The present study, conducted among first-year students attending upper secondary school in Northern Norway, identified adolescent’s own study program as a common social determinant for overweight/obesity and untreated dental caries among boys. Mother’s education was identified as a common social determinant also among boys and only when general and oral health conditions were considered simultaneously.
To our knowledge, this is the first study investigating association between SEP indicators and overweight and obesity, and untreated dental caries among the same adolescents using the WHO conceptual model for social determinants of health employing two approaches, when general and oral health conditions were analyzed separately and simultaneously. The two approaches gave similar results, suggesting that both strategies may be used to investigate common social determinants of general and oral health, however using the model where general and oral health outcomes were considered simultaneously resulted in higher Nagelkerke R2.
All general and oral health outcomes were measured using objective criteria during clinical examination. Moreover, to detect untreated dental caries in dentine, radiographies were used.
However, the study has some limitations. This was a cross-sectional study, whose design in general is prone to confounding and does not allow to establish causality . To control for confounders, we used a multivariable binary logistic analysis . Given a high prevalence of our outcomes (more than 10%), results of the current study are interpreted in terms of prevalence odds ratios.
The initial participation rate in FF1 was high, reaching 93%, and participation in the oral health part of FF1 was only slightly lower (90%). It is possible that this decrease in attendance to the dental evaluation that constituted the oral health part of FF1 was associated with low parental education, unemployment, and low income . After exclusions, our final study sample represented 86% of all students invited to FF1, but in multivariable binary logistic regression, the number of participants was reduced to 63% among girls and 62% among boys due to missing data; therefore self-selection bias cannot be ruled out. The sample was collected from both a densely populated urban area (Tromsø, seven schools) and a sparsely populated rural area (Balsfjord, one school) including all upper secondary schools in Tromsø school district, Troms County, Northern Norway. In this county, 29% of the population resides in sparsely populated areas; therefore, the population residing in densely populated areas might be overrepresented in the study sample (7 schools in urban area versus 1 school in rural area). It has been shown that living in densely populated areas is associated with higher physical activity and thus probably better health outcomes among adolescents in Norway . It must be noted that 16–18% of adolescents in Troms County do not live in their parents’ household. Indeed, as Troms County is large, adolescents sometimes have to move from where their parents live to where the school is located – creating the household composition of “living without adults”. This living situation occurs due to adolescents’ need for education; not necessarily because they have a higher level of maturity and hence, their health may be jeopardized. It has been also shown that having an immigrant background was related to worse general and oral health outcomes among children and adults in Norway [31,32,33]. In Tromsø municipality in 2012, 4.8% of immigrants were aged 16–19 years . In our study sample 6% of girls and 5% of boys reported that they were born outside Norway, indicating that our sample might be representative of the national population with respect to immigrant background.
A pretested, electronic, self-administered questionnaire was employed to collect data on SEP indicators and most of the covariates. Structure and content of the questionnaire were to a large degree adapted from the Tromsø Study among adults . In general, questionnaires are prone to bias, especially regarding sensitive data, like alcohol intake and tobacco use. However, self-administration has been shown to decrease reporting bias .
Previous Norwegian study investigated association between health behavior and SEP among adolescents and suggested that adolescent’s own study program in upper secondary school is a potential proxy of an adolescent’s SEP . Therefore, study program was chosen as the SEP indicator in this study. In the Norwegian school system, there is a lawful right, but not an obligation, to complete 1 year of upper secondary school. Students can apply for a general studies program, including a sub-path of a sports, or a vocational study program. The general studies program gives possibility for admission to higher education after three years. At the vocational study program, normally after two years of school training, a student goes in apprenticeship for two years. The completion rates (by normative length of study) differ according to study path (75% in general study program, 37% in vocational study program, during 2013–2018, respectively), and varies by sex, geographic area and parent’s education. Adolescents’ choice of study program has been shown to correlate with their social background  and health-related behaviors [37, 39]. As in the present study, the same previous Norwegian study also indicated that parents’ education and occupation are applicable when investigating association between SEP and health outcomes among adolescents . In addition, in Norway, previous studies also have shown that mother’s and father’s education associated with child’s health behavior and adverse health events [37, 40, 41]. We had no data on parents’ occupation, therefore, parents’ employment was used as a substitute variable in this study, as it has been associated with health and health behaviors among adolescents .
