Poor Social Functioning: A Potentially Modifiable Risk Factor for Pneumonia in the Elderly.

Background Most risk factors for developing community-acquired pneumonia (CAP) are age-related and chronic medical conditions; modifying these factors can be challenging, especially in the elderly. Poor social functioning, however, has a negative impact on medical conditions but can be improved through interventions. Therefore, the social functioning domain of health-related quality of life (HRQOL) may be a modifiable risk factor for the development of CAP. This study investigated the association between poor social functioning and the incidence of CAP in elderly individuals. Methodology We conducted a retrospective cohort study using a dataset from 2018 to 2021, derived from an annual questionnaire-based survey of a cohort of community-dwelling people aged 75 years or older (the Sukagawa Study). The dataset included social functioning subscale scores of HRQOL obtained from the Eight-Item Short Form (SF-8) questionnaire. Health insurance claims data were matched with these HRQOL data. For each participant, the exposure (HRQOL) was measured, and outcomes (incidence of CAP) were observed yearly from 2018 through 2021. Results The four observation years had a total of 17,016 observation periods among 6,513 participants. The annual incidence rate of CAP was 0.90-1.77%. Lower social functioning was associated with a higher risk of CAP. Specifically, for each standard deviation difference in social functioning score, the adjusted rate ratio for CAP incidence was 1.26 (95% confidence interval (CI) = 1.08-1.48). In a subgroup analysis, the association between social functioning and CAP differed by sex (p = 0.037). Specifically, the adjusted rate ratio for CAP incidence was 1.41 (95% CI = 1.17-1.70) in men and 1.00 (95% CI = 0.76-1.35) in women. Conclusions Poor social functioning is an important risk factor for CAP in the elderly, especially in men. Interventions that improve social functioning may help to prevent CAP.