Cohort Profile: The EPIC-NL study

Plasma advanced glycation end products are associated with incident cardiovascular events in individuals with type 2 diabetes: a case-cohort study with a median follow-up of 10 years (EPIC-NL)

Experimental data suggest a role for advanced glycation end products (AGEs) in cardiovascular disease (CVD), particularly in type 2 diabetes (T2DM). However, epidemiological evidence of an association between high plasma AGEs and increased cardiovascular risk remains inconclusive. Therefore, in a case-cohort study comprising 134 cardiovascular case subjects and a random subcohort of 218 individuals (including 65 cardiovascular case subjects), all with T2DM and nested in the European Prospective Investigation into Cancer and Nutrition in the Netherlands (EPIC-NL) study, plasma levels of protein-bound Nε-(carboxymethyl)lysine, Nε-(carboxyethyl)lysine, and pentosidine were measured with liquid chromatography. AGEs were loge-transformed, combined in a z-score, and the association with incident cardiovascular events was analyzed with Cox proportional hazard regression, adapted for case-cohort design (Prentice method). After multivariable adjustment (sex, age, cohort status, diabetes duration, total cholesterol to HDL-cholesterol ratio, smoking, systolic blood pressure, BMI, blood pressure-, cholesterol- and glucose-lowering treatment, prior cardiovascular events, and triglycerides), higher plasma AGE z-scores were associated with higher risk of incident cardiovascular events in individuals without prior cardiovascular events (hazard ratio 1.31 [95% CI: 1.06-1.61]). A similar trend was observed in individuals with prior cardiovascular events (1.37 [0.63-2.98]). In conclusion, high plasma AGEs were associated with incident cardiovascular events in individuals with T2DM. These results underline the potential importance of AGEs in development of CVD.

Degree of urbanization and mammographic density in Dutch breast cancer screening participants: results from the EPIC-NL cohort

It has been observed that women living in urban areas have a higher mammographic density (MD) compared to women living in rural areas. This association might be explained by regional differences in reproductive and lifestyle factors or perhaps by variation in exposure to ambient air pollution as air pollution particles have been described to show estrogenic activity. We investigated the association between degree of urbanization and MD, and aimed to unravel the underlying etiology. 2,543 EPIC-NL participants were studied, and general linear models were used. Urbanization was categorized into five categories according to the number of addresses/km(2). Information on reproductive and lifestyle factors was obtained from the recruitment questionnaire. Air pollution exposure was estimated using land-use regression models. MD was expressed as percent density (PD) and dense area (DA), and was quantified using Cumulus. Women living in extremely urbanized areas had a higher PD (21.4%, 95% confidence interval (CI) 20.5-22.3%) compared to women living in not urbanized areas (16.1, 95% CI 14.5-17.8%, P trend < 0.01).The association persisted after adjustment for reproductive and lifestyle factors as well as for individual exposure to air pollution (adjusted PDextremely_urbanized = 22.1%, 95% CI 18.0-26.5% versus adjusted PDnot_urbanized = 16.9%, 95% CI 13.0-21.2, P trend < 0.01).The results for DA showed close similarity to the results for PD. We found evidence that degree of urbanization is associated with MD. The association could not be explained by differences in reproductive and lifestyle factors or by variation in air pollution exposure.

Association between lifestyle factors and quality-adjusted life years in the EPIC-NL cohort

The aim of our study was to relate four modifiable lifestyle factors (smoking status, body mass index, physical activity and diet) to health expectancy, using quality-adjusted life years (QALYs) in a prospective cohort study. Data of the prospective EPIC-NL study were used, including 33,066 healthy men and women aged 20–70 years at baseline (1993–7), followed until 31-12-2007 for occurrence of disease and death. Smoking status, body mass index, physical activity and adherence to a Mediterranean-style diet (excluding alcohol) were investigated separately and combined into a healthy lifestyle score, ranging from 0 to 4. QALYs were used as summary measure of healthy life expectancy, combining a person's life expectancy with a weight for quality of life when having a chronic disease. For lifestyle factors analyzed separately the number of years living longer in good health varied from 0.12 year to 0.84 year, after adjusting for covariates. A combination of the four lifestyle factors was positively associated with higher QALYs (P-trend <0.0001). A healthy lifestyle score of 4 compared to a score of 0 was associated with almost a 2 years longer life in good health (1.75 QALYs [95% CI 1.37, 2.14]).

The effect of including an opt-out option in discrete choice experiments

Objective

to determine to what extent the inclusion of an opt-out option in a DCE may have an effect on choice behaviour and therefore might influence the attribute level estimates, the relative importance of the attributes and calculated trade-offs.

Methods

781 Dutch Type 2 Diabetes Mellitus patients completed a questionnaire containing nine choice tasks with an opt-out option and nice forced choice tasks. Mixed-logit models were used to estimate the relative importance of the five lifestyle program related attributes that were included. Willingness to pay (WTP) values were calculated and it was tested whether results differed between respondents who answered the choice tasks with an opt-out option in the first or second part of the questionnaire.

Results

21.4% of the respondents always opted out. Respondents who were given the opt-out option in the first part of the questionnaire as well as lower educated respondents significantly more often opted out. For both the forced and unforced choice model, different attributes showed significant estimates, the relative importance of the attributes was equal. However, due to differences in relative importance weights, the WTP values for the PA schedule differed significantly between both datasets.

Conclusions

Results show differences in opting out based on the location of the opt-out option and respondents' educational level; this resulted in small differences between the forced and unforced choice model. Since respondents seem to learn from answering forced choice tasks, a dual response design might result in higher data quality compared to offering a direct opt-out option. Future research should empirically explore how choice sets should be presented to make them as easy and less complex as possible in order to reduce the proportion of respondents that opts-out due to choice task complexity. Moreover, future research should debrief respondents to examine the reasons for choosing the opt-out alternative.

Adherence to the Dutch Guidelines for a Healthy Diet and cancer risk in the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) cohort

OBJECTIVE

To examine the association between adherence to the Dutch Guidelines for a Healthy Diet created by the Dutch Health Council in 2006 and overall and smoking-related cancer incidence.

DESIGN

Prospective cohort study.

SETTING

Adherence to the guidelines, which includes one recommendation on physical activity and nine on diet, was measured using an adapted version of the Dutch Healthy Diet (DHD) index. The score ranged from 0 to 90 with a higher score indicating greater adherence to the guidelines. We estimated the hazard ratios (HR) and 95 % confidence intervals for the association between the DHD index (in tertiles and per 20-point increment) at baseline and cancer incidence at follow-up.

