Educational inequality in cardiovascular diseases: a sibling approach.

AIMS: Educational inequality in diseases in the circulatory system (here termed cardiovascular disease) is well documented but may be confounded by early life factors. The aim of this observational study was to examine whether the associations between education and all cardiovascular diseases, ischaemic heart disease and stroke, respectively, were explained by family factors shared by siblings. METHODS: The study population included all individuals born in Denmark between 1950 and 1979 who had at least one full sibling born in the same period. Using Cox regression, data were analysed in conventional cohort and within-sibship analyses in which the association was examined within siblings discordant on education. Assuming that attenuation of associations in the within-sibship as compared with the cohort analyses would indicate confounding from factors shared within families. RESULTS: A lower educational status was associated with a higher risk of cardiovascular disease, ischaemic heart disease and stroke. All associations attenuated in the within-sibship analyses, in particular in the analyses on ischaemic heart disease before age 45 years. For instance, in the cohort analyses, the hazard rate of ischaemic heart disease among women less than 45 years who had a primary school education was 94% (hazard ratio 1.94 (1.78-2.12) higher than among those with a vocational education, while it attenuated to 51% (hazard ratio 1.51 (1.34-1.71)) in the within-sibship analysis. CONCLUSIONS: Confounding from factors shared by siblings explained the associations between education and the cardiovascular disease outcomes but to varying degrees. This should be taken into account when planning interventions aimed at reducing educational inequalities in the development of cardiovascular disease, ischaemic heart disease and stroke.

Alcohol-related morbidity and mortality within siblings.

AIMS: To estimate the association between educational status and alcohol-related somatic and non-somatic morbidity and mortality among full siblings in comparison with non-related individuals. DESIGN: Cohort study. SETTING: Denmark. PARTICIPANTS: Approximately 1.4 million full siblings born in Denmark between 1950 and 1979 were followed from age 28-58 years or censoring due to alcohol-related hospitalization and mortality. MEASUREMENTS: Cox regression analyses were used to estimate associations of educational status with alcohol-related outcomes. Results from cohort analyses based on non-related individuals and inter-sibling analyses were compared. FINDINGS: A lower educational status was associated with a higher rate of alcohol-related outcomes, especially among the youngest (aged 28-37 years) and individuals born 1970-79. Compared with the cohort analyses, the associations attenuated slightly in the inter-sibling analysis. For example, in the cohort analysis, females with a basic school education born 1970-79 had an increased rate of alcohol-related non-somatic morbidity and mortality [hazard rate ratio (HR) = 4.05, 95% confidence interval (CI) = 3.27-5.02] compared to those with a vocational education. In the inter-sibling analysis, the HR attenuated (HR = 2.66, 95% CI = 1.95-3.63). For alcohol-related somatic outcomes the corresponding figures were HR = 3.47 (95% CI = 2.63-4.58) and HR = 3.36 (95% CI = 2.10-5.38), respectively. In general, the associations were stronger among females than males (aged 28-37) in the analyses of alcohol-related non-somatic outcomes. Health conditions earlier in life explained only a minor part of the associations. CONCLUSIONS: The association between educational status and alcohol-related somatic and non-somatic morbidity and mortality is only driven by familial factors to a small degree.

Social inequality in breast, lung and colorectal cancers: a sibling approach.

OBJECTIVE: To examine whether family factors shared by siblings explained the association between education and risk of lung, colorectal and breast cancer. DESIGN: We used conventional cohort and intersibling Cox regression analyses to analyse the association between education and risk of cancer. SETTING: Denmark. PARTICIPANTS: We retrieved register data from Statistics Denmark on individuals born in Denmark 1950-1979 with at least one full sibling. The cohorts included between 391 931 and 1 381 369 individuals followed from age 28 for incident lung, colorectal and breast cancer until the end of 2009. RESULTS: In the cohort analysis, low education was associated with an increased risk of colorectal cancer before age 45 and lung cancer, and with a decreased risk of colorectal cancer after age 45 and breast cancer. When compared with the cohort analyses, the intersibling associations were stronger for colorectal cancer after age 45 and weaker for lung cancer. Serious health conditions in childhood/young adulthood did not explain the associations. CONCLUSIONS: Family factors shared by siblings confounded some of the association between education and colorectal cancer after age 45 and lung cancer, but not the associations found for colorectal cancer before age 45 or breast cancer.

