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BACKGROUND: Loneliness and social inequality in health are important public health concerns. We examined (i) trends in loneliness among adolescents from 1991 to 2014 in Denmark and (ii) trends in social inequality in loneliness. METHODS: Study population: 11-15-year olds in random samples of schools in 1991, 1994, 1998, 2006 and 2014, n = 19 096. Loneliness was measured by a single item and social background by parents' occupational social class (OSC). We calculated absolute (%) differences in loneliness between high and low OSC and relative differences by odds ratio for loneliness. RESULTS: Across all surveys, 6.3% reported feeling lonely. The prevalence increased from 4.4% in 1991 to 7.2% in 2014. The prevalence of loneliness in high, middle and low OSC was 5.8, 5.9 and 8.0%. The increase in loneliness was more pronounced in higher than lower OSC, resulting in a decreasing absolute social inequality in loneliness. The statistical interaction between OSC and survey year was significant, P = 0.0176, i.e. the relative social inequality in loneliness also decreased from 1991 to 2014. CONCLUSION: The prevalence of loneliness increased from 1991 to 2014. The social inequality in loneliness decreased in both absolute and relative terms because of a rising prevalence of loneliness among children from high OSC.

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BACKGROUND: The association between socio-economic status (SES) and headache among adolescents is an understudied issue, and no study has examined whether such an association changes over time. The aim was to examine trends in socio-economic inequality in frequent headache among 11- to 15-year-olds in Denmark from 1991 to 2014, using occupational social class (OSC) as indicator of SES. METHODS: The study applies data from the Danish part of the international Health Behaviour in School-aged Children (HBSC) study. HBSC includes nationally representative samples of 11-, 13- and 15-year-olds. This study combines data from seven data survey years from 1991 to 2014, participation rate 88.6%, n = 31,102. We report absolute inequality as per cent difference in frequent headache between high and low OSC and relative inequality as odds ratio for frequent headache by OSC. RESULTS: In the entire study population, 10.4% reported frequent headache. There was a significant increase in frequent headache from 8.0% in 1991 to 12.9% in 2014, test for trend, p < 0.0001. This increasing trend was significant in all OSCs. The prevalence of frequent headache was significantly higher in low than high OSC, OR = 1.50 (95% CI: 1.34-1.67). This socio-economic inequality in frequent headache was persistent from 1991 to 2014. CONCLUSION: There was a significant and persistent socio-economic inequality, i.e. increasing prevalence of frequent headache with decreasing OSC. The association between socio-economic position and headache did not significantly change over time, i.e. the statistical interaction between OSC and survey year was insignificant. SIGNIFICANCE: The prevalence of frequent headache among adolescents increases with decreasing SES. This socio-economic inequality has been persistent among adolescents in Denmark from 1991 to 2014. Clinicians should be aware of this social inequality.

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More children from lower social backgrounds are physically inactive than those from higher ones. We studied whether bullying was a mediating factor between lower social background and physical inactivity. We also examined the combined effect of low social class and exposure to bullying on physical inactivity. The Danish sample of the Health Behaviour in School-aged Children (HBSC) study 2006 included 6269 schoolchildren in three age groups: 11-, 13-, and 15-year-olds from a random sample of 80 schools. The students answered the internationally standardized HBSC questionnaire. The applied definition leaves 4.0% in the category physically inactive. The sex and age-adjusted OR (95% CI) for physical inactivity was 2.10 (1.39-3.18) among students with low social class and unclassifiable 3.53 (2.26-5.53). Exposure to bullying was associated with physical inactivity, sex and age-adjusted OR = 2.39 (1.67-3.41). Exposure to bullying did not explain the association between social class and physical inactivity. The association between social class and physical inactivity was more pronounced among participants also exposed to bullying. In conclusion, there was a significantly increased odds ratio for physical inactivity among students from lower social classes and for students exposed to bullying. There was a combined effect of low social class and bullying on physical inactivity.

