Factors associated with human papillomavirus infection among women in the Northwest Territories.

Brassard, Paul ; Jiang, Ying ; Severini, Alberto 等

Cervical cancer is the second leading cause of cancer-related deaths among women worldwide. Human papillomavirus (HPV) has been found to be the precursor for cervical cancer in 99% of the cases. Global HPV prevalence among women is estimated at 10%, with approximately 75% of the female population acquiring an HPV infection at least once in their lives. Furthermore, some population groups appear to be at higher risk for infection than others. (1,2)

In Canada, approximately 1,300 new cervical cancer cases are diagnosed each year and 380 deaths are due to the disease. (1) In some regions, Aboriginal women have higher rates of cervical cancer compared to other Canadian women. (3-6) Data from Manitoba show that in comparison with non-Aboriginal women, Aboriginal women had 1.8 and 3.6 times the age-standardized incidence rates of in situ and invasive cervical cancer, respectively. (4) In addition to oncogenic high-risk HPV (HR-HPV), several co-factors are needed in cervical carcinogenesis and little data are available regarding the determinants of HPV infection in the Aboriginal population of Canada. (7)

Aboriginal groups make up approximately half of the population of the Northwest Territories (NWT). (8) A recent study among women in the NWT found that HPV prevalence was approximately 50% higher among Aboriginal than non-Aboriginal women (28% versus 18.8%, respectively). (9) We wished to examine co-factors associated with HR-HPV infection in a population of women (both Aboriginal and non-Aboriginal) in the Northwest Territories. The identification of various factors associated with high-risk HPV could help in the planning of cervical cancer prevention and intervention programs in this region. (10-12)

METHODS

This cross-sectional design consisted of a convenience sample of all women aged 14 years or older presenting for a Papanicolaou (Pap) test across all regions of the NWT from March 2009 to March 2010. Participants were asked by their local health care provider to complete a questionnaire and to give written consent to both the questionnaire and HPV testing. Refusals to participate were not tabulated. The questionnaire consisted of 20 short multiple-choice questions and collected information known to be associated with HPV infection such as demographic characteristics, sexual behaviour, and gynaecological and obstetrical events. It was self-administered and reviewed by the health care provider in order to ensure completeness and to clarify any misunderstandings the study participant may have.

To avoid repeated measures, if more than one Pap test was performed over the study period, only the first sample (and accompanying questionnaire) was kept for analysis. Universal coverage of health care is present in the NWT, thus there are no other Pap test providers in the area. As of 2008, 88% of NWT women aged 18-69 reported having had a Pap test in the previous 3 years. (8)

Samples were collected through liquid-based cervical scrapes, stored in the NWT regional laboratory, and shipped to the [DynaLIFE.sub.Dx] Laboratory in Edmonton, Canada. Approximately half of the medium was retained for Pap testing. The remainder was shipped to the Public Health Agency of Canada National Microbiology Laboratory (NML) in Winnipeg, Canada for HPV typing.

HPV types are classified as being high-risk (HR) or low-risk (LR) based on their oncogenic potential in cervical cancer. (13)

HPV typing was done using a Luminex assay, a method developed at the NML in Canada which detects 46 HPV types. (14,15) These include 24 of the 25 IARC high-risk (HR) types found in group 1, 2a, and 2b (HPV 16, 18, 26, 30, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 67, 68, 69, 70, 73, 82, 85 and 97) as well as 22 types considered of low (LR) or unknown risk (6, 11, 13, 32, 40, 42, 43, 44, 54, 61, 62, 71, 72, 74, 81, 83, 84, 86, 87, 89, 90, and 91). (13) The sensitivity and specificity of the NML Luminex assay, using direct sequencing as a gold standard, were 98.8% and 96.4%, respectively. (15,16)

When present, contraception methods were classified as either hormonal-based or non-hormonal. Birth control pills and medroxy-progesterone injections were classified as hormonal, while IUDs, condoms, diaphragms, and tubal ligations were classified as non-hormonal. Sexually transmitted infections are reported as a subset for participants who answered "yes" to ever having had an STI. STI categories were not mutually exclusive as participants could report having had more than one STI. Lifetime number of sexual partners was dichotomized based on the median distribution. Grade school was defined as attendance from grades 1 through 12. The number of lifetime deliveries was reported as the number of live birth deliveries.