SUBJECTS

We studied 35 608 men and women aged 20-70 years recruited into the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) study during 1993-1997.

RESULTS

After an average follow-up of 12·7 years, 3027 cancer cases were documented. We found no significant association between the DHD index (tertile 3 v. tertile 1) and overall (HR = 0·97; 95 % CI 0·88, 1·07) and smoking-related cancer incidence (HR = 0·89; 95 % CI 0·76, 1·06) after adjustment for relevant confounders. Excluding the components physical activity or alcohol from the score did not change the results. None of the individual components of the DHD index was significantly associated with cancer incidence.

CONCLUSIONS

In the present study, participants with a high adherence to the Dutch Guidelines for a Healthy Diet were not at lower risk of overall or smoking-related cancer. This does not exclude that other components not included in the DHD index may be associated with overall cancer risk.

Dietary patterns in relation to disease burden expressed in Disability-Adjusted Life Years

BACKGROUND

Although diet is related to chronic disease risk and mortality, its association with total disease burden is not clear.

OBJECTIVE

We investigated the minimum impact of different dietary patterns on disability-adjusted life years (DALYs) by using individual longitudinal data.

DESIGN

A prospective cohort study was conducted in 33,066 healthy men and women aged 20-70 y recruited into the European Prospective Investigation into Cancer and Nutrition-Netherlands study during 1993-1997. We measured adherence to 3 a priori dietary patterns [the modified Mediterranean diet score (mMDS), the WHO-based Healthy Diet Indicator, and the Dutch Healthy Diet index] and 2 a posteriori dietary patterns. Two a posteriori methods were used to extract Western and prudent patterns. Participants were followed until the end of 2007 for the occurrence of and mortality from the most important chronic diseases. The disease burden was expressed in DALYs, which are the sum of Years Lost due to Disability and Years of Life Lost because of premature mortality. The associations between dietary patterns (per SD change in score) and DALYs were estimated by using a 2-part model and adjusted for relevant confounders (sex, age at recruitment, smoking status and intensity, educational level, marital status, job status, energy intake, and physical activity).

RESULTS

After an average follow-up of 12.4 y, higher adherence to the mMDS or prudent pattern was most strongly associated with healthy survival; per SD higher adherence to the mMDS or prudent pattern, fewer healthy life years were lost [51 d (-0.14 DALYs; 95% CI: -0.21, -0.08 DALYs) and 58 d (-0.16 DALYs; 95% CI: -0.23, -0.09 DALYs), respectively].

CONCLUSION

In this Dutch study, of various dietary patterns evaluated, higher adherence to the mMDS or prudent dietary pattern was associated with a lower disease burden as assessed by DALYs.

A systematic review and meta-analysis of 130,000 individuals shows smoking does not modify the association of APOE genotype on risk of coronary heart disease

Background

Conflicting evidence exists on whether smoking acts as an effect modifier of the association between APOE genotype and risk of coronary heart disease (CHD).

Methods and results

We searched PubMed and EMBASE to June 11, 2013 for published studies reporting APOE genotype, smoking status and CHD events and added unpublished data from population cohorts. We tested for presence of effect modification by smoking status in the relationship between APOE genotype and risk of CHD using likelihood ratio test.

In total 13 studies (including unpublished data from eight cohorts) with 10,134 CHD events in 130,004 individuals of European descent were identified. The odds ratio (OR) for CHD risk from APOE genotype (ε4 carriers versus non-carriers) was 1.06 (95% confidence interval (CI): 1.01, 1.12) and for smoking (present vs. past/never smokers) was OR 2.05 (95%CI: 1.95, 2.14). When the association between APOE genotype and CHD was stratified by smoking status, compared to non-ε4 carriers, ε4 carriers had an OR of 1.11 (95%CI: 1.02, 1.21) in 28,789 present smokers and an OR of 1.04 (95%CI 0.98, 1.10) in 101,215 previous/never smokers, with no evidence of effect modification (P-value for heterogeneity = 0.19). Analysis of pack years in individual participant data of >60,000 with adjustment for cardiovascular traits also failed to identify evidence of effect modification.

Conclusions

In the largest analysis to date, we identified no evidence for effect modification by smoking status in the association between APOE genotype and risk of CHD.

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We examined evidence for an interaction between APOE genotype, smoking and risk of coronary heart disease.

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This was conducted in the largest meta-analysis of published and unpublished data sets to date (>130,000 individuals).

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Our analysis did not identify evidence of interaction.

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These findings bring into question presence of a clinically meaningful interaction between APOE genotype and smoking.

A posteriori dietary patterns: how many patterns to retain?

Principal component analysis (PCA) and cluster analysis are used frequently to derive dietary patterns. Decisions on how many patterns to extract are primarily based on subjective criteria, whereas different solutions vary in their food-group composition and perhaps association with disease outcome. Literature on reliability of dietary patterns is scarce, and previous studies validated only 1 preselected solution. Therefore, we assessed reliability of different pattern solutions ranging from 2 to 6 patterns, derived from the aforementioned methods. A validated food frequency questionnaire was administered at baseline (1993-1997) to 39,678 participants in the European Prospective Investigation into Cancer and Nutrition-The Netherlands (EPIC-NL) cohort. Food items were grouped into 31 food groups for dietary pattern analysis. The cohort was randomly divided into 2 halves, and dietary pattern solutions derived in 1 sample through PCA were replicated through confirmatory factor analysis in sample 2. For cluster analysis, cluster stability and split-half reproducibility were assessed for various solutions. With PCA, we found the 3-component solution to be best replicated, although all solutions contained ≥1 poorly confirmed component. No quantitative criterion was in agreement with the results. Associations with disease outcome (coronary heart disease) differed between the component solutions. For all cluster solutions, stability was excellent and deviations between samples was negligible, indicating good reproducibility. All quantitative criteria identified the 2-cluster solution as optimal. Associations with disease outcome were comparable for different cluster solutions. In conclusion, reliability of obtained dietary patterns differed considerably for different solutions using PCA, whereas cluster analysis derived generally stable, reproducible clusters across different solutions. Quantitative criteria for determining the number of patterns to retain were valuable for cluster analysis but not for PCA. Associations with disease risk were influenced by the number of patterns that are retained, especially when using PCA. Therefore, studies on associations between dietary patterns and disease risk should report reasons to choose the number of retained patterns.

Circulating desphospho-uncarboxylated matrix γ-carboxyglutamate protein and the risk of coronary heart disease and stroke

BACKGROUND

High vitamin K intake is associated with a reduced risk of coronary heart disease (CHD). This is thought to be mediated by increased activation of the vitamin K-dependent matrix γ-carboxyglutamate protein (MGP). Desphospho-uncarboxylated MGP (dp-ucMGP) is associated with both vitamin K status and vascular calcification. However, the association of dp-ucMGP with CHD and stroke in the general population has not been investigated to date.

