IJC
International Journal of Cancer
The association of hormonal contraceptive use and HPV
prevalence
Morgan Marks1, Patti E. Gravitt1,2, Swati B. Gupta3, Kai-Li Liaw3, Esther Kim1, Amha Tadesse3, Chailert Phongnarisorn4,
Virach Wootipoom5, Pissamai Yuenyao6, Charoen Vipupinyo7, Sungwal Rugpao8†, Somchai Sriplienchan9
and David D. Celentano1
1
Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
3
Merck & Co. Inc., West Point, PA
4
Division of Gynecologic Onocology, Department of Obstetrics and Gynecology, Chiang Mai University, Chaing Mai, Thailand
5
Department of Gynecologic Oncology Unit, OB-GYN, Prince of Songkla University, HadYai, Thailand
6
Department of Obstetrics and Gynecology, Khon Kaen University, Khon Kaen, Thailand
7
Department of Obstetrics and Gynecology, Rajavithi Hospital, Bangkok, Thailand
8
Obstetric and Gynecology department, Chiang Mai University, Chaing Mai, Thailand, Chiang Mai, Thailand
9
Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
2
Epidemiology
Women diagnosed with cervical cancer report longer duration and more recent use of combined oral contraceptives (COCs). It
is unclear whether COC use is associated with upstream events of human papillomavirus (HPV) infection prior to development
of clinical disease. The objective of our study was to assess the association of contraceptive use on the risk for prevalent HPV
infection in a cohort of long-term hormonal contraceptive (HC) users. One thousand and seventy (n 5 1,070) HIV-negative
women aged 20–37 from Thailand enrolled in a prospective study of the natural history of HPV. Baseline HPV genotype
information, recency and duration of HC use, sexual behavior, other sexually transmitted infection (STI) information and
cervical cytology and histology were assessed. At enrollment, 19.8% and 11.5% of women were infected with any HPV or
any high-risk (HR)-HPV, respectively. After adjustment for age, current and past sexual risk behaviors, STI history and
cytology, the use of COCs for >6 years was found to be associated with an increased risk of infection with any HPV
[prevalence ratio (PR): 1.88 (1.21, 2.90)] and any HR-HPV [PR: 2.68 (1.47, 4.88)] as compared to never users. Recent,
long-term COC use was associated with an increased risk for prevalent HPV infection independent of sexual behavior and
cervical abnormalities. No similar association was observed for recent or long duration use of progestin-only contraceptives
(i.e., depomedroxyprogesterone acetate). These data suggest that COC use may impact early upstream events in the natural
history of HPV infection.
Cervical cancer is the second most common cancer among
women worldwide and a leading cause of cancer-related mortality in the developing world.1 Genital human papillomavirus (HPV) infections have been identified as a necessary
Key words: HPV, COC, epidemiology, Thailand
†
Deceased.
Conflict of interest: SG: Employee of Merck Research Laboratories
who funded research; KLL: Employee of Merck, Sharp and Dohme,
which manufacturers the quadrivalent HPV vaccine, and owns
Merck stocks and options; AT: Employee of Merck.
Grant sponsor: NIAID (Predoctoral Training Fellowship in Sexually
Transmitted Infections); Grant number: 5T32AI050056-09; Grant
sponsor: Merck & Co. Inc
DOI: 10.1002/ijc.25628
History: Received 12 Mar 2010; Accepted 21 Jul 2010; Online 23
Aug 2010
Correspondence to: Patti E. Gravitt, Department of Epidemiology,
Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe St.,
Rm. E6148, Baltimore, MD 21205, USA, Tel.: þ443-287-6179,
Fax: þ410-955-1393, E-mail: pgravitt@jhsph.edu
C 2010 UICC
Int. J. Cancer: 128, 2962–2970 (2011) V
cause of cervical cancer.2–4 More than 35 different types of
HPVs infect the genital tract, with 18 types considered oncogenic or potentially oncogenic.5,6 Roughly 291 million
women worldwide are currently infected with one of these
anogenital HPVs, and approximately 80% of women will be
exposed at some point in their lifetime, making HPV the
most common sexually transmitted infection (STI).7 However, a majority of HPV infections spontaneously resolve
within 1–2 years postdetection. Therefore, other environmental, host and viral cofactors are likely required for the development of cervical cancer.8
Long-term use of combined oral contraceptives (COCs)
has been shown in several case–control studies to be associated with cervical cancer diagnosis among HPV-positive
women.9–12 However, it is unclear whether this association is
driven by COCs’ effect on carcinogenesis or on upstream
subclinical endpoints of the natural history such as HPV acquisition and persistence as prospective studies assessing
these relationships are inconsistent.13–19 A systematic review
of 19 studies looking at COC use and prevalent HPV infection demonstrated an inconsistent association with a high
Marks et al.
