 354-399). 36 incident MS cases were registered in 2016 (88.8% females; mean age 40.4 ± 12.1 years). Annual incidence in Highlands was 18.2 per 100,000 inhabitants (95% CI: 14-24). The mean period of time from symptom onset to diagnosis was 38.8 ± 43.2 months. 47.2% (17/36) did not take any DMT during the first year after the diagnosis. ConclusionPrevalence and incidence of MS in the Scottish Highlands is high. Although the gap period between symptom onset and diagnosis is moderate, a significant proportion of recently diagnosed MS patients were not keen to start a DMT the first year after the diagnosis.