Table 3.
Association of selected potential risk/protective factors a with any new HPV infection among 105 adolescent girls who reported previous sex
| Number of infections b /person-years (rate/100 pys) | Crude RR (95% CI) | Adjusted RR (95% CI) c | |
|---|---|---|---|
| Sociodemographic (enrolment) | |||
| Age at enrolment | P = 0.45 | ||
| 15 years | 32/19.1 (189) | 1 | |
| 16 years | 87/37.3 (244) | 1.29 (0.67-2.47) | |
| Religion | P = 0.83 | P = 0.83 | |
| Christian | 99/49.2 (213) | 1 | 1 |
| Muslim | 16/5.5 (333) | 1.56 (0.59-4.12) | 1.57 (0.60-4.16) |
| Other | 4/1.7 (219) | 1.16 (0.11-12.30) | 1.07 (0.10-11.30) |
| Socioeconomic status score (tertiles) | P = 0.57 | P = 0.63 | |
| Low | 58/25.5 (246) | 1 | 1 |
| Middle | 33/20.3 (174) | 0.70 (0.35-1.43) | 0.72 (0.36-1.48) |
| High | 28/10.6 (256) | 1.04 (0.48-2.23) | 1.03 (0.48-2.21) |
| Sociodemographic (time-varying) | |||
| Current residence | P = 0.80 | P = 0.53 | |
| Urban | 50/20.7 (235) | 1 | 1 |
| Rural | 65/34.6 (217) | 0.92 (0.49-1.72) | 0.82 (0.44-1.53) |
| Current occupation | P = 0.05 | P = 0.06 | |
| School | 5/2.9 (164) | 1.13 (0.30-4.26) | 1.15 (0.30-4.36) |
| Work | vocational training | 29/23.1 (144) | 1 | 1 |
| Not working | 85/30.4 (283) | 1.96 (1.12-3.43) | 1.95 (1.11-3.42) |
| Currently married | P = 0.66 | P = 0.79 | |
| No | 90/43.9 (217) | 1 | 1 |
| Yes | 29/12.5 (248) | 1.14 (0.63-2.09) | 0.92 (0.50-1.70) |
| Alcohol since last visit | P = 0.42 | P = 0.48 | |
| No | 116/55.2 (228) | 1 | 1 |
| Yes | 3/1.2 (134) | 0.59 (0.16-2.22) | 0.62 (0.16-2.40) |
| Behavioural (time-varying) | |||
| Total partners ever | P = 0.09 | P = 0.09 | |
| 1 | 86/43.1 (225) | 1 | 1 |
| 2 | 16/10.0 (155) | 0.69 (0.35-1.34) | 0.77 (0.38-1.54) |
| 3+ | 16/2.5 (509) | 2.26 (0.83-6.17) | 2.76 (0.95-8.04) |
| Number of times had sex in past 3 months | P = 0.005 | P = 0.008 | |
| 0 | 49/31.4 (159) | 1 | 1 |
| 1 | 30/9.3 (400) | 2.52 (1.44-4.42) | 2.48 (1.40-4.37) |
| 2+ | 39/15.5 (257) | 1.62 (0.95-2.77) | 1.52 (0.88-2.63) |
| Most recent male sexual partner circumcised | P = 0.22 | P = 0.23 | |
| No | 33/16.1 (182) | 1 | 1 |
| Yes | 80/31.5 (263) | 1.47 (0.79-2.72) | 1.48 (0.77-2.85) |
| Don't know d | 5/8.0 (109) | – | – |
| Most recent sexual partner was in a concurrent relationship | P = 0.06 | P = 0.25 | |
| No | 53/31.1 (171) | 1 | 1 |
| Yes | 12/2.7 (402) | 2.37 (0.99-5.68) | 1.83 (0.66-5.07) |
| Don't know d | 53/21.7 (287) | – | – |
| Age difference of most recent partner | P = 0.11 | P = 0.10 | |
| ≤ 2 years | 8/8.9 (82) | 1 | 1 |
| 3–5 years | 26/11.0 (215) | 2.65 (1.03-6.83) |
|
| >5 years | 35/13.1 (237) | 2.64 (1.04-6.73) | 2.33 (0.94-5.77) |
| Don't know d | 49/22.6 (316) | – | – |
| Used condom at most recent sex | P = 0.93 | P = 0.90 | |
| No | 105/46.5 (226) | 1 | 1 |
| Yes | 13/9.1 (235) | 1.04 (0.45-2.40) | 0.95 (0.41-2.20) |
| Does partner put saliva on penis | P = 0.58 | P = 0.26 | |
| No | 78/33.5 (229) | 1 | 1 |
| Yes | 7/1.7 (309) | 1.34 (0.48-3.75) | 1.87 (0.64-5.48) |
| Don't know d | 2/0.5 (292) | – | – |
| Does partner use vaseline for sex | P = 0.007 | P = 0.17 | |
| No | 77/35.7 (208) | 1 | 1 |
| Yes | 10/1.1 (717) | 3.44 (1.47-8.04) | 2.06 (0.76-5.63) |
| Time had known most recent partner before first sex (with that partner) | P = 0.14 | P = 0.03 | |
| < 1 month | 26/16.1 (143) | 1 | 1 |
| 1-6 months | 64/28.0 (252) | 1.76 (0.89-3.47) | 1.76 (0.90-3.46) |
| 6+ months | 28/11.0 (314) | 2.19 (0.92-5.20) | 3.15 (1.32-7.50) |
| Cleansed vagina in past 3 months e | P = 0.02 | P = 0.11 | |
| No | 68/29.8 (300) | 1 | 1 |
| Yes | 51/26.6 (169) | 0.56 (0.35-0.90) | 0.69 (0.43-1.10) |
a Potential risk/protective factors were examined using a conceptual framework with three levels; age was considered an a priori confounder and included in all models. Age-adjusted sociodemographic factors at enrolment were retained in a core model if associated with HPV infection at P < 0.10. Time-varying sociodemographic factors were added sequentially and retained if associated at P < 0.10. Time-varying behavioural factors were then added sequentially, and retained at P < 0.10. All P -values presented in the table are from the likelihood ratio test.
b Girls are assumed to be continually at risk and can acquire > 1 infection at each visit. Observation time after gaps > 180 days contributes to the analysis; therefore, the total number of infections (119) is different from that in Table 1 .
c Sociodemographic factors at enrolment adjusted for age (a priori). Time-varying sociodemographic factors adjusted for age (a priori) and all independent sociodemographic predictors of HPV infection (at P < 0.1) (occupation). Behavioural factors adjusted for age, occupation and all independent behavioural predictors of HPV infection (number of times had sex in past 3 months and time knew most recent partner before sex (variables in bold).
d ‘Don’t know’ responses considered missing data and not included in analysis.
e Vaginal cleansing is cleaning inside the vagina with water, soap or other products using fingers or a cloth.