What have we learned?

Below are given some examples of results derived from the Tromsø study. 

The good cholesterol that protects the heart

In 1975, Miller suggested that HDL-cholesterol (High Density Lipoprotein) reduces atheroclerosis (delays hardening of the arteries). The large number of men examined in the first Tromsø Study in 1974 and availability of frozen blood samples from that study enabled the hypothesis to be tested as early as 1976. The study showed, for the first time, that HDL-cholesterol had a significant protective effect.   

Miller NE, Førde OH, Thelle DS, Mjøs OD. The Tromsø Heart Study. High-density lipoprotein and coronary heart disease: a prospective case-control study. Lancet 1977;i:965-968.

Is coffee dangerous?

In Tromsø Study II a connection was observed between coffee consumption and cholesterol. After the completion of the study, 33 men with a high serum total cholesterol participated in a 10-week study. They were divided at random into three groups. One group did not consume any coffee for the 10-week duration of the study, the second group continued to consume coffee as they did prior to the study, while the third group did not consume coffee for the first five weeks then consumed either percolated or unfiltered coffee. The study showed that unfiltered coffee led to an increase in cholesterol, something that was confirmed in Tromsø Study III. A Dutch research team later discovered that the fatty substances cafestol and kahweol caused an increase in the cholesterol level. These fatty substances are removed by the filtering process in percolated coffee and are, therefore, found only in unfiltered coffee.

Thelle DS, Arnesen E, Førde OH. The Tromsø Heart Study. Does coffee raise serum cholesterol? Br Med J 1983;308:1454-1457.

Førde OH, Knutsen SF, Arnesen E, Thelle DS. The Tromsø Heart Study: coffee consumption and serum lipid concentrations in men with hypercholesterolaemia: a randomised intervention study. Br Med J 1985;290:893-895.

Bønaa KH, Arnesen E, Thelle DS, Førde OH. Coffee and cholesterol: is it all in the brewing? The Tromsø Study. Br Med J 1988;297:1103-1104.

Does physical activity help to prevent cancer?

A study encompassing both risk factors and preventive factors for cancer requires a long observation period and a relatively large number of participants. Data from the Tromsø Study (Tromsø II) together with data from other Norwegian community studies, show that physical activity protects against various forms of cancer. These include colorectal cancer in men and women, lung cancer in men and breast cancer in women. The work was the basis for the formulation in 1999 of new protective advice against cancer entitled "Make time to be more physically active" (The Cancer Society of Norway).

Thune I, Lund E. Physical activity and risk of colorectal cancer in men and women. Br J Cancer 1996;73:1134-1140.

Thune I, Lund E. The influence of physical activity on lung-cancer risk. A prospective study of 81,516 men and women. Int J Cancer 1997;70:57-62.

Is homocysteine dangerous for your heart?

In a follow-up study of participants in Tromsø Study III it was discovered that people who develop myocardial infarctions had higher levels of homocysteine than healthy people. The level of homocysteine in the blood can be favourably improved by taking dietary supplements containing folate and vitamin B12. These finds have provided support for a national multi-centre study (NorVit), which studied whether such dietary supplements can reduce the chance of known heart patients suffering a new myocardial infarction. The results from this study indicate that there were no beneficial effects of these supplements on cardiovascular morbidity in spite of reduced homocysteine levels.

Arnesen E, Refsum H, Bønaa KH, Ueland PM, Førde OH, Nordrehaug JE. Serum total homocysteine and coronary heart disease. Int J Epidemiol 1995;24:704-709.

What causes abdominal aortic aneurysm? 

When the abdominal aortic aneurysm bursts, it is often too late to save the patient's life. Such aneurysms result from a weakening of the vessel wall, probably due to arteriosclerosis. The Tromsø Study (mainly Tromsø IV) has shown us that this is a relatively frequent condition. Among participants 55 years of age or elder, such aneurysms were discovered in 10 percent of the men and two percent of the women. Regardless of gender, increasing age, smoking, low levels of HDL-cholesterol (the good cholesterol) and blood pressure are important risk factors. Our findings from the Tromsø Study indicates that the growth of an aneurysms is faster in women than in men. 

