Multiple sclerosis causes muscle weakness that can make it difficult or impossible for patients to walk, or even stand. In the worst cases, it can lead to paralysis.

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Neurologists say a healthy appetite for coffee may reduce the risk of developing multiple sclerosis.

In a new study, researchers found that Americans who downed at least four cups of coffee a day were one-third less likely to develop multiple sclerosis than their counterparts who drank no coffee. They also found that Swedish adults who guzzled at least six cups of coffee each day were also one-third less likely to get MS.

Put another way: People who eschewed coffee were 1.5 times more likely to be diagnosed with MS than people with a serious coffee habit.

Multiple sclerosis, a disease of the central nervous system, causes weakness that can make it difficult or impossible for patients to walk. Researchers think the disease is triggered by a misguided immune system, which attacks the myelin sheath that protects nerve fibers. There is no cure, though newer treatments can slow damage.

Previous studies have found that people who drink coffee were less likely to develop Alzheimer’s and Parkinson’s, two other neurological diseases. So there was reason to think the health benefits of coffee — or more specifically, its caffeine — might also apply to multiple sclerosis.

The international group of researchers started with data from a Swedish study that tracked 1,629 people who developed MS and 2,807 people who didn’t. When they compared coffee consumption in both groups, they found that those who drank six or more cups of coffee a day were 33 percent less likely than nondrinkers to be diagnosed with MS the next year.

Going back further in time, they discovered that people who were heavy coffee drinkers five years earlier were 30 percent less likely to get MS in the index year. They also found that those who were drinking lots of coffee 10 years earlier were 28 percent less likely to develop MS symptoms in the index year.

The U.S. data was from Kaiser Permanente patients in Northern California. Researchers compared 584 people with multiple sclerosis and 581 controls. In this group, people who drank at least four cups of coffee a day were 33 percent less likely to have MS symptoms a year later.

In both groups, researchers controlled for other factors that might influence MS risk, including age, gender and smoking history.

The results don’t prove that coffee was responsible for reducing the risk of MS. Nor did the study explain why coffee might offer some protection against the disease.

However, researchers noted that cell-signaling proteins known as cytokines that promote inflammation throughout the body appear to play a role in the development of MS. Caffeine has been shown to suppress production of some of these cytokines, at least in laboratory conditions.

Coffee drinking is also associated with a reduced risk of type 2 diabetes, liver cancer and stroke, researchers say.

The new findings will be presented in April at the American Academy of Neurology’s annual meeting in Washington, D.C.