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The Hi Five study was a three-armed cluster randomized controlled trial designed to reduce infections and improve hygiene and well-being among pupils. Participating schools (n = 43) were randomized into either control (n = 15) or one of two intervention groups (n = 28). The intervention consisted of three components: (i) a curriculum (ii) mandatory daily hand washing before lunch (iii) extra cleaning of school toilets. The aim of this study was to evaluate the implementation and to identify challenges to program implementation. Several data sources were used, including observations of school toilets, semi-structured interviews with school coordinators (n = 4), focus groups with pupils (n = 6) and teachers (n = 5), and questionnaires among pupils (n = 5440), teachers (n = 387) and school coordinators (n = 28). This study indicates that the curriculum was successfully implemented at most schools, and that teachers and pupils reacted positively to this part of the intervention. However, daily hand washing before lunch seems to be difficult to implement. Overall, the implementation process was affected by several factors such as poor sanitary facilities, lack of time and prioritization and objections against the increasing tendency to place the responsibility for child-rearing tasks on schools. This study reveals the strong and weak parts of the Hi Five study and can guide program improvement.

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OBJECTIVES: To examine 9-year trends and relationships regarding misperceptions of body size and dieting for weight loss among adolescents from 24 countries, and explore the influence of country-level overweight prevalence. METHODS: Sociodemographic characteristics, body size perception and dieting for weight loss were assessed in the Health Behaviour in School-aged Children survey conducted in 24 countries cross-sectionally at three time points (2001/2002, 2005/2006 and 2009/2010). Logistic regression models examined change over time in overestimation of body size in non-overweight adolescents, underestimation of body size in overweight adolescents, dieting for weight loss in non-overweight and overweight adolescents and relationships between body size perception and dieting. Analyses were stratified by weight status and sex. Covariates included country-level overweight prevalence, family affluence and country level of development. Body mass index was only included in models examining dieting for weight loss. RESULTS: Country-level overweight prevalence increased over time (11.6-14.7%). Compared with Time 1, overweight adolescents had greater odds of body size underestimation at Time 3 (odds ratio (OR)=1.68 for girls; OR=1.10 for boys), whereas non-overweight adolescents had lower odds of body size overestimation at Time 3 (OR=0.87 for girls; OR=0.89 for boys). Controlling for country-level overweight prevalence attenuated these relationships. Compared with Time 1, overweight and non-overweight boys were 10% more likely to diet at Time 3, whereas overweight and non-overweight girls were 19% and 16%, respectively, less likely to diet at Time 3. Controlling for country-level overweight prevalence did not impact trends in dieting for weight loss. Additionally, the association of self-perceived overweight with increased odds of dieting diminished over time. CONCLUSIONS: Body size perceptions among adolescents may have changed over time concurrent with shifts in country-level body weight. However, controlling for country-level overweight prevalence did not impact trends in dieting for weight loss, suggesting a potentially stronger impact of social comparison on weight-related perceptions than on behavior.

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BACKGROUND: Overweight may hinder achievement of gross motor milestones and delayed achievement of milestones may increase the risk of later overweight for reasons involving physical activity and the building of lean body mass. OBJECTIVE: To investigate whether increased birth weight and body mass index (BMI) at 5 months is associated with the achievement of the ability to sit up and walk and whether delayed achievement of these milestones is associated with overweight at age 7 years. METHODS: We used data from the Danish National Birth Cohort on 25,148 children born between 1998 and 2003. Follow-up took place from 2003 to 2010. Mean age at follow-up was 7.04 years. We used logistic and linear regression analyses. RESULTS: Birth weight and BMI at 5 months were marginally associated with earlier achievement of the ability to sit up and walk (regression coefficients between -0.027 months; [CI -0.042; -0.013] and -0.092 months [CI -0.118; -0.066]). Age in months of sitting and walking were not associated with overweight at age 7 years (ORs between 0.97 [CI 0.95-1.00] and 1.00 [CI 0.96-1.04]). Later achievement of sitting and walking predicted lower BMI at age 7 years (ln-BMI -z-scores between -0.023 [CI -0.029; -0.017] and -0.005 [CI -0.015; 0.005)). CONCLUSIONS: All observed associations were of negligible magnitude and we conclude that birth weight or BMI at age 5 months and motor milestones appear largely independent of each other and that timing of achievement of motor milestones seems not to be associated with later overweight or increased BMI.