Material and Methods
Study population and enrollment
Women attending family planning clinics in the north-eastern (Chiang Mai/Khon Kaen), central (Bangkok) and southern (Songkla/HatYai) districts in Thailand between 2002 and
2003 were recruited into a prospective study investigating the
natural history of HPV and CIN 2/3 who were between 20
and 37 years of age. These women were formally enrolled in
a study addressing the effects of hormonal contraceptive use
on HIV acquisition (HC-HIV). Selection criteria are described
in detail elsewhere.25 Briefly, inclusion criteria for enrollment
in the HC-HIV study were as follows: (i) HIV negative; (ii)
not pregnant; (iii) intact uterus; (iv) used some form of contraception in the 3 months prior to enrollment and (v) willing
to adhere to the self-selected contraceptive method for at least
1 year of follow-up. Among women who participated in the
HC-HIV, 79% were reconsented for inclusion in the current
study (n ¼ 1,256). The study protocols were reviewed and
approved by the committees on human subject research at the
Johns Hopkins Bloomberg School of Public Health, Baltimore,
MD, Merck Research Laboratories, West Point, PA, each study
recruitment site and the Institutional Review Board of the
Thailand Ministry of Health, Thailand.
At HC-HIV enrollment and reconsent, information on
sociodemographic characteristics, sexual risk behavior, reproductive and contraceptive history, current contraceptive usage
status, self-reported medical history and woman’s report of the
sexual behavior of her partner was collected at each study site
by trained interviewers using a standardized questionnaire.
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Int. J. Cancer: 128, 2962–2970 (2011) V
Sexual behavior variables measured included age of sexual
debut, lifetime number of sexual partners, number of sexual
partners in the last 6 months and/or new sexual partners
acquired in the last year, primary partner risk behaviors, commercial sex work in the last 6 months, frequency of sexual
intercourse and frequency of male/female condom use per sexual act. Reproductive information regarding recent pregnancy
and total number of live births was collected. Within each
class of contraceptive use, there was little variability in the
brand or formulation reported by the participants of this
study. Therefore, contraceptive use was broadly classified as (i)
combined low-dose oral contraceptives (COC), (ii) depomedroxyprogesterone acetate (DMPA), or (iii) nonhormonal contraceptive (NHC) use and nonuse. Current use, duration of
use prior to enrollment and time since last use (i.e., recency)
for each category of hormonal contraception was assessed.
Questionnaire and physical examination data from the
original HC-HIV study were extracted and linked to the participants. Laboratory-confirmed STI status from the 2 years
prior to the current study, including gonorrhea (GC), chlamydia (CT), syphilis (SYP) and trichomoniasis, was included
in this analysis.
Physical examination and specimen collection
At enrollment, each participant underwent a pelvic examination. Exfoliated cervical cells were collected using a cytobrush
and placed in PreservCytTM for ThinprepTM liquid-based cytology. CT and GC detection from an ectocervical mucus specimen was performed using the Roche Amplicor assay per manufacturer’s instructions (Roche Molecular Systems, Alameda,
CA). An endo/ectocervical swab specimen was collected for
HPV DNA genotyping using a Dacron swab stored in Specimen Transport Medium (STM; Digene) at 20 C until testing.
All Pap smear specimens were read by trained cytopathologists (Covance, Indianapolis, IN). Cytological smears were
classified according to the Bethesda System.26 Participants
with an abnormal Pap smear diagnosis of atypical squamous
cell of undetermined significance (ASC-US) or more severe
(ASC-US) were referred for colposcopic examination with
biopsy and treatment as indicated.
HPV DNA testing
All HPV DNA testing was performed on cervical cell samples
stored in STM (Digene) at the Johns Hopkins University,
Baltimore, MD. DNA was extracted using the QIAamp DNA
Blood Kit (Qiagen, Courtaboeuf, France) according to the
manufacturer’s instructions with modification. After extraction, 8 ll of DNA (4% of total volume of extracted DNA)
was tested using the Roche HPV Linear Array PCR Assay
(Roche Diagnostics, Indianapolis, IN). The HPV Linear
C is based on the PGMY09/11 primer system that
ArrayV
allows for high-efficiency amplification of >40 types of
HPV.27,28 The quality and validity of the extracted DNA
specimen were assessed by inclusion of b-globin gene-specific
Epidemiology
degree of heterogeneity across studies.20 Most of the studies
included in this review sampled either young women (<30
years of age) or older women (>35 years of age). Studies that
sampled younger women and used highly sensitive PCRbased HPV DNA detection methods were more likely to see
an association among current users21 as well as users who
reported short-duration (<5 years)22,23 and medium-duration
(5–9 years) users.22,24 Conversely, studies that addressed the
association of COC use and HPV prevalence among women
>35 years who were selected as age-matched controls in
case–control studies assessing the effects of COCs on either
cervical carcinoma9 or cervical intraepithelial neoplasia 3
(CIN3)19 showed no association with current, short-, medium- or long-term COC use. The difference in association
across studies by age suggests that COCs are exerting their
influence on a very narrow window in the HPV natural history either at the point of HPV acquisition or at the point of
the establishment of a persistent infection prior to the development of high-grade precancerous lesions or cervical cancer.