Univariate unconditional logistic regression was performed on all independent variables to assess their association with HR-HPV infection. Multivariate analysis was conducted on variables found statistically significant on univariate analysis results and predictors of HR-HPV infection that were identified in previous literature. Odds ratios (ORs) and their associated 95% confidence intervals (CIs) were calculated. Findings were considered to be statistically significant when the 2-sided p-value was [less than or equal to]0.05.

Ethics approval was obtained from the Health Canada Ethics Review Board, McGill University, and Stanton Territorial Health Authority. A license to conduct research was also obtained from the Aurora Research Institute in accordance with the NWT Scientists Act.

RESULTS

A total of 1,279 women participated in this study. Overall, 478 (37.4%) participants self-identified as Aboriginal and 677 (52.9%) self-identified as non-Aboriginal (9.7% had missing information on their cultural background). Among the Aboriginal women, 286 (59.8%) were of First Nations origin, 138 (28.9%) were Metis and 54 (11.3%) were Inuit. Most women were married or living with a partner (65.1%), had either grade school or community college education (63.4%), reported at least one full-term pregnancy (59.6%), and reported one sexual partner in the past year (72.1%).

When comparing our sample of women to the Canadian 2006 Census results for the NWT, our study had a statistically significant larger coverage of more educated, married, and younger women, as well as a smaller representation of Aboriginal women. Our participants matched the NWT general population on smoking and employment. (17)

Of the 1,279 participants, there were 178 (13.9%) women with missing HPV results (sample mislabelled or lost during transport). These were excluded from the logistic regression analysis. For the remaining 1,101 women, overall HR-HPV prevalence was 14.2%. HR-HPV was most prevalent among women aged 20 years or less (30.2%), with decreasing prevalence with increasing age (Table 1).

We examined co-factors of HR-HPV infection for the entire cohort in univariate and multivariate analysis. In the multivariate model, increasing age and number of lifetime deliveries were protective, while single marital status, Aboriginal background, use of hormonal contraceptives, current smoking, and the number of sexual partners in the last year increased the risk of prevalent HR-HPV (Table 1).

We then explored the co-factors for HR-HPV among women of Aboriginal background (First Nations, Metis and Inuit) and among non-Aboriginal women in the NWT (Tables 2 and 3). In multivariate analysis, only the number of lifetime deliveries was found to be protective of prevalent HR-HPV in non-Aboriginal women. In Aboriginal women, being single, hormonal contraception, current smoking, and age at first sexual intercourse were significant risk factors, while increasing age and number of lifetime deliveries were found to be protective. Among Aboriginal women, no difference in risk of HR-HPV infection was noted for the three different cultural groups.

DISCUSSION

This study demonstrates the differences in predictors of HR-HPV infection for different population groups. Aboriginal women were more than twice as likely to have HR-HPV as non-Aboriginal women (OR=2.40, 95% CI: 1.65-3.49, Table 1). It is important to note that between the different cultural groups of Aboriginal women in the NWT, there was no group that was more at risk than another. Overall, ever having had a sexually transmitted infection (STI) was not associated with a higher risk for HR-HPV, although this has been previously identified as a predictor of HPV infection. (12) We recorded self-reported information and may be dealing with a recall bias influencing our results. We also observed a decrease in risk of HPV infection with an increase in parity. Previous studies have reported similar findings. (18,19) However, some studies have reported an increase in risk with number of births. (20) More studies are needed to better conclude the effects of parity on the risk of HPV infection.

Overall, the number of sexual partners in the previous year was more indicative of current infection than was the number of lifetime partners. When we looked at this characteristic by Aboriginal status, although showing a clear trend in both groups, the number of sexual partners in the previous year did not reach statistical significance after adjusting for covariates.

