Incidence rate and sex ratio in multiple sclerosis in Lithuania

To determine the temporal changes in incidence rates of multiple sclerosis (MS) over the past 15 years in Lithuania with prediction up to 2020, and to estimate female-to-male sex ratio and its changes among MS patients.

We conducted a descriptive incidence study. The crude incidence rates (CIR) were calculated using 15-year period, sex, age-groups, and the number of newly registered MS patients. Standardized incidence rates (SIR) were calculated using European standard in order to evaluate the influence of resident structure changes on incidence of MS during the last 15 years. The data were processed using Minitab set to estimate a linear trend model for the temporal changes of 16 parameters.

The data showed a substantial growth of the incidence rate of MS in Lithuania during the period of 2001-2015. In 2001, MS was diagnosed to 162 new individuals, whereas 343 new cases of MS were diagnosed in 2015. During 2001-2015, the incidence of MS was on average 6.5 (95% CI 5.70-7.30) cases per 100,000 residents, and 4.9 (95% CI 4.46-5.34) and 8.1 (5.86-9.34) for 100,000 male and female, respectively. Female-to-male sex ratio in MS in Lithuania had a tendency to increase over the period. Females were affected from 1.5 to 2 times more often than males.

In 2020, the incidence rate of MS is estimated to reach 13 cases per 100,000 persons and females are expected to be diagnosed with MS two times more often than males.