In what they term a “surprising” result, Johns Hopkins researchers have found that men with a history of asthma are nearly 30 percent less likely to develop lethal prostate.

According to the new study, men with asthma were 29 percent less likely to be diagnosed with prostate cancer that spread or to have died of prostate cancer. Overall, asthmatic men were 36 percent less likely to die of the disease, they found.

The study, conducted by cancer researchers at John Hopkins University in Baltimore, Md., looked at 47,880 men ages 40 to 75 who initially did not have a cancer diagnosis and were followed for 26 years. There were 798 confirmed lethal prostate cancer cases in the group.

The study was sparked by the finding of a possible connection between asthma and prostate cancer based on work in mice showing that the immune cells that infiltrate prostate tumors produce an inflammatory immune response.

But as prostate cancer is often thought of as being fueled by inflammation, they had expected the mice would have a higher rate of the disease. Instead, this new analysis found the opposite.

Dr. Elizabeth A. Platz, co-leader of the Cancer Prevention and Control Program at the Johns Hopkins Kimmel Cancer Center, cautioned that it’s not possible to say from the study that asthma protects men from prostate cancer.

"We don't know yet whether the association we see in this observational study is a case of cause and effect," she said.

The study also looked at men with a history of hay fever and lethal prostate cancer and found a smaller but opposite association: Men with hay fever were 10 to 12 percent more likely to have lethal or fatal prostate cancer.