Selection bias is a potential limitation associated with convenience sampling and could have influenced our findings. Our study had a larger coverage of more educated, married, and younger women, and a smaller representation of Aboriginal women than the overall NWT population. Women who participated in this study were those who presented for a Pap test and therefore, they could be prone to more preventive behaviour and healthier lifestyles than the general population. However, as of 2008, 88% of NWT women aged 18-69 reported having had a Pap test in the previous three years. (7) As very few women do not access the service over a three-year period, we can consider our sample somewhat representative in terms of accessing time-appropriate cervical cancer screening. Although recent literature is showing a pattern of increasing cervical cancer screening coverage among several different Aboriginal populations across Canada, (21) there is still cause for concern, given that there is a high prevalence of HR-HPV in this population. Additionally, it is not yet clear if the increase in screening rates will lead to a reduction in cervical cancer incidence and mortality if high-risk subsets of the population are systematically underscreened for cervical cancer. Unfortunately, we were not able to explore coverage according to geographical areas in the NWT as there could well be differences among rural/urban centres.

Our sample of women matched the general NWT population on smoking coverage, with 36.1% being smokers in the Census and 30.8% being smokers in our sample. (17) Furthermore, regardless of an under-representation of Aboriginal women, where in the worst scenario the most at risk would not attend Pap screening, had missing HPV results, or refused to participate in our study, we were able to describe a number of significant predictors for HR-HPV infection. Indeed, a notable number of co-factors were found among Aboriginal women and not among the non-Aboriginal group and tend to indicate that the former group have been exposed to a different degree to risk factors that affect HPV progression to cervical cancer that may be amenable to individual lifestyle promotion programs.

Although different according to cultural background, overall determinants of HR-HPV for this cohort of women are consistent with the literature, which has identified age, multiparity, hormonal contraceptive use, smoking, and markers of sexual activity as risk factors for HPV infection. This study was not designed to investigate the complex social determinant pathways of cervical cancer risk; nonetheless, these findings can help to better target current public health practices for women at greater risk of HPV infection and cervical cancer. Future research should evaluate the efficacy of improvements that have been made in terms of screening and prevention. (22)

Received: December 2, 2011

Accepted: May 21, 2012

REFERENCES

(1.) Canadian Cancer Society's Steering Committee on Cancer Statistics. Canadian Cancer Statistics 2011. Toronto, ON: Canadian Cancer Society, 2011.

(2.) Bosch FX, Lorincz A, Munoz N, Meijer CJ, Shah KV. The causal relationship between human papillomavirus and cervical cancer. J Clin Pathol 2002;55:244-65.

(3.) Marrett LD, Chaudhry M. Cancer incidence and mortality in Ontario First Nations, 1968-1991 (Canada). Cancer Causes Control 2003;14:259-68.

(4.) Young TK, Kliewer E, Blanchard J, Mayer T. Monitoring disease burden and preventive behavior with data linkage: Cervical cancer among Aboriginal people in Manitoba, Canada. Am J Public Health 2000;90(9):1466-68.

(5.) Louchini R, Beaupre M. Cancer incidence and mortality among Aboriginal people living on reserves and Northern villages in Quebec, 1988-2004. Int J Circumpolar Health 2008;67:445-51.

(6.) Circumpolar Inuit Cancer Review Working Group, Kelly J, Lanier A, Santos M, Healey S, Louchini R, et al. Cancer among the Circumpolar Inuit, 1989-2003: Patterns and trends. Int J Circumpolar Health 2008;67(5):408-20.

(7.) Canadian Partnership Against Cancer. 2010 System Performance Report. Canadian Partnership Against Cancer, November 2010.

(8.) Annual Population Estimates by Community & Other Characteristics of the Northwest Territories. NWT Bureau of Statistics, 2009. Available at: http://www.stats.gov.nt.ca/Statinfo/Demographics/population/popest.htlm (Accessed November 14, 2011).

(9.) Jiang Y, Brassard P, Severini A, Goleski V, Santos M, Leamon A, et al. Type-specific prevalence of human papillomavirus infection among women in the Northwest Territories, Canada. J Infect Public Health 2011;4(5-6):219-27.

(10.) Franco EL, Duarte-Franco E, Ferenczy A. Cervical cancer: Epidemiology, prevention and the role of human papillomavirus infection. CMAJ 2001;164:1017-25.

(11.) Hamlin-Douglas LK, Coutlee F, Roger M, Hanley J, Franco EL, Brassard P. Determinants of human papillomavirus infection among Inuit women of Northern Quebec, Canada. Sex Transm Dis 2001;37(6):377-81.

(12.) Bosch XF, Qiao Y, Castellsague X. The epidemiology of human papillomavirus infection and its association with cervical cancer. Int J Gynaecol Obstet 2006;94:8-21.