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OBJECTIVE: It is important to understand levels and social inequalities in childhood overweight within and between countries. This study examined prevalence and social inequality in adolescent overweight in 35 countries, and associations with macroeconomic factors. DESIGN: International cross-sectional survey in national samples of schools. SUBJECTS: A total of 11-, 13- and 15-year-olds from 35 countries in Europe and North America in 2001-2002 (N=162 305). MEASUREMENTS: The main outcome measure was overweight based on self-reported height and weight (body mass index cut-points corresponding to body mass index of 25 kg/m(2) at the age of 18 years). Measures included family and school affluence (within countries), and average country income and economic inequality (between countries). RESULTS: There were large variations in adolescent overweight, from 3.5% in Lithuanian girls to 31.7% in boys from Malta. Prevalence of overweight was higher among children from less affluent families in 21 of 24 Western and 5 of 10 Central European countries. However, children from more affluent families were at higher risk of overweight in Croatia, Estonia and Latvia. In Poland, Lithuania, Macedonia and Finland, girls from less affluent families were more overweight whereas the opposite was found for boys. Average country income was associated with prevalence and inequality in overweight when considering all countries together. However, economic inequality as measured by the Gini coefficient was differentially associated with prevalence and socioeconomic inequality in overweight among the 23-high income and 10-middle income countries, with a positive relationship among the high income countries and a negative association among the middle income countries. CONCLUSION: The direction and magnitude of social inequality in adolescent overweight shows large international variation, with negative social gradients in most countries, but positive social gradients, especially for boys, in some Central European countries. Macroeconomic factors are associated with the heterogeneity in prevalence and social inequality of adolescent overweight.

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OBJECTIVE: To examine the agreement between parents' and children's reports on four items of family affluence: number of cars, own bedroom, number of family holidays and number of computers, and to analyse predictors of disagreement. DESIGN: Cross-sectional child-parent validation study of selected items from an internationally standardised questionnaire. SETTING: Survey conducted in schools in Denmark, Germany, Hungary, Italy, Poland and Scotland. PARTICIPANTS: 972 11-year-old children and their parents responded to the questionnaires. RESULTS: The child item response rates were high (above 93%). The per cent agreement was low for holidays spent with family (52.5%), but high for the other three items of family affluence (76.2-88.1%). The kappa coefficients were good or excellent for all items (between 0.41 and 0.74) and the gamma coefficients were strong for all items (between 0.56 and 0.96). Children from single-parent families were more likely to over-report family affluence (OR 2.67; CI 1.83 to 3.89). CONCLUSIONS: Young adolescents' self-reports of family affluence are fairly valid across the six countries. This finding suggests that the variables measured can be used in epidemiological studies that aim at ranking children according to socioeconomic position.

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OBJECTIVE: To investigate potential personal, social and physical environmental predictors of daily fruit intake and daily vegetable intake in 11-year-old boys and girls in nine European countries. SUBJECTS: The total sample size was 13 305 (90.4% participation rate). RESULTS: Overall, 43.2% of the children reported to eat fruit every day, 46.1% reported to eat vegetables every day. Daily fruit intake and daily vegetable intake was mainly associated with knowledge of the national recommendations, positive self-efficacy, positive liking and preference, parental modeling and demand and bringing fruit to school (odds ratio between 1.40 and 2.42, P<0.02). These factors were associated fairly consistently with daily fruit intake across all nine European countries, implying that a rather uniform intervention strategy to promote fruit can be used across Europe. For vegetables, the pattern was, however, less consistent. Differences between countries in cooking and preparing vegetables might be responsible for this larger diversity. CONCLUSIONS: This study showed that especially a combination of personal and social factors is related to daily fruit and vegetable intake in schoolchildren. This shows that a comprehensive multilevel intervention strategy based upon a series of individual and social correlates will be most promising in the promotion of daily fruit and vegetable intake in children.

