- Sat. Sep 6, 2008
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SCIENCE AND TECHNOLOGY
Birth of a Number
Does one of every four American teenagers really have a sexually transmitted disease? No, despite headlines given to a recent federal study.
On March 11, the Centers for Disease Control and Prevention announced that one in four teenage girls has a sexually transmitted disease.
This eye-opening statistic landed like a dead rat on the doorsteps of America’s 37 million households and 30 million teenagers. The New York Times, among other papers, put the news on the front page. CBS news anchor Katie Couric told her viewers that “at least one in four teenage girls in America has a sexually transmitted disease,” and she ended by saying, “I know what I’ll be talking about at the dinner table tonight.”
The one-in-four number “really caught every parent in America’s attention,” said Cecile Richards, the president of the Planned Parenthood Federation of America, because it is so simple and “so stunning.” Richards said that her 17-year-old daughter read it “and personalized it, and said, ‘There are some girls I know who have an STI’ ”—shorthand for sexually transmitted infection. “It really brought it home.”
Rival Washington advocates pounced on the CDC’s startling statistic. One faction, led by Planned Parenthood and other groups that get federal grants, said the number shows that the Bush administration’s abstinence-promotion programs don’t work and that funding should be transferred to sex-education and condom-distribution programs. The rival faction, led by social conservatives, said that the one-in-four number demonstrates the failure of condoms and sex-education classes.
An April 23 hearing of the House Oversight and Government Reform Committee showcased this dispute. Chairman Henry Waxman opened the hearing by declaring: “A few weeks ago, the CDC released data showing that one in four teenage girls in the U.S. has a sexually transmitted infection.… We will hear today from multiple experts that after more than a decade of huge government spending, the weight of the evidence doesn’t demonstrate abstinence-only programs to be effective.”
But how useful or valid is that one-in-four number? Are 25 percent of America’s teenage girls really in imminent danger from HIV/AIDS, gonorrhea, and the human papilloma virus (HPV) that leads to cervical cancer?
A close examination of the CDC’s star statistic reveals several serious shortcomings that undermine its validity, as well as its usefulness to parents, legislators, health officials, and advocacy groups on the left and the right.
For instance, Couric’s and Waxman’s shorthand summaries were misleading. The CDC’s study referred to “infections,” but most biological infections never turn into diseases; the body suppresses them before symptoms appear. This conflation of disease and infection was commonplace, in part because the headline on the CDC press release said, “1 in 4 Teenage Girls Has a Sexually Transmitted Disease.” Most news accounts, including the first line of an Associated Press story that ran in many newspapers, likewise referred to “diseases” rather than infections. The CDC did little to correct this inflated interpretation.
Other problems were numerous.
• The infections referred to in the study are not the ones that leap to people’s minds when they worry about sexually transmitted diseases. The data excluded the two most-feared diseases, HIV/AIDS and syphilis. The most common infection was from HPV, which can have serious consequences but in the vast majority of cases disappears on its own.
• The focus on “teenagers” covers a broad age range, from those who are 14 (only 13 percent of whom have had sexual intercourse, according to other studies) to women of 18 and 19 (70 percent of whom have had sex before their 19th birthday). CDC officials declined to describe to National Journal the infection rates in each of the two-year age groupings, even though they have the data.
• The one-in-four number was culled from a complex database that included only several hundred women under age 20. The finding carries a large margin of error, and critics won’t be able to review the study until it gets published in a peer-reviewed journal next year, at the earliest. CDC officials initially said that 838 girls and women participated in the survey. The data for the one-in-four number, however, came from a smaller core group of 615.
Perhaps most critical, the CDC’s March 11 news conference, and the materials distributed there, failed to put the numbers into historical context. Other CDC research shows that infection rates for most serious sexual diseases, including syphilis, gonorrhea, and chancroid, are sharply below 1990 levels—syphilis reached a historic low in 2000. The CDC’s tests showed that none of the 18- and 19-year-old women in the study were infected with HIV or syphilis, but officials did not mention this success in the press release. Teenagers’ exposure to STDs has also dropped because their sexual activity declined from 1998 to 2002. The decline was 20 percent among girls, and 40 percent among boys, according to the CDC report, “Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002,” last updated in March 2006.