(13.) Special Report: Policy. The Lancet 2009;10(4):321-22. Available at: www.thelancet.com/oncology (Accessed November 14, 2011).

(14.) Luminex xMAP Technology. Luminex Corporation, 2010. Available at: http://www.luminexcorp.com/ (Accessed November 14, 2011).

(15.) Zubach V, Smart G, Ratnam S, Severini A. Novel microsphere-based method for detection and typing of 46 mucosal human papillomavirus types. J Clin Microbiol 2012;50(2):460. DOI: 10.1128/JCM.06090-11.

(16.) Rebbapragada A, Perusini S, Di Prima A, Salit I, Goleski V, Ratnam S, et al. Evaluation of test performance characteristics and operational parameters of 5 hpv genotyping assays. 26th International Papillomavirus Conference, Montreal, QC, July 3-8, 2010.

(17.) Statistics Canada, 2006 Census. Population by Age and Gender Northwest Territories & Canada. 2006. Available at: http://www.stats.gov.nt.ca/census/2006/Age%20and%20Sex_2006.pdf (Accessed November 14, 2011).

(18.) Molano M, Posso H, Weiderpass E, van den Brule AJ, Ronderos M, Franceschi S, et al. Prevalence and determinants of HPV infection among Colombian women with normal cytology. Br J Cancer 2002;87(3):324-33.

(19.) Kasap B, Yetimalar H, Keklik A, Yildiz A, Cukurova K, Soylu F. Prevalence and risk factors for human papillomavirus DNA in cervical cytology. Eur J Obstet Gynecol Reprod Biol 2011;159(1):168-71.

(20.) Hildesheim A, Gravitt P, Schiffman MH, Kurman RJ, Barnes W, Jones S, et al. Determinants of genital human papillomavirus infection in low-income women in Washington, D.C. Sex Transm Dis 1993;20(5):279-85.

(21.) Demers AA, Kliewer EV, Remes O, Onysko J, Dinner K, Wong T, Jayaraman GC. Cervical cancer among Aboriginal women in Canada. CMAJ 2012;184(7):743-44.

(22.) Elias B, Kliewer EV, Hall M, Demers AA, Turner D, Martens P, et al. The burden of cancer risk in Canada's indigenous population: A comparative study of known risks in a Canadian region. Int J Gen Med 2011;4:699-709.

Paul Brassard, MD, MSc, [1,2] Ying Jiang, MSc, [3] Alberto Severini, MD, [4] Vanessa Goleski, BSc, [4] Maria Santos, MHSc, [5] Susan Chatwood, BScN, MSc, [6,7] Candice Lys, MA, [7] Gordon Johnson, MD, [8] Tom Wong, MD, MPH, [7,9] Andrew Kotaska, MD, [10] Kami Kandola, MD, MPH, [5] Howard Morrison, PhD, [3] Yang Mao, PhD [3]

Author Affiliations

[1.] Division of Clinical Epidemiology, McGill University Health Centre, Montreal, QC

[2.] Department of Medicine, McGill University, Montreal QC

[3.] Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, Ottawa, ON

[4.] National Microbiology Laboratory, PHAC, Winnipeg, MB

[5.] Department of Health & Social Services, Yellowknife, NT

[6.] Institute for Circumpolar Health Research, Yellowknife, NT

[7.] University of Toronto, Toronto, ON

[8.] Dynacare Kasper Medical Laboratories, Edmonton, AB

[9.] Centre for Communicable Diseases and Infection Control, PHAC, Ottawa, ON

[10.] Department of Obstetrics and Gynaecology, Stanton Territorial Hospital, Yellowknife, NT

Correspondence: Dr. Paul Brassard, Division of Clinical Epidemiology, McGill University Health Centre, 687 Pine Avenue West, R4-29, Montreal, QC H3A 1A1, Tel: 514-340-7563, Fax: 514-340-7564, E-mail: paul.brassard@mcgill.ca

Acknowledgements: This study was financially supported by the Government of Canada International Polar Year Program and the Public Health Agency of Canada. P. Brassard was supported by a clinician scientist career award from the Fonds de la Recherche en Sante du Quebec (FRSQ).

Conflict of Interest: None to declare.