OBJECTIVE

To investigate the association of dp-ucMGP with incident CHD or stroke.

METHODS

A prospective case-cohort study with a representative baseline sample of 1406 participants and 1154 and 380 incident cases of CHD and stroke, respectively, was nested within the EPIC-NL study. Circulating dp-ucMGP levels were measured with ELISA in baseline plasma samples. The incidence rates of fatal and non-fatal CHD and stroke were obtained by linkage to national registers. Cox proportional hazard models were used to calculate hazard ratios (HRs) per standard deviation (SD) and per quartile of circulating dp-ucMGP levels.

RESULTS AND CONCLUSION

The average follow-up was 11.5 years. Levels of dp-ucMGP were not associated with CHD risk, with an HR per SD of 1.00 (95% confidence interval [CI] 0.93-1.07) and an HRQ4 vs. Q1 of 0.94 (95% CI 0.79-1.13) after adjustment for cardiovascular risk factors. There was no association of dp-ucMGP stroke risk (HRSD  0.98, 95% CI 0.90-1.08; and HRQ4 vs. Q1  1.09, 95% CI 0.78-1.51). This study could not confirm that high dp-ucMGP levels, reflecting poor vitamin K status, are associated with increased CHD or stroke risk in the general population.

Mortality and cancer incidence in the EPIC-NL cohort: impact of the healthy volunteer effect

BACKGROUND

Prospective cohort studies recruit relatively healthy population samples, resulting in lower morbidity and mortality rates than in the source population. This is known as the healthy volunteer effect. The aim of this study was to define the magnitude and the development over time of the healthy volunteer effect in the EPIC-NL cohort.

METHODS

We studied mortality rates in the EPIC-NL cohort, which comprises 37 551 men and women aged 20-70 years at recruitment in 1993-97. The date and cause of death of deceased participants until 2010 were obtained through linkage with the municipal registry and Statistics Netherlands. Standardized mortality ratios (SMRs) were computed by dividing the observed number of deaths by the number of deaths expected from the general Dutch population. Additionally, standardized incidence ratios were calculated to compare cancer incidence.

RESULTS

After an average follow-up of 14.9 years, 3029 deaths were documented. Overall mortality in men [SMR 73.5%, 95% confidence interval (CI): 68.1-79.3] and women (SMR 65.9%, 95% CI: 63.2-68.6) was lower compared with the general population for the whole follow-up period. The SMRs clearly increased over the follow-up period. Among women, the SMR was lower for death due to cardiovascular diseases than death due to cancer. Cancer incidence was also lower in EPIC-NL than in the general population (SMR 78.3 and 82.7% for men and women, respectively).

CONCLUSION

The results show a healthy volunteer effect in the EPIC-NL cohort, which tapers off with longer follow-up. Therefore, in the first years of follow-up, power might not be sufficient to detect small associations.

Reducing our environmental footprint and improving our health: greenhouse gas emission and land use of usual diet and mortality in EPIC-NL: a prospective cohort study

BACKGROUND

Food choices influence health status, but also have a great impact on the environment. The production of animal-derived foods has a high environmental burden, whereas the burden of refined carbohydrates, vegetables and fruit is low. The aim of this study was to investigate the associations of greenhouse gas emission (GHGE) and land use of usual diet with mortality risk, and to estimate the effect of a modelled meat substitution scenario on health and the environment.

METHODS

The usual diet of 40011 subjects in the EPIC-NL cohort was assessed using a food frequency questionnaire. GHGE and land use of food products were based on life cycle analysis. Cox proportional hazard ratios (HR) were calculated to determine relative mortality risk. In the modelled meat-substitution scenario, one-third (35 gram) of the usual daily meat intake (105 gram) was substituted by other foods.

RESULTS

During a follow-up of 15.9 years, 2563 deaths were registered. GHGE and land use of the usual diet were not associated with all-cause or with cause-specific mortality. Highest vs. lowest quartile of GHGE and land use adjusted hazard ratios for all-cause mortality were respectively 1.00 (95% CI: 0.86-1.17) and 1.05 (95% CI: 0.89-1.23). Modelled substitution of 35 g/d of meat with vegetables, fruit-nuts-seeds, pasta-rice-couscous, or fish significantly increased survival rates (6-19%), reduced GHGE (4-11%), and land use (10-12%).

CONCLUSIONS

There were no significant associations observed between dietary-derived GHGE and land use and mortality in this Dutch cohort. However, the scenario-study showed that substitution of meat with other major food groups was associated with a lower mortality risk and a reduced environmental burden. Especially when vegetables, fruit-nuts-seeds, fish, or pasta-rice-couscous replaced meat.

Novel genetic approach to investigate the role of plasma secretory phospholipase A2 (sPLA2)-V isoenzyme in coronary heart disease: modified Mendelian randomization analysis using PLA2G5 expression levels

BACKGROUND

Secretory phospholipase A2 (sPLA2) enzymes are considered to play a role in atherosclerosis. sPLA2 activity encompasses several sPLA2 isoenzymes, including sPLA2-V. Although observational studies show a strong association between elevated sPLA2 activity and CHD, no assay to measure sPLA2-V levels exists, and the only evidence linking the sPLA2-V isoform to atherosclerosis progression comes from animal studies. In the absence of an assay that directly quantifies sPLA2-V levels, we used PLA2G5 mRNA levels in a novel, modified Mendelian randomization approach to investigate the hypothesized causal role of sPLA2-V in coronary heart disease (CHD) pathogenesis.

METHODS AND RESULTS

Using data from the Advanced Study of Aortic Pathology, we identified the single-nucleotide polymorphism in PLA2G5 showing the strongest association with PLA2G5 mRNA expression levels as a proxy for sPLA2-V levels. We tested the association of this SNP with sPLA2 activity and CHD events in 4 prospective and 14 case-control studies with 27 230 events and 70 500 controls. rs525380C>A showed the strongest association with PLA2G5 mRNA expression (P=5.1×10(-6)). There was no association of rs525380C>A with plasma sPLA2 activity (difference in geometric mean of sPLA2 activity per rs525380 A-allele 0.4% (95% confidence intervals [-0.9%, 1.6%]; P=0.56). In meta-analyses, the odds ratio for CHD per A-allele was 1.02 (95% confidence intervals [0.99, 1.04]; P=0.20).

