Impact of social isolation on mortality and morbidity in 20 high-income, middle-income and low-income countries in five continents.

Objective: To examine the association between social isolation and mortality and incident diseases in middle-aged adults in urban and rural communities from high-income, middle-income and low-income countries.

Design: Population-based prospective observational study.

Setting: Urban and rural communities in 20 high income, middle income and low income.