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There has been a pronounced, distinctive increase of the prevalence of obesity within almost all age groups of the Danish population, during the last 25-30 years. The largest increase has been documented in studies based on objective data from total populations and the latest data show the increase will continue. The Danish studies show heterogeneity in the development of the obesity epidemic. A close association with birth cohorts indicates a need for further aetiological research, not only into behavioural factors, but also into early life factors that may explain some of this developmental pattern.

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BACKGROUND/AIMS: The Pro Children Project was designed to assess fruit and vegetable consumption in European schoolchildren and their parents, as well as determinants of the children's consumption patterns. A second objective was to develop and test strategies, applicable across Europe, for promoting consumption of fruits and vegetables among schoolchildren and their parents. In this paper, the rationale, theoretical background, overall design and implementation of the project is presented. METHODS: Surveys of national, representative samples of 11-year-old schoolchildren and their parents were conducted in 9 countries, i.e. in Austria, Belgium, Denmark, Iceland, the Netherlands, Norway, Portugal, Spain and Sweden. Comprehensive school-based educational programmes have been developed and tested in three settings, i.e. in Spain, the Netherlands and in Norway. A precoded 24-hour recall form combined with a set of food frequency questions assessing regular intake were used to assess fruit and vegetable consumption. Determinants were assessed employing a comprehensive theoretical framework including personal, social and environmental factors related to fruit and vegetable consumption. The intervention programmes have been tested employing a group-randomized trial design where schools have been randomly allocated to an intervention arm and a delayed intervention arm. Surveys among all participating children and their parents were conducted prior to the initiation of the intervention, immediately after the end of the intervention and at the end of the subsequent school year. CONCLUSION: The project is expected to provide new information of great importance for improving our understanding of consumption patterns of fruits and vegetables and for guiding future efforts to promote increased consumption patterns across Europe.

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OBJECTIVES: To investigate the internal consistency of the scales and the test-retest reliability and predictive validity of behaviour theory-based constructs measuring personal, social and environmental correlates of fruit and vegetable intake in 10-11-year-old children. DESIGN: Test-retest with one-week interval. SETTING: Five European countries: Norway, Spain, Denmark, Portugal, Belgium. SUBJECTS: Three hundred and twenty-six children completed the questionnaire during class hours. RESULTS: For the total sample across all countries, the test-retest reliability was good to very good (intra-class correlation coefficient (ICC) >0.60) for 12 out of the 15 fruit constructs and also for 12 out of the 15 vegetable constructs. Acceptable ICCs, ranging between 0.50 and 0.59, were found for the remaining constructs. Test-retest reliability was comparable across countries. Only in Portugal were some significantly lower ICCs found for some constructs (knowledge and barriers related to fruit, general self-efficacy related to fruit and vegetables) compared with the other countries. Cronbach's alpha values were moderate to high (range 0.52 to 0.89) with the exception of the general self-efficacy scale, which had a value below 0.50 for both fruit (alpha=0.42) and vegetables (alpha=0.49). Spearman correlations with intake ranged between -0.16 and 0.54 for personal determinants and between 0.05 and 0.38 for environmental determinants. Compared with other studies, predictive validity can be considered moderate to good. CONCLUSIONS: The questionnaire provides a reliable, valid and easy-to-administer tool for assessing personal, social and environmental factors of potential influence on fruit and vegetable intake in 10-11-year-olds.

