Oral Health in Norway. The HUNT Study.


Oral Health in Norway. The HUNT Study.

Protocol 11.9.2011

Oral Health in Norway.

The HUNT Study.

Prof. Dorthe Holst

Odontologisk fakultet


Kari Strand


Nord-Trøndelag Fylkeskommune

Tannhelsetjenestens kompetansesenter Midt-Norge

Steinar Krokstad

HUNT forskningssenter

Institutt for samfunnsmedisin




The oral health studies in Trøndelag

Oral health may obviously be associated with many other health factors. But data on

oral health was for the first time collected in a general health survey in Norway in the HUNT

Study 2006-08 ( HUNT3). Thus, this new joint initiative between the HUNT Research Centre,

Faculty of Medicine NTNU and the Odontological Faculty Oslo University, opens up new

opportunities. And due to that HUNT is population based and data is collected in 24

municipalities, oral health in the general population aged 20-100 years old may be mapped.

However, both questionnaire and clinical data have been collected in Norway earlier, as

part of the first WHO International Collaborative Study (WHO ICS-I) in 1973 (1). In 1983,

1994 and in 2006 oral health has been examined again in random samples of the same birthcohorts

that were selected in 1973 (11) (Figure 1). An analysis within 1983 showed that

social inequality in oral health was found in 13-14 year olds, and the inequality increased in

the older adult age-groups assessed cross-sectionally (2). Schuller (1999) analysed whether

the oral health improvement from 1983 to 1994 among 23-24 olds in Trøndelag was equally

distributed among high and low social status groups (2). Schuller found that improved oral

health was accompanied by more inequality among young adults. In the present study it has

been possible to follow samples of two birth-cohorts (1959-1960 and 1929-1938) and samples

of 35-44 year olds in time series for more than 30 years (Table 1).

Figure 1. The basic design of the Oral Health Trøndelag studies

Age 1973 1983 1994 2006 (HUNT3)

13-14 X X

23-24 X X

33-34 X

35-44 X X X X (+46,47)

45-54 X X

55-64 X

68-77 X

At the start of the 21 st century, all European countries are faced with substantial

inequalities in health and disease within their populations (3). Health and disease inequalities

are mainly caused by a higher exposure to material, psychosocial and behavioural risk factors

in lower socio-economic groups. A number of studies suggest that the relationship between

socio-economic status and disease forms of a social gradient from the top to the bottom of the

social hierarchy (4-6). According to the gradient theory inequality of health is not only

confined to the poorest members of society but runs right across the social spectrum (Marmot

5,6). The challenge in the gradient research is to provide further evidence of the obvious

interplay between psycho-social, material, cultural and behavioural explanations. In Norway

researchers and national health authorities have adopted the gradient explanation, and a

national strategy to reduce inequalities in disease and health outcomes has been launched (7-


The social distribution of oral health among adults in Norway has been studied

recently (3). The relationship between income quintiles and edentulousness and having a

functional dentition was analysed from 1975 to 2002 by four datasets from Statistics Norway.

The main finding was that in absolute terms oral health was more equally distributed in 2002

than in 1975, and the lowest income groups benefited the most. Among the elderly, however,

having a functional dentition was less equally distributed in 2002 than in 1985. The relative

differences increased for the oldest for each new birth cohort; thus the chances of being

edentulous was 7.5 times higher in the lowest income group versus the highest group in 2002,

whereas the chances were only 2 times higher in 1972.

Based on epidemiological clinical data on oral health of young and older adults gathered

by epidemiological field studies in 1973, 1983, 1994 and 2006, time series analyses of social

status and oral health have shown a socially unequal distribution of oral health most

pronounced during the period from 1973 to 1983. From 1983 to 2006 the inequalities in oral

health caused by social position did not seem to increase further (11). The direction of the

results seems to be dependent upon the choice of outcome measure. Ongoing research uses

outcome measures of both pathogenic and salutogenic nature as effect measures of social

inequality. It has been pointed out that social inequality research of oral health must make a

careful distinction between inequality of disease occurrence and inequality of treatment.


The purpose of this project is to map the distribution of oral health in the population, explore

the impact of health related behavior on oral health, to examine how self-perceived oral health

relate to clinical dimensions of oral health, and explore how periodontal status in 2006 will be

related to previous diabetic status.

Material and methods

The HUNT Study

The Nord-Trøndelag health study (HUNT) is one of the largest health studies ever performed.

It is a unique database of personal and family medical histories. So far three health surveys of

the general adult population in the Nord-Trøndelag County, Norway have been completed.

The HUNT1 cohort aged 20+ (established 1984-86)

In 1984-86 every citizen of Nord-Trøndelag County being 20 years or older (or turning 20

years during the year of survey) were invited. Totally 77 214 persons participated (89.3% of

those invited). Questionnaires and clinical measurements were applied. The design applied in

HUNT1 was largely repeted in HUNT2 and HUNT3.

