NEW YORK (Reuters Health) - It is possible that long-term exposure to environmental tobacco smoke may raise the risk of chronic lymphocytic leukemia, Canadian researchers report.
As investigator Dr. Patrick Levallois told Reuters Health, "We have found an excess risk of leukemia in those who were the most exposed to environmental tobacco smoke."
However, when the team looked at specific subtypes of leukemia, they did not find a clear increase of acute myeloid leukemia -- which has been linked to active smoking -- "but a statistically significant increase of chronic lymphoid leukemia."
Levallois of Institut National de Sante Publique du Quebec and colleagues note in the medical research journal Epidemiology that they analyzed data on 266 people with confirmed adult leukemia, and on 1326 matched but unaffected "controls" for comparison. None had been smokers.
No association was found for passive smoking and most leukemia subtypes, but in those with the longest exposure to residential smoking the chances of developing chronic lymphocytic leukemia were more than doubled.
However, Levallois continued, "We don't know if our finding is real or due to chance or bias. It is therefore premature to make clinical recommendations based on the results of this study."
"On the other hand," he concluded, "there is a sufficient well-proved link between lung cancer and environmental tobacco smoke to support the recommendation to abstain from smoking in public areas."
SOURCE: Epidemiology, September 2005.