Long-Term Cognitive Impairment after Hospitalization for Community-Acquired Pneumonia: a Prospective Cohort Study

Abstract

Background: Recent studies suggest older patients hospitalized for community-acquired pneumonia are at risk for new-onset cognitive impairment. The characteristics of long-term cognitive impairment after pneumonia, however, have not been elucidated.

Objective: To characterize long-term cognitive impairment among adults of all ages hospitalized for community-acquired pneumonia.

Design: Prospective cohort study.

Participants: Adults without severe preexisting cognitive impairment who were hospitalized with community-acquired pneumonia.

Main measures: At enrollment, we estimated baseline cognitive function with the Short Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). At 2- and 12-month follow-up, we assessed cognition using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and tests of executive function, diagnosing cognitive impairment when results were ≥ 1.5 standard deviations below published age-adjusted means for the general population. We also identified subtypes of mild cognitive impairment using standard definitions.

Key results: We assessed 58 (73%) of 80 patients who survived to 2-month follow-up and 57 (77%) of 74 who survived to 12-month follow-up. The median [range] age of survivors tested was 57 [19-97] years. Only 8 (12%) had evidence of mild cognitive impairment at baseline according to the Short IQCODE, but 21 (38%) at 2 months and 17 (30%) at 12 months had mild cognitive impairment per the RBANS. Moderate-to-severe cognitive impairment was common among adults ≥ 65 years [4/13 (31%) and 5/13 (38%) at 2 and 12 months, respectively] but also affected many of those < 65 years [10/43 (23%) and 8/43 (19%) at 2 and 12 months, respectively]. Deficits were most often noted in visuospatial function, attention, and memory.

Conclusions: A year after hospitalization for community-acquired pneumonia, moderate-to-severe impairment in multiple cognitive domains affected one-third of patients ≥ 65 years old and 20% of younger patients, and another third of survivors had mild cognitive impairment.

Keywords: cognition disorders; dementia; hospitalization; mild cognitive impairment; pneumonia.

Figure 1

Enrollment and follow-up

Figure 2

Cognitive function 2 and 12 months after community-acquired pneumonia according to age and comorbid illness burden per the Charlson Comorbidity Index. *The Charlson Comorbidity Index was measured at baseline; range 0–33, 0 = no comorbidities, 1 = one comorbidity. †Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) Global Cognition Score; age-adjusted population mean ± SD is 100 ± 15, with lower scores indicating worse cognition. The dashed line marked TBI indicates the expected population mean for moderate traumatic brain injury, and the dashed line marked AD indicates the expected population mean for mild Alzheimer’s disease based on data collected in other cohort studies. The latter is shown only for patients ≥ 65 years of age since RBANS population norms for AD were generated in that age group.