The Fourth Tromsø Study

The fourth survey of the Tromsø Study (Tromsø4), which was carried out in 1994-95, is the largest of the Tromsø Studies. This study included a total of 27,158 people (12,865 men and 14,293 women in the 25-97 age group). Everyone in Tromsø aged 25 or elder (born before 1970) was invited to participate in this study.

Participation in Tromsø4, 1994-95:

Age	Men invited	Women invited	Male participants	Women participants	% men	% Women
25-29	2919	3138	1515	1794	51,9	57,2
30-34	2651	2681	1556	1798	58,7	67,1
35-39	2474	2359	1649	1811	66,7	76,8
40-44	2324	2138	1681	1718	72,3	80,4
45-49	2094	1981	1604	1665	76,6	84,0
50-54	1595	1449	1306	1281	81,9	88,4
55-59	1077	1025	918	941	85,2	91,8
60-64	906	855	796	774	87,9	90,5
65-69	810	970	691	860	85,3	88,7
70-74	733	824	592	701	80,8	85,1
75-79	483	724	343	539	71,0	74,4
80-84	249	521	154	293	61,8	56,2
85-89	110	291	43	106	39,1	36,4
90+	55	122	17	12	30,9	9,8
TOTAL	18480	19078	12865	14293	69,6	74,9

If you do not take into account people who had moved or died before the study, the participation rate was 77 percent.

Examination methods and measurements

A brief questionnaire accompanied the invitation. The questionnaire included questions on general health condition, diagnosed heart and cardiovascular diseases or diabetes and history of heart and family cardiovascular diseases, muscle pains and physical discomfort, passive smoking and smoking habits, physical leisure activity, coffee, alcohol and fat consumption, education level and current work situation. Measurements of height, weight and blood pressure were taken. A blood sample was also taken to measure serum total cholesterol, HDL cholesterol, triglycerides, gamma-glutamyltransferase (GT), haemoglobin and blood cell count ("plot"). People who attended the study received another questionnaire that they were asked to complete and send back. Separate questionnaires were prepared for people aged under 70 and for those aged 70 or elder.

Everyone in the 55-74 age group, along with 5-10 percent in the 25-54 and 75-85 age groups were given the opportunity to undergo an extensive special study. A total of 7965 people accepted this offer. This included also measurement of bone density as a part of the TROST study

What did we discover?

Tromsø4 provided the opportunity for a host of longitudinal studies, in which findings from previous studies could be compared with findings that were currently being collected. Examples included showing how age influences the development of obesity (Jacobsen et al, 2001) over a 20-year period, and if people who in 1979 had high cholesterol still suffered from this 15 years later (Wilsgaard et al, 2001).