Does shared family background influence the impact of educational differences on early mortality?

The mechanisms behind social differences in mortality rates have been debated. The authors examined the extent to which shared family background and health in early life could explain the association between educational status and all-cause mortality rates using a sibling design. The study was register-based and included all individuals born in Denmark between 1950 and 1979 who had at least 1 full sibling born in the same time period (n = 1,381,436). All individuals were followed from 28 years of age until death, emigration, or December 2009. The authors used Cox regression analyses to estimate hazard ratios for mortality according to educational level. Conventional cohort and intersibling analyses were carried out and conducted separately for deaths occurring before and after the age of 45 years, respectively. The cohort analyses showed an inverse association between educational status and all-cause mortality that was strongest for males, increased with younger birth cohorts, and tended to be strongest in the analyses of death before 45 years of age. The associations were attenuated slightly in the intersibling analyses and after adjustment for serious health conditions in early life. Hence, health selection and confounding by factors shared by siblings explained only a minor part of the association between educational level and all-cause mortality.

Time trends in socio-economic factors and risk of hospitalisation with infectious diseases in pre-school children 1985-2004: a Danish register-based study.

The purpose of this study was to examine socio-economic differences in the risk of hospitalisation among children aged 0-5 years in Denmark from 1985 to 2004. All children born between 1985 and 2004 (n=1,278,286) were followed for hospital admissions for infectious diseases from the 29th day of life until the children reached the age of 6 years or the end of 2004, whichever came first. Information on parental socio-economic position (education, labour market attachment and household income) was gathered through record linkage with administrative registries. Infections were grouped into upper respiratory, lower respiratory, gastrointestinal, ear and fever infections. The data were analysed using Cox regression. Children of parents on sick leave or early retirement had an increased risk of being hospitalised with an infection compared with children of employed parents. A clear inverse educational gradient in risk of offspring hospitalisation was also found. From 1985 to 2004 the inverse associations between parental education and risk of hospitalisation grew stronger, whereas the comparatively weaker association between household income and risk of offspring hospitalisation decreased in magnitude. The association between socio-economic status and hospitalisation was strongest for lower respiratory, gastrointestinal and ear infections. This study documented a socially patterned hospitalisation of pre-school children in Denmark. Future studies should investigate possible explanations for the increased risk among children from families with low socio-economic status.

Non-participation in preventive child health examinations at the general practitioner in Denmark: a register-based study.

OBJECTIVE: To examine demographic and socioeconomic characteristics of parents and children in families not participating in preventive child health examinations at the general practitioner in a society with free and easy access to healthcare. DESIGN: Population-covering register linkage study. SETTING: Denmark, 2002-2004. SUBJECTS: Two cohorts comprising all children born in Denmark between 1 July 1998 and 30 June 1999 (n =70 891) and in 2002 (n =65 995), respectively. The demographic and socioeconomic characteristics of these children and the adults living in the same household as these were identified through register linkage. MAIN OUTCOME MEASURES: Crude and mutually adjusted odds ratios for non-participation in scheduled preventive child health examinations at the GP (age 5 weeks, 5 months, 12 months, 4 years, and 5 years) according to child characteristics (sex, number of hospitalizations, and older siblings) and parental characteristics (age, educational level, attachment to labour market, ethnicity, household income, and number of adults in the household). RESULTS: Children of young and single parents were less likely to receive a preventive child health examination. Increased odds ratios for non-participation were found for children of parents outside the labour market, with low educational level, and especially for the combination of these. Non-participation increased with decreasing household income and with the number of older siblings. CONCLUSION: Despite the fact that Denmark has free and easy access to the GP, the utilization of preventive child health examinations is lower among the more deprived part of the population.