Socio-economic status and incident diabetes mellitus among employees in Denmark: a prospective analysis with 10-year follow-up.

AIMS: To contribute to the research on diabetes and social inequality by presenting national data on incident diabetes mellitus, stratified according to socio-economic status. METHODS: National registers were combined, linking socio-economic status with incident diabetes over a 10-year period (2001-2010). The study population comprised employees in Denmark aged 20-59 years at baseline. Poisson regression analysis was used to estimate socio-economic rate ratios. Excess fraction analysis was used to determine the proportion of cases that would not have occurred if morbidity rates in each socio-economic group had been as low as those in the reference group. Monte Carlo simulation was used to calculate 95% CIs for excess fraction estimates RESULTS: A total of 1 005 572 men and 951 039 women were included in the analysis. The follow-up yielded 43 439 cases in 9 533 199 person-years at risk among men and 29 266 cases in 9 163 405 person-years at risk among women. Using 'professionals' as a reference group, higher levels of relative risk were observed among every other socio-occupational group. The excess fraction was, 0.342 (95% CI 0.329-0.354) among men and 0.359 (95% CI 0.349-0.369) among women. CONCLUSIONS: Excess fraction analysis suggests that more than a third of cases of diabetes could be prevented if all employees were exposed to the same working conditions as the reference population. Acknowledging potential confounders, the observed levels of incident diabetes among the workforce highlight the potential gains to be had by better use of the workplace as an arena for prevention. Greater integration of occupational health and general healthcare is required to achieve this.

Psychosocial job strain and risk of congenital malformations in offspring--a Danish National cohort study.

OBJECTIVE: To investigate if maternal exposure to psychosocial job strain at work (high demands and low control) measured by questionnaire early in pregnancy (median week 15) is associated with malformations in the offspring. DESIGN: Population-based cohort study. SETTING: The Danish National Birth Cohort. POPULATION: A cohort of 60,386 singleton children with full information on mother's occupational status, exposure to psychosocial job strain and all covariates during pregnancy. METHODS: Logistic regression analysis was used to calculate the odds of congenital malformations as a function of job strain with adjustment for maternal age, body mass index, parity, smoking, alcohol use, manual versus nonmanual work, maternal serious disease and gestational age at interview. MAIN OUTCOME MEASURES: Circulatory malformation, musculoskeletal malformation or any malformation. RESULTS: Logistic regression analyses, both crude and adjusted, indicated no associations between working under high strain and giving birth to a child with circulatory malformation (adjusted odds ratio [OR] 1.04, 95% confidence interval [95% CI] 0.75-1.44), musculoskeletal malformation (aOR 0.88, 95% CI 0.71-1.10) or any malformation (aOR 0.99, 95% CI 0.85-1.15). Supplementary analyses including restriction to first-borns and a stratified analysis with respect to manual and nonmanual work did not change the results. CONCLUSIONS: Association between exposure to high job strain during pregnancy and elevated risk of circulatory, muscle and any malformations is not supported by this study.

Meningitis, sepsis and endocarditis among workers occupationally exposed to pigs.

BACKGROUND: Workers exposed to pigs can develop meningitis, sepsis or endocarditis due to infection with Streptococcus suis transmitted from pigs to man. AIMS: To estimate the risk of these diseases. METHODS: We used the Occupational Hospitalization Register (OHR) which holds information about occupation and hospital treatments for all adults in Denmark. A dynamic population of male workers exposed to pigs was identified every year from 1995 to 2006 by occupational and industrial groups. First hospital treatment or death in the following year due to meningitis, sepsis or endocarditis was identified by ICD-10 codes from the OHR. By comparison with all other economically active men in Denmark, the standardized incidence ratio (SIR) was calculated for these diseases. RESULTS: Among those exposed, we observed 32 cases of meningitis, sepsis and endocarditis during 140,118 person-years. In the reference group, we observed 2680 cases during 15,209,394 person-years. The SIR of the exposed group was 1.35 (95% CI: 0.95-1.92). Among the 32 cases, 7 cases of meningitis and sepsis were specified as caused by infection with streptococci. The SIR for these seven cases was 2.4 (95% CI: 1.1-5.0). CONCLUSIONS: Our study did not find that workers exposed to pigs had an overall increased risk of developing meningitis, sepsis or endocarditis.

The risk of infertility among hairdressers. Five-year follow-up of female hairdressers in a Danish national registry.

