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. 2020;76(4):1609-1626.
doi: 10.3233/JAD-200303.

Common Bacterial Infections and Risk of Dementia or Cognitive Decline: A Systematic Review

Rutendo Muzambi  1 , Krishnan Bhaskaran  1 , Carol Brayne  2 , Jennifer A Davidson  1 , Liam Smeeth  1 , Charlotte Warren-Gash  1
Affiliations

Common Bacterial Infections and Risk of Dementia or Cognitive Decline: A Systematic Review

Rutendo Muzambi et al. J Alzheimers Dis. 2020.

Abstract

Background: Bacterial infections may be associated with dementia, but the temporality of any relationship remains unclear.

Objectives: To summarize existing literature on the association between common bacterial infections and the risk of dementia and cognitive decline in longitudinal studies.

Methods: We performed a comprehensive search of 10 databases of published and grey literature from inception to 18 March 2019 using search terms for common bacterial infections, dementia, cognitive decline, and longitudinal study designs. Two reviewers independently performed the study selection, data extraction, risk of bias and overall quality assessment. Data were summarized through a narrative synthesis as high heterogeneity precluded a meta-analysis.

Results: We identified 3,488 studies. 9 met the eligibility criteria; 6 were conducted in the United States and 3 in Taiwan. 7 studies reported on dementia and 2 investigated cognitive decline. Multiple infections were assessed in two studies. All studies found sepsis (n = 6), pneumonia (n = 3), urinary tract infection (n = 1), and cellulitis (n = 1) increased dementia risk (HR 1.10; 95% CI 1.02-1.19) to (OR 2.60; 95% CI 1.84-3.66). The range of effect estimates was similar when limited to three studies with no domains at high risk of bias. However, the overall quality of evidence was rated very low. Studies on cognitive decline found no association with infection but had low power.

Conclusion: Our review suggests common bacterial infections may be associated with an increased risk of subsequent dementia, after adjustment for multiple confounders, but further high-quality, large-scale longitudinal studies, across different healthcare settings, are recommended to further explore this association.

Keywords: Cognition; Systematic review registration number: CRD42018119294, registered in December 2018; dementia; infections; prevention; systematic review.

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Conflict of interest statement

Authors’ disclosures available online (https://www.j-alz.com/manuscript-disclosures/20-0303r2).

Figures

Fig. 1.
Fig. 1.
Study selection PRISMA flow diagram.
Fig. 2.
Fig. 2.
Forest plot showing the effect of infections on dementia. *Unadjusted effect estimates. The mean age (SD) in this study was 72.8 years (5.6).
Fig. 3.
Fig. 3.
Forest plot showing the effect of common bacterial infections on cognitive decline. *Unadjusted effect estimates for the study by Davydow et al., 2013 [26]. The median age in years (SD) in this study for each exposure was as follows: pneumonia 77.1 (9.4), myocardial infarction, 75.5 (8.2) and stroke 77.0 (8.4).
See this image and copyright information in PMC

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