Abstract
Toxoplasma gondii establishes latent infection in a substantial proportion of the global population, yet the long-term health consequences of this infection remain incompletely characterized. We conducted a retrospective observational matched cohort study using longitudinal electronic health record data from a nationwide integrated healthcare provider, including members aged 18–45 years who underwent routine Toxoplasma serologic screening, typically performed in obstetric evaluation, excluding patients with clinical toxoplasmosis, immunosuppression, or HIV. Seropositive individuals were matched 1:1 without replacement to seronegative controls to align demographic, temporal, and socioeconomic variables. Time-to-event associations with predefined medical conditions were evaluated using Cox proportional hazards models with false discovery rate correction. The final cohort included 19,443 seropositive individuals and 19,443 matched controls (96.7% female), with a tight baseline balance of demographic and temporal characteristics. During follow-up, seropositivity was associated with increased risks of tobacco dependence (aHR 1.65), alcohol dependence (2.32), suicide attempt (1.82), motor vehicle accidents (1.22), and work accidents (1.27), as well as multiple infectious conditions, including hepatitis B (1.55), hepatitis C (2.15), and syphilis (2.43), with an overall trend toward increased all-cause mortality (1.32, 95% CI [1.00–1.74]). These findings suggest that asymptomatic Toxoplasma infection in young adults is associated with increased long-term behavioral and medical comorbidity.