Tokelau Island Studies
Years: 1968 - 1982
Principal Investigator: Prior, Ian
Growing out of an interest in Maori health in New Zealand and the Pacific Islands, and a government plan for major migration from the Tokelau atolls, Ian Prior took the opportunity to study the presumed effects of acculturation in development of risk characteristics and “Western” diseases of the Pacific Island residents compared to the islanders who migrated to New Zealand. A major emphasis was on the important interim characteristics of blood pressure, body mass, and serum cholesterol levels, as well as psychosocial measures. It was a truly multi-disciplinary study in which epidemiologists and anthropologists joined effectively. The assumptions of little change of living in the Islands and major changes by migrants in New Zealand were not entirely correct.
From 1968-1972 the first cross-sectional surveys were made of 99 % of all Tokelauans in Tokelau and in New Zealand. Round 2 in 1975-77 saw 92 % and Round 3 in 1980-82, 82%. Logistic problems were major (e.g.special skills were needed to unload and navigate through the atoll’s reefs).
The Tokelau Island Migrant Study confirmed the greater prevalence of chronic diseases among the migrant population. Mean blood pressure levels were higher among migrants than non-migrants. Moreover, migrant men were twice as likely as non-migrants to be hypertensive by WHO definitions and migrant women were three times more likely to be so. This could be explained by the tendency for migrants at all ages to be heavier than non-migrants. Migrants had more diabetes and smoked more, drank more alcohol, and exercised less. Migrants tended to have higher levels of “incipient coronary disease,” with mean cholesterol levels near those of the host New Zealand society, while non-migrant levels remain relatively low. Migrants showed electrocardiographic changes and reported chest pain more frequently than did non-migrants. Because this small population involved young ages overall the study could not demonstrate significant differences in mortality from coronary disease or from cancer or stroke.
The Tokelau Island Migrant Study contributed to understanding “of the social epidemiology and health affairs of the Pacific and the relevance of an understanding of social and biological adaptations to the conditions of modern societies. The study demonstrated that knowledge of the history and the changing situation of small communities can enhance understanding of their epidemiological situation, with individual adjustment at a physiological level to pervasive changes.” According to his biographers: “The Tokelau Island Migrant Study stands as a worthy monument to a professional life well spent” (Health of Pacific Societies; 23-5).
[Another direct contribution to CVD epidemiology was Ian Prior’s influence on Michael Marmot, who says: “Ian was more or less directly responsible for my entering epidemiology and public health.” Peter Harvey came back from a meeting that Ian had organized in Wellington to tell Marmot that he had found the right branch of medicine for him. It was called ‘epidemiology.’ “In the type of work that Ian was doing, doctors, social scientists and statisticians all worked together to understand health problems in society. That was sufficient stimulus to set me on a path,” said Marmot (Ibid., 49). (HB)
Howden-Chapman, Phillipa and Alistair Woodward, eds. 2001. The health of Pacific societies: Ian Prior’s life and work, a celebration at Wellington School of Medicine 25 February 2000.Wellington: Steele Roberts, LTD.
Prior, I. A. M., Stanhope, J. M., Evans, J. Grimley, Salmond, Clare E. “The Tokelau Island Migrant Study.” International Journal of Epidemiology 3 (April 16, 1974): 225-232.