Cohort profile: the Social Inequality in Cancer (SIC) cohort study

Underlying pathways of social inequality in tooth loss: The mediating role of sugary beverages and diabetes

BACKGROUND

Previous studies show social inequality in tooth loss, but the underlying pathways are not well understood. The aim was to investigate the mediated proportion of sugary beverages (SBs) and diabetes and the association between educational level and tooth loss, and to investigate whether the indirect effect of SBs and diabetes varied between educational groups in relation to tooth loss.

METHODS

Data from 47,109 Danish men and women aged 50 years or older included in the Danish Diet, Cancer and Health Study was combined with data from Danish registers. Using natural effect models, SBs and diabetes were considered as mediators, and tooth loss was defined as having <15 teeth present.

RESULTS

In total, 10,648 participants had tooth loss. The analyses showed that 3% (95% confidence interval 2-4%) of the social inequality in tooth loss was mediated through SBs and diabetes. The mediated proportion was mainly due to differential exposure to SBs and diabetes among lower educational groups.

CONCLUSIONS

The findings show that SBs and diabetes to a minor degree contribute to tooth-loss inequalities. The explanation indicates that individuals in lower educational groups have higher consumption of SBs and more often suffer from diabetes than higher educational groups.

Serum Progesterone is Negatively Associated with Hypertension and Blood Pressure Indicators Among Men and Postmenopausal Women

Sex hormones have been shown to be negatively associated with hypertension, but the relationship between serum progesterone levels and hypertension has not been adequately studied. Therefore, we aimed to evaluate the association between progesterone and hypertension among Chinese rural adults. A total of 6222 participants were recruited, which included 2577 men and 3645 women. The concentration of serum progesterone was detected by liquid chromatography-mass spectrometer system (LC-MS/MS). Logistic regression and linear regression were used to assess the associations between progesterone levels and hypertension and blood pressure related indicators, respectively. Constrained splines were used to fit the dose-response relationships of progesterone with hypertension and blood pressure related indicators. Moreover, the interactive effects of several lifestyle factors and progesterone were identified by a generalized linear model. After fully adjusting the variables, progesterone levels were inversely associated with hypertension in men [odds ratio (OR): 0.851, 95% confidence interval (CI): 0.752, 0.964]. Among men, a 2.738 ng/ml increase in progesterone was associated with a 0.557 mmHg decrease in diastolic blood pressure (DBP) (95% CI: -1.007, -0.107) and a 0.541 mmHg decrease in mean arterial pressure (MAP) (95% CI: -1.049, -0.034), respectively. Similar results were observed in postmenopausal women. Interactive effect analysis showed that only a significant interaction was observed between progesterone and educational attainment on hypertension in premenopausal women (p=0.024). Elevated levels of serum progesterone were associated with hypertension in men. Except for premenopausal women, a negative association of progesterone with blood pressure related indicators was observed.

Education and incident type 2 diabetes: quantifying the impact of differential exposure and susceptibility to being overweight or obese

AIMS/HYPOTHESIS

Educational inequality in type 2 diabetes incidence is evident in many high-income countries. Previous studies have shown that differential exposure to being overweight/obese across educational groups may partly explain this inequality. Whether differential susceptibility to being overweight/obese across educational groups contributes to this inequality has been investigated less frequently, even though it is a plausible mechanism. The two mechanisms may even be highly intertwined. In this longitudinal cohort study, we investigated the simultaneous contribution of differential exposure and differential susceptibility to being overweight/obese to educational inequality in type 2 diabetes incidence.

METHODS

The study population comprised 53,159 Danish men and women aged 50-64 years at baseline who were followed for a mean of 14.7 years. We estimated rate differences of type 2 diabetes by education level per 100,000 person-years. Using counterfactual mediation analysis, these rate differences were decomposed into proportions attributable to differential exposure, differential susceptibility and all other pathways, respectively. We compared this approach with conventional approaches to mediation and interaction analysis.

RESULTS

Compared with a high level of education, a low education level was associated with 454 (95% CI 398, 510) additional cases of type 2 diabetes, and a medium education level with 316 (CI 268, 363) additional cases. Differential exposure to being overweight/obese accounted for 37% (CI 31%, 45%) of the additional cases among those with a low education level and 29% (CI 24%, 36%) of the additional cases among those with a medium education level. Differential susceptibility accounted for 9% (CI 4%, 14%) and 6% (CI 3%, 10%) of the additional cases among those with a low and medium education level, respectively. Compared with the counterfactual approach, the conventional approaches suggested stronger effects of both mechanisms.