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OBJECTIVE: To examine the relation between socioeconomic position in early life and mortality in young adulthood, taking birth weight and childhood cognitive function into account. DESIGN: A longitudinal study with record linkage to the Civil Registration System and Cause of Death Registry. The data were analysed using Cox regression. SETTING: The metropolitan area of Copenhagen, Denmark. SUBJECTS: 7493 male singletons born in 1953, who completed a questionnaire with various cognitive measures, in school at age 12 years, and for whom birth certificates with data on birth and parental characteristics had been traced manually in 1965. This population was followed up from April 1968 to January 2002 for information on mortality. MAIN OUTCOME MEASURES: Mortality from all causes, cardiovascular diseases, and violent deaths. RESULTS: Men whose fathers were working class or of unknown social class at time of birth had higher mortality rates compared with those whose fathers were high/middle class: hazard ratio 1.39 (95% CI 1.15 to 1.67) and 2.04 (95% CI 1.48 to 2.83) respectively. Birth weight and childhood cognitive function were both related to father's social class and inversely associated with all cause mortality. The association between father's social class and mortality attenuated (HR(working class)1.30 (1.08 to 1.56); HR(unknown class)1.81 (1.30 to 2.52)) after control for birth weight and cognitive function. Mortality from cardiovascular diseases and violent deaths was also significantly higher among men with fathers from the lower social classes. CONCLUSION: The inverse association between father's social class at time of birth and early adult mortality remains, however somewhat attenuated, after adjustment for birth weight and cognitive function.

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STUDY OBJECTIVE: To investigate the role of different types of social relations in adolescent health inequalities. DESIGN: Cross sectional study. Measures included family social class, indices of social relations to parents, friends, teachers, and school. SETTING: Random sample of 55 schools in Denmark. PARTICIPANTS: Nationally representative sample of 5205 students from grades 5, 7, and 9. MAIN OUTCOME MEASURES: Self reported physical and psychological symptoms. RESULTS: Adolescents from families of lower socioeconomic position reported more physical and psychological symptoms. This ranged from 40% increased odds for multiple physical symptoms among less advantaged girls, to 90% increased odds of multiple psychological symptoms for less advantaged boys. Relationships with friends or teachers showed small social class differences, while strong and consistent social class differences were found in the ways adolescents reported their own and their parents relations to school. For example, girls from families of lower socioeconomic position were more than four times as likely to report their parents unwilling to attend school meetings (odds ratio=4.54, 95% confidence intervals: 2.68 to 7.69). Poorer relations with parents, peers, teachers, and school were all associated with worse health. Patterns of parent-child relations with the school were the greatest contributors to socioeconomic differences in physical and psychological symptoms. CONCLUSIONS: The school is one of the first important social institutions directly experienced by children and socioeconomic differences in how adolescents and their parents relate to the school may be part of the cascade of early life influences that can lead to later social and health disadvantage.

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OBJECTIVE: To determine whether adolescent smoking behaviour is associated with their perceived exposure to teachers or other pupils smoking at school, after adjustment for exposure to smoking at home, in school, and best friends smoking. DESIGN: Logistic regression analysis of cross sectional data from students in Denmark. SUBJECTS: 1515 grade 9 students (mean age 15.8) from 90 classes in 48 Danish schools. OUTCOME MEASURE: Self reported smoking behaviour; daily smoking and heavy smoking, defined as those smoking more than 20 cigarettes per week. RESULTS: Of the students in this study, 62% of boys and 60% of girls reported being exposed to teachers smoking outdoors on the school premises. The proportion of boys and girls reporting to have been exposed to teachers smoking inside the school building were 86% and 88%, respectively. Furthermore, 91% of boys and 92% of girls reported that they had seen other students smoking outdoors on the school premises. Adolescents' perceived exposure to teachers smoking outdoors on the school premises was significantly associated with daily smoking, having adjusted for sex, exposure to teachers smoking indoors at school and pupils smoking outdoors at school, as well as the smoking behaviour of mother, father, and best friend (odds ratio (OR) 1.8, 95% confidence interval 1.2 to 2.8). Adolescents' perceived exposure to teachers smoking inside the school building was not associated with daily smoking (OR 0.9, 95% CI 0.5 to 1.6) and perceived exposure to pupils smoking outdoors was not associated with daily smoking (adjusted OR 1.5, 95% CI 0.5 to 4.4). There were similar findings with heavy smoking as the outcome variable. CONCLUSIONS: Teachers smoking during school hours is associated with adolescent smoking. This finding has implications for future tobacco prevention strategies in schools in many countries with liberal smoking policies where it might provide support for those working to establish smokefree schools.