In this study, one of the indicators of the general health condition, overweight and obesity, body weight (expressed by BMI), was measured. BMI is commonly used as an indicator of overweight and obesity. Indeed, BMI is a ratio between weight and height, and it cannot distinguish between body fatness and fat-free mass . On the other hand, it has been shown that BMI-for-age was a good indicator of body fatness, especially among heavier children and adolescents . In addition to BMI, we used waist circumference as another general health indicator. Waist circumference is a specific measure to define abdominal fatness . In our study, the two measures gave quite similar results, but using BMI presented results with a higher Nagelkerke R2 implying that the variability of the studied independent variables explained to a greater extent the variability in BMI than in waist circumference.
In this study, the indicator of the oral health condition, dental caries, was untreated caries in dentine (D3–5 T); it was measured and expressed as DT component of DMFT index. The DT component reflects the treatment need, or in other words, the severity of disease, but does not take into consideration dental caries experience (filled and missing due to caries teeth).
Discussion of the results
Among boys, the statistically significant associations were observed between study program and all the outcomes, i.e. body weight, waist circumference, untreated dental caries, and combined general and oral health outcome. It must be noted, that adolescents enrolled in the sports program may have a better general health because of the fact that they are in this study program. Previous prospective Norwegian cohort study demonstrated association between admission to given study programs and health behaviors , and our study showed association between study program, and general and oral health outcomes among boys. This finding may be explained that the choice of study program has been shown to depend mainly on the occupation of role models, role models for adolescents being mostly their friends and acquaintances, persons from the same social environment . Therefore, one may assume that not the study program itself is a risk factor of poor general and oral health, but the social context that leads the adolescent to choose a particular program.
Lower mother’s education, another SEP indicator used in this study, was associated with higher BMI and combined general and oral health outcome also only among boys. This finding might refer to gender orientation in adolescents’ behavior. It might be that boys are less mature and more dependent on their mothers, as mothers have been shown to be “the prime mover in the health and welfare of the child” . Our findings regarding mother’s education and boy’s health is in contrast to a study from the USA, in which father’s health-risk lifestyle, which consisted of diet, physical activity, smoking, alcohol use, and sleep, affected boys’ health-risk behavior, while mother’s behavior affected girls’ behavior; however parents’ health-risk lifestyle was not included in this study . It has been shown in Norway that father’s occupation predicted changes in health behavior among 13–21-year-old girls . We may speculate that father’s occupation is linked to father’s education, in the present study, higher father’s education was associated with untreated dental caries among boys, and this finding is in contrast with the previously mentioned study. Even though it has been demonstrated that only few adolescents based their choice of the study program on their parents’ opinions, the indirect influence may not be ruled out . The associations between parents’ education, and general and oral health conditions should be interpreted with caution given a high proportion of the adolescents who did not know or did not report the education level of their parents. Given the differences across genders of parents and children, future studies investigating association between SEP and health outcomes in adolescents should address the issue of gender in the relation between parents and their children.
A study in Hungary showed that incomplete parental employment (unemployed, retired, housewife) resulted in inconsistent associations; it was positively associated with health conditions, like depressive and psychosomatic symptoms, but negatively associated with behavioral factors, like smoking, drinking, and drug use among adolescents . Contrary, a study among adolescents in Hong Kong found the association between full time employed parents and overweight/obesity, when both sexes were analyzed together . In the present study parents’ employment, another SEP indicator, did not associate with any of the outcomes.
A recent study among chief dental officers showed that the majority of the countries acknowledged common risk factor approach when implementing shared preventive strategies for general and oral health, however the approach was interpreted too narrow as strategies addressed mainly intermediary rather than social determinants of health . Our results suggest that public health policymakers should focus on common health promotion strategies for general and oral health that would address common social determinants for general and oral health conditions.