Table 1. Determinants of Prevalent HR-HPV Infection

Characteristics                  Other       HR-HPV
                                 n (%)        n (%)

Demographic
  Age (years) (N=1064)
    <20                         44 (69.8)   19 (30.2)
    20-29                      235 (78.3)   65 (21.7)
    30-39                      222 (89.5)   26 (10.5)
    40-49                      240 (90.9)   24 (9.1)
    50-59                      149 (92.0)   13 (8.0)
    60+                         24 (88.9)    3 (11.1)
  Marital status (N=1077)
    Married or living with
      partner                  647 (89.1)   79 (10.9)
    Single                     276 (78.6)   75 (21.4)
  Educational attainment
  (N=1075)
    Grade school               323 (81.4)   74 (18.6)
    College                    273 (86.4)   43 (13.6)
    University                 326 (90.1)   36 (9.9)
  Cultural background
  (N=993)([dagger])
    Non-Aboriginal             514 (90.3)   55 (9.7)
    Aboriginal
      First Nations            200 (79.1)   53 (20.9)
      Metis                     97 (80.2)   24 (19.8)
      Inuit                     39 (78.0)   11 (22.0)
  All Aboriginals (N=998)
  ([dagger])
    Yes                        341 (79.5)   88 (20.5)

** Ratio is adjusted without Aboriginal variable

*** Ratio is adjusted without cultural background variable

  Employed (N=1044)
    Yes                        755 (87.1)   112 (12.9)
    No                         139 (78.5)    38 (21.5)

Clinical
  Ever had sexually
  transmitted infection
  (N=1033)
    Yes                        312 (83.9)    60 (16.1)
    No                         576 (87.1)    85 (12.9)
  Lifetime deliveries
  (N=1060)
    0                          308 (78.8)    83 (21.2)
    1                          155 (82.4)    33 (17.6)
    2+                         445 (92.5)    36 (7.5)
  Birth control method
  (N=547)
    Non-hormonal               218 (88.6)    28 (11.4)
    Hormonal                   234 (77.7)    67 (22.3)

Behavioural
  Current smoker (N=1079)
    No                         655 (88.8)    83 (11.2)
    Yes                        269 (78.9)    72 (21.1)
  Lifetime no. of sexual
  partners (N=981)
    <10 partners               637 (87.1)    94 (12.9)
    [greater than or equal     206 (82.4)    44 (17.6)
      to]10 partners
  Age at first sexual
  intercourse (N=1040)
    11-15                      232 (81.1)    54 (18.9)
    16-19                      524 (86.6)    81 (13.4)
    20+                        136 (91.3)    13 (8.7)
  No. of sexual partners in
  past year (N=1053)
    0                           90 (92.8)     7 (7.2)
    1                          694 (87.2)   102 (12.8)
    2-4                         97 (76.4)    30 (23.6)
    5+                          22 (66.7)    11 (33.3)

                                            OR (95%)

Characteristics                     Crude            Adjusted *

Demographic
  Age (years) (N=1064)
    <20                        1.00(Ref)          1.00(Ref)
    20-29                      0.64 (0.34-1.17)   0.62 (0.35-1.12)
    30-39                      0.27 (0.14-0.53)   0.30 (0.15-0.61)
    40-49                      0.22 (0.12-0.45)   0.27 (0.13-0.55)
    50-59                      0.20 (0.08-0.44)   0.27 (0.12-0.61)
    60+                        0.28 (0.08-1.08)   0.33 (0.08-1.33)
  Marital status (N=1077)
    Married or living with
      partner                  1.00(Ref)          1.00(Ref)
    Single                     2.23 (1.58-3.15)   2.07 (1.45-2.95)
  Educational attainment
  (N=1075)
    Grade school               1.00(Ref)          1.00(Ref)
    College                    0.69 (0.46-1.04)   0.69 (0.45-1.06)
    University                 0.48 (0.31-0.74)   0.64 (0.39-1.02)
  Cultural background
  (N=993)([dagger])
    Non-Aboriginal             1.00(Ref)          1.00(Ref) **
    Aboriginal
      First Nations            2.48 (1.64-3.74)   2.54 (1.65-3.91) **
      Metis                    2.31 (1.37-3.91)   2.24 (1.31-3.82) **
      Inuit                    2.46 (1.16-5.21)   2.40 (1.11-5.19) **
  All Aboriginals (N=998)
  ([dagger])
    Yes                        2.41 (1.68-3.47)   2.40 (1.65-3.49) ***