To better examine the association of hormonal contraceptive (HC) use on early virologic endpoints, we examined the
cross-sectional association of duration and recency of COC
use on HPV prevalence in a cohort of 20- to 37-year-old
women recruited from family planning clinics in Thailand.
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2964
primers in the PCR reaction. Only specimens with detectable
b-globin were used in this analysis.
HPV types considered to be high-risk (HR)-HPV for this
analysis included 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 55, 56,
58, 59, 68, 73, 82 and 66.5,7 Low-risk (LR)-HPV types
included all other HPV types detected by the HPV Linear
C . Multiple infections that include a HR-HPV type
ArrayV
were classified as high risk regardless of the presence of lowrisk coinfection.
Epidemiology
Statistical analysis
The primary outcome of this analysis is detection of any
HPV or any HR-HPV type as previously defined. At enrollment, 6 (0.4%) of the 1,256 samples were b-globin-negative
leaving a total of 1,250 with adequate HPV DNA results. The
primary exposure(s) of interest in this analysis is the current
and prior usage of COC or DMPA. Other contraceptives
reported included other injectable contraceptives (n ¼ 2),
norplant (n ¼ 2) and intrauterine device (n ¼ 1). Because of
low frequency of use, women reporting use of other injectable and noninjectable contraception (n ¼ 5) were excluded
from the analysis. History of usage of DMPA or COC was
initially defined as ‘‘ever versus never’’ and ‘‘current versus
former versus never.’’ Prior usage was defined as duration of
use prior to enrollment (categorized into ‘‘never,’’ ‘‘<4 years,’’
‘‘4–6 years" and ‘‘>6 years’’) and time since last use (i.e.,
recency) among those reporting no current use (categorized
into ‘‘never,’’ ‘‘<6 months,’’ ‘‘6 months to 3 years,’’ ‘‘3–4
years" and ‘‘>4 years’’). These categorizations were based on
both categorization in prior studies9,11,24 and the observed
distribution of the values. Lastly, a variable combining both
current and former use with cumulative duration of use was
created to assess the joint effects of current and prior use on
HPV detection.
Age was categorized as 20–25 years, 26–30 years, 31–33
years and 34–37 years. Study site was categorized by region
as North (Chiang Mai), North-East (Khon Kaen), Central
(Bangkok) and South (Hat Yai/Songkla). Lifetime number of
sexual partners was categorized as 1, 2, 3 or 4, and sexual
partners in the last 6 months was categorized as 0, 1 or >1.
The number of live births was categorized as 0, 1 or >1.
STIs including laboratory-confirmed GC, CT and SYP diagnosed prior to enrollment were categorized individually as
‘‘ever’’ versus ‘‘never.’’
Cytological diagnosis by Pap smear was categorized as
‘‘normal’’ versus ‘‘inflammation,’’ ‘‘ASC-US,’’ ‘‘low-grade
squamous intraepithelial lesion’’ and ‘‘high-grade squamous
intraepithelial lesion." Histological diagnosis was categorized
as ‘‘normal’’ versus ‘‘CIN1’’ versus ‘‘CIN 2/3.’’
To control for the effects of unmeasured sexual behavior
or HPV infections that have advanced to the stage of detectable clinical disease on the association of contraceptive use on
HPV prevalence, women who engaged in commercial sex
work within the last 6 months prior to enrollment (n ¼ 42)
and/or who were diagnosed with CIN 2/3 by histology at
Hormonal contraceptive use and HPV prevalence
enrollment (n ¼ 11) and/or with unsatisfactory Pap smear
information (n ¼ 2) or a Pap smear interpretation of ASCUS (n ¼ 86) were excluded from this analysis. In addition,
there were 33 women (2.6%) with missing parity data and 1
woman (0.1%) with a missing STI diagnosis data at enrollment. The results were unchanged when missing data were
excluded versus included; therefore, these women were
excluded from the analysis.
Contingency tables were created to assess the distribution
of the primary exposures and covariates on any HPV and
any HR-HPV detection. Differences in outcome probability
across the covariate distributions were evaluated using the v2
statistic or Fisher’s exact test where appropriate.
