Herpes Simplex Virus, APOEɛ4, and Cognitive Decline in Old Age: Results from the Betula Cohort Study.

BACKGROUND

Herpes simplex virus (HSV) has been suggested to play a role in Alzheimer's disease (AD) development.

OBJECTIVE

The aim of the present study was to investigate the early AD-related symptom episodic memory decline in relation to HSV and carriage of allele 4 of the apolipoprotein E gene (APOEɛ4) in a large population-based cohort with a long follow-up time.

METHODS

The study included 3,413 persons, with longitudinal data available for 1,293 persons with a mean follow-up time of 11.6 years. The associations between HSV carriage, APOEɛ4 carriage, and episodic memory was investigated at baseline, as well as in longitudinal analyses where individuals with and without HSV antibodies (HSV1/2 non-specific) were matched and episodic memory decline compared.

RESULTS

Cross-sectional analyses revealed an age-dependent association of HSV carriage with lower episodic memory function, particularly among APOEɛ4 carriers (p = 0.008). Longitudinal analyses showed an increased risk of episodic memory decline in HSV carriers (≥65 years: p < 0.001, all ages: non-significant), and a significant interaction between HSV and APOEɛ4 for episodic memory decline (p < 0.001).

CONCLUSION

In this large population-based cohort study, both cross-sectional and longitudinal results support an association between HSV carriage and declining episodic memory function, especially among APOEɛ4 carriers. The results strengthen the hypothesis that HSV is associated with AD development.