LONDON (Reuters) - People with multiple sclerosis may have a lower risk of cancer, possibly because of lifestyle changes they make after they are diagnosed with the neurological condition, researchers said on Monday.

An analysis of the medical records of more than 20,000 people with multiple sclerosis showed that patients had a 10 percent lower risk of cancer over 35 years than people without MS.

"We speculate that the lower risk for cancer among people with MS could be a result of lifestyle changes or treatment following diagnosis," Shahram Bahmanyar of Sweden's Karolinksa Institute, who led the study, said in a statement.

The effect was more pronounced among women, who are more prone to MS, an incurable condition that affects more than 1 million people worldwide.

MS can cause mild symptoms in some people and permanent disability in others. Symptoms may include numbness or weakness in one or more limbs, partial or complete loss of vision, tingling or pain, electric-shock sensation with certain head movements, tremors and an unsteady gait.

Bahmanyar and colleagues, who published their findings in the journal Neurology, compared the records of the men and women with MS with those of more than 200,000 people without the disease over 35 years.

They also analyzed records of parents of people with MS to see if there was a genetic link, but found no overall increased or decreased risk among parents.

The findings suggested MS patients are more likely to be diagnosed with certain cancers such as brain or bladder tumors, which the researchers said may happen because these patients are being examined more often than other people.

"The increase in brain tumor diagnoses may be due to brain inflammation, but this finding may not reflect a real increase in cancer risk, as there is some evidence that more frequent neurological investigations in these patients mean that brain tumors are more likely to be found sooner," Bahmanyar said.

(Reporting by Michael Kahn, editing by Maggie Fox, Tim Pearce)

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