Dorthe Holst

Validity of a questionnaire survey: response patterns in different subgroups and the effect of social desirability

Questionnaire surveys are often used in epidemiology and survey research. However, investigations have shown that the method suffers from biases. If the intention is to examine differences between subgroups in a sample, studies have shown that people tend to give answers to questionnaires more according to a social norm than to the actual situation. This has been called social desirability. The aim of this study was to investigate response bias in subgroups of a sample in a large questionnaire survey (n = 9,200) and to study whether social desirability has an impact on survey results in dental research. The answers were divided into subgroups according to gender, age, and residence and were compared with corresponding data from dental insurance claims. The levels of agreement were found to vary considerably and the differences were highly statistically significant. The variation in agreement showed that bias on the group level increased when the distance from an anticipated social norm was larger. This implies that the divergence from a socially desirable mode of action influences the magnitude of the bias.

Validity of a questionnaire survey: the role of non-response and incorrect answers.

Errors in questionnaire surveys are usually of one of two sources: non-responses or incorrect answers. The aim was to investigate the validity of a questionnaire survey and to estimate the respective bias of these answers. Of 9,283 subjects selected to receive a questionnaire by post, 3,949 (43%) responded, and, of these, 3,400 correctly reported their Swedish social security number. Answers in the questionnaire survey were given as proportions of the claims registered at local insurance offices. In the group of respondents who had correctly reported their social security number, the answers were compared individually with the registrations in dental insurance claims. In Sweden, these claims are labeled with the patients social security number and it is thereby possible to make such comparisons. It was shown that errors were caused by non-response and also by respondents giving incorrect answers. Incorrect answers accounted for approximately one-third of the total bias. The remaining bias was caused by a non-response error. It is concluded that questionnaire studies have a bias caused by both non-response and incorrect answers and that together these can be substantial. Scientific reports that include questionnaire surveys must describe the procedure carefully. If possible, other sources of information should be considered.

Supplier inducement: Its effect on dental services in Norway

In many western countries, supply of dental services exceeds demand, mainly because of the marked reduction in the prevalence of dental diseases during the last 10-15 years. An important issue is whether dentists can counteract this fall in demand by stimulating increased demand and/or utilization for their services. Some evidence that this may be the case was found in the present study, in Norway. The results indicate that demand and utilization for dental services are influenced by supplier inducement.

Oral health equality during 30 years in Norway

OBJECTIVES To study the relationship between income and edentulousness and having a functional dentition from 1975 to 2002, and to examine whether or not the findings can be characterized as a social gradient. METHODS Four datasets were collected by personal interviews and precoded questionnaires by Statistics Norway in 1975, 1985, 1995 and 2002. The datasets were representative of the non-institutionalized adult population in Norway. Each year, the sampled persons were distributed into five income quintiles. Four effects were examined of the relationship between income quintiles and edentulousness and functional dentition (1) the absolute equality effect, (2) the period effect, (3) the relative equality effect, and (4) the gradient effect. RESULTS The main finding is that in absolute terms oral health is more equally distributed in 2002 than in 1975, and the lowest income groups benefited the most in oral health. Among the elderly, however, having a functional dentition was less equally distributed in 2002. 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 two times higher in 1972. Having lost all natural teeth was infrequent in 2002, and inequality wiped out in the population below > or = 60 years. A small social gradient was still in 2002. CONCLUSIONS The condition of edentulousness is a result of accumulated incidences of dental diseases and fragmented access to dental care. Economic barriers and unavailability of dental care postponed necessary restorative dental care and resulted in more drastic treatment solutions previously especially in the rural areas in Norway.

Incentives and remuneration systems in dental services

The aim of this study was to examine the effects of an incentive-based remuneration system on number of individuals under supervision and on quality of public dental services in Norway. The basis for the study was a natural experiment in which all public dental officers in one county were given the opportunity to renegotiate their contract from a fixed salary contract to a combined per capita and fixed salary contract. Comprehensive data were collected before and after the change. A main finding is that the transition to an incentive-based remuneration system led to an increase in the number of individuals under supervision without either a fall in quality or a patient selection effect.

Socioeconomic inequalities in dental services utilisation in a Norwegian county: The third Nord-Trøndelag Health Survey

Aim: To assess the level of socioeconomic inequity in dental care utilisation in Norway and enable comparison with recent international comparative studies. Methods: We studied dental care utilisation among 17,136 men and 21,414 women in the third Nord-Trøndelag Health Survey (2006–08). Respondents aged 20 years and above were included in the study, and analyses were also performed within subgroups of age and gender (20–39, 40–59, and ≥60 years). Income-related horizontal inequity was estimated by means of concentration indices. Education-related inequity was estimated as relative risks. Results: We found consistent pro-rich income inequity among men and women of all ages. The level of income inequity was highest among men and women ≥60 years, and in this group the income gradient was steepest between the poorest and the middle quintiles. Pro-educated inequity was found exclusively among men and women ≥60 years. General attendance was high (77%). Conclusion: The overall level of income-related inequity in dental services utilisation was low compared to other European countries as reported in two recent international studies of socioeconomic inequalities in dental care utilisation. Pro-rich and pro-educated inequity is a public health challenge mainly in the older part of the population.