** Ratio is adjusted without Aboriginal variable

*** Ratio is adjusted without cultural background variable

  Employed (N=1044)
    Yes                        1.00(Ref)          1.00(Ref)
    No                         1.84 (1.22-2.78)   1.54 (0.99-2.40)

Clinical
  Ever had sexually
  transmitted infection
  (N=1033)
    Yes                        1.00(Ref)          1.00(Ref)
    No                         0.77 (0.54-1.09)   0.99 (0.97-1.01)
  Lifetime deliveries
  (N=1060)
    0                          1.00(Ref)          1.00(Ref)
    1                          0.79 (0.51-1.24)   0.73 (0.46-1.17)
    2+                         0.30 (0.20-0.46)   0.25 (0.16-0.39)
  Birth control method
  (N=547)
    Non-hormonal               1.00(Ref)          1.00(Ref)
    Hormonal                   2.23 (1.38-3.59)   2.25 (1.38-3.66)

Behavioural
  Current smoker (N=1079)
    No                         1.00(Ref)          1.00(Ref)
    Yes                        2.11 (1.49-2.98)   1.81 (1.24-2.62)
  Lifetime no. of sexual
  partners (N=981)
    <10 partners               1.00(Ref)          1.00(Ref)
    [greater than or equal     1.45 (0.98-2.14)   1.21 (0.81-1.81)
      to]10 partners
  Age at first sexual
  intercourse (N=1040)
    11-15                      1.00(Ref)          1.00(Ref)
    16-19                      0.66 (0.45-0.97)   0.74 (0.50-1.09)
    20+                        0.41 (0.22-0.78)   0.62 (0.31-1.23)
  No. of sexual partners in
  past year (N=1053)
    0                          1.00(Ref)          1.00(Ref)
    1                          1.89 (0.85-4.19)   1.64 (0.73-3.70)
    2-4                        3.97 (1.66-9.50)   2.90 (1.18-7.11)
    5+                         6.43 (2.23-18.48)  5.41 (1.79-16.39)

OR (95%) = Odds ratio (95% confidence interval).

* Odds ratios are adjusted for all other characteristics.

HR-HPV = high-risk human papillomavirus; Other = HPV negative and
low-risk human papillomavirus.

** or *** = adjusted ratio using a different model (see details in
table) to avoid over-adjustment.

([dagger]) The reason for the different numbers (N=993 vs. N=998)
is that 5 Aboriginal subjects could not be classified as Metis,
First Nations or Inuit.

Table 2. Determinants of Prevalent HR-HPV Infection Among Aboriginal
Women

Characteristics                      Other       HR-HPV
                                     n (%)        n (%)
Demographic
  Age (years) (N=418)
    <20                            19 (59.4)    13 (40.6)
    20-29                          94 (70.1)    40 (29.9)
    30-39                          90 (85.7)    15 (14.3)
    40-49                          82 (91.1)     8 (8.9)
    50-59                          42 (87.5)     6 (12.5)
    60+                             7 (77.8)     2 (22.2)
  Marital status (N=427)
    Married or living with
      partner                      220 (84.3)   41 (15.7)
    Single                         120 (72.3)   46 (27.7)
  Educational attainment (N=424)
    Grade school                   181 (77.0)   54 (23.0)
    College                        119 (82.6)   25 (17.4)
    University                      38 (84.4)    7 (15.6)
  Cultural background (N=422)
    First Nations                  200 (79.1)   53 (20.9)
    Metis                           97 (80.2)   24 (19.8)
    Inuit                           38 (79.2)   10 (20.8)

Clinical
  Ever had sexually transmitted
  infection (N=391)
    Yes                            185 (81.1)   43 (18.9)
    No                             127 (77.9)   36 (22.1)
  Lifetime deliveries (N=415)
    0                               75 (64.1)   42 (35.9)
    1                               59 (75.6)   19 (24.4)
    2+                             196 (89.1)   24 (10.9)
  Birth control method (N=219)
    Non-hormonal                    83 (84.7)   15 (15.3)
    Hormonal                        82 (67.8)   39 (32.2)

