I went most of my adult life multiple sclerosis-free, with only an occasional symptom. Then in 1981, I quit cold turkey after 35 years of smoking and never went back to it. Shortly after I quit, my MS started full blown. Is it possible that smoking kept the MS in remission all those years? I am now 72 and in a wheelchair full-time. I will not go back to smoking for any reason, but it may always haunt me: What if?

Valerie Stutts
Chambersburg, Pa.

The thrust of the article indicates that it’s the enzyme heme-oxygenase-1 (HO-1) that reduces myelin damage. Why do research on administrating carbon monoxide when it’s not the active ingredient? How can we increase the supply of HO-1 rather than worry about the by-product of its action?

Victor E. Arnold
Houston, Texas

Studies suggest that smoking worsens multiple sclerosis symptoms, and doctors typically recommend quitting. There is little evidence that carbon monoxide—whether from smoking or received in some other way—is a good anti-inflammatory agent in people. As for studying carbon monoxide instead of HO-1 in mice, since externally applied carbon monoxide mimicked the anti-inflammatory effects of the enzyme in the animals, the researchers hypothesize that carbon monoxide contributes to the protective action of HO-1 in multiple sclerosis. —N. Seppa