Clinical characteristics and factors related to antibiotic-associated diarrhea in elderly patients with pneumonia: a retrospective cohort study.

BACKGROUND: Antibiotic-associated diarrhea (AAD) is a common problem among elderly inpatients because many elderly patients are admitted for pneumonia or other conditions that necessitate antibiotic treatment. In the super aging population, more patients are suffering from pneumonia than before, but the incidence or risk factors for AAD among many elderly patients have not been well scrutinized. METHODS: We conducted a retrospective cohort study of elderly patients diagnosed with pneumonia from April 2014 to March 2019 who were admitted to the Department of General Medicine of a Tertiary Care Hospital in Japan. Patients (≥ 65 years of age) who were diagnosed with bacterial pneumonia or aspiration pneumonia and treated with antibiotics were included. We defined AAD by diarrhea with more than three loose or watery stools per day and included patients who had these symptoms for either one day or two or more consecutive days. We also assessed the length of hospital stay and in-hospital mortality. The potential risk factors for AAD included age, sex, body weight, body mass index, smoking, alcohol, activities of daily living (ADL),　comorbidities, vital signs, laboratories, the severity of pneumonia, antibiotic and other medication use. RESULTS: There were 1,067 patients, the mean age was 83 years, and men accounted for 59 %. ß-Lactamase inhibitors were frequently prescribed antibiotics in 703 patients (66 %), and proton pump inhibitors (PPIs) were also commonly administered (48 %). AAD developed in 322 patients (30 %). The multivariate logistic regression model showed that ß-lactamase inhibitors (OR 1.43, 95 % CI 1.05-1.95) and PPIs (OR 1.37, 95 % CI 1.03-1.83) were associated with AAD as well as age (OR 1.03 per year, 95 % CI 1.01-1.05). CONCLUSIONS: AAD was common among elderly inpatients with pneumonia, and ß-lactamase inhibitors and PPIs were associated with AAD. Strict use of such medication should be considered to decrease the risk of AAD.