Living alone or feeling lonely? Distinct associations with multimorbidity among adults from the EPIPorto cohort.

OBJECTIVES: Multimorbidity (MM) is a major public health challenge, particularly in ageing populations. Living alone and loneliness are distinct psychosocial conditions linked to adverse health outcomes. This study aimed to investigate the association of living alone and loneliness with MM among middle- and older-aged Portuguese adults. METHODS: Data were drawn from EPIPorto, a cohort study encompassing 2485 adults evaluated from 1999-2003 to 2022. Based on international consensus criteria, MM outcomes included: (1) a count of all chronic conditions; (2) a count of specific aggregated conditions (cardiovascular, metabolic-endocrine, mental-behavioural, and musculoskeletal); (3-6) counts specific by body system. Living alone was assessed through household size. Loneliness was measured using the Portuguese version of the UCLA Loneliness Scale, analysing the total score and its two dimensions (UCLA Social Isolation [UCLA-SI] and UCLA Affinities [UCLA-A]). Missing data were handled through multiple imputation by chained equations. Generalized linear models with a Poisson distribution were used to estimate adjusted relative risks (aRR) and 95% confidence intervals (95% CI). RESULTS: Larger households (living with two or more persons) were associated with an increased risk of metabolic-endocrine conditions (aRR = 1.50, 95% CI: 1.11-2.02). Loneliness increased the risk of MM for the specific aggregation of conditions (aRR = 1.13, 95% CI: 1.05-1.21), particularly mental-behavioural conditions (aRR = 1.25, 95% CI: 1.11-1.40). Higher UCLA-SI scores increased the risk for the specific aggregation of conditions (aRR = 1.20, 95% CI: 1.08-1.35), cardiovascular (aRR = 1.17, 95% CI: 1.05-1.32), metabolic-endocrine (aRR = 1.20, 95% CI: 1.05-1.37), and mental-behavioural conditions (aRR = 1.29, 95% CI: 1.07-1.56). CONCLUSION: Living alone and loneliness were differently associated with MM. Public health interventions should consider these distinctions to promote healthy ageing and reduce MM burden.