Singh K, Bønaa KH, Jacobsen BK, Bjørk L, Solberg S. Prevalence of and risk factors for abdominal aortic aneurysms in a population-based study: the Tromsø Study. Am J Epidemiol 2001;154:236-44.

Solberg S.Singh K, Wilsgaard T, Jacobsen BK. Increased growth rate of abdominal aortic aneurysms in women. The Tromsø study. Eur J Vasc Endovasc Surg 2005; 29: 145-9.

Weight development in Tromsø - We are getting bigger...

A lot of fuss has been made about the increasing weight of the world's population, and the World Health Organisation predicts that the weight increase will increase the frequency of cardiovascular diseases and particularly diabetes mellitus. This development is also reflected in the Tromsø Study. We are finding a steady increase in weight with age among both men and women. However, women with the same age also recorded a notable increase in weight between 1986 and 1994. A much higher proportion of young people are overweight in 1994 (and 2001) than in the 1970's, so something is happening with our youth.

Jacobsen BK, Njølstad I, Thune I, Wilsgaard T, Løchen ML, Schirmer H. Increase in weight in all birth cohorts in a general population. The Tromsø Study 1974-1994. Arch Intern Med. 2001;161:466-472.

Does it help to change your lifestyle to prevent heart and cardiovascular disease?

Data from the Tromsø Study (Tromsø III and IV) show that changes in body weight are related to changes in blood pressure. Weight increase for men results in a noticeable increase in blood pressure, and the increase is unrelated to the initial weight. Thin women can increase their weight without consequences for their blood pressure. However, fatter women who further increase their weight will also suffer from increased blood pressure. People who lose weight will also reduce their blood pressure.

Wilsgaard T, Schirmer H, Arnesen E. Impact of body weight on blood pressure with a focus on gender differences. The Tromsø Study 1986 - 1995. Arch Intern Med 2000;160:2847-2853.

How reliable is a bone densitometry?

Norway has the world's highest rate of hip and forearm fractures. Low bone density is strongly connected with the chance of spinal compression and fractures of the upper arm, forearm and neck of the femur. Correct interpretation of bone densitometry is, therefore, important for every patient. Forearm measurements of bone density from the Tromsø Study (the Osteoporosis-study) showed incorrectly raised bone density in 70 percent of the pictures, and correcting of the mistake significantly affected the diagnosis. Reproduction is good, but proved to be lower among elder women, the group that most frequently requires bone densitometry.

Berntsen GKR, Tollan A, Magnus JH, Søgaard A.J, Fønnebø V. The Tromsø Study: Artifacts in bone densitometry - prevalence and effects. Osteoporosis Int. 1999: 10:5:425-32.

Berntsen GKR, Fønnebø V, Tollan A, Søgaard AJ, Joakimsen RM, Magnus JH. The Tromsø Study: Determinants of precision in bone densitometry. J Clin Epidemiol 2000, 53:1104-1112.

Bone fracture in Tromsø

The Tromsø Study has followed up all participants with regards to fractures from 1988 to 2006. The fractures register has been created in co-operation with the radiographic register at the University Hospital of Northern Norway. The fractures register is reliable. We found 97 percent of all wrist fractures and 93 percent of all hip fractures also appeared in the radiographic register. The Tromsø Study's data has shown that physical activity is also important for the skeleton. Active people have a reduced risk of fractures in the weight-bearing part of the skeleton, but not in the non weight-bearing part. Also other conditions like microalbuminuria and diabetes mellitus have proved to predict the fracture rate. 

Joakimsen RM, Fønnebø V, Magnus JH, Tollan A, Søgaard AJ, Størmer J. The Tromsø Study: Physical activity and the incidence of fractures in a population. J. Bone Miner Res. 1998;13: 1149-57.

Joakimsen RM, Fønnebø V, Magnus JH, Tollan A, Søgaard AJ, Størmer J. Registration of fractures - How good are self-reports, a computerized radiographic register and a discharge register vs. review of radiographic reports. Osteoporosis int. 2001; 12:1001-5

Ahmed L, Joakimsen RM, Berntsen G, Fønnebø VM, Schirmer H. Diabetes mellitus and the risk on non-vertebral fractures: the Tromsø study. Osteoporosis Int 2006; 17:495-500.

