People moving to the United States, Canada, and Australia tend to be healthier and live longer than non-immigrants in their host countries, new research has found.

The study found that once adjustments have been made for income and education the future health of migrants was much better than those who stay in the country where they are born.

There has been a great deal of speculation as to why this healthy migrant effect exists and one hypothesis suggests that it is due to self-selection so particularly healthy individuals are more likely to choose to move to a different country, while those who are in poor health may be less willing or able to do so.


The study released by the University of Toronto and the UK's Medical Research Council (MRC) Unit for Lifelong Health and Ageing at University College London compared the childhood circumstances of 984 future emigrants with 4,378 non-emigrants.

It used data from the MRC National Survey of Health and Development (NSHD), a large nationally representative longitudinal study of British children born in early March 1946 who have been surveyed more than 20 times over their lifetime.

"The childhood health of future migrants was much better than those who did not move to other countries," said Professor Esme Fuller-Thomson, Sandra of the University of Toronto's Factor-Inwentash Faculty of Social Work and the Institute for Life Course and Aging.

Researchers found that future emigrants in the NSHD were less likely to have been born with a low birth weight or to have a serious illness before the age of five and they were taller at age six, which reflects childhood nutrition, than the children who did not emigrate.

It appears that factors contributing to positive health selection in migrant populations begin as far back as childhood and the study also found that future emigrants had superior cognitive ability at age eight in comparison to their counterparts who stayed in Britain.

"Higher cognitive ability has been shown in other studies to be associated with better health in adulthood and a lower likelihood of developing dementia in old age," said Sarah Brennenstuhl of the Lawrence Bloomberg Faculty of Nursing at the University of Toronto.

Future emigrants came from families with a higher socioeconomic position than those who remained permanently in the UK. They were more likely to have fathers who were professionals, their mothers had a higher level of education, their housing quality at age four was better, their parents showed more interest in the children's school progress, and their parents were more likely to own their own home when the child was six years old.

Professor Diana Kuh, a co-author and Director of LHA and NSHD, pointed out that childhood socio economic position has been shown in the NSHD and many other studies to be highly associated with adult health.

"This study supports the healthy migrant hypothesis for migration between high-resource countries," she added.