This study was preceded by the The Oslo Health Study (HUBRO) in 2000-2001 and both studies followed the same protocol. It encompassed five of the largest immigrant groups in Oslo, namely persons born in Turkey, Iran, Pakistan, Sri Lanka and Vietnam. The participants filled in questionnaires and attended a clinical screening including measurements of height, weight, waist and hip circumference, blood pressure, heart rate, and a non-fasting blood test to analyse serum total cholesterol, HDL-cholesterol, triglycerides, glucose and HbA1c. Those with elevated random blood sugar were invited to take a fasting blood sample.
Main cohort: All Oslo citizens born in Turkey, Iran, Sri Lanka and Vietnam between 1942 and 1982 were invited, except for 7 birth cohorts (1940/41, 1954/55, 1960, 1969/70) who had been previously invited to HUBRO. For those born in Pakistan, the largest immigrant group, a 30% random sample was invited. One reminder was sent.
Young cohort: Persons born between 1972 and 1982 were invited following the same criteria as for the main cohort. However, for this group no reminder was sent.
A total of 3726 persons attended the study, 3019 persons in the main cohort and 707 persons in the young cohort. The attendance rate was comparable to that among non-western immigrants in the Oslo Health Study, where a large comprehensive analysis of the non-attendance has been conducted.
Invitation and questionnaires
The letter of invitation including an information brochure, the main questionnaire and consent form were sent by post. the main questionnaire and consent form were sent by post. The main questionnaire was identical to that used in HUBRO. The contents of the postal package were all translated into the 5 appropriate languages of the 5 immigrant groups in addition to the official Norwegian version. The supplementary questionnaire was handed out at the screening station, and was only translated to English.