Syndemic effects of social isolation on mental health, health behaviours and diabetes management in older adults with diabetes: a gender-based cross-sectional study in South Korea

OBJECTIVES: To examine the associations between social isolation (SI) and mental health, health behaviours and diabetes management among older adults with diabetes in South Korea, focusing on gender-specific syndemic patterns. DESIGN: Cross-sectional secondary analysis. SETTING: 2023 Korea Community Health Survey, a nationwide community-based survey. PARTICIPANTS: 18 924 adults aged ≥65 years with physician-diagnosed diabetes. OUTCOME MEASURES: Mental health (depressive symptoms, perceived stress), health behaviours (smoking, high-risk drinking, physical activity) and diabetes management (medication use, complication screening, diabetes education) were assessed. Multivariable logistic regression was used to estimate the adjusted associations between SI and study outcomes. RESULTS: SI was more prevalent among women (33.6%) than among men (14.1%). In men, SI was associated with depressive symptoms (aOR=1.60, 95% CI 1.18 to 2.18, p=0.003), smoking (aOR=1.51, 95% CI 1.25 to 1.82, p<0.001), high-risk drinking (aOR=1.76, 95% CI 1.36 to 2.28, p<0.001) and lower diabetes education participation (aOR=0.80, 95% CI 0.65 to 0.99, p=0.031). Among women, SI was associated with depressive symptoms (aOR=1.35, 95% CI 1.07 to 1.69, p=0.010), smoking (aOR=2.53, 95% CI 1.69 to 3.78, p<0.001), lower physical activity (aOR=0.56, 95% CI 0.44 to 0.71, p<0.001), lower medication use (aOR=0.51, 95% CI 0.38 to 0.69, p<0.001), reduced complication screening (aOR=0.86, 95% CI 0.76 to 0.97, p=0.016) and lower diabetes education participation (aOR=0.81, 95% CI 0.69 to 0.95, p=0.010). SI was not significantly associated with perceived stress in either gender. CONCLUSIONS: SI was associated with poorer mental health and unhealthy behaviours among older adults with diabetes, with distinct gender-specific patterns. The SI also showed non-uniform associations with diabetes management, indicating that its impact may differ across management domains. Addressing SI may support improvements in selected aspects of diabetes care. Further research should clarify the mechanisms linking SI and disease management.