BACKGROUND: One in seven married couples is involuntarily infertile. Several chemical exposures in the work environment have been hypothesized to affect female reproduction, and some are present in products used in hairdressing and related trades. Recent Swedish findings indicate that employment in hairdressing poses a risk for female reproductive function. This study examined the possible association between work as a hairdresser and subsequent hospital contact due to female infertility. METHODS: A cohort of all women in Denmark aged 20-44 years on 1 January 1998 (baseline) and registered as economically active hairdressers, according to national registers, was formed to calculate age-standardized risk ratios (RRs) for hospital contacts due to female infertility during a 5-year follow-up period. Hairdressers were compared to a standard population, that is, all economically active women in Denmark aged 20-44 years at baseline, and to women working as shop assistants. RESULTS: Sixty-eight cases of hospital contact due to female infertility were observed among the female hairdressers. On the basis of the standard population, the expected number was 73.27, which gives an observed RR of 0.928 (95% CI: 0.72-1.18). Hairdressers and shop assistants exhibited similar rates of hospital contact due to female infertility (1.01; 95% CI: 0.77-1.29). CONCLUSION: The findings are not corroborating the hypothesis that hairdressers are at increased risk of infertility, but small risks in the entire group or high risks in small subgroups may not be detected by the study.

A 12 year prospective study of circulatory disease among Danish shift workers.

BACKGROUND: Previous studies of the risk of heart disease after shift work reached different estimates and review authors disagree about the validity of some of the studies. A cross sectional study showed that shift workers had a higher prevalence of nearly every unfavourable work environment factor investigated. Conflicts at work and low decision latitude were more frequent among shift workers, and all-day walking or standing work and part-time jobs were more often found among female shift workers. OBJECTIVES: To estimate the risk of circulatory disease in a prospective follow up of a representative sample of gainfully employed Danes, considering known or suspected confounding factors. METHODS: A cohort of 5517 people who were gainfully employed in 1990 were followed up for all hospital treatments due to circulatory diseases (390-458, ICD-8; I00-I99, ICD-10) from 1991 to 2002 inclusive. A log linear Poisson regression model was applied to control confounding factors and calculate the relative risk for 927 men and women working nights, evenings, or other non-day shifts compared to 4579 day workers. RESULTS: Non-day workers compared to day workers had a relative risk (RR) for all circulatory diseases of 1.31 (95% CI 1.06-1.63). Without control for BMI and smoking, the RR estimate was 1.33 (95% CI 1.07-1.65). For a subgroup of workers with at least three years' seniority, the RR was 1.40 (95% CI 1.09-1.81). The population based aetiological fraction of shift work was estimated to 5%. CONCLUSION: This study adds to a growing body of evidence suggesting that shift work carries an excess risk of circulatory diseases.

Stroke among male professional drivers in Denmark, 1994-2003.

OBJECTIVES: (1) To estimate the relative risk of stroke among various groups of professional drivers; (2) to determine if any excess risk should be attributed to infarction or haemorrhage; (3) to estimate the relative risk ratio for stroke among professional drivers living in Greater Copenhagen compared to those living outside the metropolis. METHODS: A cohort of 6285 bus drivers, 4204 car, taxi, and van drivers, and 25,879 heavy truck and lorry drivers were followed up for hospital admission due to stroke and sub-diagnoses in the period 1994-2003. Using hospital admission for all economically active men as the standard, the standardised hospitalisation ratios (SHR) were calculated, taking age and county into consideration. RESULTS: There was a high SHR for stroke among all groups of professional drivers (SHR = 132; 95% CI 121-141). Among car, taxi, and van drivers the SHR was 157 (95% CI 132-189), among bus drivers it was 139 (95% CI 119-163), and among heavy truck and lorry drivers it was 124 (95% CI 113-136). The excess risk for all groups of professional drivers was highest for cerebrovascular infarction (SHR = 139; 95% CI 124-155) and lowest for non-traumatic intracranial haemorrhage (SHR = 113; 95% CI 96-133). The excess risks for all groups were significantly higher for cerebrovascular infarction than for non-traumatic intracranial haemorrhage (relative risk ratio (RRR) 1.23; 95% CI 1.01-1.51). The RRR of stroke among drivers in the metropolitan area compared to rural areas was 1.13 (95% CI 0.94-1.36). The RRR for stroke among car, taxi, and van drivers compared to drivers of heavy trucks and of lorries was 1.28 (95% CI 1.03-1.57). CONCLUSION: All groups of professional drivers are at increased risk of stroke. The excess risk is more due to cerebral infarctions than to non-traumatic intracranial haemorrhage. The risk of stroke is higher among drivers carrying passengers than among drivers carrying goods.

