Evidence against a geographic gradient of Alzheimer's disease and the hygiene hypothesis

Abstract

<jats:title>Abstract</jats:title> <jats:p>A significant positive correlation was previously reported (Fox et al., Evol. Med. Public Health 2013, 173–186) between hygiene and the global prevalence of Alzheimer's disease (AD) based on World Health Organisation (2004) data. These data have now been updated by the Global Burden of Disease (GBD; 2016) dataset that takes into account under-registration and other potential confounds. We therefore addressed whether the association between hygiene and AD is maintained in light of these more recent data. We report a significant positive correlation between GBD AD prevalence rates and parasite burden, and a negative association with hygiene. These newer data argue that hygiene is not a risk factor for AD, and instead suggest that parasite burden may increase AD risk.</jats:p>