The HUNT2 cohort aged 20 + (established 1995-97)

HUNT2 constituted both a new cross sectional survey and a follow-up of HUNT1. The

scientific programme was extended to include several large public health issues in accordance

with current national health priorities. These were cardiovascular diseases, diabetes,

obstructive lung disease, osteoporosis, headache, mental health, chronic musculoskeletal pain

and urinary incontinence. In addition to questionnaires, interviews and clinical examinations,

the participants contributed with blood samples for instant analysis and storage. A total of

65 237 participated in HUNT2 (69.5% of those invited).

The HUNT3 cohort aged 20+ (established 2006-08)

The scientific programme of HUNT3 included several main public health issues as in

HUNT2, but included also topics on oral health. In the HUNT3 survey participants were

asked about visiting a dentist last 12 mnds, how their dental health was perceived and the

impact of dental health on the general health. In addition, there was done a general dental

health examination on 600 participants in age-group

The oral health Trøndelag studies

The material comprised data from independently selected random samples of a population

living in four municipalities in the county of Nord-Trøndelag in 1973, 1983, 1994 and 2006.

The age-groups were selected according to the rules of cohort analysis in such a way that the

difference in years between the studies matches the age of the birth-cohort in the same year

(Figure 1). In addition, in each survey year samples of 35-44 year olds were draw. Table 1

shows that the 1959-1960 birth-cohort was 13-14 years old in 1973, 23-24 years old in 1983,

34-35 years old in 1994 and 46-47 in 2006 in 2006. The birth-cohort 1929-1938 was 35-44

years old in 1973, 45-54 years old in 1983, 46-54 in 1994 and 68-77 in 2006. Thus random

samples of two birth-cohorts were followed longitudinally. Thirty-five to forty-four year olds

were examined in 1973, 1983, 1994 and 2006, following a pattern of repeated cross-sectional

studies The age specific sample size for each of the participating counties were 500 in 1973

and in 1983 and was reduced to 350 in 1994 and 250 in 2006. The sample in the two-year

age-group 46-47 was 100 persons. Table 1 shows the size of the samples and the participation


The methods of data collection comprised standardized clinical measurements and selfadministered

questionnaires (10-11). In 1973, 1983, 1994, and in 2006 two, ten, eleven and

two calibrated dental teams, respectively, collected the data. Two senior researchers (DH and

AAS) followed and guided the procedures since 1973 in order to secure standardized

conditions and comparability among the surveys. Calibration exercises were conducted each

study year, and the results found satisfactory (15). The examinations took place at the public

dental clinics of the Nord-Trøndelag County. Permission was granted by public authorities

and by the participants’ informed consent. All necessary permissions were given through out

the study period and by the participants’ informed consent. In 2006 the study was approved

by the Regional ethical committee Middle of Norway and approved by the Norwegian

Council of Research.

The clinical variables were number of present teeth (PT), sound teeth and surfaces (ST,

SS) and functional teeth and surfaces (SFT, SFS) and DMFT and DMFS index. DMFT and

DMFS are the sums of DT/S, MT/S and FT/S, where DT/S is defined as the number of

teeth/surfaces with primary and secondary caries, including root and coronal caries. Only

caries with a distinguishable brake in the surface was recorded. Missing Teeth is the number

of missing teeth irrespective of cause. FT/S is the number of teeth/surfaces filled, both root

and coronal restorations, including all types of filling materials and crowns. The clinical

examination comprised recording of the condition of the visible part of the tooth.The analyses

were based on 28 teeth, because third molars were excluded for reasons of comparability

among the study years. DMFT was measured only at the tooth level in 1973. Unfortunately

the data files from 1973 were no longer available at the WHO Headquarters in Geneva.

Published results (10, 11) were used for descriptive statistics. In order to obtain an estimate of

DMF surfaces in 1973 the DMF parameters in 1973 was multiplied by the ratio between teeth

and surfaces for the parameters in 1983 in comparable age-groups.

Periodontal recordings

Planned papers

1. Oral Health in a Norwegian County, The HUNT Study

In the first part of the planned study self-perceived oral health will be analyzed, and the

variation between age groups, gender, municipalities and socio-economic groups analyzed:

The epidemiology of oral health. Nord-Trøndelag has been considered a national average of

Norway with respect to many indicators of health and living conditions. Cause specific

mortality and trends in disability pension follows national trends closely. The data of selfperceived

oral health in Nord-Trøndelag will be related to a smaller national dataset (Holst

2008) that includes the same variable in order to rank self-perceived oral health in Nord-

Trøndelag compared to the national variation between counties. Cross tabulations and

regression based analyses will be utilized.

2. Self perceived oral health and health related behavior

In the second study we want to explore the impact of health related behavior, diet and BMI on

oral health. The ongoing marked changes in behavior, diet and BMI might have consequences

for oral health. Differences in oral health according to these factors might reveal unknown

important oral health promotion potentials. Data will also be used to analyze the role of health

related behavior regarding socioeconomic inequalities (Sabbah et al 2009). Data from

HUNT3 includes variables on diet components, physical exercise, smoking, alcohol

consumption and measurements of height and weight. Regression analyses will be utilized,

with control for confounding between relevant factors.

