Background: The World Health Organization (WHO) estimated the global incidence of syphilis among adults to be approximately 7.1 million in 2020. The following year, the American Centers for Disease Control and Prevention (CDC) reported a 32% increase in the incidence of primary/secondary (early) syphilis in the United States between 2020-2021. Treponemal central nervous system (CNS) invasion is estimated to occur in approximately 25-60% of cases, however, the current WHO/CDC standard of care for early syphilis does not achieve CNS clearance. This raises concern for a preventable burden of neurologic morbidity secondary to treponemal CNS persistence and subsequent neurosyphilis. Our central hypothesis is that individuals with history of syphilis infection will experience greater odds of neurologic morbidity relative to their uninfected counterparts.
Methods: An FQHC-based, preliminary 10-year retrospective analysis (01/2013-12/31/2022) of deidentified electronic medical records (EMR) was undertaken in summer of 2023. The exposure of interest consisted of grouped ICD-10 codes representative of early syphilis infection with neurologic outcomes defined as ICD-10 diagnoses reflective of the principle clinical manifestations of neurosyphilis. Unadjusted, bivariate analysis was performed for preliminary assessment of exposure-outcome association.
Results: 3,711,053 EMR from an academic health system were included in final analysis. 5,981 patients were found to have a diagnosis of syphilis. Patients with syphilis exposure had significantly higher odds for stroke (OR = 5.14; 95%CI = 4.71-5.61), dementia (OR = 20.68 ; 95%CI = 19.27–22.19 ), sensorineural hearing loss (OR= 5.75; 95% CI= 5.07-6.2), and blindness (OR= 15.74 ; 95%CI = 14.31-16.54) relative to unexposed patients.
Conclusion: Syphilis infection was associated with significantly increased odds of neurologic morbidity across all representative outcome measures queried. These data are concerning as they suggest a clinically significant limitation to the current WHO/CDC standard of care for early syphilis. We plan to more rigorously evaluate our hypothesis in a follow-up study that will utilize regression analysis to determine the independent effect of syphilis exposure adjusting for multiple confounders.