The data are from two cross sectional total population studies conducted in one county in Central Norway, the second (HUNT 2, conducted 1995-97) and third (HUNT 3, conducted 2006-08) Nord-Trøndelag Health Study (http://www.medisin.ntnu.no/hunt/). The county and its population is considered fairly representative of Norway concerning geographical, demographic and occupational structure [15], but have no larger cities and the population has an income and education level slightly below the national average. For both surveys, all residents aged 20 years or over were invited to participate by post and received the first questionnaire (Q1) attached to the invitation. This was to be returned at a screening station where a brief medical examination was conducted and a second questionnaire (Q2) to be returned by post was handed out. The HUNT studies have been approved by the Regional Committee for Medical and Health Research Ethics, Central Norway and the Norwegian Data Inspectorate.
In HUNT 2, 92,936 inhabitants were invited and a total of 65,495 (70.5%) persons participated. Of these, 41,734 (63.7%) participants answered a question on CAM use which was in Q2 and were included in the present study. In HUNT 3, 94,194 were invited, 50,827 participated (54.0%) and 50 713 (99.8%) answered a question on CAM use in Q1.
The total population in Norway is nearly 5 million and it is among the countries that have highest total expenditure on health per capita. The Norwegian health care system includes provision of health care services for all citizens based on need regardless of personal income. CAM practitioners operate outside the government-funded health care system and everyone can call themselves a CAM practitioner and treat patients.
CAM visitor
A CAM visitor was defined as a participant who had consulted one or more CAM practitioners by answering yes to the question: "During the last 12 months, have you visited homeopath, acupuncturist, reflexologist, layer on of hands or another alternative treatment practitioner? (Yes/No)". There was a separate question about visits to chiropractors immediately before the CAM question, but as they are authorised health personnel in Norway, visit to a chiropractor was not included in CAM visits.
Demographics
The participants' gender, age, marital status and education level were taken from public registers and a question on cohabitation. Level of education was reclassified as compulsory school, middle level education (including vocational education below university level) and university degree. Currently working were those answering yes to being in paid employment.
Lifestyle
Participants were classified as smokers or non-smokers based on whether or not they were daily smokers of cigarettes, cigar and/or pipe. Activity level was dichotomised to doing more or less than 3 hours of hard physical activity weekly during spare time last year.
Health status
Several measures of self reported health status were used (question with answering categories):
1. Global health: How is your health at the moment? (poor, fair, good, very good).
2. Anxiety and depression: The Hospital Anxiety and Depression Scale (HADS-T) was used (14 items, score ranging from 0 to 42, the cut off point for the detection of any mental disorder is found to be 17 [16].
3. Recent complaint (yes to one or more of these questions):
- Have you suffered from Nausea/Heartburn/Diarrhoea/Constipation/Breathlessness in the last 12 months? (Never = No/Sometimes = Yes/Often = Yes).
- Have you experienced any stiffness or pain in your muscles or joints that has lasted for more than three consecutive months during the last year? (Yes/No).
- Have you suffered from headache in the last 12 months (Yes/No).
4. Chronic complaint: Do you suffer from any long standing (for at least one year) limiting somatic or psychiatric illness, disease or disability? (Yes/No).
5. Psychiatric complaint: Do you have or have you had psychiatric complaints that you have sought help for? (Yes/No).
6.- 8. Asthma, Diabetes, or Cancer: Do you have or have you had asthma/diabetes/cancer? (Yes/No).
9. Hay fever: Do you have hay fever? (Yes/no).
10. Cardiovascular disease (yes to one or more of these questions): Do you have or have you had Acute myocardial infarction/Angina pectoris/Stroke? (Yes/No).
11. Musculoskeletal disease (yes to one or more of these questions): Have you been diagnosed with Osteoporosis/Fibromyalgia/Arthritis/Artroses/Bechterew/Other longstanding musculoskeletal disease? (Yes/No).
Health care utilisation
Health care utilisation was answering yes to questions about visits the last 12 months:
- Physician: During the past 12 months, have you visited a General practitioner/Specialist outside hospital/Psychiatric specialist in hospital/Somatic specialist in hospital? (Yes/No).
- Chiropractor: During the last 12 months, have you visited a chiropractor? (Yes/No).
Statistical Analyses
Pearson chi-square tests were used to compare users with non-users for each year separately. Spearman's rho was used to check for co-linearity and the correlation coefficient was highest both years for currently working/age (1997; 0.410, 2008; 0.561) and chronic complaint/global health (1997; 0.409, 2008; 0.507). The multivariable analysis (adjusted odds ratio - adjOR) was undertaken by logistic regression using models where all variables were included to identify associations between CAM use and the other variables also for both years. Due to the large size of the dataset and the number of comparisons, statistical significance was accepted at the 1% level (p < 0.01) for these tests. To compare the findings of the bivariable and multivariable analysis for each year with each other, a test of difference for comparison of two independent studies was used [17]. For the multivariable analysis, the Ratio Odds Ratio (ROR) was calculated, which is the ration from a comparison of two odds ratios. A ROR higher than 1 indicates higher odds of visiting a CAM practitioner in 2008 than in 1997. Statistical significance accepted at the 5% level (p < 0.05) for these tests. The adjOR and ROR are given with 95% confidence intervals (95%CI). All data were analysed using SPSS statistics version 17.0.0 released Aug 23. 2008 (SPSS Inc, Chicago, USA).