3. Health perception, an indicator of oral health or oral disease?

The third paper will examine at the validity of the general dental health perception question in

the HUNT Study, by comparing answers to the self-perceived oral health question with

dimensions of clinical registrations undertaken in the oral health subsample. Recent studies

indicate that the decayed missing and filled teeth (DMFT) index showed more variation than

the dental fluorosis according to the Thylystrup Fejerskov Index (TFI) in populations with

low level of disease and treatment experience. In populations with high levels of disease and

treatment experience, FST was more suitable to describe variation than DMFT. In their

analysis of the relationship between socio-economic status and oral status over time, socioeconomic

status was not clearly related to the oral status in young adults in 1994 when

expressed by the DMFT. Yet, socio-economic status was clearly related to oral status in the

same young adults when expressed by the FST. In older adults the conclusions were the other

way round. Holst and Schuller (1) concluded that the indices should not be used

interchangeable. They concluded that the choice of index must depend on whether a

salutogenic or a pathogenic index approch is relevant.

In then planned study the epidemiologically recorded data of oral health status comprise at

least five dimensions: 1) Sound conditions, good oral health, 2) untreated disease

unsatisfactory oral health, 3) past disease and treatment 4) total disease and treatment

experience and 5) lost oral health, no teeth left. It will be of great relevans to investiate how of

these dimensions are reflected in the self-perceived assessment of oral health. A better

understanding of these relationships may create a new platform for oral health promotion.

4. Inflammation and periodontal health

The association between diabetes/chronic inflammation and periodontal health is of interest.

A large part of the Norwegian adult population shows signs of past and present periodontal

disease in the gums. A lot of attention has been devoted to risk factors of development of

periodontal disease (11). Diabetes is one such often mentioned risk factor. The HUNT studies

offer a phenomenal opportunity to study the relationship between inflammation in the

periodontal tissues of the mouth and predisposing medical conditions. The Oral health

Trøndelag studies in 1994 and 2006 comprised an epidemiological assessment of the

periodontal status of the participants by clinical and x-ray examinations (Figure 1). By linking

anonymously the Oral Health Trøndelag data of periodontal status to previously registered

diabetic status in HUNT I and II the relationship can be longitudinal studied. The data are

ready for empirical analyses, but requires a careful linkage of files.

Organization and research community

The project is organized as a PhD project affiliated at the Dept. of Public Health and General

Practice at the Medical Faculty, NTNU. The student is affiliated at the HUNT Research

Centre. The major supervisor is Ass. prof. Steinar Krokstad at the HUNT Research Centre,

and the first co-supervisor is Prof. Dorthe Holst at the Odontological Faculty, University of

Oslo. A supervisor group is established in co-operation with Tannhelsetjenestens

kompetansesenter for Midt-Norge IKS. Krokstad and Holst developed a research co-operation

in 2004 during planning of HUNT3. Krokstad has as PI of HUNT3 thorough knowledge of

methods utilized in HUNT3, expertise in social epidemiology, and a wide research network

nationally and internationally. Holst has a long research career in oral epidemiology. Kari

Strand and the spesialists in Tannhelsetjenestens kompetansesenter for Midt-Norge IKS

ensure relevant clinical competence in the project.

Publication of results

The papers will be published in international referee based journals.


1. Holst D, Schuller AA, Dahl KE. Bedre tannhelse for alle? Tannhelseutvikling i den

voksne befolkning i Norge fra 1973 til 2006. Nor Tannlegeforen Tid 2007; 117: 804

– 11.

2. Schuller AA. Better oral health, more equality? Empirical analysis among

young adults. Community Dental Health 1999.

3. Machenbach JP. Health inequalities: Europe in profile. Expert report commissioned

by, and published under the auspices of, the UK Presidency of the EU 2005.

4. Marmot M, Wilkinson RG. Social determinants of health. Oxford: Oxford

University Press; 1999.

5. Marmot M. Status Syndrome. London: Bloomsbury; 2005.

6. Krokstad S. Socioeconomic inequalities in health and disability. Social

epidemiology in the Nord-Trøndelag Health Study (HUNT), Norway. Verdal:

Norwegian University of Science and Technology, 2004. Thesis.

7. Næss Ø. Life course approaches to socio-economic inequalities in cause specific

mortality. A registry based epidemiological study of the population in Oslo. Oslo:

University of Oslo; 2005.

8. http://www.shdir.no/gradienten/publikasjoner/

9. http://statbank.ssb.no/statistikkbanken/

10. Holst D. Den orale helses sosiale determinanter. Er oral helse fortsatt skjevt fordelt?

In press. Temanummer i 4 nordiske tannlegetidsskrifter 2008: 118

11. Sabbah W, Tsakosa G, Sheihama A, Watta RG. The role of health-related behaviors

in the socioeconomic disparities in oral health. Soc Sci Med 2009;68:298-303.

12. Holst D. Social equality in oral health over 30 years in Norway. Community Dent

Oral Epidemiol 2008.

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