Equality in adults' oral health in Norway. Cohort and cross-sectional results over 33 years

OBJECTIVE To assess social inequality in dental clinical parameters from 1973 to 2006. METHODS Samples from two birth-cohorts born between 1929-1938 and 1959-1960, respectively, and 35-44-year-olds were drawn in 1973, 1983, 1994 and in 2006 in the county of Nord-Trøndelag in Norway. Standard procedures were followed all the time. The examination comprised caries and caries treatment experience by DMF criteria and a questionnaire. Length of education in years was divided into quartiles in 1983, 1994 and 2006 to analyse the association between social status and clinical parameters. Statistical analyses were conducted within the same study year and between the years 1983 and 2006 by descriptive statistics and anova. RESULTS The study showed that the DMFT/S index increased in the two birth-cohorts from 1973 to 1983 where after fewer changes occurred. However, there was a great improvement in oral health among 35-44-year old during the period from 1973 to 2006. The inequalities observed in 1983 remained or decreased and there was equality in number of present teeth all the time. The DMF results from the birth-cohorts showed that if social differences appear at an early age, they will persist in the cohorts the next 30 years and more. This is mainly because of the irreversibility of the DMF registrations. CONCLUSIONS Social inequality was reduced but found in some indicators of dental status in 2006. Part of it can be explained by the insensitivity of the applied indexes. There is still a social divide in oral health and it affects elderly more than younger adults.

Accessibility of dental services according to family income in a non-insured population

The aim of this study was to examine the effect of family income on accessibility to dental services among adults in Norway. The analysis was performed on a set of national data collected in 1989, which was representative of the non-institutionalized Norwegian population aged 20 years and above. The sample size was 1200 individuals. The data were analyzed according to a two-part model. The first part determined the probability of whether the consumer had demanded the services or not during the last year according to family income. The second part estimated how the amount of services utilized depended on family income, for those with demand. The elasticity of the odds of having demanded the services with respect to family income was 0.48. Family income had no effect on the amount of services utilized. Additional analyses also showed that there was no effect of family income on the probability of having received a filling or a crown when visiting the dentist. In Norway, almost all costs for dental services are paid by the consumer. It is not possible from the data alone to say whether subsidized dental care is an effective way of reducing the inequalities in demand.

Oral health‐related quality of life among adults 68–77 years old in Nord‐Trøndelag, Norway

Dental health has mostly been measured by dental staff disregarding patients experiences. However, clinical conditions alone do not fully indicate how people feel affected by their oral status. The aim of this study was to investigate how clinical recorded dental health, self-rated dental health, satisfaction with dental health were related to oral health-related quality of life (OHRQoL) assessed by Oral Health Impact Profile (OHIP-14) in 68-77 years old. A total of 151 individuals completed a questionnaire on self-rated dental health, satisfaction with dental health and the short form of OHIP-14. Clinical examination was performed registering number of teeth and dental caries. In total 63% of the individuals rated their dental health as good, and 59% were satisfied with their dental health. Using the OHIP-14 42% reported no problems or oral discomfort at all. The proportion of individuals reporting problems or discomfort varied between 13% and 43% according to the dimensions of OHIP-14. The most frequently reported problems were physical pain (43%), psychological discomfort (28%) and psychological disability (28%). Individuals who rated their dental health as poor and those who were dissatisfied with their dental health had significantly lower OHRQoL than other individuals. The study showed relationship between self-evaluations of dental health and OHRQoL in 68-77 years old. Individuals with few teeth reported lower OHRQoL than others, but no association between clinical caries status and OHRQoL could be found.

Causal patterns of dental health in populations. An empirical approach.

In the present investigation we aimed to analyse causally the pattern of determinants leading to the maintenance of functional teeth in adults. Clinical and self-reported information was used. The hypothesis was that socio-economic conditions operate through psychosocial circumstances that influence lifestyle, and are thus related to oral hygiene and levels of remaining teeth. Testing of the patterns for adults residing in high- and low-fluoride areas did not reveal any principal differences in dental health, therefore further testing was combined for both fluoride areas. Further analysis also indicated that testing should be performed separately for each gender. Social structure and dental health-related lifestyle were important in an overall pattern of maintaining functional teeth, but general lifestyle and psychosocial conditions were not found to be part of the pattern influencing dental health. Gender-specific patterns were revealed. New hypotheses may be suggested for further research with regard to studying patterns of dental health in Lithuanian adults.