The Tromsø Study series (I-VI) are prospective studies in the municipality of Tromsø, Northern Norway. The design includes repeated population health surveys to which total birth cohorts and random samples are invited. This paper is based on data from the Tromsø V study conducted in 2002.
A total of 10353 men and women were invited to participate in this study. This included individuals participating in the extended fourth survey in 1994-1995 (Tromsø IV) [28
]. In addition, all inhabitants who turned 30, 40, 45, 60 or 75 during 2001 were invited to participate. As 2313 did not attend, the study included 8040 subjects, 4565 women and 3475 men, aged between 29 and 87 (response rate 77.6%).
The Tromsø studies have been linked electronically to the Cancer Registry of Norway (CRN) enabling the identification of cancer patients by two methods; through self-reporting of cancer in the survey and through registration in the CRN. Registration of cancer has been mandatory by law since 1952, and the registry is therefore considered virtually complete.
A total of 1280 participants had not answered the question regarding visits to a CAM provider and were therefore excluded from the current analysis. Further, 169 persons were excluded due to the following two reasons: They had experienced both cancer and CHD, or they had reported having cancer without this being registered in the CRN (Figure ). The analysis of visits to a CAM provider in cancer and CHD patients thus included 6591 respondents.
Flow chart that shows the selection of the studied population.
The letter of invitation contained a questionnaire developed specifically for the Tromsø study. Individuals who attended the survey by undergoing a health screening and answering the first questionnaire received subsequently a second questionnaire that they were asked to complete and return by mail.
The two questionnaires included questions on general state of health, diseases suffered by the respondent or their family, muscle pain and physical discomfort, food habits, alcohol consumption, smoking habits, physical activity in leisure time, level of education, use of medicine and use of health services including a CAM provider [29
The question regarding visits to a CAM provider was not directly related to any specific disease condition. The questions concerning CAM and CHD were included in the first questionnaire completed before the health screening, while the question concerning cancer was placed in the second questionnaire returned by mail after the health screening.
A CAM user in this study is defined as a respondent who checked one or more visits on the question: How many visits have you made during the past year to an alternative medical provider? A "no CAM user" is a respondent who checked for no visits. This question was one item in a list including 12 other non-CAM health care providers (for example general practitioner (GP), psychologist, psychiatrist, emergency room physician, home nurse, physiotherapist, chiropractor, dentist etc.).
In Norway, an alternative medical provider is commonly understood by the public as a practitioner providing CAM both as alternative and complementary treatment. A CAM provider offers therapies that are not commonly offered within the public health care service and are paid out-of-pocket by the patients themselves.
CAM use was compared between three groups:
1. The cancer group (n = 331)
2. The CHD group (n = 579)
3. The no cancer/CHD group (n = 5681)
The cancer group consisted of informants who had checked Yes for: Have you ever had, or do you have cancer? and were registered with a cancer diagnosis in the CRN. Informants were also included in this group if they had left the question unanswered (due to deliberate choice or failing to return the second questionnaire) but were registered with a cancer diagnosis in the CRN. Informants in this group were also required to have checked No or have a missing value for both: Do you have, or have you had a heart attack AND Do you have, or have you had angina pectoris (heart cramp)? The members of this group are referred to as "cancer patients" even though the time of their clinical cancer disease may have been several years ago and/or they considered themselves to be healed from their cancer.
The CHD group consisted of respondents who had checked Yes for: Do you have, or have you had a heart attack OR Do you have, or have you had angina pectoris (heart cramp)? and who were not included in the cancer group.
The no cancer/CHD group consisted of respondents who had checked No or had a missing value for: Have you ever had, or do you have cancer?, and were not registered with cancer in the CRN nor were included in the CHD group.
The primary endpoint in this study was reported visits to a CAM provider over the previous 12 months in the cancer group compared to the CHD group and the no cancer/CHD group. The secondary endpoint was visits to a CAM provider over the previous 12 months within the cancer group.
With a statistical power of 80% and using an alpha of 0.05 we were able to report as statistically significant differences in reported use of approximately 6.5 percentage points between the two smallest groups.
The endpoints were analyzed using chi-square tests and logistic regression in SPSS Windows (version 17.0, SPSS Inc., Chicago, IL). When the compared groups differed significantly from each other in terms of baseline characteristics with possible influence on CAM use, the comparison between groups are also reported with adjusted p-values.
The data inspectorate has been notified about the study and the regional ethics committee has recommended it.