It's a bigger killer than cancer and heart disease combined—and it seems to be an unrecognised cause of heart disease, and could also be a trigger for cancer, say researchers from the American Cancer Society.
It can also cause hypertension (high blood pressure), inflammation and people who live alone also adopt poor lifestyle habits, such as smoking and physical inactivity.
Social isolation—defined as little or no contact with close friends or family, and having little or no social activity, such as with a local church or community group—affects the racial groups differently.
Among white people, it's more likely to cause cancer, while black people run a higher risk of heart disease.
Isolation doubles the risk of premature death from any cause among black people, and the risk among white men was 60 per cent and 84 per cent for white women, the researchers discovered.