Bilateral Blindness Due to Radiation-Induced Optic Neuropathy in a Patient with Nasal Mucosal Melanoma.

Loneliness and social isolation are increasingly recognized as important public health concerns with relevance to adult health and chronic disease prevention. The World Health Organization has emphasized social connection as a major determinant of health and has highlighted the health, social, and economic consequences of loneliness and social isolation []. These forms of social disconnection may influence chronic disease prevention and long-term disease risk through health behaviors, self-management, healthcare engagement, and stress-related responses. This concern is especially relevant in the context of noncommunicable diseases because long-term illness is shaped not only by biological risk but also by social conditions that affect prevention, treatment, and daily self-management. Chronic diseases, including cardiovascular disease, diabetes, chronic respiratory disease, chronic kidney disease, and other long-term conditions, remain major contributors to morbidity and mortality worldwide []. These conditions are influenced by genetic, physiological, behavioral, environmental, and social determinants, making social disconnection a plausible social factor associated with chronic disease risk, progression, and prognosis []. In this review, social disconnection is used as an umbrella term that includes both loneliness and social isolation. Loneliness refers to the subjective feeling that social or emotional connection is inadequate or unsatisfying, whereas social isolation refers to a more objective lack of social contact, participation, or network engagement []. This distinction is important because individuals may be socially isolated without feeling lonely or may feel lonely despite regular social contact []. Previous evidence has shown that stronger social relationships are associated with lower mortality risk, while loneliness, social isolation, and living alone are associated with higher premature mortality [,]. Cardiovascular disease is one of the most studied outcomes in this field, with longitudinal evidence showing that loneliness and social isolation are associated with increased risk of coronary heart disease and stroke []. Several mechanisms may help explain these associations. Behavioral pathways may include reduced physical activity, unhealthy lifestyle patterns, and weaker healthcare engagement. Psychological pathways may include stress, depressive symptoms, and reduced motivation for self-care. Biological pathways may include neuroendocrine dysregulation, inflammation, impaired immune regulation, vascular dysfunction, and metabolic dysregulation [-]. These pathways suggest that loneliness and social isolation may be associated with chronic disease-related outcomes through overlapping behavioral, psychological, and biological mechanisms.