Demographic characteristics of the study population
Table 1 demonstrates the population distribution of different characteristics for 62,544 patients with BPH, PCa, or BC and 187,632 controls from 2000 to 2015. There were no significant differences in age between groups after matching. The proportion with trichomoniasis in the case group was 0.02% (14/62,544), while it was 0.01% (14/187,632) in the control group (P < 0.001).
Variable evaluation in the multiple logistic regression
We present the results of the multivariable logistic regression analyses in Table 2. Patients with trichomoniasis had a significantly higher risk of BPH, PCa, or BC (adjusted odds ratio [AOR] = 2.999, 95% confidence interval [CI] = 1.426–5.301, p=0.002). There was also a significantly higher risk for patients with depression (AOR = 3.124, 95% CI = 1.808–4.838, P < 0.001). The opposite result was noted in patients with middle or high insurance premiums (insurance premium NT$18,000–34,999: AOR = 0.745, 95% CI = 0.688–0.799, P < 0.001; insurance premium >NT$35,000: AOR = 0.836, 95% CI = 0.701–0.979, P = 0.019). Patients diagnosed in summer, autumn, or winter also had significantly lower risk than the control group (summer: AOR = 0.938, 95% CI = 0.902–0.953, P < 0.001; autumn: AOR = 0.790, 95% CI = 0.758–0.805, P < 0.001; winter: AOR = 0.862, 95% CI = 0.824–0.878, P < 0.001). Patients who lived in areas with a higher urbanization level had a significantly higher risk of BPH, PCa, or BC (urbanization level 1: AOR = 1.160, 95% CI = 1.124–1.189, P < 0.001; urbanization level 2: AOR = 1.211, 95% CI = 1.179–1.235, P < 0.001) but had significantly lower risk when diagnosed at a higher level of care (hospital center: AOR = 0.819, 95% CI = 0.796–0.902, P < 0.001; regional hospital: AOR = 0.745, 95% CI = 0.724–0.808, P < 0.001) instead.
Risk of BPH/PCa and BC in the trichomoniasis group stratified by covariates
The risk of BPH, PCa, or BC stratified based on variables using multivariable logistic regression is shown in Table 3. Patients with trichomoniasis had a 2.999 times higher risk of BPH, PCa, or BC than the control group (AOR = 2.999, 95% CI = 1.426–5.301). In the case of trichomoniasis, there were significantly higher risks of BPH, PCa, or BC in patients aged >65 years old, with lower insurance premiums, with/without depression, first diagnosed in winter, urbanization level 2, and first diagnosed in a local hospital (age > 65 years: AOR = 3.685, 95% CI = 1.704–8.015; insurance premium < NT$18,000: AOR = 2.999, 95% CI = 1.326–5.301; with depression: AOR = 3.104, 95% CI = 1.706–5.972; without depression: AOR = 2.545, 95% CI = 1.138–4.289; first diagnosed in winter: AOR = 4.806, 95% CI = 1.104–19.675; urbanization level 2: AOR = 3.284, 95% CI = 1.057–10.978; first diagnosed in local hospital: AOR = 15.121, 95% CI = 1.762–118.976).
Risk of BPH/PCa and BC in subgroup with T. vaginalis exposure and the joint effect
Table 4 presents the T. vaginalis exposure ratio in each subgroup of BPH/PCa and BC. T. vaginalis exposure is significantly associated with a higher risk of BPH and PCa (BPH: AOR = 2.685, 95% CI = 1.233–4.286, P = 0.013; PCa: AOR = 5.801, 95% CI = 1.296–26.035, P = 0.016), but has no significant association with BC (AOR = 4.012, 95% CI = 0.524–31.145, P = 0.151). In addition, patients with both depression and T. vaginalis exposure had a significantly higher risk of developing BPH, PCa, or BC in comparison with other groups with only one condition or without them (AOR = 7.682, 95% CI = 5.730–9.451, P < 0.001) (Fig. 2).