CONCLUSIONS/INTERPRETATION

Differential exposure and susceptibility to being overweight/obese are both important mechanisms in the association between education and type 2 diabetes incidence.

An attempt to explain the bidirectional association between ischaemic heart disease, stroke and depression: a cohort and meta-analytic approach

BACKGROUND

Depression and cardiovascular diseases (CVDs) are common diseases and associated in a bidirectional manner.

AIMS

To examine whether a bidirectional association between CVD and depression could be explained by shared risk factors, misclassification of disease measures or non-response.

METHOD

A total of 10 population-based cohorts including 93 076 men and women (mean age 54.4 years, s.d. = 9.2) and an additional 10 510 men (mean age 51.2 years, s.d. = 0.3) were followed for subsequent depression, ischaemic heart disease (IHD) and stroke in the Danish National Patient Registry from health examinations between 1982 and 2015 and until end of follow-up in 2017-2018. Exposures were physicians' diagnoses of IHD, stroke, depression or self-reported chest pain, depression, use of antidepressant medication and the Major Depression Inventory at the time of study entry in the Metropolit study. Associations were analysed using Cox proportional hazard regression with disease as time-dependent variables.

RESULTS

IHD and stroke were associated with subsequent depression (hazard ratio (HR) for IHD: 1.79, 95% CI 1.43-2.23 and HR for stroke: 2.62, 95% CI 2.09-3.29) and the associations were present in both men and women. Adjustment for the shared risk factors socioeconomic status, lifestyle, body mass index, statin use and serum lipids did not change the risk estimates. Furthermore, depression was associated with higher risk of subsequent IHD (HR = 1.63, 95% CI 1.36-1.95) and stroke (HR = 1.94, 95% CI 1.63-2.30). The associations were also present when the analyses were based on self-reported disease measures or restricted to include non-responders.

CONCLUSIONS

The bidirectional association between CVD and depression was not explained by shared risk factors, misclassification or non-response.

The respective parts of incidence and lethality in socioeconomic differences in cancer mortality. An analysis of the French network Cancer registries (FRANCIM) data

Background

To determine relevant public health actions and to guide intervention priorities, it is of great importance to assess the relative contribution of incidence and lethality to social inequalities in cancer mortality.

Methods

The study population comprised 185,518 cases of cancer diagnosed between 2006 and 2009 recorded in the French registries. Survival was known for each patient (endpoint: 30/06/2013). Deprivation was assessed using the European Deprivation Index. We studied the influence of deprivation on mortality, incidence and lethality rates and quantified the respective proportions of incidence and lethality in social inequalities in mortality by calculating attributable deaths.

Results

For cancers with social inequalities both in incidence and lethality, excess mortality in deprived was mainly caused by social inequalities in incidence (e.g. men lung cancer: 87% of excess deaths in the deprived caused by inequalities in incidence). Proportions were more balanced for some cancer sites (e.g. cervical cancer: 56% incidence, 44% lethality). For cancer sites with a higher incidence in the least deprived (e.g. breast cancer), the excess-lethality in deprived leads entirely the higher mortality among the deprived.

Conclusions

Most of the excess mortality in deprived is due to the excess incidence of tobacco-dependent cancers and the excess lethality of screenable cancers.

Association of physical functioning of persons with dementia with caregiver burden and depression in dementia caregivers: an integrative data analysis

OBJECTIVES

To determine whether caregiver relationship and race modify associations between physical functioning of persons with dementia (PWD) and their caregiver's burden and general depressive symptoms.

METHOD

We pooled data from four behavioral intervention trials (N = 1,211). Using latent growth modeling, we evaluated associations of PWD physical functioning with the level and rate of change in caregiver burden and caregivers' general depressive symptoms and stratified these associations by caregiver relationship and race.

RESULTS

PWD were, on average, 81 years old (68% female) with mean follow-up of 0.5 years. More baseline PWD physical impairment was associated with less worsening in caregiver burden over time (β = -0.23, 95% CI: -0.29, -0.14), but this relationship was not modified by caregiver characteristics. More impaired baseline PWD physical functioning was not associated with changes in depressive symptoms (β = -0.08, 95% CI: -0.17, 0.00), but was associated with less worsening in depressive symptoms among spousal (β = -0.08, 95% CI: -0.17, 0.00) and non-white (β = -0.08, 95% CI: -0.17, 0.00) caregivers.

CONCLUSIONS

Dementia caregivers may experience reduced caregiver-related burden because of adjustment to PWD functional status, while spousal and non-white caregivers may experience less depressive symptoms resultant of adjustment to functional status.

