Past research has linked early childhood infection with a bacterium called Helicobacter pylori to lower risk of MS, but Prof. Kermode, Dr. Fabis Pedrini and their team say such studies have included small samples and produced “contradictory results.” As such, the team set out to establish a clearer understanding of this association.

Onset of MS is most common between the ages of 20 and 40, and women are more than twice as likely to develop the disease than men.

Multiple sclerosis (MS) is a chronic neurological disease believed to occur when the immune system attacks healthy tissues in the central nervous system . Symptoms of the condition include weak, stiff muscles, tingling or numbness in limbs, trunk of the body or face, vision problems, dizziness, mobility and balance problems and fatigue .

Lead researchers Prof. Allan Kermode and Dr. Marzena Fabis Pedrini, both of the Western Australian Neuroscience Research Institute (WANRI) in Australia, and their team say the findings provide further evidence that the “hygiene hypothesis” – the idea that exposure to pathogens in childhood can protect against later-life disease – may play a role in autoimmune disorders.

Approximately 200 new cases of multiple sclerosis are diagnosed in the US every week. Now, a new study published in the Journal of Neurology, Neurosurgery & Psychiatry – a journal of The BMJ – suggests a common gut bacteria known to cause stomach ulcers could reduce the risk of this disabling disease in women.

Found in the stomach, H. pylori infects more than half of the world’s population – the majority of whom reside in developing countries. Most people acquire H. pylori before the age of 2 years, and the bacterium lives in the stomach for life.

Fast facts about MS Approximately 250,000-350,000 people in the US have MS

Experts believe MS can be inherited; around 15% of people with the condition have one or more family members with MS

MS can cause severe disability, but the disease is rarely fatal and the majority of people with the condition have a normal life expectancy. Learn more about MS

While the majority of individuals infected with H. pylori do not experience illness, some can develop gastritis – inflammation of the stomach lining. The bacterium is also responsible for more than 90% of duodenal ulcers (ulcers in the first part of the small intestine) and more than 80% of stomach ulcers.

For their study, the researchers analyzed data from the Perth Demyelinating Disease Database, which allowed them to assess presence of H. pylori antibodies in the stomach of 550 patients who had been diagnosed with MS.

For comparison, they also looked at the presence of H. pylori antibodies among 299 age- and sex-matched healthy individuals without MS, drawn from the Busselton Community Health Study.

The results of the analysis revealed that women who did not have MS were significantly more likely to be infected with H. pylori than women with MS, suggesting the bacterium may have a protective effect against the condition.

This association, however, was not found in men. In fact, men infected with the bacterium were more likely to have MS.

Explaining the possible reasons behind the protective effect of H. pylori found in women, the researchers say the bacterium may move the immune system into a less inflammatory state, which may reduce its sensitivity and lower the risk of autoimmune disorders like MS.

The team, however, says they are unable to explain why H. pylori did not appear to protect men against MS, and that this is something that needs to be investigated in future research.

Still, the researchers say their findings may lead to the development of new drugs that simulate the effects of H. pylori, opening the door to new treatment strategies for MS and other autoimmune disorders.