Social
Social Isolation and Mortality in the UK Biobank: The Modifying Role of Transportation Mode Hiroshi Mamiya* Emily Hum Hum Hum Hum McGill University
Background: Social isolation is an established risk factor for chronic disease and mortality and has reached epidemic levels in many high-income countries. Daily transportation modes (e.g., active and public transport, car use) may mitigate the harmful impacts of social isolation by facilitating social interaction. This study aimed to assess the role of transportation mode as an effect modifier in the association between social isolation and mortality among adults using the UK Biobank.
Methods: We analyzed cohort data from 450,032 UK Biobank participants aged 40-69 years, followed from 2006 to 2022. Baseline social isolation was derived from a three-item index and dichotomized. We used Cox models to estimate the associations between social isolation and mortality outcomes (all-cause and cause-specific), adjusting for socioeconomic factors, health behaviours, and comorbidities. Effect modification by participants’ primary mode of transportation was assessed using interaction terms.
Results: Social isolation was associated with increased hazard of all-cause (Hazard ratio [HR] = 1.33, 95% CI: 1.30-1.36), cardiovascular (HR = 1.45, CI: 1.37-1.53), and cancer mortality (HR = 1.22, CI: 1.17-1.27). Associations with all-cause and cardiovascular mortality were stronger among participants who only used public transport compared with those who only used a car (interaction HR = 1.08, CI: 1.00-1.18; interaction HR = 1.22, CI: 1.03-1.45, respectively). In contrast, using a car alongside active or public transport, compared to using a car alone, attenuated the association between social isolation and all-cause mortality (interaction HR = 0.92, CI: 0.87-0.99).
Conclusions: This is the first study to investigate the modifying role of transportation mode to reduce the harms of social isolation. Our findings motivate further exploration of public health strategies that support social connectivity by reducing motor vehicle dependency and improving public transport infrastructure.