Association between Toxoplasma gondii seropositivity and Alzheimer's disease: a case-control study

Alzheimer's disease (AD) is a progressive neurodegenerative condition marked by declining cognitive function and memory deterioration. Emerging evidence suggests that infectious agents, including Toxoplasma gondii, may contribute to the risk of developing this disorder. Because previous studies on this association have produced limited and inconsistent results, we examined the link between T. gondii infection and Alzheimer's disease. This case-control study included 90 recently diagnosed AD patients from Ayatollah Rouhani Hospital and Clinic in Babol, Iran, and 91 healthy individuals as controls. After obtaining written informed consent, serum samples were collected from both groups. AD was determined through expert clinical evaluation, and the Mini-Mental State Examination (MMSE) was used to assess cognitive status and disease severity. Anti-T. gondii IgG antibodies were detected using ELISA. Data were analyzed in SPSS using chi-square tests, and odds ratios with 95% confidence intervals were calculated. The seroprevalence of T. gondii was 77.7% in cases and 89.0% in healthy controls. T. gondii seropositivity showed a significant inverse association with AD in both univariate analysis (OR: 0.43, 95% CI: 0.18-0.98; P = 0.04) and multivariate analysis (OR: 0.35, 95% CI: 0.14-0.92; P = 0.03). Additionally, T. gondii seropositivity was significantly associated with lower odds of greater AD severity in multivariate analysis (OR: 0.44, 95% CI: 0.20-0.97; P = 0.04). Our findings suggest an inverse association between T. gondii seropositivity and AD. Moreover, seropositivity was associated with lower odds of more severe disease. Further research is warranted to clarify the biological basis and clinical significance of this association.