Writing in the Journal of Neurology Neurosurgery & Psychiatry, researchers analysed data from more than 500 people with MS and nearly 300 healthy controls, after previous research suggested a link between early childhood infection and reduced risk of developing the condition.
The comparison tested for the presence of antibodies to Helicobacter pylori – a common gut bacterium that is present in about half of the world’s population and is generally acquired before the age of 2 and lasts for life in the stomach, unless treated.
The team found that the prevalence of the infection was significantly lower in those with MS than in the comparison group, but only among women, in whom it was around 30% lower.
“In recent years, a relationship between Helicobacter pylori and many disease conditions has been reported, however, studies in its relationship with multiple sclerosis (MS) have had contradictory results,” said the research team – led by Professor Allan Kermode from The University of Western Australia.
“Our results could reflect a protective role of H. pylori in the disease development,” they suggested. “However, it may be that H. pylori infection is a surrogate marker for the ‘hygiene hypothesis’, a theory which postulates that early life infections are essential to prime the immune system and thus prevent allergic and autoimmune conditions later in life.”
The authors said that if the findings are confirmed in other studies, the link might prove the hygiene hypothesis.
Kermode and colleagues analysed data from 550 people with confirmed MS and a comparison group of 299 healthy people, matched for age and sex – finding that H. pylori presence was found to be lower in the patients with MS than in controls (16% vs 21%), with the decrease relating to females (14% vs 22%, p=0.027) but not males (19% vs 20%, p=1.0).
Furthermore, after taking account of influential factors, such as age at diagnosis, year of birth, and duration of symptoms, those women with MS who tested positive for H. pylori seemed to be less disabled by their condition than those who tested negative for the infection, said the team.
Meanwhile, they data suggested that the reverse was true in men, among whom a positive test result was linked to higher rates of disability.
According to Kermode and his team, there is no obvious explanation for the gender disparity, which they say definitely warrants further study.
Writing in a linked editorial, Professor Jun-ichi Kira, of Kyushu University, Japan, pointed out that the lower disability scores reported by the women with MS who tested positive for H. pylori, suggests that the infection might be protective.
"Collectively, such an inverse correlation of H. pylori infection with MS in developing countries where MS and allergic disorders have increased, may support the 'hygiene hypothesis,'" he suggested.
"Although why the protective effects of H. pylori against MS were observed only in women remains to be elucidated, but might explain the recent increase in female to male ratio of MS in developed countries," he added.