Temporal trends of incidence and prevalence of multiple sclerosis in Razavi Khorasan Province, Northeast Iran

Prevalence and incidence of multiple sclerosis in Isfahan, Iran between 1996 and 2021: A population-based study

BACKGROUND

There has been no recent comprehensive epidemiological study on a large and stable population of multiple sclerosis (MS) in Isfahan. Therefore, we conducted this study to estimate the incidence and prevalence of MS in Isfahan province from 1996 to 2021.

METHOD

In this population-based study, we utilized the dataset from the Vice-Chancellor's Office of Isfahan University of Medical Sciences, which registers all people diagnosed with MS (PDWM) in Isfahan province, excluding those residing in Kashan city. We measured crude incidence and prevalence of MS, separated by sex, and based on age of MS onset, as well as changes in age of MS onset during observation.

RESULTS

A total of 9,909 PDWM were included in our study. The incidence during the time period of 1996-2000 was 5.4/100,000 (1.1/100,000 per year), which subsequently increased to 14.1 (2.8/100,000 per years) and 31.1 per 100,000 (6.2/100,000 per year) during 2001-2005 and 2006-2010, respectively. There was a further increase to 70.9/100,000 (14.2/100,000 per year) in 2011-2015, but it remained stable at 71.8/100,000 (12/100,000 per year) during the period of 2016-2021. In 2016, the age-standardized incidence rates of pediatric-onset, adult-onset, and late-onset MS were 1.8/100,000, 31.4/100,000, and 17.5/100,000, respectively. The prevalence of MS in 2021 was 183.9/100,000. The female/male new case ratio was 4.5 during 1996-2000, decreasing to 4.0, 3.9, 3.9, and 2.9 in the subsequent four five-year periods. The mean age of RRMS onset was 26.3 ± 8.1 between 1990 and 1999, 28.5 ± 8.3 during 2000-2009, and increased to 32.8 ± 9.6 in 2010-2019.

CONCLUSION

This study shows that Isfahan has one of the highest incidence rate and prevalence ratio of MS in the region. We observed an increase in the incidence rate during the first decade, followed by stability in the last two five- and six-year periods. Further studies are needed to identify the reasons behind the change in incidence of MS in Iran.

Multiple sclerosis incidence temporal trend in the Northeast of Iran: Using the Empirical Bayesian method

BACKGROUND

In recent years dramatic changes in multiple sclerosis (MS) incidence have been reported in different provinces in Iran. This study was conducted to assess MS incidence temporal trends from March 21, 2005, to March 20, 2020, and provide a forecast until the end of 2025 in Shahroud county.

METHODS

This longitudinal study was carried out based on the data obtained from the MS registration system in Shahroud county. First, the annual incidence rates were calculated based on the year of diagnosis and smoothed using the Empirical Bayesian Method. Then temporal trends and annual percent change (APC) of MS incidence were analyzed using Joinpoint (JP) regression. Finally, the univariate time series model analysis was used to estimate the MS incidence trend until the end of 2025.

RESULTS

A total of 234 newly diagnosed cases (60 [25.64%] males and 174 [74.36.4%] females) were examined in this study. The mean age of patients at the time of diagnosis was 31.40 ± 3.78. It was 32.01 ± 6.35 and 30.66 ± 4.27 years for males and females, respectively (P<0.22). The mean annual MS incidence was 5.99 ± 1.46, 3.03 ± 0.21, and 8.98 ± 2.79 per 100,000 in overall, males and females respectively. The MS incidence increased significantly from 5.67 (95% CI: 3.63-7.99) in 2005 to 7.58 (95% CI: 5.17-10.28) in 2020 with an APC of 4.5 (2.8 - 6.1). The MS incidence had a non-linear time trend in the study period and the best time trend fitted to the annual MS incidence trend was the non-linear quadratic curve. Based on this model, the annual MS incidence is expected to increase until the end of 2025.

CONCLUSION

Shahroud county is one of the high-risk areas for MS and the increasing trend of MS incidence in it is similar to regional and global changes. This study, also, showed that MS incidence in Shahroud county will be increasing in the coming years.