CONCLUSIONS

This novel approach for single-nucleotide polymorphism selection for this modified Mendelian randomization analysis showed no association between rs525380 (the lead single-nucleotide polymorphism for PLA2G5 expression, a surrogate for sPLA2-V levels) and CHD events. The evidence does not support a causal role for sPLA2-V in CHD.

Causal effects of body mass index on cardiometabolic traits and events: a Mendelian randomization analysis

Elevated body mass index (BMI) associates with cardiometabolic traits on observational analysis, yet the underlying causal relationships remain unclear. We conducted Mendelian randomization analyses by using a genetic score (GS) comprising 14 BMI-associated SNPs from a recent discovery analysis to investigate the causal role of BMI in cardiometabolic traits and events. We used eight population-based cohorts, including 34,538 European-descent individuals (4,407 type 2 diabetes (T2D), 6,073 coronary heart disease (CHD), and 3,813 stroke cases). A 1 kg/m(2) genetically elevated BMI increased fasting glucose (0.18 mmol/l; 95% confidence interval (CI) = 0.12-0.24), fasting insulin (8.5%; 95% CI = 5.9-11.1), interleukin-6 (7.0%; 95% CI = 4.0-10.1), and systolic blood pressure (0.70 mmHg; 95% CI = 0.24-1.16) and reduced high-density lipoprotein cholesterol (-0.02 mmol/l; 95% CI = -0.03 to -0.01) and low-density lipoprotein cholesterol (LDL-C; -0.04 mmol/l; 95% CI = -0.07 to -0.01). Observational and causal estimates were directionally concordant, except for LDL-C. A 1 kg/m(2) genetically elevated BMI increased the odds of T2D (odds ratio [OR] = 1.27; 95% CI = 1.18-1.36) but did not alter risk of CHD (OR 1.01; 95% CI = 0.94-1.08) or stroke (OR = 1.03; 95% CI = 0.95-1.12). A meta-analysis incorporating published studies reporting 27,465 CHD events in 219,423 individuals yielded a pooled OR of 1.04 (95% CI = 0.97-1.12) per 1 kg/m(2) increase in BMI. In conclusion, we identified causal effects of BMI on several cardiometabolic traits; however, whether BMI causally impacts CHD risk requires further evidence.

All-cause mortality risk of metabolically healthy abdominal obese individuals: the EPIC-MORGEN study

OBJECTIVE

It appears that a certain proportion of obese individuals have a normal metabolic profile despite having excess weight. Whether these so-called "metabolically healthy" obese express lower disease and mortality risks than "metabolically unhealthy" obese is still unclear. The mortality risk of "metabolically healthy" abdominal obese (MHAO) individuals was investigated.

DESIGN AND METHODS

Prospective cohort study (EPIC-MORGEN) among 22,654 individuals aged 20-59 years followed for an average of 13.4 years (SD 2.3). MHAO was assessed at baseline (1993-1997) and defined as abdominal obesity (waist circumference ≥102 cm/≥88 cm (men/women)) with normal glucose, blood pressure, and plasma lipids. All-cause mortality risks adjusted for age and sex were estimated using Cox proportional hazards models.

RESULTS

Individuals who were "metabolically healthy" nonabdominal obese (MHNAO) comprised the reference group. As compared to MHNAO, mortality risk for MHAO was around 40% higher (Hazard ratio (HR) 1.43; 95% confidence interval (CI): 1.00-2.04) and of the same magnitude as that for "metabolically unhealthy" nonabdominal obese (MUNAO) (HR 1.31; 95% CI: 1.08-1.59). The HR for MUAO was 1.99 (95% CI: 1.62-2.43).

CONCLUSIONS

Mortality risk of MHAO individuals was significantly higher than that of MHNAO individuals and lower than, but not statistically significantly different from, that of MUAO individuals.

Intake of dietary phylloquinone and menaquinones and risk of stroke

Background

Dietary vitamin K intake is thought to decrease the risk of cardiovascular disease (CVD) by reducing vascular calcification, although vitamin K is also involved in coagulation. Studies investigating the association between phylloquinone intake and risk of stroke are scarce, and the relation with menaquinones has not been investigated to date.

Methods and Results

We investigated the association between intake of phylloquinone and menaquinones and stroke in a prospective cohort of 35 476 healthy subjects. Information on occurrence of stroke was obtained by linkage to national registries, and stroke was further specified into ischemic and hemorrhagic stroke. Vitamin K intake was estimated using a validated food‐frequency questionnaire. Multivariate Cox proportional hazards models adjusted for cardiovascular risk factors, lifestyle, and other dietary factors were used to estimate the associations. During a follow‐up of 12.1±2.1 years, 580 incident cases of stroke were identified, 163 of which were hemorrhagic and 324 were ischemic. Phylloquinone intake was not associated with risk of stroke with a hazard ratio (HR) of 1.09 (95% CI: 0.85 to 1.40, P_trend 0.41) for the highest versus lowest quartile. For intake of menaquinones similar results were found, with an HR_{Q4 versus Q1} of 0.99 (95% CI: 0.75 to 1.29, P_trend 0.82). When specifying hemorrhagic and ischemic stroke or menaquinone subtypes, no significant associations were detected.

Conclusion

In our study, neither dietary phylloquinone nor dietary menaquinones intake were associated with stroke risk.

Type 2 diabetes patients' preferences and willingness to pay for lifestyle programs: a discrete choice experiment

BACKGROUND

Participation rates of lifestyle programs among type 2 diabetes mellitus (T2DM) patients are less than optimal around the globe. Whereas research shows notable delays in the development of the disease among lifestyle program participants. Very little is known about the relative importance of barriers for participation as well as the willingness of T2DM patients to pay for participation in such programs. The aim of this study was to identify the preferences of T2DM patients with regard to lifestyle programs and to calculate participants' willingness to pay (WTP) as well as to estimate the potential participation rates of lifestyle programs.

METHODS

A Discrete Choice Experiment (DCE) questionnaire assessing five different lifestyle program attributes was distributed among 1250 Dutch adults aged 35-65 years with T2DM, 391 questionnaires (31%) were returned and included in the analysis. The relative importance of the program attributes (i.e., meal plan, physical activity (PA) schedule, consultation structure, expected program outcome and out-of-pocket costs) was determined using panel-mixed logit models. Based on the retrieved attribute estimates, patients' WTP and potential participation rates were determined.

RESULTS

The out-of-pocket costs (β = -0.75, P < .001), consultation structure (β = -0.46, P < .001) and expected outcome (β =0.72, P < .001) were the most important factors for respondents when deciding whether to participate in a lifestyle program. Respondents were willing to pay €128 per year for individual instead of group consultation and €97 per year for 10 kilograms anticipated weight loss. Potential participation rates for different lifestyle-program scenarios ranged between 48.5% and 62.4%.

