Men with a history of asthma appear to have a lower risk of developing lethal prostate cancer as compared to those without asthma.
Data collected from 47,880 men, the scientists found that asthmatic men were 36 percent less likely to die of prostate cancer.
"The findings are particularly surprising, because some studies suggested that prostate cancer is linked to the kind of inflammation associated with asthma, which itself is a chronic inflammatory condition," said one of the researchers Elizabeth Platz, professor at Johns Hopkins Bloomberg School of Public Health.
"We don't know yet whether the association we see in this observational study is a case of cause and effect," she noted.
The analysis suggested that men with asthma had a lower risk of developing lethal prostate cancer even when researchers considered such factors as whether the men took medication for asthma or whether their asthma was diagnosed early or later in life.
The 47,880 men ages 40 to 75 participated in Harvard's Health Professionals Follow-Up Study from 1986 through 2012 and did not have a cancer diagnosis before 1986.
There are several possible reasons why asthma might not be linked to a higher risk of lethal prostate cancer, the researchers noted.
"It is possible that the Th2 inflammation that drives asthma is not the same as the Th2 inflammation that drives cancer," one of the researchers Charles Drake from Johns Hopkins Kimmel Cancer Center in the US noted.
It may also be that asthmatics have higher levels of other immune cells which might attack tumor cells, according to the study published in the International Journal of Cancer.