Breast cancer is one of the most commonly diagnosed cancers among women in Western countries. In North America, for example, there are an estimated 233,000 new cases every year and 45,000 deaths. Despite the well-characterized role of genetics and reproductive risk factors, as well as the suggested roles of physical activity and alcohol, more than half of breast cancer risk remains unexplained.
A new study, published
Breast cancer is one of the most commonly diagnosed cancers among women in Western countries. In North America, for example, there are an estimated 233,000 new cases every year and 45,000 deaths. Despite the well-characterized role of genetics and reproductive risk factors, as well as the suggested roles of physical activity and alcohol, more than half of breast cancer risk remains unexplained.
May 31, 2005 in the
breast cancer, the official journal of the
cancer, suggests that long-term exposure to passive smoking (second-hand smoke) may increase premenopausal
breast cancer risk. The study is available via <<
>>.
Researcher Kenneth C. Johnson, PhD. of the <<>>--which is part of the Government of Canada--analyzed data from the 20 published studies which had examined the relationship of passive smoking to breast cancer. Most but not all of the 20 studies reported increased risk, leading the author to explore what might explain the differences in observed risks among the studies. Factors he evaluated included the impact of study design (case-control or cohort); when the study was published (before or after the year 2000); where the study was conducted (Asia, Europe, North America); what outcome measure was used (breast cancer death or diagnosis); and the quality of the second-hand smoke exposure measure.
The completeness of the second-hand smoke measures varied widely. Studies that collected quantitative long-term information on the three major potential lifetime sources of passive smoking exposure (childhood exposure from parents, adult residential exposure and adult occupational exposure) were considered to have the most complete exposure measures.