CONCLUSIONS

When deciding whether to participate in a lifestyle program, T2DM patients are mostly driven by low levels of out-of-pocket costs. Thereafter, they prefer individual consultation and high levels of anticipated outcomes with respect to weight loss.

Welding and lung cancer in a pooled analysis of case-control studies

Several epidemiologic studies have indicated an increased risk of lung cancer among welders. We used the SYNERGY project database to assess welding as a risk factor for developing lung cancer. The database includes data on 15,483 male lung cancer cases and 18,388 male controls from 16 studies in Europe, Canada, China, and New Zealand conducted between 1985 and 2010. Odds ratios and 95% confidence intervals between regular or occasional welding and lung cancer were estimated, with adjustment for smoking, age, study center, and employment in other occupations associated with lung cancer risk. Overall, 568 cases and 427 controls had ever worked as welders and had an odds ratio of developing lung cancer of 1.44 (95% confidence interval: 1.25, 1.67) with the odds ratio increasing for longer duration of welding. In never and light smokers, the odds ratio was 1.96 (95% confidence interval: 1.37, 2.79). The odds ratios were somewhat higher for squamous and small cell lung cancers than for adenocarcinoma. Another 1,994 cases and 1,930 controls had ever worked in occupations with occasional welding. Work in any of these occupations was associated with some elevation of risk, though not as much as observed in regular welders. Our findings lend further support to the hypothesis that welding is associated with an increased risk of lung cancer.

Matrix Gla protein species and risk of cardiovascular events in type 2 diabetic patients

OBJECTIVE

To investigate the relationship of circulating matrix Gla protein (MGP) species with incident cardiovascular disease (CVD) or coronary heart disease (CHD) in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

EPIC-NL is a prospective cohort study among 40,011 Dutch men and women. At baseline (1993-1997), 518 participants were known to have type 2 diabetes. MGP levels were measured by ELISA techniques in baseline plasma samples. The incidence of fatal and nonfatal CVD and CVD subtypes-CHD, peripheral arterial disease (PAD), heart failure, and stroke-were obtained by linkage to national registers. Cox proportional hazard models were used to calculate hazard ratios (HRs), adjusted for sex, waist-to-hip ratio, physical activity, and history of CVD.

RESULTS

During a median 11.2 years of follow-up, 160 cases of CVD were documented. Higher circulating desphospho-uncarboxylated MGP (dp-ucMGP) levels were significantly associated with higher risk of CVD, with an HR per SD (HRSD) of 1.21 (95% CI 1.06-1.38), PAD (HRSD 1.32 [95% CI 1.07-1.65]), and heart failure (HRSD 1.75 [95% CI 1.42-2.17]) after adjustment. Higher circulating dp-ucMGP levels were not related to risk of CHD (HRSD 1.12 [95% CI 0.94-1.34]) or stroke (HRSD 1.05 [95% CI 0.73-1.49]). Circulating desphospho-carboxylated MGP and circulating total-uncarboxylated MGP levels were not associated with CVD or CVD subtypes.

CONCLUSIONS

High dp-ucMGP levels were associated with increased CVD risk among type 2 diabetic patients, especially with the subtypes PAD and heart failure, while other MGP species were not related to CVD risk. These results suggest that a poor vitamin K status is associated with increased CVD risk.

Development of methodology for disability-adjusted life years (DALYs) calculation based on real-life data

Background

Disability-Adjusted Life Years (DALYs) have the advantage that effects on total health instead of on a specific disease incidence or mortality can be estimated. Our aim was to address several methodological points related to the computation of DALYs at an individual level in a follow-up study.

Methods

DALYs were computed for 33,507 men and women aged 20–70 years when participating in the EPIC-NL study in 1993–7. DALYs are the sum of the Years Lost due to Disability (YLD) and the Years of Life Lost (YLL) due to premature mortality. Premature mortality was defined as death before the estimated date of individual Life Expectancy (LE). Different methods to compute LE were compared as well as the effect of different follow-up periods using a two-part model estimating the effect of smoking status on health as an example.

Results

During a mean follow-up of 12.4 years, there were 69,245 DALYs due to years lived with a disease or premature death. Current-smokers had lost 1.28 healthy years of their life (1.28 DALYs 95%CI 1.10; 1.46) compared to never-smokers. The outcome varied depending on the method used for estimating LE, completeness of disease and mortality ascertainment and notably the percentage of extinction (duration of follow-up) of the cohort.

Conclusion

We conclude that the use of DALYs in a cohort study is an appropriate way to assess total disease burden in relation to a determinant. The outcome is sensitive to the LE calculation method and the follow-up duration of the cohort.

Quantifying the contributions of behavioral and biological risk factors to socioeconomic disparities in coronary heart disease incidence: the MORGEN study

Quantifying the impact of different modifiable behavioral and biological risk factors on socioeconomic disparities in coronary heart disease (CHD) may help inform targeted, population-specific strategies to reduce the unequal distribution of the disease. Previous studies have used analytic approaches that limit our ability to disentangle the relative contributions of these risk factors to CHD disparities. The goal of this study was to assess mediation of the effect of low education on incident CHD by multiple risk factors simultaneously. Analyses are based on 15,067 participants of the Dutch Monitoring Project on Risk Factors for Chronic Diseases aged 20-65 years examined 1994-1997 and followed for events until January 1, 2008. Path analysis was used to quantify and test mediation of the low education-CHD association by behavioral (current cigarette smoking, heavy alcohol use, poor diet, and physical inactivity) and biological (obesity, hypertension, diabetes, and hypercholesterolemia) risk factors. Behavioral and biological risk factors accounted for 56.6 % (95 % CI 42.6-70.8 %) of the low education-incident CHD association. Smoking was the strongest mediator, accounting for 27.3 % (95 % CI 17.7-37.4 %) of the association, followed by obesity (10.2 %; 95 % CI 4.5-16.1 %), physical inactivity (6.3 %; 95 % CI 2.7-10.0 %), and hypertension (5.3 %; 95 % CI: 2.8-8.0 %). In summary, in a Dutch cohort, the majority of the relationship between low education and incident CHD was mediated by traditional behavioral and biological risk factors. Addressing barriers to smoking cessation, blood pressure and weight management, and physical activity may be the most effective approaches to eliminating socioeconomic inequalities in CHD.

