Infection Hospitalization Increases Risk of Dementia in the Elderly*

Abstract

Objectives Severe infections, often requiring intensive care unit (ICU) admission, have been associated with persistent cognitive dysfunction. Less severe infections are more common and whether they are associated with an increased risk of dementia is unclear. We determined the association of pneumonia hospitalization with risk of dementia in well-functioning older adults. Design Secondary analysis of a randomized multicenter trial to determine the effect of Gingko biloba on incident dementia. Setting and Subjects Community volunteers (n=3069) with a median follow-up of 6.1 years. Measurement and Main Results We identified pneumonia hospitalizations using ICD-9CM codes and validated them in a subset. Less than 3% of pneumonia cases necessitated ICU admission, mechanical ventilation or vasopressor support. Dementia was adjudicated based on neuropsychological evaluation, neurological exam, and magnetic resonance imaging. Two hundred twenty one participants (7.2%) incurred at least one hospitalization with pneumonia (mean time to pneumonia=3.5 years). Of these, 38 (17%) developed dementia after pneumonia with half of these cases occurring 2 years after the pneumonia hospitalization. Hospitalization with pneumonia was associated with increased risk of time to dementia diagnosis (unadjusted hazard ratio [HR] = 2.3, CI: 1.6–3.2, p<0.0001). The association remained significant when adjusted for age, sex, race, study site, education, and baseline Mini-Mental Status Exam (HR=1.9, CI 1.4–2.8, p<.0001). Results were unchanged when additionally adjusted for smoking, hypertension, diabetes, heart disease, and pre-infection functional status. Results were similar using propensity analysis where participants with pneumonia were matched to those without pneumonia based on age, probability of developing pneumonia, and similar trajectories of cognitive and physical function prior to pneumonia (adjusted incidence rates: 91.7 vs. 65 cases per 1,000 person-years, adjusted incidence rate ratio=1.6, CI:1.06–2.7, p=0.03). Sensitivity analyses showed that the higher risk also occurred among those hospitalized with other infections. Conclusion Hospitalization with pneumonia is associated with increased risk of dementia.

Why Mental Status Standards are Recommended on Medical Surgical Units in Hospitals?

“…Another challenge is the way infections of the lungs compromise the oxygen and carbon dioxide exchange, followed by symptoms of confusion and irritability [6]. These patients may have a degree of infection so severe that it limits their ability to participate in a study.…”

“…In addition to factors such as degree of the illness, age, or other reference points, sound mentation measurement tools must be used, or the patient may fail to internalize the framed message. Recent secondary analysis by Tate and Snitz [6] explored N=3,069 patients hospitalized with pneumonia, and found that the pneumonia increased their risk for dementia. The findings showed that 17% of patients with pneumonia develop dementia.…”

“…Literature has recently addressed such needs for clarification to improve consistent practice in mentation measurement [6,14]. In addition to factors such as degree of the illness, age, or other reference points, sound mentation measurement tools must be used, or the patient may fail to understand the questions as requested by nurses during assessments.…”

“…Patients diagnosed with pneumonia are at higher risk for temporary cognitive changes due to the severity of the disease [6]. Following strict criteria, subjects whom were unable to consent to participate in the study and/or if they had altered mental status secondary to dementia or found to have cognitive changes affecting their judgment as reflected in the medical record were excluded [2].…”

“…We found patients diagnosed with pneumonia are at higher risk for temporary cognitive changes due to the severity of the disease. Mentation is affected when oxygen saturation is altered via hypoxemia from a respiratory infection [4,6].…”