1132 — Systemic Bacterial Infections and the Risk of Dementia among U.S. Veterans: A Retrospective Cohort Study

Mawanda F, Iowa City Veterans Health Care System; McCoy KD, Iowa City Veterans Health Care System; Wallace R, University of Iowa; Abrams TE, Iowa City Veterans Health Care System;

Objectives:
The epidemiological evidence base has found associations between bacterial infections and risk of dementia. In general, data are lacking on the exposures to other (e.g., non-sepsis) bacterial infections and suffer from insufficient control for psychiatric comorbidity. With a retrospective cohort design, we conducted a comprehensive assessment for associations between several different severity levels of bacterial infections: septicemia, bacteremia, pneumonia, osteomyelitis, septic arthritis, cellulitis, and urinary tract infections (UTI), with risk of developing dementia with aggressive risk factor adjustment.

Methods:
The Veterans Health Administration (VHA) administrative data bases were used to identify n = 543,157 U.S. veterans at least 56 years during fiscal year (FY) 2003. Eligibility required: 1) no physician codes for dementia or mild cognitive impairment during the baseline FY02-03, 2) at least one visit every two years during follow-up (FY04-12). Modeled covariates included demographics, psychotropic medications, and clinical encounters identifying the date of the first exposure of interest (e.g. bacterial infection), confounding medical comorbidities (e.g., heart disease), psychiatric comorbidities, and date of first dementia diagnosis. Adjusted Cox proportion hazards determined the independent risk for each bacterial infection exposure occurring prior to the date of a dementia illness.

Results:
The average age of the sample was 68.0 (±8.09) and 97.3% were male. In unadjusted cox proportional hazards models, any exposure to a bacterial infection was associated with a hazard ratio (HR) for dementia (1.75; [95% CI 1.70-1.80]); the HR remained significant after controlling for demographic, medical, and psychiatric comorbidity (HR = 1.60; [1.55-1.64]). Exposure to sepsis (HR = 3.45; [3.08-3.88]), bacteremia (2.56; [2.22-2.88]), osteomyelitis (1.6; [1.44-1.78]), pneumonia (2.42; [2.11-2.78]), septic arthritis (1.46; [1.26-1.90]), UTI (2.08; [2.01-2.16]), and cellulitis (HR = 1.48; [1.42-1.54]), were each independently associated with a risk of developing dementia. However, exposure to cellulitis or a UTI alone (without a more serious bacterial infection) was not associated with dementia.

Implications:
Among older U.S. veterans several different types of bacterial infections are independently associated with a risk of developing dementia.

Impacts:
Further research is needed to determine if systemic inflammation is detrimental to neuronal health placing individuals at a higher risk for developing dementia in later life.