Are loneliness and social isolation risk factors for ill health?

Introduction: Social relationships are increasingly being acknowledged as determinants of wellbeing and health in later life. We know that people who feel lonely – i.e. who are unhappy about their relationships – or who are socially isolated – i.e. have few ties or contacts with others – are more likely to experience early death. Whether they are at greater risk of morbidity is unclear. Aim: This thesis examines whether loneliness and social isolation are risk factors for developing ill health, with a primary focus on incident cardiovascular disease (CVD). The aim is to gauge the potential health gain from tackling loneliness and social isolation. Methods: Four pieces of empirical research make up the main body of my thesis. First, I designed a novel framework for distinguishing between measures of loneliness and social isolation. I then systematically reviewed the evidence from longitudinal observational studies on loneliness, social isolation and incident CVD. I studied changes in loneliness and social isolation over time in the English Longitudinal Study of Ageing (ELSA), a cohort of adults aged over 50 years old. Finally, I investigated associations between loneliness and social isolation over time, and incident CVD. Results: My systematic review found that loneliness and social isolation were associated with a 29% increase in risk of incident coronary heart disease (relative risk: 1.29, 95% CI 1.04 to 1.59) and a 32% increase in risk of stroke (relative risk: 1.32, 95% CI 1.04 to 1.68). Among ELSA participants, patterns of social relationships varied substantially over time, both within and between individuals. In survival analyses of ELSA data, loneliness but not social isolation was identified as a risk factor for incident CVD. Conclusions: Weaker social relationships are risk factors for developing CVD. Intervening to tackle loneliness and social isolation has the potential to improve health outcomes in later life.