Since March 11, experts such as Heather Boonstra, a senior policy associate in the Guttmacher Institute’s D.C. office, and Moira Gaul, director of Women’s and Reproductive Health at the Family Research Council, have raised questions about the data when queried about the study. But they’re reluctant to criticize it until they see a detailed, peer-reviewed article describing the findings.
To be sure, recent attention to the link between some types of HPV and cervical cancer, which is a leading cause of cancer deaths among women, has increased awareness of a lurking health problem in a vulnerable age group. Anti-HPV campaigns have reduced the death rate by 70 percent since the 1940s, and these campaigns were boosted once the Food and Drug Administration approved the Gardasil vaccine in 2006.
So what’s a parent to think? When asked for a more accurate estimate of the risk of serious sexual disease among, say, 15-year-olds, the health experts interviewed for this article would not go near the question. A review of other CDC literature indicates that among girls younger than 18 who are sexually active, the infection rate might be as high as 6 percent. The rate of diseases meriting medical intervention would be a small fraction of that.
CDC officials say they acted appropriately when they prepared and released the one-in-four number. “The last thing we want is for people to believe that 25 percent of girls have something that will bring them serious harm,” John Douglas, director of the CDC’s STD prevention division, told the Chicago Tribune in April. Asked about the substitution of “disease” for “infection,” CDC officials replied in an e-mailed statement: “We use STD because it is more widely understood than STI among both health professionals and the lay public.”
CDC Director Julie Gerberding declined to be interviewed for this article. In a statement to National Journal, she said, “As the nation’s health protection agency … we pride ourselves in following three core values—accountability, respect, and integrity. In all my years as director, I have never been pressured or asked to make any decisions which were not based on the sound scientific research that the world expects from CDC.”
Origins and Impact
Officials at the CDC’s Division of STD Prevention at the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention arrived at the one-in-four number in 2007. The center, located in Atlanta, has a 2008 budget of $152 million. Officials already knew the approximate STI rates among teenagers, but they sought to reframe the existing data on young women, Douglas told NJ. “They’re the cutting edge of prevention.”
To get the new number, CDC researcher Sara Forhan turned to a database—the CDC’s National Health and Nutrition Examination Survey—that goes back to the 1960s. The CDC’s Center for Health Statistics, which collects information on the health and nutritional status of Americans, sends a mobile laboratory to 15 counties every year to survey and give laboratory tests to approximately 5,000 randomly selected volunteers. Since the 1960s, officials have used the NHANES database to expose problems caused by iron deficiency, cholesterol, lead, and many other hazards. Its data served as the basis for children’s growth charts, for guidelines to reduce exposure to lead, and for awareness of obesity as a public health hazard.
Forhan examined the 2003-04 database for the age groups covering 14 to 19. She found good records on 615 women, of whom 18.3 percent had HPV, 3.9 percent carried chlamydia, 2.5 percent had trichomonias, and 1.9 percent had HSV-2 (herpes simplex virus). The four mini-surveys were combined, and CDC officials determined that 25.7 percent of the 615 women had one or more of the four diseases, according to a CDC briefing chart.
CDC officials, including Douglas, announced the number in Chicago at the CDC’s biannual National STD Prevention Conference, which is attended by many experts, state officials, and reporters. The subsequent media reports and editorials generally echoed the recommendations of CDC officials, and their advocacy allies, for greater government-funded testing and intervention. For example, the second paragraph of the 8:51 p.m. version of the March 11 AP article said, “Some doctors said the [infection] numbers might be a reflection of both abstinence-only sex education and teens’ own sense of invulnerability.” The AP article also quoted Planned Parenthood’s Richards as saying that “the national policy of abstinence-only programs is a $1.5 billion failure, and teenage girls are paying the real price.” Neither that dispatch nor The New York Times quoted advocates of abstinence-only programs.
“The half [of the adolescents] that weren’t having sex did not have” sexually transmitted infections. --Moira Gaul, Family Research Council
The one-in-four figure immediately became fodder in the ongoing debate over whether the government should support comprehensive sex education or fund advocacy for sexual abstinence until marriage. Sex-education advocates were first out of the gate, announcing even before the press conference (in time for initial news reports) that funding should be transferred from “failed” abstinence-only programs to education that includes lessons on the use of contraceptives.