Adherence to the WHO's healthy diet indicator and overall cancer risk in the EPIC-NL cohort

Background

A healthy dietary pattern defined by international recommendations of the World Health Organisation (WHO) has been shown to reduce overall mortality risk. It is unknown whether this healthy dietary pattern is associated with overall cancer incidence.

Design

In total 35,355 men and women within the Dutch European Prospective Investigation into Cancer and Nutrition-cohort were followed for cancer occurrence. Diet was assessed through a validated food-frequency questionnaire. We computed a dietary score for all participants based on the seven WHO dietary guidelines for the prevention of chronic diseases (Healthy Diet Indicator (HDI)). We used the existing HDI score based on the 1990 WHO guidelines, and adapted it to meet with the 2002 WHO guidelines. Multivariate-adjusted Cox proportional hazards analysis was used to examine the association between adherence to the HDI and subsequent overall cancer risk.

Results

A number of 3,007 new cancers were identified during a mean follow-up of 12.7 years. Adherence to the HDI was not associated with a reduced overall cancer risk. The hazard ratio (HR) of overall cancer associated with a one-point increment of the HDI was 0.96 (95% CI 0.89–1.03) in men, and 1.00 (95% CI 0.96–1.04) in women. Adherence to the HDI was not associated with smoking-related cancer ((HR men: 0.94 (95% CI 0.84–1.04); HR women: 1.00 (95% CI 0.94–1.07)), or alcohol-related cancer ((HR men: 1.02 (95% CI 0.87–1.20); HR women: 1.03 (95% CI 0.98–1.08)).

Conclusions

Greater adherence to the WHO’s Healthy Diet Indicator, a dietary pattern for prevention of chronic diseases, was not associated with reduced overall, smoking-related or alcohol-related cancer risk in men or women.

The contribution of diet and lifestyle to socioeconomic inequalities in cardiovascular morbidity and mortality

BACKGROUND

The role of differences in diet on the relationship between socioeconomic factors and cardiovascular diseases remains unclear. We studied the contribution of diet and other lifestyle factors to the explanation of socioeconomic inequalities in cardiovascular diseases.

METHODS

We prospectively examined the incidence of coronary heart disease (CHD) and stroke events amongst 33,106 adults of the EPIC-NL cohort. Education and employment status indicated socioeconomic status. We used Cox proportional models to estimate hazard ratios ((HR (95% confidence intervals)) for the association of socioeconomic factors with CHD and stroke and the contribution of diet and lifestyle.

RESULTS

During 12 years of follow-up, 1617 cases of CHD and 531 cases of stroke occurred. The risks of CHD and stroke were higher in lowest (HR=1.98 (1.67;2.35); HR=1.55 (1.15;2.10)) and lower (HR=1.50 (1.29;1.75); HR=1.42 (1.08;1.86)) educated groups than in the highest. Unemployed and retired subjects more often suffered from CHD (HR=1.37 (1.19;1.58); HR=1.20 (1.05;1.37), respectively), but not from stroke, than the employed. Diet and lifestyle, mainly smoking and alcohol, explained more than 70% of the educational differences in CHD and stroke and 65% of employment status variation in CHD. Diet explained more than other lifestyle factors of educational and employment status differences in CHD and stroke (36% to 67% vs. 9% to 27%).

CONCLUSION

The socioeconomic distribution of diet, smoking and alcohol consumption largely explained the inequalities in CHD and stroke in the Netherlands. These findings need to be considered when developing policies to reduce socioeconomic inequalities in cardiovascular diseases.

Sufficient sleep duration contributes to lower cardiovascular disease risk in addition to four traditional lifestyle factors: the MORGEN study

BACKGROUND

The contribution of sufficient sleep duration to lower CVD risk in addition to sufficient physical activity, a healthy diet, (moderate) alcohol consumption, and non-smoking has not been investigated yet.

DESIGN

The MORGEN study is a prospective cohort study including 8128 men and 9759 women aged 20-65 years, free of CVD at baseline.

METHODS

Sufficient physical activity (≥3.5 h/week cycling or sports), a healthy diet (Mediterranean Diet Score ≥5), (moderate) alcohol consumption (≥1 beverage/month), non-smoking, and sufficient sleep duration (≥7 hours) were assessed by self-administered questionnaires between 1994 and 1997. Cardiovascular morbidity and mortality were ascertained through linkage with national registers. Hazard ratios and preventable proportions were calculated adjusted for age, sex, and educational level.

RESULTS

During 10-14 years of follow up, 607 composite CVD events (fatal CVD, nonfatal myocardial infarction and stroke) occurred, of which 129 were fatal. Those with the four traditional healthy lifestyle factors had a 57% lower risk of composite CVD (HR 0.43, 95% CI 0.31-0.59) and a 67% lower risk of fatal CVD (HR 0.33, 95% CI 0.16-0.68) compared with those with none or one healthy lifestyle factor. Sleeping sufficiently in addition to the four traditional lifestyle factors resulted in a 65% lower risk of composite CVD (HR 0.35, 95% CI 0.23-0.52), and an 83% lower risk of fatal CVD (HR 0.17, 95% CI 0.07-0.43).

CONCLUSIONS

Sufficient sleep and adherence to all four traditional healthy lifestyle factors was associated with lower CVD risk. When sufficient sleep duration was added to the traditional lifestyle factors, the risk of CVD was further reduced.

Age-related changes in mammographic density and breast cancer risk

High mammographic density is a strong breast cancer risk factor. Density normally declines with aging. We investigated whether the level of decline in mammographic density is related to breast cancer risk using a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Prospect cohort. This cohort was recruited among participants of a population-based breast cancer screening program in the Netherlands between 1993 and 1997. We examined whether age-related changes in mammographic density were different for 533 cases and 1,367 controls who were 49-69 years of age at the time of recruitment into the cohort. We used mixed models with linear and quadratic terms for age and interaction terms between age terms and case status. The percent mammographic density at the first available mammogram was higher for cases than for controls (25.2% vs. 22.5%) (P = 0.003). The average decline in density over 10 years was 11% in both cases and controls (P = 0.56). When studying changes among 4 categories of density, we saw some indication that large changes may influence breast cancer risk. Although no difference was seen in the average decline, we cannot exclude that large changes may influence breast cancer risk.

Metabolic syndrome model definitions predicting type 2 diabetes and cardiovascular disease

OBJECTIVE

Metabolic syndrome (MetS) is a cluster of abdominal obesity, hyperglycemia, hypertension, and dyslipidemia, which increases the risk for type 2 diabetes and cardiovascular diseases (CVDs). Some argue that MetS is not a single disorder because the traditional MetS features do not represent one entity, and they would like to exclude features from MetS. Others would like to add additional features in order to increase predictive ability of MetS. The aim of this study was to identify a MetS model that optimally predicts type 2 diabetes and CVD while still representing a single entity.