Job-exposure matrices addressing lifestyle to be applied in register-based occupational health studies

Objectives

Information about lifestyle factors in register-based occupational health studies is often not available. The objective of this study was therefore to develop gender, age and calendar-time specific job-exposure matrices (JEMs) addressing five selected lifestyle characteristics across job groups as a tool for lifestyle adjustment in register-based studies.

Methods

We combined and harmonised questionnaire and interview data on lifestyle from several Danish surveys in the time period 1981–2013 for 264 054 employees registered with a DISCO-88 code (the Danish version of International Standard Classification of Occupations (ISCO)-88) in a nationwide register-based Danish Occupational Cohort. We modelled the probability of specified lifestyles in mixed models for each level of the four-digit DISCO code with age and sex as fixed effects and assessed variation in terms of intraclass correlation coefficients (ICCs) and exposure-level percentile ratios across jobs for six different time periods from 1981 through 2013.

Results

The ICCs were overall low (0.26%–7.05%) as the within-job group variation was large relative to the between job group variation, but across jobs the calendar period-specific ratios between highest and lowest predicted levels were ranging from 1.2 to 6.9, and for the 95%/1% and the 75%/5% percentile ratios ranges were 1.1–2.8 and 1.1–1.6, respectively, thus indicating substantial contrast for some lifestyle exposures and some occupations.

Conclusions

The lifestyle JEMs may prove a useful tool for control of lifestyle-related confounding in register-based occupational health studies where lacking information on individual lifestyle factors may compromise internal validity.

Joint Effect of Alcohol Consumption and Educational Level on Alcohol-related Medical Events: A Danish Register-based Cohort Study

BACKGROUND

Alcohol-related mortality is more pronounced in lower than in higher socioeconomic groups in Western countries. Part of the explanation is differences in drinking patterns. However, differences in vulnerability to health consequences of alcohol consumption across socioeconomic groups may also play a role. We investigated the joint effect of alcohol consumption and educational level on the rate of alcohol-related medical events.

METHODS

We pooled seven prospective cohorts from Denmark that enrolled 74,278 men and women age 30-70 years (study period, 1981 to 2009). We measured alcohol consumption at baseline using self-administrated questionnaires. Information on highest attained education 1 year before study entry and hospital and mortality data on alcohol-related medical events were obtained through linkage to nationwide registries. We performed analyses using the Aalen additive hazards model.

RESULTS

During follow-up (1,085,049 person-years), a total of 1718 alcohol-related events occurred. The joint effect of very high alcohol consumption (>21 [>28] drinks per week in women [men]) and low education on alcohol-related events exceeded the sum of their separate effects. Among men, we observed 289 (95% confidence interval = 123, 457) extra events per 100,000 person-years owing to education-alcohol interaction (P < 0.001). Similarly, among women, we observed 239 (95% confidence interval = 90, 388) extra events per 100,000 person-years owing to this interaction (P < 0.001).

CONCLUSIONS

High alcohol consumption is associated with a higher risk of alcohol-related medical events among those with low compared with high education. This interaction may be explained by differences in vulnerability and drinking patterns across educational groups.See video abstract at, http://links.lww.com/EDE/B267.

Combined effects of socioeconomic position, smoking, and hypertension on risk of ischemic and hemorrhagic stroke

BACKGROUND AND PURPOSE

Combined effects of socioeconomic position and well-established risk factors on stroke incidence have not been formally investigated.

METHODS

In a pooled cohort study of 68 643 men and women aged 30 to 70 years in Denmark, we examined the combined effect and interaction between socioeconomic position (ie, education), smoking, and hypertension on ischemic and hemorrhagic stroke incidence by the use of the additive hazards model.

RESULTS

During 14 years of follow-up, 3613 ischemic strokes and 776 hemorrhagic strokes were observed. Current smoking and hypertension were more prevalent among those with low education. Low versus high education was associated with greater ischemic, but not hemorrhagic, stroke incidence. The combined effect of low education and current smoking was more than expected by the sum of their separate effects on ischemic stroke incidence, particularly among men: 134 (95% confidence interval, 49-219) extra cases per 100 000 person-years because of interaction, adjusted for age, cohort study, and birth cohort. There was no clear evidence of interaction between low education and hypertension. The combined effect of current smoking and hypertension was more than expected by the sum of their separate effects on ischemic and hemorrhagic stroke incidence. This effect was most pronounced for ischemic stroke among women: 178 (95% confidence interval, 103-253) extra cases per 100 000 person-years because of interaction, adjusted for age, cohort study, and birth cohort.

CONCLUSIONS

Reducing smoking in those with low socioeconomic position and in those with hypertension could potentially reduce social inequality stroke incidence.