Paul Brassard

INTRODUCTION Our population‐based study assessed whether clinically apparent Helicobacter pylori infection (CAHPI) is associated with the risk of Alzheimer's disease (AD). METHODS We assembled a population‐based cohort of all dementia‐free subjects in the United Kingdom's Clinical Practice Research Datalink (UK CPRD), aged ≥50 years (1988–2017). Using a nested case‐control approach, we matched each newly developed case of AD with 40 controls. Conditional logistic regression estimated odds ratios (ORs) with 95% confidence intervals (CIs) of AD associated with CAHPI compared with no CAHPI during ≥2 years before the index date. We also used salmonellosis as a negative control exposure. RESULTS Among 4,262,092 dementia‐free subjects, 40,455 developed AD after a mean 11 years of follow‐up. CAHPI was associated with an increased risk of AD (OR, 1.11; 95% CI, 1.01–1.21) compared with no CAHPI. Salmonellosis was not associated with the risk of AD (OR, 1.03; 95% CI, 0.82–1.29). DISCUSSION CAHPI was associated with a moderately increased risk of AD. Highlights CAHPI was associated with an 11% increased risk of AD in subjects aged ≥50 years. The increase in the risk of AD reached a peak of 24% a decade after CAHPI onset. There was no major effect modification by age or sex. Sensitivity analyses addressing several potential biases led to consistent results.