Given the high prevalence of HPV detected in this study
population, odds ratios as a measure of association calculated
using logistic regression may overestimate the strength of the
association.29,30 Therefore, prevalence ratios were estimated
using Poisson regression with robust variance.31
Separate multivariate models were constructed for each
outcome of any HPV and any HR-HPV. Backward stepwise
removal from the full multivariate model was performed.
Covariates with a p-value of <0.1 were considered for inclusion in the multivariate regression model. All multivariate
models adjusted for age and study site. Covariates that, on
removal, showed a >10% change in the effect size of the primary exposure and outcome association or had a p-value of
<0.05 were retained in the final model. Final multivariate
models were constructed to estimate the independent association of HC use and prevalent HPV adjusted for age, number
of live births, number of lifetime partners, number of partners in the last 6 months, smoking, prior diagnosis of each
STI and cytologic diagnosis at enrollment. A p-value of
<0.05 was considered statistically significant in the final multivariate model for the association of a given variable and
detection of HPV DNA. All analyses were conducted using
STATA 9.2 (STATACORP, College Station, TX).
Results
One thousand seventy women were included in this analysis.
The overall prevalence of any HPV and any HR-HPV detection was 19.8% and 11.5%, respectively (Table 1). The mean
age of the study population was 29.6 years (SD: 4.3). A majority of women reported 1 live birth (98.1%), one lifetime
sexual partner (73.0%), one recent sexual partner (97.1%)
and were nonsmokers (96.7%). Infection with any bacterial
STI in the 2 years prior to enrollment was detected in 15.0%
of women. Diagnosis of either GC or CT at study enrollment
was detected in 1.1% of women.
A higher prevalence of any HPV and any HR-HPV was
observed among women recruited from Bangkok, women
reporting a greater number of lifetime and recent sexual partners and women who smoked or had a history of STIs prior
to and at enrollment (Table 1). Conversely, a lower prevalence of any HPV and any HR-HPV was observed among
women with greater than or equal to one live birth.
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Int. J. Cancer: 128, 2962–2970 (2011) V
Table 1. Univariate association of demographic, reproductive history, contraceptive use, sexual behavior, clinical variables and prevalent
HPV infection status at enrollment
Variable
Total sample, N (%)
% HPV1
N 5 1,070
n 5 212 (19.8%)
p-Value
n 5 123 (11.5%)
p-Value
p ¼ 0.878
12.2%
p ¼ 0.980
% HR-HPV1
Age category (years)
<26
197 (18.4)
19.3%
26–30
380 (35.5)
18.3%
11.3%
31–33
246 (22.9)
21.5%
10.9%
34–37
247 (23.1)
19.8%
11.7%
Study site
North (Chiang Mai)
394 (36.8)
17.5%
NE (Khon Kaen)
244 (22.8)
15.9%
p ¼ 0.032
10.2%
p ¼ 0.025
7.8%
S (Songkla/Hat Yai)
267 (24.9)
23.2%
13.9%
Central (Bangkok)
165 (15.4)
25.5%
16.4 %
0
20 (1.9)
55.0%
1
533 (49.8)
19.3%
12.0%
>1
517 (48.3)
18.9%
10.1%
NHC
404 (37.8)
21.3%
DMPA
307 (28.7)
16.3%
10.8%
COC
359 (33.6)
21.2%
12.8%
45 (4.2)
13.3%
COC only
193 (18.0)
22.3%
11.4%
DMPA only
125 (11.7)
17.6%
8.8%
COC and DMPA
707 (66.1)
19.9%
12.2%
Parity
p < 0.001
35.0%
p ¼ 0.002
Current contraceptive use
p ¼ 0.185
10.9%
p ¼ 0.629
Ever use of HC
Never
p ¼ 0.508
8.9%
p ¼ 0.681
Number of lifetime partner
p < 0.001
1
788 (73.6)
14.9%
2
163 (15.2)
29.5%
15.9%
8.5%
3
55 (5.1)
27.3%
23.6%
4
64 (5.9)
48.4%
26.6%
<7
199 (18.6)
19.6%
7–9
282 (26.4)
15.6%
9.9%
10–13
340 (31.8)
20.6%
11.8%
>13
249 (23.3)
23.7%
12.5%
p < 0.001
Years since sexual debut
p ¼ 0.130
12.1%
p ¼ 0.804
Number of partners L6M
0
1
>1
27 (2.5)
1,038 (97.0)
5 (0.5)
7.4%
p ¼ 0.001
0.0%
19.9%
11.6%
80.0%
60.0%
p ¼ 0.001
Smoked cigarettes L6M
No
Yes
1,037 (96.9)
18.9%
33 (3.1)
48.5%
No
912 (85.2)
18.1%
Yes
158 (14.8)
29.8%
p < 0.001
10.8%
p < 0.001
33.3%
Ever GC/CT/SYP
p ¼ 0.001
9.9%
p < 0.001
20.3%
Current GC/CT infection
No
Yes
Abbreviation: L6M, last 6 months.
