In The Arizona Sun, a reader asks Robert Rosenberg, DO, about the link between multiple sclerosis and narcolepsy.

Dear Dr. Rosenberg: I was diagnosed with Multiple Sclerosis about eight years ago. Over the last year, I have been having a very hard time staying awake. I sleep seven to eight hours per night. Do you have any ideas?

A: Yes. First, MS is frequently accompanied by fatigue, but you are describing sleepiness. The two causes I can think of include sleep apnea and narcolepsy. Sleep apnea is very common and frequently overlooked in MS. In fact, one recent study revealed 30 percent of patients with MS had sleep apnea. A second but rarer cause is narcolepsy. Although rare, MS is listed as the most common secondary cause of narcolepsy.

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