Incidence and prevalence of multiple sclerosis in Spain: a systematic review.

Introduction: Greater understanding of the prevalence and incidence of multiple sclerosis in Spain and their temporal trends is necessary to improve the allocation of healthcare resources and to study aetiological factors.

Methods: We performed a systematic search of the MedLine database and reviewed the reference lists of the articles gathered. We collected studies reporting prevalence or incidence rates of multiple sclerosis in any geographical location in Spain, with no time limits. In 70% of cases, data were extracted by 2 researchers (FGL and EAC); any discrepancies were resolved by consensus.

Results: We identified 51 prevalence and 33 incidence studies published between 1968 and 2018. In the adjusted analysis, the number of prevalent cases per 100 000 population increased by 26.6 (95% confidence interval [CI], 21.5-31.8) every 10 years. After adjusting for year and latitude, the number of incident cases per 100 000 population increased by 1.34 (95% CI, 0.98-1.69) every 10 years. We observed a trend toward higher prevalence and incidence rates at higher latitudes.

Conclusions: The prevalence of multiple sclerosis in Spain has increased in recent decades, although case ascertainment appears to be incomplete in many studies. Incidence rates have also increased, but this may be due to recent improvements in the detection of new cases.