1,061 (99.2)
9 (0.8)
19.7%
33.3%
p ¼ 0.307
11.4%
22.2%
p ¼ 0.311
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Hormonal contraceptive use and HPV prevalence
Table 2. Association of ever/former/current COC and DMPA use on risk of any HPV and any HR-HPV infection at enrollment
N
Any HPV infection
Any HR-HPV infection
N 5 1,070
n (%) HPV1
n 5 212
Never
170
28 (16.5)
1.0
1.0
Ever
900
221 (20.4)
1.24 (0.87, 1.78)
1.13 (0.79, 1.61)
108 (12.0)
1.36 (0.81, 2.28)
1.20 (0.72, 2.00)
Former
541
128 (19.9)
1.21 (0.83, 1.77)
1.14 (0.79, 1.65)
62 (11.5)
1.29 (0.76, 2.22)
1.21 (0.71, 2.05)
Current
359
93 (21.2)
1.29 (0.87, 1.90)
1.11 (0.75, 1.65)
46 (12.8)
1.45 (0.83, 2.53)
1.19 (0.68, 2.09)
Variable
PR (95% CI)
aPR1 (95% CI)
n (%) HPV1
n 5 123
PR (95% CI)
aPR1 (95% CI)
COC
15 (8.8)
1.0
1.0
DMPA
Never
238
49 (20.6)
1.0
1.0
26 (10.9)
1.0
1.0
Ever
832
163 (19.6)
0.95 (0.72, 1.27)
1.05 (0.79, 1.39)
97 (11.7)
1.07 (0.71, 1.61)
1.21 (0.79, 1.82)
Former
525
113 (21.5)
1.05 (0.78, 1.41)
1.14 (0.85, 1.53)
64 (12.2)
1.12 (0.73, 1.71)
1.25 (0.81, 1.92)
Current
307
50 (16.3)
0.79 (0.55, 1.13)
0.89 (0.63, 1.28)
33 (10.8)
0.98 (0.61, 1.59)
1.13 (0.69, 1.86)
1
All models adjusted for age, lifetime number of partners, number of partners L6M, smoking, number of live births ever and ever GC/CT/SYP
infection.
COC use history and prevalent HPV infection
Ever use of COCs prior to enrollment was reported by 84.1%
of women (Table 2). Current use of COCs was reported by
33.6% of women at study enrollment. Current and former
COC use was not associated with detection of any HPV or
any HR-HPV type. A majority of women reported ever use
of both COCs and DMPA (66.1%).
Epidemiology
Duration of COC use and prevalent HPV infection. Half
(51.6%) of all women reported using COCs for <4 years and
7.6% reported using COCs for >6 years (Table 3). The use
of COCs for >6 years was associated with detection of any
HPV and any HR-HPV. After stratification by current use
status, COC use for >6 years was significantly associated
with detection of any HPV and any HR-HPV among both
former and current users (Table 4).
In multivariate analysis, long-term use of COCs for >6
years remained independently associated with an increased
risk of infection with any HPV and any HR-HPV (Table 3).
After stratification by current use status, use of >6 years
remained significantly associated with any HPV among current users only and any HR-HPV among both former and
current users (Table 4).
Recency of COC use and prevalent HPV infection. Among
women who reported former use of COCs and are noncurrent
users, a majority (93.7%) reported stopping use >6 months
prior to enrollment (Table 3). Increasing time since last use of
COCs among noncurrent users was not found to be significantly associated with any or any HR-HPV infection.
DMPA use history and prevalent HPV infection
Ever use of DMPA prior to enrollment was reported by
77.7% of women (Table 2). Current DMPA use was reported
by 28.7% of women at study enrollment. Current use of
DMPA was nonsignificantly associated with a decreased prevalence of any HPV infection.
Duration of DMPA use and prevalent HPV infection. Nearly
half (46.7%) of all women reported using DMPA for <4
years and 4.4% reported using DMPA for >6 years (Table
3). The use of DMPA for 4–6 years was associated with a
nonsignificant decrease in prevalence of any HPV infection
(Table 4).
Recency of DMPA use and prevalent HPV infection. Among
women who reported former use of DMPA and are noncurrent users, a majority (90.7%) reported stopping use >6
months prior to enrollment (Table 3). Increasing time since
last use of DMPA among current nonusers was not found to
be significantly associated with any or any HR HPV infection.
Discussion
The current study demonstrates an association between the
use of COCs for >6 years and prevalent HPV infection
among 20- to 37-year-old women from Thailand after controlling for sexual behavior and cytological abnormalities.
