Table 1.
Univariate and multivariable risk factors associated with incidently detected human papillomavirus 16 (HPV16) infection*
| Risk factor | PY | No. of new HPV16 infections | Incidence per 100/PY | Univariate, RR (95% CI) | Multivariable, RR (95% CI)† |
| Age at enrollment, y | |||||
| 18 | 1149 | 53 | 4.61 | 1 | 0.95 (0.89 to 1.00)‡ |
| 19 | 1189 | 47 | 3.95 | 0.86 (0.58 to 1.27) | |
| 20 | 988 | 46 | 4.66 | 1.01 (0.68 to 1.50) | |
| 21 | 864 | 28 | 3.24 | 0.70 (0.44 to 1.10) | |
| 22 | 1017 | 40 | 3.93 | 0.85 (0.56 to 1.28) | |
| 23 | 903 | 29 | 3.21 | 0.70 (0.44 to 1.09) | |
| 24 | 908 | 28 | 3.08 | 0.67 (0.42 to 1.05) | |
| 25 | 826 | 20 | 2.42 | 0.52 (0.31 to 0.86) | |
| Education, y | |||||
| <7 | 2367 | 71 | 3.00 | 1 | 1 |
| 7–9 | 1785 | 65 | 3.64 | 1.21 (0.87 to 1.70) | 1.08 (0.76 to 1.52) |
| ≥10 (technical) | 2498 | 99 | 3.96 | 1.32 (0.98 to 1.80) | 1.08 (0.78 to 1.50) |
| University | 1158 | 55 | 4.75 | 1.58 (1.11 to 2.25) | 1.29 (0.88 to 1.88) |
| Marital status | |||||
| Married | 3775 | 95 | 2.52 | 1 | 1 |
| Single | 3839 | 181 | 4.72 | 1.87 (1.47 to 2.41) | 1.64 (1.24 to 2.17) |
| Divorced/widowed | 221 | 14 | 6.34 | 2.52 (1.38 to 4.27) | 2.40 (1.31 to 4.11) |
| No. of lifetime partners | |||||
| 1 | 3879 | 122 | 3.15 | 1 | 1 |
| 2 | 1683 | 72 | 4.28 | 1.36 (1.01 to 1.82) | 1.42 (1.05 to 1.92) |
| 3 | 949 | 40 | 4.21 | 1.34 (0.93 to 1.90) | 1.36 (0.93 to 1.96) |
| ≥4 | 989 | 44 | 4.45 | 1.41 (0.99 to 1.98) | 1.44 (0.98 to 2.10) |
| Oral contraceptive use | |||||
| Never | 2593 | 111 | 4.28 | 1 | |
| Past | 1455 | 51 | 3.51 | 0.82 (0.58 to 1.13) | |
| Current (past month) | 3780 | 129 | 3.41 | 0.80 (0.62 to 1.03) | |
| Smoking | |||||
| Never | 6809 | 229 | 3.36 | 1 | 1 |
| Past | 457 | 26 | 5.69 | 1.69 (1.10 to 2.49) | 1.54 (0.99 to 2.30) |
| Current | 568 | 35 | 6.17 | 1.83 (1.26 to 2.58) | 1.42 (0.94 to 2.07) |
| Chlamydia infection | |||||
| No | 5712 | 208 | 3.64 | 1 | |
| Yes | 925 | 44 | 4.76 | 1.31 (0.93 to 1.79) | |
| Pregnancy | |||||
| Never | 3677 | 153 | 4.16 | 1 | |
| Ever | 4166 | 138 | 3.31 | 0.80 (0.63 to 1.00) | |
| Gravidity | |||||
| 0 | 3677 | 153 | 4.16 | 1 | |
| 1 | 2622 | 87 | 3.32 | 0.80 (0.61 to 1.04) | |
| 2 | 1109 | 36 | 3.25 | 0.78 (0.54 to 1.11) | |
| 3 | 324 | 13 | 4.01 | 0.96 (0.52 to 1.63) | |
| ≥4 | 111 | 2 | 1.80 | 0.43 (0.07 to 1.35) | |
| Years since first sex | |||||
| 0/1 | 754 | 37 | 4.91 | 1 | |
| 2 | 676 | 36 | 5.32 | 1.08 (0.68 to 1.72) | |
| 3 | 848 | 45 | 5.31 | 1.08 (0.70 to 1.68) | |
| 4 | 947 | 37 | 3.91 | 0.80 (0.50 to 1.26) | |
| ≥5 | 3423 | 96 | 2.80 | 0.57 (0.40 to 0.85) | |
*
Factors evaluated at enrollment. We used Poisson regression to compare enrollment risk factors for detection of a new HPV16 over the follow-up. CI = confidence interval; PY = person-years; RR = rate ratio.
†
Model adjusted for all the other variables.
‡
Age entered as continuous variable in the multivariable model.