Prolonged standing at work and hospitalisation due to varicose veins: a 12 year prospective study of the Danish population.

BACKGROUND: Recent studies suggest that prolonged standing at work is associated with the development of diseases of varicose veins (VV). AIMS: To assess the risk of hospitalisation due to VV in the lower extremities prospectively in workers standing or walking at least 75% of their time at work. METHODS: A representative random sample of 9653 working age adults was drawn from the Central Population Register of Denmark in 1991. Of these, 8664 accepted to be interviewed by telephone (response rate 90%). Respondents (2939 men and 2708 women) were 20-59 years old and employed in 1990. Risk ratios for VV were estimated by log-linear Poisson regression models separately for men and women with adjustment for smoking status, body mass index (BMI), heavy lifting, and, for females only, number of children at baseline. RESULTS: During 12 years of follow up, 40 hospitalisations due to VV were observed among the men and 71 among the women. For employees with jobs that require prolonged standing or walking compared to all other employees, the relative risk was 1.75 (95% CI 0.92 to 3.34) for men and 1.82 (95% CI 1.12 to 2.95) for women. The pooled estimate of the relative risk was 1.78 (95% CI 1.19 to 2.68). The aetiological fraction of prolonged standing or walking at work was estimated as 22.5% for men and 22.6% for women. CONCLUSIONS: This prospective study confirms that prolonged standing at work constitutes an excess risk of hospital treatment due to varicose veins and accounts for more than one fifth of all cases of working age.

Disability retirement among former employees at the construction of the Great Belt Link.

OBJECTIVE: To investigate incidences of disability retirement among men who had been employed at the construction of a large traffic link in Denmark, which involved long working hours and long distances between home and work place. METHODS: Men aged 20-54 years at baseline who had been engaged in the construction of the Great Belt Link (n = 5882) were followed-up for disability retirements from 1996 to 2000. Age-standardized incidence ratios (SIR) were calculated and compared with those of other construction workers (n = 117,157). All economically active men in Denmark were used as the standard population. RESULTS: The SIRs for the two groups were 2.29 (95% confidence intervals (CI): 1.95-2.67) and 0.98 (95% CI: 0.93-1.03), respectively. CONCLUSIONS: The Great Belt construction workers had an elevated risk for disability retirement compared with other construction workers and with economically active men in general.

Hospitalisations among seafarers on merchant ships.

AIMS: To study morbidity among active seafarers in the merchant navy in order to clarify possible work related morbidity and the morbidity related to work and lifestyle where possible preventive measures may be initiated. METHODS: From a register in the Danish Maritime Authority a cohort of Danish merchant seafarers who had been actively employed at sea in 1995 was identified. For each seafarer, information on all employment periods at sea, charge aboard, and ship was available. The cohort was linked with the National In-patient Register in Denmark. Standardised hospitalisation ratios (SHRs) were calculated for all major diagnostic groups using all gainfully employed as reference. RESULTS: Seafarers were shown to be inhomogeneous, with significant differences in SHRs for the same disease groups between different groups of seafarers depending on charge and ship type. SHRs for lifestyle related diseases were high, although rates for acute conditions, such as acute myocardial infarction, were low, probably due to referral bias, as acute conditions are likely to cause hospitalisation abroad, and thus are not included in the study. SHRs for injury and poisoning were high, especially for ratings and officers aboard small ships. CONCLUSION: Despite pre-employment selection, a large proportion of the seafarers constitute a group of workers with evidence of poor health probably caused by lifestyle. The subgroups with high risk of hospitalisation due to lifestyle related diseases also had an increased risk of hospitalisation due to injury and poisoning.

Building camps and work related injuries.

AIMS: To focus on one possible predictor of reported work related injuries--the role of living in building-site camps versus daily commuting from home to construction sites. METHODS: A cohort of construction workers was collected, based on personnel files from contractors involved in the building of the Great Belt Bridge. The files included information on employment periods and whether or not the employees lived in building-site camps. The cohort was followed up for injuries reported to the National Work Environment Authority. RESULTS: Construction workers living in camps reported 217 accidents, of which 24 were serious or fatal. Among those not living in camps we found 262 accidents, of which 29 were serious or fatal. The relative risk for all accidents for camp versus non-camp was 0.84 (95% CI 0.69 to 1.00). The respective figure for serious or fatal accidents was RR = 0.85 (95% CI 0.47 to 1.52). CONCLUSION: Results suggest that high accident rates at large construction sites may be reduced, if commuting is replaced by living on-site.