RESEARCH DESIGN AND METHODS

In a random sample (n = 1,928) of the EPIC-NL cohort and a subset of the EPIC-NL MORGEN study (n = 1,333), we tested the model fit of several one-factor MetS models using confirmatory factor analysis. We compared predictive ability for type 2 diabetes and CVD of these models within the EPIC-NL case-cohort study of 545 incident type 2 diabetic subjects, 1,312 incident CVD case subjects, and the random sample, using survival analyses and reclassification.

RESULTS

The standard model, representing the current MetS definition (EPIC-NL comparative fit index [CFI] = 0.95; MORGEN CFI = 0.98); the standard model excluding blood pressure (EPIC-NL CFI = 0.95; MORGEN CFI = 1.00); and the standard model extended with hsCRP (EPIC-NL CFI = 0.95) had an acceptable model fit. The model extended with hsCRP predicted type 2 diabetes (integral discrimination index [IDI]: 0.34) and CVD (IDI: 0.07) slightly better than did the standard model.

CONCLUSIONS

It seems valid to represent the traditional MetS features by a single entity. Extension of this entity with hsCRP slightly improves predictive ability for type 2 diabetes and CVD.

Plasma uric acid is associated with increased risk of type 2 diabetes independent of diet and metabolic risk factors

Current evidence suggests a direct association of uric acid with diabetes risk, but it is still unclear whether this is independent of risk factors such as obesity and diet. We aimed to investigate whether plasma uric acid concentrations are independently associated with incident type 2 diabetes and to investigate the role of a uric acid-related dietary pattern in this association. We used a case-cohort nested in the European Prospective Investigation into Cancer and Nutrition-Netherlands study. The study included 2318 subcohort members and 845 incident diabetes cases, with a mean follow-up of 10 y. At baseline, blood samples were taken and diet was assessed using a validated FFQ. A uric acid-related dietary pattern was derived with reduced rank regression. Diabetes was mainly self-reported and verified against general practitioner records. Plasma uric acid was (mean ± SD) 231 ± 54.6 μmol/L in the subcohort. After adjustment for established diabetes risk factors such as age, the HR (highest vs. lowest quartile of uric acid) for diabetes was 4.36 (95% CI: 3.22, 5.90). Further adjustment for adiposity attenuated the HR to 1.86 (95% CI: 1.32, 2.62). Additional adjustment for hypertension and biochemical markers, such as TG, slightly attenuated the association [HR = 1.43 (95% CI: 0.97, 2.10)]. A uric acid-related dietary pattern did not confound the association. In conclusion, this study supports that high uric acid concentrations are associated with increased diabetes risk, although a large part of the association can be explained by the degree of adiposity.

Liver function tests and risk prediction of incident type 2 diabetes: evaluation in two independent cohorts

Background

Liver function tests might predict the risk of type 2 diabetes. An independent study evaluating utility of these markers compared with an existing prediction model is yet lacking.

Methods and Findings

We performed a case-cohort study, including random subcohort (6.5%) from 38,379 participants with 924 incident diabetes cases (the Dutch contribution to the European Prospective Investigation Into Cancer and Nutrition, EPIC-NL, the Netherlands), and another population-based cohort study including 7,952 participants with 503 incident cases (the Prevention of Renal and Vascular End-stage Disease, PREVEND, Groningen, the Netherlands). We examined predictive value of combination of the Liver function tests (gamma-glutamyltransferase, alanine aminotransferase, aspartate aminotransferase and albumin) above validated models for 7.5-year risk of diabetes (the Cooperative Health Research in the Region of Augsburg, the KORA study). Basic model includes age, sex, BMI, smoking, hypertension and parental diabetes. Clinical models additionally include glucose and uric acid (model1) and HbA1c (model2). In both studies, addition of Liver function tests to the basic model improved the prediction (C-statistic by∼0.020; NRI by∼9.0%; P<0.001). In the EPIC-NL case-cohort study, addition to clinical model1 resulted in statistically significant improvement in the overall population (C-statistic = +0.009; P<0.001; NRI = 8.8%; P<0.001), while addition to clinical model 2 yielded marginal improvement limited to men (C-statistic = +0.007; P = 0.06; NRI = 3.3%; P = 0.04). In the PREVEND cohort study, addition to clinical model 1 resulted in significant improvement in the overall population (C-statistic change = 0.008; P = 0.003; NRI = 3.6%; P = 0.03), with largest improvement in men (C-statistic change = 0.013; P = 0.01; NRI = 5.4%; P = 0.04). In PREVEND, improvement compared to clinical model 2 could not be tested because of lack of HbA1c data.

Conclusions

Liver function tests modestly improve prediction for medium-term risk of incident diabetes above basic and extended clinical prediction models, only if no HbA1c is incorporated. If data on HbA1c are available, Liver function tests have little incremental predictive value, although a small benefit may be present in men.

Single nucleotide polymorphisms (SNPs) involved in insulin resistance, weight regulation, lipid metabolism and inflammation in relation to metabolic syndrome: an epidemiological study

BACKGROUND

Mechanisms involved in metabolic syndrome (MetS) development include insulin resistance, weight regulation, inflammation and lipid metabolism. Aim of this study is to investigate the association of single nucleotide polymorphisms (SNPs) involved in these mechanisms with MetS.

METHODS

In a random sample of the EPIC-NL study (n = 1886), 38 SNPs associated with waist circumference, insulin resistance, triglycerides, HDL cholesterol and inflammation in genome wide association studies (GWAS) were selected from the 50K IBC array and one additional SNP was measured with KASPar chemistry. The five groups of SNPs, each belonging to one of the metabolic endpoints mentioned above, were associated with MetS and MetS-score using Goeman's global test. For groups of SNPs significantly associated with the presence of MetS or MetS-score, further analyses were conducted.

RESULTS

The group of waist circumference SNPs was associated with waist circumference (P=0.03) and presence of MetS (P=0.03). Furthermore, the group of SNPs related to insulin resistance was associated with MetS score (P<0.01), HDL cholesterol (P<0.01), triglycerides (P<0.01) and HbA1C (P=0.04). Subsequent analyses showed that MC4R rs17782312, involved in weight regulation, and IRS1 rs2943634, related to insulin resistance were associated with MetS (OR 1.16, 95%CI 1.02-1.32 and OR 0.88, 95% CI 0.79; 0.97, respectively). The groups of inflammation and lipid SNPs were neither associated with presence of MetS nor with MetS score.

