The role of noninfectious comorbidities in the association between severe infections and risk of dementia in Finland: A nationwide registry study

24 Mar 20264 min read0 viewsJournal Feed

GIST

by Pyry N. Sipilä, Kaarina Korhonen, Joni V.

Lindbohm, Mika Kivimäki, Pekka Martikainen Background Severe infections have been linked to an increased risk of dementia, but both conditions often coexist with other illnesses that may confound this association. Using nationwide Finnish health registry data, we examined the role of noninfectious mental and physical illnesses in the association between severe infections and dementia.

Methods and findings This register-based study included 62,555 individuals aged 65 or older in Finland in 2016 who were diagnosed with late-onset dementia between 2017 and 2020 and 312,772 dementia-free controls matched for year of birth, sex, and the follow-up period. Analyses were adjusted for education, marital status, employment, and area of residence, with age and sex accounted for through the matched conditional design and analysis.

Clinical Editorial

Investigative framing and study purpose

The study interrogates whether noninfectious comorbidities, including mental and physical illnesses, help explain the observed link between severe infections and subsequent dementia.
Data derive from nationwide Finnish health registries, focusing on adults aged 65 years and older.

Cohort design and population characteristics

The analysis used 62,555 individuals diagnosed with late-onset dementia between 2017 and 2020, along with 312,772 dementia-free controls matched on year of birth, sex, and follow-up window.
A one-year lag period was applied to separate prior medical history from dementia outcomes.

Exposure assessment and adjustment strategy

Researchers identified 29 hospital-treated diseases that occurred 1–21 years before dementia diagnosis (or index date for controls) and met criteria of prevalence ≥1% before dementia and a confounder-adjusted rate ratio of at least 1.20.
Analyses adjusted for education, marital status, employment, and area of residence; age and sex were managed through the matched design.

Key findings and interpretation

Across the dataset, a spectrum of mental and physical noninfectious conditions were associated with elevated dementia risk.
Crucially, the increased incidence of dementia among those with severe infections persisted after accounting for these comorbidities, suggesting that severe infections function as independent risk factors for dementia rather than simply reflecting clustering with other illnesses.

Contextual considerations and limitations

The study relies on registry-derived diagnoses, with the one-year lag implemented to mitigate reverse causation, but residual confounding cannot be completely excluded.
The scope is limited to hospital-treated conditions and Finnish population data, which may affect generalizability to other settings or non-hospital presentations.