Socioeconomic status, occupation, and risk of hospitalisation due to coxarthrosis in Denmark 1981-99.

OBJECTIVES: To predict the relative risk and time trend in hospitalisation due to coxarthrosis (CA) among groups of different socioeconomic status and occupations in order to test existing aetiological hypotheses. METHODS: Four consecutive cohorts of all gainfully employed Danish men were followed up for CA. Standardised hospitalisation ratios (SHR) and time trends were calculated. RESULTS: Self employed men had an SHR due to CA of 140 (95% confidence interval (CI) 130 to 151) in 1994-99. It changed -1.2% (95% CI -2 to -0.4) annually from 1981 to 1999. Self employed farmers had an SHR of 286 (95% CI 262 to 313) during 1994-99, increasing 0.14% a year (95% CI -0.9 to 1.1) from 1981 to 1999. Unskilled men had an SHR of 121 (95% CI 113 to 130) in 1994-99. The SHR increased 1.6% annually (95% CI 0.7 to 2.4) from 1981 to 1999. Employed agricultural workers had an SHR of 189 (95% CI 158 to 227) from 1994 to 1999. The SHR increased 3.7% annually (95% CI 1.2 to 6.2) from 1981 to 1999. CONCLUSIONS: The relative risk of hospitalisation due to CA was consistently high among farmers in four successive analyses spanning an 18 year period. The relative risks remained stable over time despite the fact that the number of farmers decreased. The risk increased among employed workers in agriculture and horticulture over that period, and an increased risk was also found among tractor drivers and a few other occupations.

Life expectancies for individuals with psychiatric diagnoses.

The aim of the study was to estimate life expectancies in different diagnostic groups for individuals treated as inpatients at Swedish psychiatric clinics. All individuals, older than 18 y and alive on the first of January 1983, who had been registered in the National Hospital Discharge Registry by a psychiatric clinic in 1978-82, were monitored for mortality during 1983 by using the National Cause of Death Registry. The study group consisted of 91 385 men and 77 217 women. The patients were divided into nine diagnostic groups according to the principal diagnosis registered at the latest discharge. Actuarial mathematics was used to construct life expectancy tables, which present the number of years expected to live, by gender and diagnostic group. Expectancies of life were significantly shortened for both genders and in all nine diagnostic groups (with one exception). Mental disorders in general are life shortening. This fact should be recognised in community health when setting health priorities. It should also be addressed in curricula as well as in treatment and preventive programmes.

Life expectancies among survivors of acute cerebrovascular disease.

BACKGROUND AND PURPOSE: Stroke survivors represent a large group of persons for whom age-differentiated life expectancy tables do not exist. Such tables are vital for many purposes. The aim of the present study was to estimate age- and sex-specific life expectancies among individuals who have survived the acute phase (1 month) of a cerebrovascular disease (CVD). METHODS: All patients who were registered with the Swedish National Hospital Discharge Registry with an admission for CVD (ICD codes 430 to 438) between January 1, 1989, and November 30, 1993, and were alive at the end of 1993 (N=103 591) were followed for mortality rates in 1994. The same was done for 1983. Actuarial analyses were used to convert death rates into life expectancies. RESULTS: Life expectancy among CVD survivors increased with time (1983 versus 1994): 22.9% for men (95% CI 18.3% to 27.6%) and 12.9% for women (95% CI 9.1% to 16.6%). The life expectancy ratio in 1983 between CVD survivors and the general population was 0.571 (95% CI 0.533 to 0.590) for men and 0.578 (95% CI 0.562 to 0.592) for women. In 1994, the corresponding ratios were 0.641 (95% CI 0.629 to 0.654) and 0.611 (95% CI 0.601 to 0.622). The life expectancy ratios between female and male survivors were 1.28 (95% CI 1.23 to 1.34) in 1983 and 1.18 (95% CI 1.15 to 1.21) in 1994. The prognosis for survivors who experienced occlusion and stenosis of the precerebral arteries was better than that for survivors of an intracerebral hemorrhage (P=4.4E-4) or occlusion of cerebral arteries (P=3.8E-8). CONCLUSIONS: Although the prognosis has improved for all ages, stroke survivors still constitute a large group of persons with a low life expectancy compared with the general population.