This finding is in agreement with other smaller cross-sectional studies conducted among college age women and
women 20–29 years of age who report COC use for >4
years.22,24 The observed trend of increased detection of HPV
in relation to increased duration of COC use parallels similar
trends of COC use and cervical cancer diagnosis previously
described.9–12 Interestingly, this study failed to see an attenuation of the association with increasing recency of use which
is inconsistent with prior work.9 Given that this study overselected younger women who had at least 2 years of prior exposure to HCs, this study may not be powered to assess difference by recency among nonusers. However, HPV
prevalence in a cross-sectional study is a function of both
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Int. J. Cancer: 128, 2962–2970 (2011) V
Marks et al.
2967
Table 3. Association of duration and recency of COC and DMPA use on risk of any HPV infection and any HR-HPV infection at enrollment
N
Variable
N 5 1,070
Any HPV infection
% HPV1
n 5 212
PR (95% CI)
Any HR-HPV infection
aPR1 (95% CI)
% HPV1
n 5 123
PR (95% CI)
aPR1 (95% CI)
COC
Duration
Never
170
28 (16.5)
1.0
1.0
15 (8.8)
1.0
1.0
<4 years
552
105 (19.0)
1.15 (0.79, 1.69)
1.07 (0.74, 1.55)
56 (10.1)
1.15 (0.67, 1.98)
1.04 (0.61, 1.78)
4–6 years
266
48 (18.1)
1.10 (0.72, 1.68)
1.02 (0.67, 1.55)
28 (10.5)
1.19 (0.66, 2.17)
1.09 (0.59, 1.98)
>6 years
82
31 (37.8)
2.30 (1.48, 3.56)
1.88 (1.21, 2.90)
24 (29.3)
3.32 (1.84, 5.98)
2.68 (1.47, 4.88)
170
28 (16.5)
1.0
1.0
15 (8.8)
1.0
1.0
Recency2
Never
<6 months
34
8 (23.5)
1.43 (0.71, 2.86)
0.97 (0.44, 2.14)
6 (17.7)
2.00 (0.84, 4.79)
1.04 (0.35, 3.07)
6 months–3 years
117
25 (21.4)
1.30 (0.79, 2.11)
1.12 (0.71, 1.79)
14 (11.9)
1.36 (0.68, 2.70)
1.13 (0.57, 2.22)
3–4 years
181
38 (20.9)
1.27 (0.82, 1.98)
1.20 (0.78, 1.83)
20 (11.1)
1.25 (0.66, 2.37)
1.16 (0.63, 2.13)
>4 years
209
37 (17.7)
1.07 (0.69, 1.68)
1.09 (0.71, 1.68)
22 (10.5)
1.19 (0.64, 2.23)
1.31 (0.71, 2.43)
DMPA
Duration
Never
238
49 (20.6)
1.0
1.0
26 (10.9)
1.0
1.0
<4 years
500
110 (22.0)
1.07 (0.79, 1.44)
1.18 (0.88, 1.58)
60 (12.0)
1.10 (0.71, 1.69)
1.24 (0.80, 1.91)
4–6 years
285
43 (15.1)
0.73 (0.51, 1.06)
0.82 (0.57, 1.19)
31 (10.9)
0.99 (0.61, 1.63)
1.13 (0.69, 1.86)
>6 years
47
10 (21.3)
1.03 (0.56, 1.89)
1.12 (0.63, 1.99)
6 (12.8)
1.17 (0.51, 2.68)
1.30 (0.59, 2.87)
238
49 (20.6)
1.0
1.0
26 (10.9)
1.0
1.0
<6 months
49
12 (24.5)
1.19 (0.69, 2.07)
1.17 (0.67, 2.07)
8 (16.3)
1.49 (0.72, 3.10)
1.42 (0.67, 3.02)
6 months–3 years
188
33 (17.6)
0.85 (0.57, 1.27)
0.87 (0.58, 1.30)
17 (9.0)
0.83 (0.46, 1.48)
0.85 (0.48, 1.51)
3–4 years
161
36 (22.4)
1.09 (0.74, 1.59)
1.21 (0.83, 1.75)
20 (12.4)
1.14 (0.66, 1.97)
1.30 (0.76, 2.24)
>4 years
127
32 (25.2)
1.22 (0.83, 1.81)
1.49 (1.00, 2.21)
19 (14.9)
1.37 (0.79, 2.38)
1.83 (1.03, 3.22)
Recency2
Never
1
rate of acquisition of new HPV infections and increased duration of pre-existing HPV infections.
Female sex steroid hormones particularly progesterone
and estrogen induce upregulation of HPV oncogenes in cell
culture and induce development of preneoplastic lesions in
mouse models.32,33 More recently, these sex steroid hormones
applied at biologically relevant concentrations to COC exposure were shown to modulate the host immune response to
the HPV 16 virus-like particle through upregulation of antiinflammatory and regulatory immune markers.34 These data
suggest that exogenous hormonal exposure in the form of
COC use could be influencing both viral and host factors
associated with subclinical and clinical outcomes in the natural history of HPV and cervical cancer.