Behavioural
  Current smoker (N=376)
    No                             182 (83.5)   36 (16.5)
    Yes                            116 (73.4)   42 (26.6)
  Lifetime no. of sexual
  partners (N=352)
    <10 partners                   198 (81.1)   46 (18.9)
    [greater than or equal to]10
      partners                      81 (75.0)   27 (25.0)
  Age at first sexual
  intercourse (N=394)
    11-15                          116 (73.4)   42 (26.6)
    16-19                          182 (83.5)   36 (16.5)
    20+                             15 (83.3)    3 (16.7)
  No. of sexual partners in past
  year (N=407)
    0                               29 (90.6)    3 (9.4)
    1                              226 (81.0)   53 (19.0)
    2-4                             56 (73.7)   20 (26.3)
    5+                              13 (65)      7 (35)

                                                OR (95%)

Characteristics                         Crude            Adjusted *

Demographic
  Age (years) (N=418)
    <20                            1.00(Ref)          1.00(Ref)
    20-29                          0.62 (0.28-1.38)   0.68 (0.30-1.55)
    30-39                          0.24 (0.10-0.59)   0.30 (0.12-0.74)
    40-49                          0.14 (0.05-0.39)   0.17 (0.06-0.50)
    50-59                          0.21 (0.07-0.63)   0.30 (0.09-0.95)
    60+                            0.42 (0.07-2.34)   0.55 (0.09-3.52)
  Marital status (N=427)
    Married or living with
      partner                      1.00(Ref)          1.00(Ref)
    Single                         2.06 (1.28-3.31)   1.83 (1.12-3.00)
  Educational attainment (N=424)
    Grade school                   1.00(Ref)          1.00(Ref)
    College                        0.70 (0.41-1.19)   0.66 (0.38-1.15)
    University                     0.62 (0.26-1.46)   0.63 (0.25-1.58)
  Cultural background (N=422)
    First Nations                  1.00(Ref)          1.00(Ref)
    Metis                          0.93 (0.54-1.60)   0.84 (0.47-1.51)
    Inuit                          0.99 (0.46-2.12)   0.96 (0.43-2.12)

Clinical
  Ever had sexually transmitted
  infection (N=391)
    Yes                            1.00(Ref)          1.00(Ref)
    No                             1.22 (0.74-2.01)   1.12 (0.66-1.91)
  Lifetime deliveries (N=415)
    0                              1.00(Ref)          1.00(Ref)
    1                              0.58 (0.30-1.09)   0.62 (0.31-1.24)
    2+                             0.22 (0.12-0.39)   0.23 (0.12-0.43)
  Birth control method (N=219)
    Non-hormonal                   1.00(Ref)          1.00(Ref)
    Hormonal                       2.63 (1.35-5.14)   2.95 (1.49-5.87)

Behavioural
  Current smoker (N=376)
    No                             1.00(Ref)          1.00(Ref)
    Yes                            1.69 (1.05-2.73)   1.89 (1.15-3.12)
  Lifetime no. of sexual
  partners (N=352)
    <10 partners                   1.00(Ref)          1.00(Ref)
    [greater than or equal to]10
      partners                     1.44 (0.83-2.46)   1.45 (0.83-2.57)
  Age at first sexual
  intercourse (N=394)
    11-15                          1.00(Ref)          1.00(Ref)
    16-19                          0.55 (0.33-0.90)   0.52 (0.30-0.88)
    20+                            0.55 (0.15-2.00)   0.70 (0.17-2.83)
  No. of sexual partners in past
  year (N=407)
    0                              1.00(Ref)          1.00(Ref)
    1                              2.27 (0.67-7.72)   1.87 (0.53-6.56)
    2-4                            3.45 (0.95-12.58)  3.04 (0.81-11.43)
    5+                             5.20 (1.16-23.38)  4.59 (0.96-21.97)

OR (95%) = Odds ratio (95% confidence interval).

* Odds ratios are adjusted for all other characteristics.

HR-HPV = high-risk human papillomavirus; Other = HPV negative and
low-risk human papillomavirus.

