Background
Methods
Study population
Questionnaire
Urine sampling
Chlamydia PCR
Follow up
Sample size calculations
Data analysis
Ethics
Results
Study sample
Characteristic | Girls | Boys | Both | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
N | (%) | nCT
| (%) | OR | 95% CI |
p
1
| N | (%) | nCT
| (%) | OR | 95% CI |
p
1
| OR | 95% CI |
p
1
| |
Total
| 565 | (100.0) | 41 | (7.3) | 466 | (100.0) | 18 | (3.9) | |||||||||
Age
| |||||||||||||||||
16 | 168 | (29.7) | 11 | (6.5) | 1.00 |
0.48
| 139 | (29.8) | 3 | (2.2) | 1.00 |
0.38
| 1.00 |
0.21
| |||
17 | 177 | (31.3) | 15 | (8.5) | 1.32 | 0.59 to 2.97 | 179 | (38.4) | 9 | (5.0) | 2.40 | 0.64 to 9.04 | 1.51 | 0.76 to 3.00 | |||
18 | 166 | (29.4) | 9 | (5.4) | 0.82 | 0.33 to 2.03 | 106 | (22.7) | 3 | (2.8) | 1.32 | 0.26 to 6.68 | 0.97 | 0.44 to 2.13 | |||
19-20 | 48 | (9.6) | 6 | (11.1) | 1.78 | 0.63 to 5.08 | 39 | (9.0) | 3 | (7.1) | 3.49 | 0.68 to 17.97 | 2.17 | 0.91 to 5.17 | |||
Family and culture
| |||||||||||||||||
Ethnicity | |||||||||||||||||
Norwegian | 402 | (71.2) | 23 | (5.7) | 1.00 |
0.093
| 325 | (70.0) | 12 | (3.7) | 1.00 |
0.73
| 1.00 |
0.21
| |||
Sami/Sami-Norwegian | 124 | (21.9) | 14 | (11.3) | 2.10 | 1.04 to 4.21 | 105 | (22.6) | 3 | (2.9) | 0.74 | 0.21 to 2.77 | 1.59 | 0.87 to 2.89 | |||
Other | 39 | (6.9) | 4 | (10.3) | 1.88 | 0.61 to 5.75 | 34 | (7.3) | 2 | (5.9) | 1.63 | 0.35 to 7.61 | 1.77 | 0.72 to 4.36 | |||
Church affiliation2
| |||||||||||||||||
Yes | 448 | (79.6) | 33 | (7.4) | 1.00 |
0.88
| 294 | (63.5) | 12 | (4.1) | 1.00 |
0.54
| 1.00 |
0.36
| |||
No | 115 | (20.4) | 8 | (7.0) | 0.94 | 0.42 to 2.10 | 169 | (36.5) | 5 | (3.0) | 0.72 | 0.25 to 2.07 | 0.74 | 0.40 to 1.40 | |||
Residence in school year | |||||||||||||||||
At home | 356 | (63.1) | 20 | (5.6) | 1.00 |
0.051
| 287 | (61.7) | 7 | (2.4) | 1.00 |
0.084
| 1.00 |
0.011
| |||
Other3
| 208 | (36.9) | 21 | (10.1) | 1.89 | 1.00 to 3.57 | 178 | (38.3) | 10 | (5.6) | 2.38 | 0.89 to 6.37 | 2.00 | 1.17 to 3.4 | |||
Mother’s education | |||||||||||||||||
≤ High school/don’t know | 313 | (55.5) | 15 | (4.8) | 1.00 |
0.013
| 304 | (65.7) | 12 | (3.9) | 1.00 |
0.66
| 1.00 |
0.03
| |||
≥ College | 251 | (44.5) | 26 | (10.4) | 2.30 | 1.19 to 4.44 | 159 | (34.3) | 5 | (3.1) | 0.79 | 0.27 to 2.28 | 1.79 | 1.05 to 3.04 | |||
High school
| |||||||||||||||||
Study category | |||||||||||||||||
Academic | 347 | (61.4) | 21 | (6.1) | 1.00 |
0.17
