Our study evaluated the epidemiology and clinical features of MS in Rafsanjan City, Iran from 2011 to 2020. The incidence rate (4.84 per 100,000) and prevalence rate (97.68 per 100,000) of MS were low compared to other regions[9, 12, 16, 17]. MS affects women in early adulthood and urban lifestyles. The representation of married housewives highlights the impact on childbearing years. Sensory dysfunction and vision loss were common initial symptoms. Younger patients had RRMS while older individuals had progressive forms. Factors such as age, sex, marital status, occupation, season of birth, and symptoms were associated with disease pattern.
Our findings are consistent with previous studies that have reported a low incidence and prevalence of MS in Kerman Province[14]. One possible explanation for this regional variation is the difference in environmental factors, such as latitude, sunlight exposure, vitamin D levels, and diet[6]. Kerman Province's location in southeast Iran yields high sun exposure and heat along with arid conditions, which prior studies suggest are protective against MS[18]. However, further studies are needed to confirm this hypothesis and to explore other potential factors that may influence MS epidemiology in this region.
We also observed a female predominance of MS in our study population, with a female-to-male ratio of 4.64. This is similar to the global trend of MS being more common in women than men [8]. The reasons for this sex disparity are not fully elucidated, but they may involve hormonal, immunological, genetic, and epigenetic factors [19]. Some studies have suggested that estrogen may have a neuroprotective role in MS, while testosterone may have an immunomodulatory role [20]. Moreover, some genes that are involved in MS susceptibility or severity are located on the X chromosome or are influenced by sex hormones [21]. Additionally, some environmental factors, such as smoking and obesity, may have different effects on MS risk or progression between men and women [22].
Another finding of our study was that the mean age of the patients was 39.44 ± 9.71 years, and most of them were in the 20–40 years age group. This is in line with previous studies that have shown that MS typically affects young adults [2]. However, we also found that the mean age of male patients was higher than that of female patients, although not significantly. This is contrary to some studies that have reported a lower mean age of onset or diagnosis in men than in women [23]. This discrepancy may be due to the small sample size of male patients in our study or to other factors that may affect the age distribution of MS patients in different populations.
We also found that most of the patients lived in urban areas and were housewives. This may reflect the socio-economic status and lifestyle of our study population. Urbanization may be associated with increased exposure to environmental pollutants or infections that may trigger or exacerbate MS [24]. Housewives may have less physical activity or social support than other occupations, which may affect their mental health or immune system [25]. However, these associations need to be further investigated in future studies.
The season of birth of the patients was another variable that we examined in our study. We found that most of the patients were born in summer, followed by spring. This is consistent with some studies that have reported a higher risk of MS among people born in summer or spring than among those born in winter or fall [26]. One possible explanation for this seasonal effect is the influence of maternal vitamin D levels during pregnancy on fetal immune system development [27]. The skin synthesizes vitamin D upon exposure to sunlight and has anti-inflammatory and immunoregulatory properties [28]. Other Dietary habits, vitamin D levels, rates of infectious triggers like Epstein-Barr virus, genetics, and ancestry within this distinct population likely also play a role.
Dietary habits, vitamin D levels, rates of infectious triggers like Epstein-Barr virus, genetics, and ancestry within this distinct population likely also play a role[6, 24, 26–30]. The family history of MS was another factor that we considered in our study. We found that only 13.2% of the patients had a positive family history of MS, which is lower than some studies that have reported a family history rate of up to 30% among MS patients [29]. This may indicate a lower genetic contribution to MS risk in our study population or a lack of awareness or diagnosis of MS among relatives. However, it is well established that MS has a vital genetic component, with more than 200 genes identified as associated with MS susceptibility or severity[30]. Therefore, further genetic studies are needed to identify the specific genes or variants involved in MS pathogenesis in our population.
The initial symptoms and disease course of the patients were also analyzed in our study. We found that sensory symptoms and vision loss were the most common initial manifestations of MS, followed by motor weakness and balance problems. This is similar to previous studies that have reported sensory and visual disturbances as frequent presenting symptoms of MS [31]. These symptoms reflect the involvement of the spinal cord, optic nerve, or cerebellum by MS lesions [32]. The least common initial symptom in our study was urinary control problems, which may reflect the brainstem or spinal cord involvement by MS lesions [33].
The disease course of the patients aligned with previous studies, showing that RRMS is the most common form of MS for about 85% of the cases[2]. However, our study found RPMS to be more prevalent than PPMS or SPMS, which differs from other studies[34].. This difference could be due to variations in disease definitions or follow-up periods. We also identified significant associations between disease course and demographic and clinical variables, indicating that these factors influence the natural history or prognosis of MS in different ways. However, further research is needed to understand the underlying mechanisms and causal relationships.