How old are young people when they start having sex? Unravelling the applicability of Cox proportional hazards regression

Purpose: How old are young people when they start having sex? Although this question is important for educators and policymakers, its answer can easily mislead due to methodology that does not take into account age-censoring and generational trends. This study investigated whether 1-year birth-year cohorts can be jointly modeled by Cox proportional hazards regression to estimate sexual debut ages and to investigate age trends for different sexual behaviors. Method: We used pooled data from three Dutch periodic population-based surveys, for which 33,377 participants, born between 1980 and 2004, completed an online questionnaire. Results: Cox proportional hazards regression is appropriate if hazard changes over birth years appear proportionally similar among ages. The Dutch data shows such hazard changes for petting, oral sex, and sexual intercourse, but not for masturbation, French kissing, or manual sex. For sexual intercourse, the Cox model estimates can be interpreted as an approximate linear increase of 1 month in the median sexual debut age per birth-year cohort, resulting in an estimated debut age of 18.17 years in the current (2020) generation of Dutch adolescents. Conclusion: If the assumptions are met, we recommend using the Cox regression modeling approach to estimate how old young people are when they start having sex, since this method yields precise and current debut ages by pooling information across birth-year cohorts without arbitrarily combining them in multiple-year groups. The age of first intercourse is increasing, so continuous sexuality education throughout high school is advisable, in addition to early sexuality education

Anorectal Chlamydia trachomatis Load Is Similar in Men Who Have Sex with Men and Women Reporting Anal Sex.

Anorectal Chlamydia trachomatis (chlamydia) is frequently diagnosed in men who have sex with men (MSM) and in women, but it is unknown whether these infections are comparable in clinical impact and transmission potential. Quantifying bacterial load and identifying determinants associated with high bacterial load could provide more insight.We selected a convenience sample of MSM who reported anal sex (n = 90) and women with concurrent urogenital/anorectal chlamydia who reported anal sex (n = 51) or did not report anal sex (n = 61) from the South Limburg Public Health Service's STI unit. Bacterial load (Chlamydia/ml) was quantified for all samples and log transformed for analyses. Samples with an unquantifiable human leukocyte antigen (n = 9) were excluded from analyses, as they were deemed inadequately sampled.The mean log anorectal chlamydia load (3.50) was similar for MSM and women who reported having anal sex (3.80, P = 0.21). The anorectal chlamydia load was significantly higher in these groups than in women who did not report having anal sex (2.76, P = 0.001). Detectable load values ranged from 1.81-6.32 chlamydia/ml for MSM, 1.74-7.33 chlamydia/ml for women who reported having anal sex and 1.84-6.31 chlamydia/ml for women who did not report having anal sex. Symptoms and several other determinants were not associated with anorectal chlamydia load.Women who did not report anal sex had lower anorectal loads, but they were within a similar range to the other two groups. Anorectal chlamydia load was comparable between MSM and women who reported anal sex, suggesting similar transmission potential

Routine universal testing versus selective or incidental testing for oropharyngeal Chlamydia trachomatis in women in the Netherlands:a retrospective cohort study