| 171 | (36.8) | 6 | (3.5) | 1.00 |
0.90
| 1.00 |
0.56
| |||
Vocational | 218 | (38.6) | 20 | (9.2) | 1.57 | 0.83 to 2.97 | 294 | (63.2) | 11 | (3.7) | 1.07 | 0.39 to 2.94 | 1.17 | 0.69 to 1.99 | |||
Year | |||||||||||||||||
1 | 210 | (37.2) | 16 | (7.6) | 1.00 |
0.68
| 178 | (38.3) | 4 | (2.2) | 1.00 |
0.44
| 1.00 |
0.83
| |||
2 | 198 | (35.0) | 16 | (8.1) | 1.07 | 0.52 to 2.19 | 209 | (44.9) | 9 | (4.3) | 1.96 | 0.59 to 6.47 | 1.20 | 0.66 to 2.21 | |||
3 | 157 | (27.8) | 9 | (5.7) | 0.74 | 0.32 to 1.72 | 78 | (16.8) | 4 | (5.1) | 2.35 | 0.57 to 9.65 | 1.08 | 0.53 to 2.21 | |||
Alcohol/drug use
| |||||||||||||||||
Low | 134 | (23.8) | 4 | (3.0) | 1.00 |
0.098
| 130 | (28.4) | 3 | (2.3) | 1.00 |
0.087
| 1.00 |
0.034
| |||
Medium | 322 | (57.3) | 27 | (8.4) | 2.98 | 1.02 to 8.67 | 198 | (43.3) | 5 | (2.5) | 1.10 | 0.26 to 4.67 | 2.41 | 1.05 to 5.53 | |||
High | 106 | (18.9) | 10 | (9.4) | 3.39 | 1.03 to 11.12 | 129 | (28.2) | 9 | (7.0) | 3.18 | 0.84 to 12.01 | 3.23 | 1.33 to 7.83 |
Characteristic | Girls | Boys | Both | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
N | (%) | nCT
| (%) | OR | 95% CI |
p
1
| N | (%) | nCT
| (%) | OR | 95% CI |
p
1
| OR | 95% CI |
p
1
| |
Sexual behaviour
| |||||||||||||||||
Age at first intercourse | |||||||||||||||||
≥ 15 years | 330 | (58.8) | 24 | (7.3) | 1.00 |
0.97
| 294 | (65.9) | 8 | (2.7) | 1.00 |
0.10
| 1.00 |
0.27
| |||
≤ 14 years | 231 | (41.2) | 17 | (7.4) | 1.01 | 0.53 to 1.93 | 152 | (34.1) | 9 | (5.9) | 2.25 | 0.85 to 5.96 | 1.35 | 0.79 to 2.30 | |||
Years sexually active | |||||||||||||||||
≤ 1 year | 149 | (26.6) | 10 | (6.7) | 1.00 |
0.74
| 158 | (35.4) | 2 | (1.3) | 1.00 |
0.055
| 1.00 |
0.099
| |||
≥ 2 years | 412 | (73.4) | 31 | (7.5) | 1.13 | 0.54 to 2.37 | 288 | (64.6) | 15 | (5.2) | 4.29 | 0.97 to 18.99 | 1.73 | 0.90 to 3.31 | |||
Condom use first intercourse | |||||||||||||||||
No2
| 223 | (39.6) | 14 | (6.3) | 1.00 |
0.46
| 206 | (45.3) | 16 | (7.8) | 1.00 |
0.003
| 1.00 |
0.13
| |||
Yes | 340 | (60.4) | 27 | (7.9) | 1.29 | 0.66 to 2.51 | 249 | (54.7) | 1 | (0.4) | 0.05 | 0.01 to 0.36 | 0.75 | 0.39 to 1.13 | |||
Currently in a relationship | |||||||||||||||||
Yes | 296 | (52.4) | 19 | (6.4) | 1.00 |
0.42
| 167 | (35.8) | 6 | (3.6) | 1.00 |
0.82
| 1.00 |
0.69
| |||
No | 269 | (47.6) | 22 | (8.2) | 1.30 | 0.69 to 2.46 | 299 | (64.2) | 12 | (4.0) | 1.12 | 0.41 to 3.05 | 1.12 | 0.66 to 1.90 | |||
Sex partners past 6 months | |||||||||||||||||