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In many gravitational interactions between galaxies, gas and stars that have been torn from the precursor galaxies can collect in tidal 'tails'. Star formation begins anew in some of these regions, producing tidal dwarf galaxies. Observations of these new galaxies provides insight into processes relevant to galaxy formation more generally, because the timescale of the interaction is well defined. But tracking the star formation process has hitherto been difficult because the tidal dwarf galaxies with young stars showed no evidence of the molecular gas out of which those young stars formed. Here we report the discovery of molecular hydrogen (traced by carbon monoxide emission) in two tidal dwarf galaxies. In both cases, the concentration of molecular gas peaks at the same location as the maximum in atomic-hydrogen density, unlike the situation in most gas-rich galaxies. We infer from this that the molecular gas formed from the atomic hydrogen, rather than being torn in molecular form from the interacting galaxies. Star formation in the tidal dwarf galaxies therefore appears to mimic the process in normal spiral galaxies like our own.

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In a follow-up study of 70-95 years old women and men (n = 911) we studied the association between change and stability in three structural aspects of social relations (contact frequency, contact diversity, cohabitation status) from 1986-1990 and mortality after the next four years in 1994. Women aged 70-74 years who developed low contact frequency or developed small contact diversity showed significantly higher mortality, adjusted ORfreq: 3.78 (1.08-13.20), adjusted ORdiv: 3.79 (1.24-11.58). Women aged 70-74 years with continuously low contact frequency showed an increased mortality compared to women constantly experiencing high contact frequency, adjusted OR: 2.75 (1.04-7.26). A tendency in the same direction for sustained small contact diversity was found, adjusted OR: 1.98 (0.70-5.61). Among women aged 75+ years no impact of frequency and diversity was demonstrated, whereas continuously living alone was a significant predictor of mortality, when compared to women continuously living with somebody, adjusted OR: 2.57 (1.29-5.09). In men, we found a significantly increased mortality among those who developed high contact frequency and developed large contact diversity ORfreq: 3.91 (1.02-14.94) and ORdiv: 6.04 (1.30-28.03). In summary, we found rather larger age differences in the strength of the association between change in structural social relations and mortality. Furthermore, the associations seemed stronger among women than men, which may however mainly be explained by the small number of men in our cohort.

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We introduce a conceptual framework with social relations as the main concept and the structure and the function of social relations as subconcepts. The structure of social relations covers aspects of formal relations and social network. The function of social relations covers social support, social anchorage and relational strain. We use this conceptual framework to describe social relations in the Danish population, with questionnaire data from the Danish Longitudinal Health Behaviour Study including a random sample of each of the age groups 25-, 50-, 60-and 70-year olds, N = 2,011. The postal questionnaires were answered by a random sample in each of the age groups. The results show marked age and gender differences in both the structure and the function of social relations. The social network, measured as weekly contacts, weakens with age and so does instrumental support. Emotional support is unrelated to this decline in contact frequency and appears to be at the same level for younger and older individuals. Relational strain, measured as conflicts, declines with age for all kinds of social relations. The weakening of the social network with age does not seem to affect the level of emotional support and in turn seems to be partly compensated for by a simultaneous decline in relational strain.

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A total of 1860 children aged 11, 13 and 15 years from a nationwide random sample of schools completed an anonymous questionnaire on their social backgrounds, social networks, perceived health, life satisfaction, and health behaviour. Boys perceived their health to be better and had fewer psychosomatic symptoms than girls. They also did more physical exercise than girls. Boys and girls showed differences in social networks. Self-reported health status, weekly psychosomatic symptoms and health behaviour (smoking, exercise, and diet) were associated with social networks for both sexes. In particular, a good relationship to adults was found to be associated with positive health behaviour and perceived health.

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