Studies have shown that immigrants to the U.S., Canada, and Australia tend to be healthier and live longer than non-immigrants in their host countries, once adjustments have been made for income and education. There has been a great deal of speculation as to why this 'healthy migrant effect' exists. One hypothesis proposes that it is due to self-selection such that 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.
A study released today by the University of Toronto and U.K.'s Medical Research Council (MRC) Unit for Lifelong Health and Ageing at UCL (LHA) found support for this hypothesis using 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 twenty times over their lifetime. The study, published online this week in the Canadian Journal of Public Health, compared the childhood circumstances of 984 future emigrants with 4378 non-emigrants.
"The childhood health of future migrants was much better than those who did not move to other countries," says Professor Esme Fuller-Thomson, Sandra Rotman Endowed Chair at 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 5 and they were taller at age 6 (which reflects childhood nutrition) than were the children who did not emigrate. It appears that factors contributing to positive health selection in migrant populations begin as far back as childhood.
"We also found that future emigrants had superior cognitive ability at age 8 in comparison to their counterparts who stayed in Britain," said co-author Sarah Brennenstuhl of the Lawrence Bloomberg Faculty of Nursing at the University of Toronto. "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."
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 4 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 6 years old" said Professor Diana Kuh, a co-author and Director of LHA and NSHD. "Childhood socioeconomic 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," said Professor Kuh.
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A copy of the paper is available to journalists upon request. Please contact University of Toronto's media relations officer, Dominic Ali at d.ali@utoronto.ca.
For more information contact:
Prof. Esme Fuller-Thomson
Professor & Sandra Rotman Endowed Chair
Factor-Inwentash Faculty of Social Work &
Institute for Life Course & Aging
University of Toronto
Cell: 416-209-3231
esme.fuller.thomson@utoronto.ca
Dominic Ali
Media Relations Officer
University of Toronto
Tel: 416-978-6974
d.ali@utoronto.ca