Associations of Inherited Chromosomally‐Integrated Human Herpesvirus 6 With Dementia Incidence, Inflammation, and Other Dementia Risk Factors in the UK Biobank

The infection theory of dementia states that viral infections and chronic inflammation play a role in its pathogenesis. We aimed to test whether testing positive for inherited chromosomally-integrated human herpesvirus 6 (iciHHV-6) is associated with an increased dementia incidence, inflammation, and other dementia risk factors. We included n = 247,731 participants of the UK Biobank in the analysis, of whom n = 3388 (1.4%) tested positive for iciHHV-6. Linear and logistic regression models were performed to assess the associations between iciHHV-6 with HHV-6 antigens, blood-based biomarkers of inflammation, and other dementia risk factors. Cox proportional hazards regression models were applied to assess the associations of iciHHV-6 with all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VD). Subjects with iciHHV-6 exhibited statistically significantly higher antibody responses to the HHV-6 antigens IE1A (p = 0.002) and IE1B (p < 0.001). IciHHV-6 positivity was significantly more frequent among subjects with European or Chinese ethnicity, with lower education, higher alcohol consumption, current smoking, and longer telomere length. Interestingly, iciHHV-6 positive subjects had lower C-reactive protein (CRP) levels (p = 0.029). All other inflammatory biomarkers did not differ according to iciHHV-6 status. Overall, 6615 participants were diagnosed with all-cause dementia during a median of 13.6 years, including 3340 with AD and 1708 with VD. There was no significant association between iciHHV-6 positivity and the risk of any dementia outcome. IciHHV-6 positivity was not a risk factor for dementia outcomes or increased inflammation in this large study, but was associated with higher antibody responses against HHV-6 antigens, ethnicity, telomere length, and lifestyle factors.