Hospital admissions among male drivers in Denmark.

OBJECTIVES: To facilitate decisions about interventions and to establish baseline values for future evaluation of preventive efforts, the aim of the present study was to elucidate the disease pattern among male professional drivers in Denmark. The study differentiated between drivers of goods vehicles and drivers of passenger transport. METHODS: Cohorts of all 20-59 year old Danish male professional drivers in the years 1981, 1986, 1991, and 1994 were formed, to calculate age standardised hospital admission ratios (SHRs) and time trends (1981-97) for many diagnostic aggregations. RESULTS: SHRs for diseases in practically all systems and organs of the body were higher among professional drivers than they were in the male working population at large. Also drivers of passenger transport, compared with drivers of goods vehicles, had significantly high SHRs due to infectious and parasitic diseases, diseases of the circulatory system, and diseases of the respiratory system, and significantly lower rates of injury. For both driver groups, the SHRs for acute myocardial infarction increased with time whereas the SHR for acute gastritis decreased, and for drivers of passenger transport an increasing SHR for chronic obstructive pulmonary disease, was found over time. CONCLUSION: Drivers of passenger transport and drivers of goods vehicles differ in their disease patterns. The results support the hypothesis that preventive efforts are needed in both groups, but underline that different strategies are required for different categories of drivers.

Standing at work and varicose veins.

OBJECTIVES: This study attempts to determine whether or not prolonged standing at work involves an excess risk for the occurrence of varicose veins. METHODS: A cohort of 1.6 million 20-to-59-year-old Danes gainfully employed in 1991 were followed for 3 years according to first hospitalization due to varicose veins of the lower extremities. The exposure data came from a representative sample of the baseline population. Altogether 5940 people were interviewed about occupational exposure and confounding factors. RESULTS: For men working mostly in a standing position, the risk ratio for varicose veins was 1.85 [95% confidence interval (95% CI) 1.33-2.36] in a comparison with all other men. The corresponding risk ratio for women was 2.63 (95% CI 2.25-3.02). The results were adjusted for age, social group, and smoking. CONCLUSIONS: Working in a standing position is associated with subsequent hospitalization due to varicose veins for both men and women.

Use of a national hospitalization register to identify industrial sectors carrying high risk of severe injuries: a three-year cohort study of more than 900,000 Danish men.

BACKGROUND: Data indicates that Denmark has relatively high risks of occupational injuries. We evaluated all injuries resulting in hospitalization by occupation. METHODS: All gainfully employed men younger than 60 in 1990 were divided into 47 industrial groups and followed using the National Inpatient Registry, for hospitalized injuries 1991-1993. Following ICD-8, injuries were grouped into six categories: head, upper extremities, back, trunk, lower extremities and ruptures, sprains and strains. Standardized industrial hospitalization ratios (SHRs) were calculated and Pearson's independence test was performed for each category. RESULTS: Industrial differences were ascertained for each injury category. The highest associated injury category was upper extremity injuries ranging from SHR = 43 (fire services and salvage corps) to SHR = 209 (slaughterhouse industry). Carpentry, joinery, bricklaying and construction work had significantly high SHRs for all injury categories, whereas administrative work was significantly low throughout. CONCLUSIONS: Occupational surveillance systems based on hospitalized injuries can be used to identify high-risk industries, and thereby suggest where to direct prevention efforts.

Mortality among persons with a history as psychiatric inpatients with functional psychosis.

BACKGROUND: An important aim in all psychiatric care should be a reduction of overall mortality. Information on mortality patterns in different types of psychiatric populations is vital for a successful design of treatment strategies and preventive programmes. The present study aims to describe mortality among persons with a history as psychiatric inpatients with functional psychosis. METHODS: All psychiatric inpatients, 17,878 men and 23,256 women, registered in the Swedish National Hospital Discharge Registry between 1978 and 1982 with a functional psychosis (ICD-8 = 295-299) as principal diagnosis were followed for mortality during the time period 1983-85. Life tables were constructed and death rates for various types of causes of death were calculated. RESULTS: Compared to the general population, the excess mortality in the study group caused a reduction in life expectancy of 22.1-27.9% (95% CI) among the men and 15.0-21.7% among the women. In the age group 2049 years, 62% of the excess mortality was caused by suicide. In the age group 50-89 years, only 8% of the excess was suicide, while 52% was caused by cardiovascular disorders. CONCLUSIONS: Reduction in mortality rates requires different strategies in different age groups. Even if the suicide rate were reduced to zero, it would only have a marginal influence on the highly elevated mortality among patients in upper middle age and among the elderly. Among the younger patients (<35 years), on the other hand, practically all excess mortality was caused by suicide and accidents.