A higher prevalence of HPV was observed among women
who were recruited from the central and southern regions of
Thailand as compared to the northern region. The highest
prevalence HPV was observed in Bangkok, which is an urban
area with a high percentage of commercial sex workers.
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Int. J. Cancer: 128, 2962–2970 (2011) V
Although this analysis excluded women who reported recent
commercial sex work, the higher prevalence of HPV could be
explained by unmeasured sexual behavior of the participant
and their partners.
Single or multiparous women in this study were observed
to have a lower prevalence of HPV.35 Interestingly, nulliparous women were more likely to report 4 lifetime sex partners as well as to report a new sexual partner in the last 12
months as compared to women with one or more live births.
Therefore, inherent differences in sexual behavior between
parous and nulliparous women may explain the observed differences in HPV prevalence.
Our study has several strengths. First, the study sample
was derived from a trial assessing the effects of hormonal contraception on HIV acquisition. As a result, detailed information regarding contraceptive usage history as well as sexual
behavior and other risk factors was collected to provide accurate assessments of (i) cumulative exposure of HC use and (ii)
covariates that may confound associations of contraceptive use
Epidemiology
All models adjusted for age, lifetime number of partners, number of partners L6M, smoking, number of live births ever and ever GC/CT/SYP
infection. 2Among current nonusers.
2968
Hormonal contraceptive use and HPV prevalence
Table 4. Association of duration of COC and DMPA use stratified by current use status on risk of any HPV infection and any HR-HPV infection
at enrollment
N
Any HPV infection
Any HR-HPV infection
N 5 1,070
% HPV1
n 5 212
170
28 (16.5)
1.0
1.0
15 (8.8)
1.0
1.0
441
81 (18.4)
1.12 (0.75, 1.65)
1.05 (0.72, 1.54)
46 (10.4)
1.18 (0.68, 2.06)
1.11 (0.64, 1.91)
4–6 years
89
22 (24.7)
1.50 (0.91, 2.47)
1.45 (0.89, 2.36)
11 (12.4)
1.40 (0.67, 2.92)
1.40 (0.67, 2.91)
>6 years
11
5 (45.5)
2.76 (1.33, 5.74)
2.22 (1.01, 4.86)
5 (45.5)
5.15 (2.29, 11.6)
3.99 (1.64, 9.77)
<4 years
111
24 (21.6)
1.31 (0.80, 2.14)
1.11 (0.67, 1.84)
10 (9.0)
1.02 (0.48, 2.19)
0.80 (0.36, 1.78)
4–6 years
177
26 (14.7)
0.89 (0.55, 1.46)
0.81 (0.50, 1.32)
17 (9.6)
1.09 (0.56, 2.11)
0.95 (0.49, 1.84)
>6 years
71
26 (36.6)
2.22 (1.41, 3.51)
1.82 (1.16, 2.85)
19 (26.8)
3.03 (1.63, 5.63)
2.47 (1.33, 4.59)
238
49 (20.6)
1.0
1.0
26 (10.9)
1.0
1.0
<4 years
414
93 (22.5)
1.09 (0.80, 1.48)
1.20 (0.88, 1.62)
51 (12.3)
1.13 (0.72, 1.76)
1.27 (0.81, 1.98)
4–6 years
104
19 (18.3)
0.89 (0.55, 1.43)
0.94 (0.58, 1.53)
12 (11.5)
1.06 (0.55, 2.01)
1.16 (0.61, 2.20)
>6 years
7
1 (14.3)
0.69 (0.11, 4.34)
0.68 (0.11, 4.22)
1 (14.3)
1.31 (0.21, 8.33)
1.22 (0.19, 7.50)
<4 years
86
17 (19.8)
0.96 (0.59, 1.57)
1.07 (0.65, 1.76)
9 (10.5)
0.96 (0.47, 1.96)
1.08 (0.53, 2.21)
4–6 years
181
24 (13.3)
0.64 (0.41, 1.01)
0.74 (0.47, 1.14)
19 (10.5)
0.96 (0.55, 1.68)
1.11 (0.63, 1.95)
>6 years
40
9 (22.5)
1.09 (0.58, 2.05)
1.21 (0.67, 2.18)
5 (12.5)
1.14 (0.47, 2.81)
1.32 (0.57, 3.07)
Variable
aPR1 (95% CI)
PR (95% CI)
% HPV1
n 5 123
PR (95% CI)
aPR1 (95% CI)
COC
Never
Former
<4 years
Current
DMPA
Never
Former
Current
1
Epidemiology
All models adjusted for age, lifetime number of partners, number of partners L6M, smoking, number of live births ever and ever GC/CT/SYP
infection.
