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

J Constance Lathe; Richard Lathe

doi:10.1093/emph/eoaa023

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

Evol Med Public Health. 2020 Jul 10;2020(1):141-144. doi: 10.1093/emph/eoaa023. eCollection 2020.

Authors

J Constance Lathe¹, Richard Lathe²

Affiliations

¹ Program in Neuroscience, University of Glasgow, Glasgow, UK.
² Division of Infection Medicine, University of Edinburgh Medical School, Edinburgh, UK.

Abstract

A significant positive correlation was previously reported (Fox et al. Evol Med Public Health 2013; 2013:173-86) between hygiene and the global prevalence of Alzheimer's disease (AD) based on World Health Organization (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. Lay summary: It was previously hypothesized that hygeine might be a risk factor for the development of Alzheimer disease (AD), based on a global gradient of dementia. Newer data that correct global AD rates for under-reporting now demonstrate that parasite burden is positively correlated with AD.

Keywords: Alzheimer; dementia; global burden of disease; hygiene hypothesis; prevalence.