(WOMENSENEWS)–Women exposed to secondhand smoke increase their risk of developing cervical cancer, according to a just-published study from Johns Hopkins Bloomberg School of Public Health.
The study published in the January issue of Obstetrics and Gynecology could have critical health implications as public health advocates work to not only educate women about reducing their risks for cervical cancer, but also lower tobacco use around the globe.
“The evidence is strong,” said lead researcher Anthony J. Alberg, an assistant professor in the department of epidemiology. “The findings should encourage smokers to quit and warn nonsmokers who live with smokers to decrease their secondhand smoke exposure.”
While researchers have long suspected that secondhand smoke raised cervical cancer rates, the study–one of the biggest in the United States–makes the link more definitive. The results are being seen as especially important for women living in developing countries, where smoking is on the rise and cervical cancer is a leading cause of death.
Alberg and his team examined the exposures of 51,173 women age 25 and older in Washington County, Md., to household smoking in 1963 and then 1975. The women filled out questionnaires about their exposure to cigarette smoke, who currently or formerly smoked in their households, household member ages, years of education and marital status. Each group was followed 15 years. Researchers then compared women who lived with nonsmokers to women who lived with smokers and monitored who developed cervical cancer.
Investigators found that women exposed to passive smoking faced a 2.1-fold increased risk for the disease in 1963. By 1975 study group, that figure dropped to a 1.4-fold greater risk.
Alberg said he was “puzzled” by this drop and had “no clear explanation for it.” He speculated that one possible reason was that the women in the 1975 group were working outside of the home and may have reduced their household exposure to tobacco.
William Au, professor in the department of preventive medicine and community health at the University of Texas Medical Branch in Galveston, Texas, said the study, which was peer-reviewed, proves a conclusive link.
“This is a well-conducted study based on scientific protocol and it has tremendous implications to human health,” he said. “We’re now seeing how low levels of toxic substances such as secondhand smoke can cause cancer in the human population.”
Passive smoking has been known to increase the risks for heart disease and lung cancer in both men and women, and active cigarette smoking has been long established as a major risk factor for cervical cancer. Although scientists have suspected a link between secondhand smoke and cervical cancer, they needed more data to prove it.
One of the more recent studies came from Singapore and was published in the April issue of Gynecologic Oncology. Researchers studied 623 women and found their risk of certain abnormal cervical cells that signal the possible onset of cervical cancer increased by 4.6 percent for every cigarette the woman’s spouse smoked.
“At this point it is difficult to discern the extent to which secondhand smoke exposure contributes to the population rates of cervical cancer,” Alberg said, “but our findings and the fact that exposure to secondhand smoke is common suggest the contribution of secondhand smoke exposure may not be trivial.”
“It’s really important people get the message that smoking does much more than we ever thought that it did and that it affects our health in ways we don’t even fully know about yet,” said Hollis Forster, executive director of the National Cervical Cancer Coalition, a nonprofit organization in Berkeley, Calif.
Special Risks for Minorities
Twenty-two percent of the U.S. population smoked in 2003, down from 24 percent in 1998, according to the federal Centers for Disease Control and Prevention. The American Cancer Society reports there are more than 10,000 cases of invasive cervical cancer every year in the United States and the disease claims 3,900 lives. In the United States, African American women are most vulnerable to cervical cancer, according to the Atlanta-based Centers for Disease Control and Prevention.
The Centers for Disease Control reports from 1992-2000, only 62.6 percent of African American women survived cervical cancer five years after being diagnosed compared to a survival rate of 73.3 percent among white women. The federal agency also reports higher Pap smear testing, the gold standard of screening for cervical cancer, among white women.
While smoking rates have been dropping steadily in this country and cervical cancer rates have followed suit thanks to detection with Pap smear tests–a gynecological screening of cervical mucous for abnormal cells–the rates for both remain a serious public health threat elsewhere around the world.
In developing nations, cervical cancer is the second-leading cause of cancer deaths among women after lung cancer with 80 percent of the 500,000 new cases every year occurring in Latin America, Africa, and Southeast Asia.
Although easily treated if detected, cervical cancer remains a top public health threat because of HPV, human papillomavirus, a sexually transmitted infection that causes the disease. Scientists around the globe are racing to develop a vaccine to block HPV infection.
Alberg said he suspects tobacco exposure may exacerbate HPV infection. “It is possible that cigarette smoke acts in concert with HPV to promote progression to cancer,” Alberg said.
Impaired Immune System
Smoking of any kind, direct or passive, can impair the immune system making it vulnerable to infection, including HPV, said Au. Carcinogens found in tobacco smoke “cause DNA damage or gene mutation” and can block cells’ abilities to repair themselves, Au said.
Women, however, should not think being around cigarette smoke will directly result in HPV infection. While smoking is unrelated to the acquisition of HPV infection, it is “related to immunity, which is important in the progression” of cervical tumors, said Janet Daling, an investigator at the Fred Hutchinson Cancer Research Center in Seattle.
The rising number of public smoking bans may make it easier for women in the United States to protect themselves, but such safeguards against public exposure to secondhand smoke are few and far between elsewhere in the world.
“The banning of smoking in public places is just the beginning,” said Au. “First, it’s the ban. Second, it’s education. We don’t want people to quit smoking in public places and then just smoke in the home. That puts family members and children at risk.”
Katrina Woznicki is a freelance journalist in Edgewater, N.J., and writes frequently about women’s health.
For more information:
Obstetrics and Gynecology 2005;105:174-181–
Active and Passive Cigarette Smoking and the Risk of Cervical Neoplasia:
Volume 93, Issue 1 , April 2004, Pages 116-120
Passive cigarette smoking is a risk factor in cervical neoplasia:
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