and HPV infection, particularly sexual behavior. In addition,
our design, which oversampled on contraceptive exposures,
results in a relatively balanced number of women using each
form of contraception, thereby increasing the power to assess
the role of contraceptive cofactors in the natural history of
HPV. Second, a pooled analysis on the effects of oral contraception and HPV infection has suggested residual confounding of this association by age even after adjustment,20 with
younger women using contraception for less time and more
likely to have a higher HPV prevalence. The current study
sample has a very narrow age range between 20 and 37 years
with a mean of 30 years and an interquartile range (IQR) of
26–33 years. Although increased duration of COC use was
found to be positively associated with older age (data not
shown), there was no association between age and HPV prevalence. Therefore, age is unlikely to be a significant confounder in our study and was retained in the final model
only for face validity. Third, the use of highly sensitive and
specific laboratory assays for HPV detection and genotyping
has allowed for a higher degree of internal validity of the outcome measures. Lastly, the study design allowed for exploration of various metrics of COC exposure including ever use,
current use, duration of use and time since last use. Ever use
of COCs in our study was found to have no association with
HPV infection. This finding is in agreement with previous
cross-sectional studies36–39 examining the association of COC
use on HPV infection among nondiseased women. This suggests that the influence of COCs on the natural history of
HPV is a result of a cumulative exposure. Studies assessing
ever use of COCs at a single time point are therefore combining short- and long-term users together in a single category, possibly diluting any association with HPV-related
outcomes.
There are several limitations to our study that should be
considered when drawing inferences from these results. First,
it is difficult to completely differentiate contraceptive use
from sexual risk behavior, thereby leaving the observed associations prone to residual confounding. Higher prevalence of
HPV has been shown to be associated with sexual behavior
of the participants and their male partners. We are limited in
this study by participants’ self-report for information about
the sexual behavior of their male partners, which is likely to
be unreliable, and the observed high prevalence of any HPV
(19.8%) and any HR-HPV (11.5%) is suggestive of unmeasured risk behaviors. The inclusion of sexual risk factors
including years since sexual debut did not significantly alter
C 2010 UICC
Int. J. Cancer: 128, 2962–2970 (2011) V
Marks et al.
2969
the association of long-term COC use with HPV prevalence.
Lastly, a high percentage of women reported ever use of both
COC and DMPA use in the past (66.1%). However, stratification of cumulative use of COCs by prior DMPA use had no
effect on the association with increased HPV prevalence
(data not shown).
The generalizability of these study findings to the general
population from which they were sampled, as well as to other
women who use hormonal contraception worldwide, may be
limited. The current study reports a prevalence of any HPV
and any HR-HPV that is almost fourfold higher than a population-based study previously conducted in Thailand.40 One
reason for this contrast is that the current study recruited
women who were previously enrolled in a trial assessing the
effects of hormonal contraception on HIV acquisition and
who were potentially at higher risk for HIV acquisition.
Although the prevalence estimates of HPV may not be representative of women in Thailand, the directionality and
strength of the association of contraceptive use on prevalent
HPV infection may be generalizable through oversampling
the primary exposure. This results in a decrease in the probability of a type II error, thereby the likelihood of seeing a
true association, assuming minimal confounding and bias, is
strengthened.
Prospective studies that have been conducted to assess the
association of COC use with HPV-related endpoints such as
acquisition and persistence of infection as well as develop-
ment of high-grade precancerous lesions have seen little to
no association with COC use, raising the question of the validity of our observed association with prevalent HPV. It is
important to consider that these studies were conducted primarily among adolescent14,41 or college-aged women13,15 or
women >35 years16,17,19 of age and measured COC exposure
as either current use or ‘‘ever’’ versus ‘‘never’’ use. Therefore,
studies among younger women who are closer to the age of
sexual debut may not have accumulated enough COC exposure time, whereas studies conducted among older women
did not measure duration of use and combined long- and
short-term users into a single ‘‘ever use’’ category, potentially
diluting the association with HPV and precancer. Prospective
studies are therefore needed to better assess what is driving
the cross-sectional observation.
In summary, our study observed that long-term use of
COCs of >6 years is associated with an increased risk of
prevalent HPV infection in a cohort of HC and NHC users
in Thailand. Conversely, no association was observed among
DMPA users; if anything, DMPA users were at a nonsignificantly decreased risk of HPV. Given the cross-sectional nature of the study design, it is difficult to determine if higher
prevalence associated with COC use is primarily driven by
increased acquisition of HPV or increased duration of preexisting HPV infection. Longitudinal studies examining the
risk of HPV acquisition and particularly HPV persistence by
contraceptive use are therefore urgently needed.
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