BACKGROUND: Pharyngeal Chlamydia trachomatis in women might contribute to autoinoculation and transmission to sexual partners. Data for effectiveness of different testing practices for pharyngeal C trachomatis are scarce. We therefore aimed to assess the prevalence of pharyngeal C trachomatis, determinants, and effectiveness of different testing practices in women. METHODS: We did a retrospective cohort study, in which surveillance data for all women visiting sexually transmitted infection clinics in all regions in the Netherlands between Jan 1, 2008, and Dec 31, 2017, were used. We collected consultation-level data and individual-level data from 2016 onwards for sociodemographic characteristics, sexual behaviour in the past 6 months, self-reported symptoms, and STI diagnoses. The primary outcome was the positivity rate of pharyngeal C trachomatis infection compared between routine universal testing (>85% tested pharyngeally per clinic year), selective testing (5-85% tested pharyngeally per clinic year), and incidental testing (<5% pharyngeally tested per clinic year). We calculated the number of missed infections by extrapolating the positivity rate assessed by routine universal testing to all selectively tested women. We used multivariable generalised estimating equations logistic regression analyses to assess independent risk factors for pharyngeal C trachomatis and used the assessed risk factors as testing indicators for comparing alternative testing scenarios. FINDINGS: Between Jan 1, 2008, and Dec 31, 2017, a total of 550 615 consultations with at least one C trachomatis test was recorded, of which 541 945 (98·4%) consultations (including repeat visits) were included in this analysis. Pharyngeal C trachomatis positivity was lower in the routine universal testing group than in the selective testing group (1081 [2·4%; 95% CI 2·2-2·5] of 45 774 vs 3473 [2·9%; 2·8-3·0] of 121 262; p<0·0001). The positivity rate was also higher among consultations done in the incidental testing group (44 [4·1%; 95% CI 3·1-5·5] of 1073; p<0·0001) than in the routine universal testing group. Based on extrapolation, selective testing would have hypothetically missed 64·4% (95% CI 63·5-65·3; 6363 of 9879) of the estimated total of C trachomatis infections. The proportion of pharyngeal-only C trachomatis was comparable between routinely universally tested women (22·9%) and selectively tested women (20·4%), resulting in a difference of 2·5% (95% CI -0·3 to 5·3; p=0·07). When using risk factors for pharyngeal C trachomatis as testing indicators, 15 484 (79·6%) of 19 459 women would be tested to detect 398 (80·6%) of 494 infections. INTERPRETATION: No optimal testing scenario was available for pharyngeal C trachomatis, in which only a selection of high-risk women needs to be tested to find most pharyngeal C trachomatis infections. The relative low prevalence of pharyngeal-only C trachomatis (0·5%) and probably limited clinical and public health effect do not provide support for routine universal testing. FUNDING: Public Health Service South Limburg

Pharyngeal Chlamydia trachomatis in Men Who Have Sex With Men (MSM) in The Netherlands: A Large Retrospective Cohort Study.

Pharyngeal Chlamydia trachomatis (CT) was diagnosed in 1.2% and pharyngeal-only CT in 0.5% of routinely universally tested men who have sex with men (MSM). In these 3-anatomic-site tested MSM, pharyngeal-only CT comprised 4.8% of all CT. The low positivity of pharyngeal-only CT indicates low public health impact of pharyngeal CT

Pharyngeal Chlamydia trachomatis in Men Who Have Sex With Men (MSM) in The Netherlands: A Large Retrospective Cohort Study

Pharyngeal Chlamydia trachomatis (CT) was diagnosed in 1.2% and pharyngeal-only CT in 0.5% of routinely universally tested men who have sex with men (MSM). In these 3-anatomic-site tested MSM, pharyngeal-only CT comprised 4.8% of all CT. The low positivity of pharyngeal-only CT indicates low public health impact of pharyngeal CT

Mean log-transformed number of chlamydia copies per millilitre (Ct/ml) (anorectal load) and associated determinants in MSM, women who reported anal sex and women who did not report anal sex by univariate linear regression analyses.

<p>^† Concurrent STIs were only assessed as a determinant for MSM since all the women had concurrent urogenital chlamydia and tested negative for TPHA and HIV; all but one woman were also negative for anorectal gonorrhoea.</p><p>^‡ The regression coefficient is represented as Δ load, which represents the change in anorectal chlamydia load between the categories.</p><p>Sensitivity analyses were performed by excluding unquantifiable (0.75 log) load samples in analyses, but results remained the same.</p><p>Na = not assessed.</p><p>* P<0.05.</p><p>Mean log-transformed number of chlamydia copies per millilitre (Ct/ml) (anorectal load) and associated determinants in MSM, women who reported anal sex and women who did not report anal sex by univariate linear regression analyses.</p

Log-transformed number of cycle threshold per millilitre (Ct/ml) (load) in MSM, women who reported anal sex and women who did not report anal sex, including load detection threshold, geometrical mean and mean difference between groups tested by univariate linear regression analyses.

<p>Log-transformed number of cycle threshold per millilitre (Ct/ml) (load) in MSM, women who reported anal sex and women who did not report anal sex, including load detection threshold, geometrical mean and mean difference between groups tested by univariate linear regression analyses.</p