Steptoe, A. et al. Proceedings of the National Academy of Science of the United States of America, March 25th 2013; doi: 10.1073/pnas.1219686110
Both social isolation and loneliness are associated with increased
mortality, but it is uncertain whether their effects are independent
or whether loneliness represents the emotional pathway through
which social isolation impairs health. We therefore assessed the
extent to which the association between social isolation and
mortality is mediated by loneliness. We assessed social isolation
in terms of contact with family and friends and participation in
civic organizations in 6,500 men and women aged 52 and older
who took part in the English Longitudinal Study of Ageing in
2004–2005. A standard questionnaire measure of loneliness was
administered also. We monitored all-cause mortality up to March
2012 (mean follow-up 7.25 y) and analyzed results using Cox proportional
hazards regression. We found that mortality was higher
among more socially isolated and more lonely participants. However,
after adjusting statistically for demographic factors and
baseline health, social isolation remained significantly associated
with mortality (hazard ratio 1.26, 95% confidence interval, 1.08–
1.48 for the top quintile of isolation), but loneliness did not (hazard
ratio 0.92, 95% confidence interval, 0.78–1.09). The association
of social isolation with mortality was unchanged when loneliness
was included in the model. Both social isolation and loneliness
were associated with increased mortality. However, the effect of
loneliness was not independent of demographic characteristics or
health problems and did not contribute to the risk associated with
social isolation. Although both isolation and loneliness impair
quality of life and well-being, efforts to reduce isolation are likely
to be more relevant to mortality.