COPENHAGEN, Denmark — A study for the first time links higher sodium intake with increased clinical and radiologic disease activity in people with multiple sclerosis (MS).

A high-sodium diet has recently been shown to worsen disease in the animal model of MS, experimental autoimmune encephalomyelitis.

"Our study adds some evidence that this effect might be also present in humans as individuals that consume high amounts of sodium have a higher number of lesions on MRI and also more clinical bouts," Mauricio Farez, MD, from the Institute for Neurological Research, Buenos Aires, Argentina, told Medscape Medical News.

Dr. Farez presented the study here at the 29th Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS).

New Observation

"This is a new observation," Bruce Bebo Jr, PhD, associate vice president of discovery research at the National Multiple Sclerosis Society, New York, New York, who wasn't involved in the study, told Medscape Medical News. "As far as I know, there are no published studies correlating Na intake and MS disease activity."

However, Dr. Bebo noted that a link between salt and MS was "alluded to" in a series of 3 articles published in Nature in March, reported at that time by Medscape Medical News.

For the current analysis, Dr. Farez and colleagues investigated the relationship between salt intake and MS disease activity in 70 patients with relapsing-remitting MS who were followed for 2 years. Sodium intake was calculated in urine samples, and clinical and radiologic assessment was performed every 3 to 6 months or in the presence of relapse.

They found a positive correlation between exacerbation rates and sodium intake in a multivariate model adjusted for age, sex, disease duration, smoking status, vitamin D levels, body mass index, and treatment.

Specifically, they documented an exacerbation rate that was 2.75 (95% confidence interval [CI], 1.30 - 5.81) times higher in people with medium sodium intake and 3.95 (95% CI, 1.39 - 11.21) times higher in patients with high sodium intake relative to patients with low sodium intake.

The study also showed that individuals with high sodium intake had a 3.4 times increased odds of developing a new lesion on MRI and on average had 8 more T2 lesions on MRI. 

Effect Size "Pretty Large"

Dr. Farez noted that the World Health Organization currently recommends a sodium intake not to exceed 2 g per day, although the average intake is much higher, "on the order of 4 to 4.8 grams per day." In this study, "adults with low to average sodium intake made up the medium sodium intake group, while the high sodium intake group included patients consuming more than 4.8 grams of salt per day," Dr. Farez said.

"The effect size is pretty large," Dr. Bebo noted, "as high as 4-fold on relapse rate and 3-fold on new MRI lesions."

However, this is "a small and preliminary study that needs to be repeated in a larger cohort. But if it holds up, it could provide important insights into MS disease mechanisms and perhaps even recommendations regarding sodium intake in MS patients," he said.

Dr. Farez agrees that more study is needed, in particular "to determine what is the recommended sodium intake for these patients."

He also noted that the study "does not relate sodium as an MS trigger, only as an environmental factor related to worsening. Future studies should address if high-sodium diets also increases the risk of having MS," Dr. Farez said.

Dr. Farez has received professional travel/accommodations stipends from Merck-Serono Argentina. Dr. Bebo has disclosed no relevant financial relationships.

29th Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS). Abstract #118. Presented October 3, 2013.

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