Proponents for abstinence and marriage programs countered that the CDC’s number demonstrates just the opposite. “The half [of the adolescents] that weren’t having sex did not have STIs,” said the Family Research Council’s Gaul. The CDC’s one-in-four number “represents a failure of contraceptive-based education,” Rep. Mark Souder, R-Ind., said at the Waxman hearing. The statistic “verifies that what we’ve been saying is true—the only safe sex is inside marriage.” Souder announced that he’s campaigning for a health warning on condom packages, akin to the warning on cigarette packs.
Boonstra, a comprehensive-education advocate at Guttmacher, responds that abstinence-until-marriage programs nearly always fail because, surveys show, 95 percent of people have sex before marriage.
Recently under the Bush administration, the federal government has spent about $180 million a year on classroom programs that promote abstinence until marriage (and don’t train in condom use) to more than 2 million youths. The federal government also gives at least $300 million to federal agencies and states to fund comprehensive sex education, STI testing, and condom distribution. In the fiscal year ending June 2007, Planned Parenthood and its state affiliates received $337 million in government money, and the group’s activities included spending $48 million on sexuality education programs, according to its annual report.
Despite the furor over the one-in-four figure, the CDC’s number can’t settle the dispute over the relative merits of abstinence or safe-sex policies, Douglas told NJ. The study did not compare STI rates among youths who participated in abstinence programs, or the teenagers’ use of condoms. “No, this study can’t address that question at all,” Douglas said.
Shortcomings
In several interviews, CDC officials offered more details about the report but declined to answer some questions.
The CDC’s announcement, and the many subsequent media reports, said that the study surveyed 838 girls and women. But the study relies on data from only 590 females who were tested for all four diseases and another 25 girls who were tested for three or fewer diseases and had one positive result. Although another 223 women were examined, they were excluded because of incomplete test results.
The data’s complexity and the small sample size mean that the study’s “relative standard error” is greater than 30 percent, according to briefing charts presented by Forhan two days after the press conference. Anne Elixhauser, a senior research scientist at the federal Agency for Healthcare Research and Quality, says that her researchers generally reject data that hit the 30 percent RSE level. With such a high error rate, each year’s results could be “unbelievably different,” she said.
“We, as a general rule, try not to report estimates with RSEs [greater than] 30 percent, and in the rare circumstances that we do, we note the estimate as unreliable,” CDC officials said in a response to a query from NJ.
The distinction between infections, which are invasions of the body by pathogenic microorganisms such as viruses and bacteria, and diseases, which cause damage to the body, is especially relevant to HPV infections. They accounted for two-thirds of the infected females in the CDC study. Yet 90 percent of all HPV infections are quietly suppressed by the body’s internal defenses within two years, often without the person exhibiting any symptoms. Persistent HPV infections do cause cancer in some women and men after many years, but less than 1 percent of females age 15 to 45 suffer from HPV-induced genital warts each year, said Laura Koutsky, a leading HPV expert who teaches at the University of Washington.
Abstinence-until-marriage programs nearly always fail because, surveys show, 95 percent of people have sex before marriage. --Heather Boonstra, Guttmacher Institute
“Technically speaking … STD refers to the situation where an infection transmitted through sexual activity has caused a problem,” a CDC statement said. “However, the term STD is in more common use among both professionals and the lay public to refer to STD/STI considered together.”
HPV-to-cancer conversion takes decades (the average age at diagnosis is 48), and the condition is routinely cured if detected in a pap-smear test. The cervical cancer rate declined 4 percent between 1996 and 2005, and it is likely to shrink further as more women use the Gardasil vaccine that became available in 2006. CDC officials champion the vaccine, which was developed by Koutsky, because it defeats HPV strains that cause 90 percent of genital warts and 70 percent of cervical cancers. It is ineffective, however, in curing infections that develop before the vaccination is given.
Douglas acknowledged to the Chicago Tribune that “HPV does inflate the [CDC] number, because it causes the majority of infections and that majority may not cause any physical harm.” This quote was published on April 5 after he had been interviewed by an editorial intern, Katie Hamilton, about the one-in-four number. When asked by NJ to explain his answer, Douglas responded, “ ‘Inflate’ isn’t intended to mean ‘hyperinflate.’ ”
“We’re lumping the [four infections] together because of how common they were,” he said. “We thought this was an important way to understand the magnitude of infection in this population.”
Yet CDC officials glossed over the fact that the NHANES database showed no HIV or syphilis infections among the 18- and 19-year-old women in the survey. The NHANES researchers did not test 14-to-17-year-olds for HIV or syphilis.
