• 3/30/2004
  • By Jennifer Warner
  • See sources at end of article

The effects of sun exposure on women’s health may be more than skin deep. A new study suggests that a woman’s risk of cervical cancer may be much higher during sunny months. Researchers tracked nearly a million Pap smear results collected over 16 years in southern Holland and found that women were twice as likely to be infected with the human papilloma virus (HPV) during the sunny days of August than in the darker days of winter. HPV is the most common sexually transmitted disease. Pap smears that test for HPV infection are commonly used worldwide as a tool to screen for signs of cervical cancer. The vast majority of women with HPV infection will not develop cervical cancer, but cervical cancer is a rare complication of this common infection. About 20 of the more than 230 types of HPV are considered high risk because of their close association with the disease.

HPV Risks Rise During Sunny Months?

In the study, researchers looked at seasonal patterns of HPV infection among 920,359 consecutive Pap smears collected from 1983 to 1998 and compared it with differences in sunlight exposure. The results showed that the number of HPV infections was twice as high in August compared with the lowest month, and the rates of HPV infection were closely linked to available sunlight exposure. “The sunnier the year, the higher the HPV rate, and the sunnier the month, the higher the HPV rate,” says researcher William Hrushesky, MD, a professor at the University of South Carolina School of Medicine.

Surprisingly, researchers say the study showed that HPV rates were not linked to sexual activity. The study looked at three centuries of birth records in Holland and found conception rates (and presumably heterosexual activity) peaked in the spring, but HPV infection rates peaked four months later. That prompted researchers to suspect that there might be a relationship between sunlight and ultraviolet (UV) light exposure and susceptibility to HPV.

Hrushesky says previous studies have suggested that UV exposure can negatively affect the body’s immune system by interfering with the production of disease-fighting T cells and therefore lower the body’s natural defenses against infection. In this case, he says that seasonal changes in sunlight exposure may make the body more prone to HPV infection even though the cervical cells aren’t directly exposed to sunlight. “Sunlight exposure and solar immune changes associated with sunlight exposure may render cervical epithelium [cells within the cervix] more sensitive to HPV infection,” says Hrushesky. In addition, Hrushesky says viruses are activated by exposure to ultraviolet rays, which may also make HPV more potent.

Connection ‘Makes Sense’

Raymond DuBois, MD, PhD, who moderated a discussion of the study’s findings at the annual meeting of the American Association for Cancer Research in Orlando, Fla., says the sunlight-HPV connection makes sense and merits further study. “I think it’s a complex biological and behavioral situation,” says DuBois, who is associate director for cancer prevention, control, and population-based research at Vanderbilt-Ingram Cancer Center in Nashville.

“We know, for example, that the amount of sunlight exposure affects a person’s mood and behavior, and that could affect downstream what things they are exposed to,” says DuBois. “All things that we’re exposed to in the environment are important, I think, because they could modulate our risk for cancer.”

SOURCES: American Association for Cancer Research 95th annual meeting, Orlando, March 27-31, 2004. William Hrushesky, MD, professor, University of South Carolina School of Medicine. Raymond DuBois, MD, PhD, associate director for cancer prevention, control, and population-based research, Vanderbilt-Ingram Cancer Center, Nashville. News release, American Association for Cancer Research. WebMD Medical News: “Women Misinformed About HPV-Cancer Link.”