Overview of the growing list of potential risk factors for MS
Dr. Ali Manouchehrinia, Assistant Professor at the Karolinska Institutet, presented an overview of the risk factors for MS. Firstly, he discussed the genetic variants associated with increased risk for developing MS. To date, there are 233 variants identified that have been linked to MS. Geographical distribution of MS also hints toward the involvement of the environmental factors in increasing MS risk. Other factors that have also increased MS risk are Epstein-Barr Virus, smoking, increased BMI (particularly in individuals that have high BMI before the age of 20). Finally, Dr. Manouchehrinia concluded the talk by discussing the interaction between genetic and lifestyle factors. Both low vitamin D levels and high BMI and genetics increase the risk of MS. Overall, there is a growing list of environmental and lifestyle factors, and interaction between the two, associated with increased risk of MS.
Salt: Is there evidence to support it as a risk factor in MS?
Dr. Ralf Linker presented on a potential emerging risk factor for MS: Salt. There are many lines of evidence suggesting salt may be associated with MS risk and disease course. Firstly, in animal models of MS, an increased salt diet aggravates MS which is shown by a worse clinical score. In humans, a higher salt diet increases the number of inflammatory cells in healthy humans. Supporting this finding is a study that shows an increase in the number of lesions with high salt intake in MS. However, in recent years, there have also been studies published that have contradicted these findings and presented that there is no association between dietary sodium intake and risk of MS. These mixed findings raise a key question: What is the best method to measure sodium load in MS patients? The two potential ways in which sodium can be measured is through dietary sodium intake and urinary sodium excretion. One limitation with measuring sodium load via dietary sodium intake is that individuals are not completely familiar with the amount of sodium present in foods, particularly processed foods. In a separate cohort study, Dr. Linker showed that individuals with relapsing-remitting MS had higher levels of skin sodium levels. Overall, the evidence presented by Dr. Linker shows the varied evidence on salt as a potential risk factor for MS. Larger clinical trials are needed to determine if salt increases the risk of MS or changes MS disease course.
Vitamin D and obesity: Are they associated with changes in brain volume in MS?
Two potential risk factors for MS include obesity and vitamin D insufficiency. Low levels of vitamin D have been linked to increased inflammatory outcomes and brain volume changes, while obesity-related comorbidities are linked with morbidity and mortality rates in people with MS. However, whether there is an association between vitamin D levels or obesity on imaging measures of neurodegeneration in a cohort of people with relapsing-remitting MS (RRMS) or clinically isolated syndrome (CIS) is unknown. Using an MS cohort study at the University of California, San Francisco, Dr. Ellen Mowry, from John Hopkins University, investigated if, in a cohort of 469 people with RRMS or CIS, there were any associations between BMI or vitamin D and changes on imaging measures. While Dr. Mowry discovered that there were no associations between vitamin D and changes in brain volume, she did present a link between BMI status and magnetic resonance imaging (MRI) measures. Each kg/m2 higher BMI was associated with reduced volume in both the grey and white matter. As obesity is a modifiable risk factor, additional studies should explore the relationship of reducing BMI on imaging clinical outcomes in MS.