0-1 | 323 | (57.9) | 12 | (3.7) | 1.00 |
<0.001
| 254 | (58.8) | 6 | (2.4) | 1.00 |
0.053
| 1.00 |
<0.001
| |||
≥ 2 | 235 | (42.1) | 29 | (12.3) | 3.65 | 1.82 to 7.31 | 178 | (41.2) | 11 | (6.2) | 2.72 | 0.99 to 7.50 | 3.33 | 1.88 to 5.90 | |||
Lifetime no of sex partners | |||||||||||||||||
1-2 | 192 | (34.5) | 6 | (3.1) | 1.00 |
0.002
| 203 | (47.8) | 4 | (2.0) | 1.00 |
0.24
| 1.00 |
<0.001
| |||
3-5 | 178 | (32.0) | 11 | (6.2) | 2.04 | 0.74 to 5.64 | 117 | (27.5) | 4 | (3.4) | 1.76 | 0.43 to 7.18 | 2.06 | 0.91 to 4.66 | |||
≥ 6 | 186 | (33.5) | 24 | (12.9) | 4.59 | 1.83 to 11.51 | 105 | (24.7) | 6 | (5.7) | 3.02 | 0.83 to 10.93 | 4.43 | 2.13 to 9.21 | |||
Last sexual partner
| |||||||||||||||||
Age difference | |||||||||||||||||
Same age or younger | 133 | (24.3) | 7 | (5.3) | 1.00 |
0.30
| 381 | (88.0) | 11 | (2.9) | 1.00 |
0.005
| 1.00 |
0.002
| |||
Older (≥ 1 year) | 414 | (75.7) | 33 | (8.0) | 1.56 | 0.67 to 3.61 | 52 | (12.0) | 6 | (11.5) | 4.39 | 1.55 to 12.42 | 2.52 | 1.42 to 4.47 | |||
How met last partner | |||||||||||||||||
At school/work | 66 | (11.7) | 2 | (3.0) | 1.00 |
0.008
| 104 | (23.0) | 2 | (1.9) | 1.00 |
0.65
| 1.00 |
0.008
| |||
Through family/friends/other | 312 | (55.4) | 16 | (5.1) | 1.73 | 0.39 to 7.71 | 187 | (41.4) | 4 | (4.2) | 1.98 | 0.40 to 9.73 | 2.01 | 0.68 to 5.89 | |||
On the Internet | 58 | (10.3) | 5 | (8.6) | 3.02 | 0.56 to 16.19 | 47 | (10.4) | 2 | (4.3) | 2.27 | 0.31 to 16.60 | 2.96 | 0.85 to 10.38 | |||
At a private party, bar, disco | 127 | (22.6) | 18 | (14.2) | 5.28 | 1.19 to 23.52 | 114 | (25.2) | 6 | (5.3) | 2.83 | 0.56 to 14.36 | 4.59 | 1.56 to 13.48 | |||
Type of relationship | |||||||||||||||||
Regular partner/sweetheart | 324 | (57.4) | 20 | (6.2) | 1.00 |
0.31
| 209 | (46.3) | 5 | (2.4) | 1.00 |
0.090
| 1.00 |
0.51
| |||
Ex partner/sweetheart | 74 | (13.1) | 8 | (10.8) | 1.84 | 0.78 to 4.36 | 51 | (11.3) | 1 | (2.0) | 0.82 | 0.093 to 7.14 | 1.58 | 0.72 to 3.47 | |||
A friend I have sex with | 103 | (18.3) | 6 | (5.8) | 0.94 | 0.37 to 2.41 | 95 | (21.1) | 8 | (8.4) | 3.75 | 1.19 to 11.79 | 1.55 | 0.79 to 3.04 | |||
Casual contact/other | 63 | (11.2) | 7 | (11.1) | 1.91 | 0.77 to 4.71 | 96 | (21.3) | 3 | (3.1) | 1.32 | 0.31 to 5.62 | 1.36 | 0.64 to 2.90 | |||
Last sexual intercourse
| |||||||||||||||||
Condom use | |||||||||||||||||
No3
| 474 | (84.0) | 39 | (8.2) | 1.00 |
0.062
| 300 | (66.5) | 16 | (5.3) | 1.00 |
