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Dementia identified as a risk factor for infection-related hospital contacts in a national, population-based and longitudinal matched-cohort study


The aim of this study was to investigate the association between incident dementia and rates of infection-related hospital contacts. We conducted a registry- and population-based matched-cohort study of all Danish residents who were born in or before 1950, included from 1 January 2000 or their 65th birthday (whichever came later), who were alive and resided in Denmark at the start of the study, excluding those who had received a dementia diagnosis before 1 January 2000 or their 65th birthday (n = 1,712,100). A total of 129,660 people (403,744 person years) with incident dementia were matched with 297,476 people (1,918,784 person years) without dementia. Incidence rate ratios (IRRs) of infection-related hospital contacts were calculated using Poisson regression, by infection type, sex and age. The IRR for any infection-related contact in dementia was 1.5, was highest for nervous and urinary system infections and sepsis, decreased with increasing age and was higher in men. More people with than without dementia had contacts five years before the index date. Our findings show that dementia is a risk factor for infection-related hospital contacts and infections might be an early sign of dementia.

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Fig. 1: Cohort population flow chart.
Fig. 2: IRRs of infection-related hospital contacts, by infection site category, in people with dementia.
Fig. 3: IRRs by sex and age group in people with dementia.
Fig. 4: Infection-related hospital contacts during the 5 years before the index date.

Data availability

All of the data used in this study are derived from the Danish National and Public Health registries. These data are collected and stored by the relevant authorities and cannot be made public or accessed by unauthorized parties. Access to such data is given via standard rules and regulations of data access outlined by the Danish Data Protection Agency and Danish Health Data Authority.

Code availability

SAS software version 9.4 was used for analysis and coding relating to all of the methods used in this study. We used the procedure PROC GENMOD.


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The Danish Dementia Research Centre is supported by the Danish Ministry of Health, which was not involved in any phase of this study (design or conduct; collection, management, analysis or interpretation of the data; preparation, review or approval of the manuscript; or decision to submit the manuscript for publication).

Author information




J.J., G.W. and N.F.-M. conceived of the study concept and performed the literature review. All authors designed the study. J.J. and N.F.-M. prepared and defined the data related to the infection codes. J.J. and T.M.L. performed the statistical analyses. J.J. wrote the manuscript as outlined by J.J. and G.W. All authors contributed equally to data interpretation and critical review of the manuscript.

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Correspondence to Janet Janbek.

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Peer review information Nature Aging thanks Louise Allan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Methods and Tables 1–10.

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Janbek, J., Frimodt-Møller, N., Laursen, T.M. et al. Dementia identified as a risk factor for infection-related hospital contacts in a national, population-based and longitudinal matched-cohort study. Nat Aging 1, 226–233 (2021).

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