Table 3. Determinants of Prevalent HR-HPV Infection Among
Non-Aboriginal Women

Characteristics                    Other        HR-HPV
                                   n (%)        n (%)
Demographic
Age (year) (N=547)
<20                              17 (77.3)     5 (22.7)
20-29                           125 (86.2)    20 (13.8)
30-39                           111 (93.3)     8 (6.7)
40-49                           133 (91.7)    12 (8.3)
50-59                            93 (93.0)     7 (7.0)
60+                              15 (93.8)     1 (6.3)

Marital status (N=564)
Married or living with
      partner                   373 (92.3)    31 (7.7)
Single                          136 (85.0)    24 (15.0)

Clinical
Ever had sexually
  transmitted
  infection (N=558)
Yes                             115 (89.1)    14 (10.9)
No                              389 (90.7)    40 (9.3)

Lifetime deliveries (N=558)
0                               210 (87.1)    31 (12.9)
1                                82 (85.4)    14 (14.6)
2+                              211 (95.5)    10 (4.5)

Use of birth control
      (N=567)
Yes                             249 (88.3)    33 (11.7)
No                              263 (92.3)    22 (7.7)

Behavioural
Current smoker (N=566)
No                              420 (91.1)    41 (8.9)
Yes                              91 (86.7)    14 (13.3)

Lifetime no. of sexual
    partners (N=544)
<10 partners                    382 (90.7)    39 (9.3)
[greater than or equal
      to] 10 partners           109 (88.6)    14 (11.4)

Age at first sexual
    intercourse (N=559)
11-15                            93 (91.2)     9 (8.8)
16-19                           293 (88.3)    39 (11.7)
20+                             118 (94.4)     7 (5.6)

No. of sexual partners in
    past year (N=560)
0                                57 (95.0)     3 (5.0)
1                               406 (91.4)    38 (8.6)
2-4                              33 (76.7)    10 (23.3)
5+                                9 (69.2)     4 (30.8)

                                             OR (95%)

Characteristics                       Crude            Adjusted *

Demographic
Age (year) (N=547)
<20                             1.00(Ref)           1.00(Ref)
20-29                           0.54 (0.18-1.63)    0.55 (0.17-1.73)
30-39                           0.25 (0.07-0.84)    0.33 (0.09-1.20)
40-49                           0.31 (0.09-0.98)    0.43 (0.13-1.49)
50-59                           0.26 (0.07-0.90)    0.39 (0.10-1.46)
60+                             0.23 (0.02-2.16)    0.47 (0.05-4.93)

Marital status (N=564)
Married or living with
      partner                   1.00(Ref)           1.00(Ref)
Single                          2.13 (1.20-3.75)    1.48 (0.79-2.78)

Clinical
Ever had sexually
  transmitted
  infection (N=558)
Yes                             1.00(Ref)           1.00(Ref)
No                              0.84 (0.44-1.61)    0.95 (0.49-1.84)

Lifetime deliveries (N=558)
0                               1.00(Ref)           1.00(Ref)
1                               1.16 (0.58-2.28)    1.27 (0.62-2.57)
2+                              0.32 (0.15-0.67)    0.37 (0.17-0.79)

Use of birth control
      (N=567)
Yes                             1.00(Ref)           1.00(Ref)
No                              0.63 (0.36-1.11)    0.80 (0.44-1.46)

Behavioural
Current smoker (N=566)
No                              1.00(Ref)           1.00(Ref)
Yes                             1.57 (0.82-3.01)    1.23 (0.61-2.50)

Lifetime no. of sexual
    partners (N=544)
<10 partners                    1.00(Ref)           1.00(Ref)
[greater than or equal
      to] 10 partners           1.26 (0.66-2.40)    0.80 (0.38-1.66)

Age at first sexual
    intercourse (N=559)
11-15                           1.00(Ref)           1.00(Ref)
16-19                           1.37 (0.62-2.94)    1.73 (0.77-3.86)
20+                             0.61 (0.22-1.71)    0.85 (0.29-2.48)

No. of sexual partners in
    past year (N=560)
0                               1.00(Ref)           1.00(Ref)
1                               1.78 (0.53-5.95)    1.71 (0.50-5.91)
2-4                             5.76 (1.48-22.42)   3.95 (0.96-16.25)
5+                              8.44 (1.61-44.14)   5.18 (0.93-28.75)

OR (95%) = Odds ratio (95% confidence interval).

* Odds ratios are adjusted for all other characteristics.

HR-HPV = high-risk human papillomavirus; Other = HPV
negative and low-risk human papillomavirus.