0.039
| 1.00 |
0.003
| |||
Yes | 90 | (16.0) | 2 | (2.2) | 0.25 | 0.06 to 1.07 | 151 | (33.5) | 1 | (0.7) | 0.12 | 0.02 to 0.90 | 0.17 | 0.05 to 0.53 | |||
Related alcohol/drug use | |||||||||||||||||
No | 460 | (81.7) | 30 | (6.5) | 1.00 |
0.15
| 343 | (76.2) | 11 | (3.2) | 1.00 |
0.26
| 1.00 |
0.10
| |||
Yes | 103 | (18.3) | 11 | (10.7) | 1.71 | 0.83 to 3.54 | 107 | (23.8) | 6 | (5.6) | 1.79 | 0.65 to 4.97 | 1.64 | 0.91 to 2.94 | |||
Chlamydia infection
| |||||||||||||||||
Test prior to study | |||||||||||||||||
No | 251 | (45.5) | 18 | (7.2) | 1.00 |
0.94
| 368 | (79.1) | 11 | (3.0) | 1.00 |
0.14
| 1.00 |
0.11
| |||
Yes | 313 | (55.5) | 23 | (7.3) | 1.03 | 0.54 to 1.95 | 97 | (20.9) | 6 | (6.2) | 2.14 | 0.77 to 5.94 | 1.55 | 0.91 to 2.63 | |||
Treatment for infection | |||||||||||||||||
No | 452 | (80.1) | 30 | (6.6) | 1.00 |
0.25
| 433 | (93.3) | 16 | (3.7) | 1.00 |
0.87
| 1.00 |
0.13
| |||
Yes | 112 | (19.9) | 11 | (9.8) | 1.53 | 0.74 to 3.16 | 31 | (6.7) | 1 | (3.2) | 0.87 | 0.11 to 6.78 | 1.67 | 0.86 to 3.24 |
Prevalence
Crude analyses
Multivariable logistic regression analysis
Characteristic | Girls | Boys | Both | ||||||
---|---|---|---|---|---|---|---|---|---|
OR | 95% CI |
p
1
| OR | 95% CI |
p
1
| OR | 95% CI |
p
1
| |
Family and culture
| |||||||||
Residence in school year | |||||||||
At home | - | - | 1.00 |
0.013
| |||||
Other2
| - | - | 2.04 | 1.17–3.57 | |||||
Mother’s education | |||||||||
≤High school/don’t know | 1.00 |
0.021
| - | - | |||||
≥College | 2.22 | 1.13–4.37 | - | - | |||||
Sexual behaviour
| |||||||||
Condom use first intercourse | |||||||||
No | - | 1.00 |
0.005
| - | |||||
Yes | - | 0.06 | 0.01–0.42 | - | |||||
Sex partners past 6 months | |||||||||
0-1 | 1.00 |
<0.001
| - | 1.00 |
<0.001
| ||||
≥ 2 | 3.59 | 1.76–7.32 | - | 2.88 | 1.60–5.18 | ||||
Last sexual partner
| |||||||||
Age difference | |||||||||
Same age or younger | - | 1.00 |
0.017
| - | |||||
Older (≥1 year) | - | 3.74 | 1.27–11.01 | - | |||||
How met last partner | |||||||||
At school/work | 1.00 |
0.038
| 1.00 |
0.026
| |||||
Through family/friends/other | 1.90 | 0.42–8.65 | - | 1.61 | 0.54–4.82 | ||||
On the Internet | 3.40 | 0.62–18.78 | - | 2.81 | 0.78–0.08 | ||||
At a private party, bar, disco | 4.99 | 1.10–22.69 | - | 3.54 | 1.18–10.61 | ||||
Last sexual intercourse
| |||||||||
Condom use | |||||||||
No | - | - | 1.00 |
0.015
| |||||
Yes | - | - | 0.23 | 0.07–0.75 |