Signs of the cancer-causing human papilloma virus in women near or at menopause may be a reawakened dormant infection, suggesting a risk for women who came of age in the "sexual revolution" in the 1960s and '70s.
About 77 percent of the infections were detected in women who reported five or more sexual partners in their lifetime, according to a study in the Journal of Infectious Diseases. The findings suggest that reactivation of the sexually transmitted virus may increase around age 50 and be responsible for more later-life infections than new ones, researchers said.
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The data raises a new concern for women now entering menopause, suggesting a significantly higher risk for HPV infections than those of the previous generation, researchers said. The findings may mean that women need to continue routine screening after age 40, said Patti Gravitt, one of the study authors.
"If we confirm this, we may want to re-evaluate our screening strategies and confirm they're sufficient," said Gravitt, an associate professor at the Johns Hopkins Bloomberg School of Public Health, in a telephone interview. "If populations change their sexual behaviors, that will contribute to how we see age-specific HPV prevalence."
HPV is found in about a quarter of teenage girls and about half of women 20 to 24, according to a 2007 study in the Journal of the American Medical Association. There isn't a good test for men. Previous studies have found that the virus isn't detected in samples after about two years.
The immune system may be controlling it, Gravitt said. If the immune system weakens, as it does with age, the virus can come back. HPV is linked to head and neck, cervical, vulvar, vaginal, penile and anal cancer, and is the most common sexually transmitted disease in the U.S.
The first vaccine to prevent HPV infection, Merck & Co.'s Gardasil, was approved in 2006 in the U.S. and is recommended to prevent cervical cancer in girls and women 9 to 26 years old. It's also approved to prevent genital warts and anal cancer in boys and men of the same ages. GlaxoSmithKline Plc's HPV vaccine Cervarix was approved in 2009 for preventing cervical cancer in females 9 to 25.
The reactivation of the infection seems similar to that of the varicella zoster virus that causes chickenpox. The virus can lie dormant in the bodies of people who were infected as children, then come raging back as shingles later in life, the authors wrote. That may be what's happening with these women around menopause, said the study authors.
Though it's not clear why the infection comes back, scientists suspect it may be due to age-related changes in the immune system, according to an editorial written by Darron Brown and Bree Weaver, doctors at the Indiana University School of Medicine in Indianapolis.
In the study, about 850 women ages 35 through 60 were receiving cervical cancer screening from 2008 to 2011. Those who reported a new sexual partner within the six months before the screening had HPV more often; however, they represented only about 3 percent of the women in the sample.
The rest of the HPV infections, about 90 percent, were detected in women who'd had more than one lifetime sexual partner.
HPV infection rates declined with age only among 50-plus women with fewer than five lifetime sex partners. That suggests that the HPV is being reactivated after 50 years, and the bulk of infections detected then aren't new.
"Women we've observed in the last 20 years of screening have lower rates than those who are currently entering menopause, because they may be entering menopause with latent infections," said Gravitt. "You can't reactivate something you never had. My mother's generation entered with a lot less HPV and had fewer consequences of reactivation."