Differences in Assessing Loneliness Among Japanese Older Adults: A Comparison of Family Physicians and Nurses

<b>Background/Objectives</b>: Loneliness is highly prevalent in Japan and has become a major public health concern. Although primary health care professionals are often the first to encounter lonely patients, loneliness is subjective and difficult to detect in routine clinical practice. This study aims to examine how family physicians and nurses assess patient loneliness, and whether their approaches differ. <b>Methods</b>: This mixed-methods study comprised two surveys administered in Japanese family medicine clinics. Survey 1 (August 2020) was a cross-sectional questionnaire involving patients aged ≥ 50 years (<i>n</i> = 470), six family physicians, and seven nurses, of whom one responded on behalf of the group. Patient loneliness was measured using the UCLA (University of California, Los Angeles) Loneliness Scale (Version 3) and served as the reference standard. Physicians and nurses independently assessed patient loneliness based on medical records. Sensitivity, specificity, and predictive values were calculated. Survey 2 (August-September 2023) used an open-ended questionnaire completed by the same physicians and nurses, with responses analyzed using quantitative text mining to explore assessment perspectives. <b>Results</b>: Based on the UCLA scale, 38% of patients were classified as lonely. Compared to each other, family physicians demonstrated a higher sensitivity (45.3%) but lower specificity (67.4%), whereas nurses showed a lower sensitivity (21.8%) but higher specificity (84.5%). Text mining revealed that family physicians emphasized relational quality and psychological context, sometimes identifying loneliness even when there is no apparent lack of social connections. In contrast, nurses tended to define loneliness in terms of clearly observable social circumstances and emphasized patients' subjective acknowledgment. <b>Conclusions</b>: Family physicians and nurses employ distinct yet complementary approaches to identifying loneliness in primary health care. Collaborative, role-based strategies may enhance the accurate detection of loneliness and support more effective patient care.