Focusing the study entirely on “teenage girls” also yielded alarming results by including women ages 18 and 19, who are far more likely to be having sex than younger teenagers. For example, only 13 percent of females have had sex by age 15, but 70 percent have had sex before their 19th birthday, according to the Guttmacher Institute, an advocacy group that was spun off from Planned Parenthood in 1977. The exclusion of women ages 18 and 19 from the survey would very likely reduce the estimate of teenage STI prevalence, Boonstra said.
CDC officials refused to say how many of the infections were in the 18-to-19 age group, or how many of the girls 14 to 17 had STIs. “I don’t have that information,” Douglas told National Journal on May 2. Maya Sternberg, a CDC researcher who co-authored the one-in-four study, said that the infection rates for girls 14 to 17 may be published next year.
But other CDC figures provide a rough guide. A CDC report on the sexual activity of teenagers says that in 2002, 30 percent of girls ages 15 to 17 had experienced sexual intercourse. The March 11 report says that females ages 14 to 19 have a one-in-five chance of getting an STI from their first sexual partner. If those figures are combined, they suggest that the STI rate, including HPV, among 15-to-17-year-old girls would be roughly one-fifth of 30 percent, or 6 percent.
Had the study included males ages 14 to 19, it would probably have shown lower rates. Gonorrhea and HSV-2 are two to three times as frequent among females as males, according to other CDC studies, and a 2007 CDC article said that chlamydia is twice as prevalent among females as males in the 14-to-19 age group.
The CDC study focused on females primarily because testing boys for sexual diseases is difficult, Douglas said.
CDC and Politics
CDC officials try to stay clear of politics, Douglas said. They present scientific conclusions, he said, and “let the chips fall where they may politically.” Yet some of the CDC’s statements fall neatly in line with liberal stances on sex policy. At the March 11 press conference, for example, Douglas promoted “expedited partner therapy,” in which doctors work with infected patients who can pass treatment information on to their sexual partners who may not visit the doctor’s office. This practice is permissible in 11 states, prohibited in 13 others, and “potentially allowable” in 28 states, according to the CDC website.
The March 11 study was closely associated with the CDC’s funding aspirations. On the day it was released, CDC officials used the study to tout their sexually transmitted disease programs. “Continued commitment to STD prevention is essential,” Kevin Fenton, the director of the CDC’s STD division and Douglas’s boss, said at the beginning of the press conference. “CDC estimates that approximately 19 million new [sexually transmitted] infections occur every year in the United States, [and] our task is to maximize the use of these new tools—from vaccines to innovative STD screening and treatment.”
Because of the study, “we got some really good press, and we’ve been able to get the [budget] discussion on the table,” said Don Clark, the executive director of the National Coalition of STD Directors, which is pushing to increase the STD budget. The CDC’s STD programs have been reduced since 2003, and they’re now stuck at about $150 million, he said. Last year, the agency asked for $267 million a year.
Overall, the CDC’s primary budget—excluding vaccine programs—has been cut 15 percent since 2005, says Karl Moeller, the executive director of the Campaign for Public Health, an industry-funded coalition formed in 2004 to boost the CDC’s core budget from $6.3 billion in 2005 to $15 billion by 2012.
The one-in-four pitch certainly had an impact on Rep. Stephanie Tubbs Jones, D-Ohio, who told NJ that it persuaded her to push for an increase in the agency’s budget.
The CDC’s March 11 conference was seemingly about health, but it was also about politics, said Robert Fullilove, a doctor, an STI expert, and the associate dean for community and minority affairs at Columbia University. It was “not so subtle, and [while] within the framework of the regulations that govern how [officials] interact with the public,” he said, it was also “absolutely political.”
The CDC is a science agency, yet it is expected to advocate for policies that aid public health, said Jeffrey Koplan, the CDC’s director from 1998 to 2002. Science demonstrates that seat belts and air bags reduce automobile deaths, so “it would be irresponsible for public health leaders not to advocate for them,” said Koplan, who is now the executive director of Emory University’s Global Health Institute. “Large parts of public health are political.”
Yet, to avert charges of politicization, CDC officials have to carefully draft every statement to ensure that they’re built on “rock-solid” science, Koplan said. When well written and based on good science, he said, an agency statement “drives the message home but does not lead to unnecessary confusion.”
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