Social and occupational differences in chronic obstructive lung disease in Denmark 1981-1993.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a common crippling disorder related to exposure to noxious dust and fumes. The purpose of this study was to estimate relative rates of COPD in socioeconomic groups and in 'classic' high-risk industries. METHODS: Cohorts of all gainfully employed 20-59 year old Danes in the years 1981, 1986, and 1991 were formed, to compare standardized hospitalization ratios (SHR) and time trends (1981-93). RESULTS: The risk ratio (RR) between unskilled workers and senior salaried staff was 2.31, (95% CI 2.13-2.51) for men and 1.62 (1.38-1.92) for women. Among classic high-risk occupations we found a decreasing SHR in farmers and an increasing SHR in the hotel and restaurant industry and for taxi and bus drivers. The study confirmed earlier reports on high risks in the metal, rubber, and bakery industries. CONCLUSIONS: Apart from the reduced SHR among farmers there were no signs of decreasing differences in COPD risk.

Ten-year follow-up study of personality traits in adults with intact and restored dentitions.

The personality traits of 69 of a sample of 70 adolescents aged 25-26 years were re-examined after 10 years by means of a personality inventory (KSP). A total of 11 subjects had intact dentitions (group I), while 18 subjects had had some fillings in their teeth since the first examination (group FI), and 40 subjects had restored dentitions from the starting-point (group F). The subjects with fillings 10 years ago had significantly higher scores in two of the anxiety variables--somatic anxiety and muscular tension--and in the hostility variable, suspicion, than did those without the fillings. Together with the finding of a significant correlation between high scores for the clinical dysfunction index (DiII and DiIII) and the muscular tension scale, the results of this study support the hypothesis of a possible correlation between dental filling therapy, craniomandibular disorders (CMD) and personality. Frequent tooth clenching (once to twice a week or more) was significantly more common among the subjects with fillings 10 years ago. The clenchers scored highest in the somatic anxiety, muscular tension and suspicion scales and constituted a well-defined subgroup within the subjects of this study. There was a highly significant increase of muscular tension among the clenchers during the 10-year examination period compared to the non-clenchers. However, the results of this study are not clear-cut. There was no statistically significant difference in personality between subjects with fillings after 10 years (group F + Fi) and the group of subjects with intact teeth (group I). Hypothetically, this may indicate that the differences found in this study could be due to how long the fillings had been in the mouth and at which age they were inserted. In order to test the hypothesis further and to establish the possible mechanisms behind this finding, more studies are necessary and especially more longitudinal comparative studies between subjects with intact and restored dentitions.

Ten-year follow-up study of signs and symptoms of craniomandibular disorders in adults with intact and restored dentitions.

Signs and symptoms of craniomandibular dysfunction (CMD) and oral parafunctions were re-examined in subjects, 25-26 years of age, 10 years after the first examination. Forty subjects had restored dentitions at both examinations (group F), 18 subjects with previously intact dentitions had had fillings in their teeth during the follow-up period (group FI), and 11 subjects had intact dentitions at both examinations (group I). Signs and symptoms of CMD were more common among the subjects in group F than in the original group of subjects with intact teeth (group 10). In accordance with the first study most of the symptoms were mild and of low frequency. However, frequent symptoms were only found among the subjects in group FI and group F and more severe frequent symptoms only in group F. There was an increase of the symptoms in group FI and group F. Frequent tooth clenching and frequent tongue pressing were more common in group F and there was a statistically significant increase in group FI concerning tooth clenching and tooth grinding and in group F concerning tooth grinding, tooth clenching and tongue pressing. Together with the correlations found between tooth clenching and signs and symptoms of CMD, the findings in this study and the personality study indicate a possible causal relationship between oral parafunctions, signs and symptoms of CMD, personality and fillings. A hypothesis for the possible mechanisms is presented. However, the findings are not conclusive and more studies are necessary, and for further interpretation of the results, studies from other research centres would be of interest.