Combined effects of loneliness and diabetes mellitus on disability incidence among older Japanese adults

Background: Developed countries worldwide face the challenge of aging populations in which loneliness is problematic, leading to mental and physical health issues. Diabetes mellitus (DM) can cause decreased physical activity, reduced functioning, and depressive symptoms. However, how interactions between loneliness and DM influence health outcomes remains unclear. We aimed to determine the effects of loneliness and DM-related complications on the incidence of disability among older individuals. Methods: We analyzed data from the Japanese National Center for Geriatrics and Gerontology Study of Geriatric Syndromes for community-dwelling adults aged >65 years without initial long-term care needs. Loneliness was assessed using the University of California Los Angeles Loneliness Scale, and DM status was determined based on medical history obtained through face-to-face interviews. Disability incidence was identified by monthly tracking of certifications under the Japanese long-term care insurance system. The combined effect of DM and loneliness on care needs was examined using Cox proportional hazard regression models. Results: Among 5,160 participants, 298 (5.8 %) developed incident disabilities within 24 months. Cox models adjusted for potential confounders revealed a significantly increased disability risk among persons with DM and loneliness. Having DM without loneliness and vice versa were not significant risk factors for disability incidence compared with having neither. Conclusions: The combination of loneliness with DM was a risk factor for disability development among community-dwelling older adults. Loneliness and DM might be interrelated and associated with disability development, suggesting that support along with assessments of mental health and illness might help to avoid disability in this population.