Jørgensen L, Jenssen T, Ahmed L, Bjørnerem Å, Joakimsen R, Jacobsen BK. Albuminuria and risk of nonvertebral fractures. Arch Intern Med 2007; 167:1379-85

How does bone density develop with age?

We have long known that the bone mineral density of women changes when they enter the menopause, but it has been unclear how the bone mass changes with age in a normal population. Data from the Tromsø Study showed that bone mineral density was relatively stable among both men and women up to 50 years of age. The bone mineral density then starts to lower among both men and women, but changes with age are greater among women. These results has resulted in the follow-up of participants in the Tromsø Study so we are able to find out how each participant's bone mineral density has changed between 1994 and 2001.

Berntsen GKR, Fønnebø V, Tollan A, Søgaard AJ, Magnus JH. The Tromsø Study: A populationbased study of forearm bone mineral density by age in 7062 men and women. Am J Epidemiol 2001; 153: 465-73.

Emaus N, Berntsen GKR, Joakimsen RM, Fønnebø V. Longitudinal changes in forearm bone mineral density in women and men aged 25-44 years: The Tromsø Study: A population-based study. Am J Epidemiol 2005; 162: 633-43.

Emaus N, Berntsen GKR, Joakimsen RM, Fønnebø V. Longitudinal changes in forearm bone mineral density in women and men aged 45-84 Years: The Tromsø Study, a population-based study. Am J Epidemiol 2006; 163: 441-9

Are there relationships between bone density and atherosclerosis?

Both osteoporsis and atherosclerosis are frequent conditions in elderly people, but women tend to have more osteoporosis and men higher rate of ischemic heart disease. In the Tromsø Study, we have investigated the correlations between the two conditions. Many of our results support that there is a significant rlationship between the two conditions that cannot be explained by age alone. In particular, atherosclerosis in the carotid artery is associated with bone mineral density and fracture rate, and microalbuminuria (which is associated with atherosclerosis) increases fracture rate in women.    

Jørgensen L, Joakimsen O, Heuch I, Berntsen GR, Jacobsen BK. Low bone mineral density is related to echogenic carotid artery plaques. A population-based study. Am J Epidemiol 2004; 160: 549-56.

Jørgensen L, Joakimsen O, Mathiesen EB, Ahmed L, Berntsen GKR, Fønnebø V, Joakimsen R, Njølstad I, Schirmer H, Jacobsen BK. Carotid plaque echogenicity and risk of nonvertebral fractures in women: A longitudinal population-based study. Calcified Tissue Int 2006; 79: 207-13.

Jørgensen L, Jenssen T, Ahmed L, Bjørnerem Å, Joakimsen R, Jacobsen BK. Albuminuria and risk of nonvertebral fractures. Arch Intern Med 2007; 167:1379-85

Hormones in the Tromsø population

Measurement of blood levels of different hormones were included in the surveys conducted in 1994/95 and 2001.

Bjørnerem Å, Straume B, Øian P, Berntsen G. Seasonal variation of estradiol, follicle stimulating hormone, and dehydroepiandrosterone sulfate in women and men. J Clin Endocrinol Metab 2006;91:3798-3802.

Svartberg J, von Muhlen D, Mathiesen E, Joakimsen O, Bønaa KH, Stensland-Bugge E. Low testosterone levels are associated with carotid atherosclerosis in men. J Intern Med 2006;259:576-82

Jorde R, Sundsfjord J. Serum TSH levels in smokers and non-smokers. The 5th Tromsø study. Exp Clin Endocrinol Diabetes 2006;114: 343-7.

Chronic obstructive pulmonary disease (COPD).

COPD is chronic lung disease which is associated with much suffering and high mortality. The 5th survey of the Tromsø Study included a test for lung function (spirometry). The lung function was studied in elderly in particular.  

Melbye H, Medbø A, Crockett A. The FEV1/FEV6 ratio is a good substitute for the FEV1/FVC ratio in the elderly. Prim Care Respir J 2006;15: 294-8.