Prevalence of multiple sclerosis in Spain. Estimates from the Primary Care Clinical Database (BDCAP)

The global prevalence of multiple sclerosis (MS) has increased in recent decades. However, there is a need for updated prevalence data for Spain.

To analyze the prevalence of MS in Spain using data from the Primary Care Clinical Database (BDCAP, for its Spanish initials) and to compare the prevalence results in different autonomous communities (AC) according to sex in 2021.

This cross-sectional study extracted data from the BDCAP on patients with MS according to sex, age, and place of residence in 2021. Crude prevalence rates were calculated, using the population assigned for each year of the study as the denominator. The geographic pattern of MS prevalence was analyzed using the following risk estimators: standardized prevalence ratio, smoothed relative risk (RR), and posterior probability of RR >1.

We estimated 61753 cases of MS, with a crude estimated prevalence rate of 132.0 cases per 100000 person-years and a female/male ratio of 2.0. The age-standardized prevalence rate was 123.5 cases per 100000 person-years. Age-specific prevalence rates were lower in men than in women. All indicators showed a north-south gradient. Seven ACs for women and 5 ACs for men showed a significant excess risk (primarily in the north of Spain), whereas 8 ACs for both women and men presented lower risk (mainly in the south).

Our results provide the most recent prevalence data for MS and the geographic patterns at the ACs level in Spain, revealing a north-south gradient. Our results pave the way for future strategies to manage the impact of MS in Spain and to understand causal hypotheses.