CONCLUSIONS

In this study we found support for the hypothesis that weight regulation and insulin metabolism are involved in MetS development.MC4R rs17782312 and IRS1 rs2943634 may explain part of the genetic variation in MetS.

Mediterranean style diet and 12-year incidence of cardiovascular diseases: the EPIC-NL cohort study

Background

A recent meta-analysis showed that a Mediterranean style diet may protect against cardiovascular diseases (CVD). Studies on disease-specific associations are limited. We evaluated the Mediterranean Diet Score (MDS) in relation to incidence of total and specific CVDs.

Methods

The EPIC-NL Study is a cohort of 40,011 men and women aged 20–70 years, examined between 1993 and 1997, with 10–15 years of follow-up. Diet was assessed with a validated food frequency questionnaire and the MDS was based on the daily intakes of vegetables, fruits, legumes and nuts, grains, fish, fatty acids, meat, dairy, and alcohol. Cardiovascular morbidity and mortality were ascertained through linkage with national registries. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) adjusted for age, sex, cohort, smoking, physical activity, total energy intake, and educational level.

Results

In 34,708 participants free of CVD at baseline, 4881 CVD events occurred, and 487 persons died from CVD. A two unit increment in MDS (range 0–9) was inversely associated with fatal CVD (HR: 0.78; 95%CI: 0.69–0.88), total CVD (HR: 0.95 (0.91–0.98)), myocardial infarction (HR: 0.86 (0.79–0.93)), stroke (HR: 0.88 (0.78–1.00)), and pulmonary embolism (HR: 0.74 (0.59–0.92)). The MDS was not related to incident angina pectoris, transient ischemic attack and peripheral arterial disease.

Conclusion

Better adherence to a Mediterranean style diet was more strongly associated with fatal CVD than with total CVD. Disease specific associations were strongest for incident myocardial infarction, stroke and pulmonary embolism.

Prediction models for risk of developing type 2 diabetes: systematic literature search and independent external validation study

OBJECTIVE

To identify existing prediction models for the risk of development of type 2 diabetes and to externally validate them in a large independent cohort.

DATA SOURCES

Systematic search of English, German, and Dutch literature in PubMed until February 2011 to identify prediction models for diabetes.

DESIGN

Performance of the models was assessed in terms of discrimination (C statistic) and calibration (calibration plots and Hosmer-Lemeshow test).The validation study was a prospective cohort study, with a case cohort study in a random subcohort.

SETTING

Models were applied to the Dutch cohort of the European Prospective Investigation into Cancer and Nutrition cohort study (EPIC-NL).

PARTICIPANTS

38,379 people aged 20-70 with no diabetes at baseline, 2506 of whom made up the random subcohort.

OUTCOME MEASURE

Incident type 2 diabetes.

RESULTS

The review identified 16 studies containing 25 prediction models. We considered 12 models as basic because they were based on variables that can be assessed non-invasively and 13 models as extended because they additionally included conventional biomarkers such as glucose concentration. During a median follow-up of 10.2 years there were 924 cases in the full EPIC-NL cohort and 79 in the random subcohort. The C statistic for the basic models ranged from 0.74 (95% confidence interval 0.73 to 0.75) to 0.84 (0.82 to 0.85) for risk at 7.5 years. For prediction models including biomarkers the C statistic ranged from 0.81 (0.80 to 0.83) to 0.93 (0.92 to 0.94). Most prediction models overestimated the observed risk of diabetes, particularly at higher observed risks. After adjustment for differences in incidence of diabetes, calibration improved considerably.

CONCLUSIONS

Most basic prediction models can identify people at high risk of developing diabetes in a time frame of five to 10 years. Models including biomarkers classified cases slightly better than basic ones. Most models overestimated the actual risk of diabetes. Existing prediction models therefore perform well to identify those at high risk, but cannot sufficiently quantify actual risk of future diabetes.

Parental history of type 2 diabetes and cardiometabolic biomarkers in offspring

BACKGROUND

Parental history of type 2 diabetes (T2D) is associated with cardiometabolic risk. We aimed to investigate the associations of parental history of T2D with cardiometabolic biomarkers and to subsequently investigate to what extent these putative associations were explained by modifiable factors.

MATERIALS AND METHODS

Cross-sectionally, we analysed a random sample of 2001 participants without T2D (20-70 years) from the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL). Plasma levels of 12 biomarkers - total, HDL and LDL-cholesterol, triglycerides, HbA1c, gamma-glutamyltransferase (GGT), alanine aminotransferase (ALT), asparate aminotransferase (AST), albumin, uric acid, creatinine and high-sensitivity CRP (hs-CRP) - were assessed according to categories of parental history of T2D.

RESULTS

In age and sex-adjusted analyses, offspring with parental history of T2D had significantly higher ALT [β = 0·074; 95% confidence interval (95%CI), 0·023-0·126] and AST levels (β = 0·033; 95%CI, 0·001 to 0·066) and a trend towards higher HbA1c (β = 0·011; 95%CI, -0·001 to 0·024) and GGT (β = 0·049; 95%CI, -0·015 to 0·112) levels. Adjustment for diet, smoking, alcohol intake, physical activity and educational level modestly attenuated the magnitude of these associations, but they remained significant for ALT and borderline significant for AST. After further adjustment for adiposity, additional attenuation was observed, but the association remained significant for ALT. Only maternal history of T2D was associated with higher ALT levels. T2D in both parents was associated with increased levels of all liver enzymes, but the association remained significant for GGT after adjustment for adiposity. Overall, the modifiable factors explained 21·2-45·4% of these associations. The contribution of adiposity was 18·2-38·9%.

CONCLUSION

We conclude that parental history of T2D was associated with higher non-fasting levels of liver enzymes in a general population without T2D. Adiposity substantially contributed to these associations. The contribution of diet and lifestyle factors was modest.

Do obesity and parental history of myocardial infarction improve cardiovascular risk prediction?

BACKGROUND

In clinical practice, individuals at increased risk of cardiovascular diseases (CVD) are identified on the basis of age, sex, smoking, blood pressure, and serum total and high-density lipoprotein cholesterol. We examined whether CVD risk prediction improved when obesity (body mass index ≥30 kg/m(2)) and premature (<70 years) parental myocardial infarction (MI) were added to the classical risk factor model.

METHODS

Risk factors were measured in 1993-97 in 12,818 participants (53% female) aged 35-65 in the Dutch MORGEN project. Cases of fatal and nonfatal CVD during 10 years of follow up were identified through record linkage. Classical risk factor equations, obtained by Cox proportional hazard analysis, were extended with obesity, paternal MI, and maternal MI. We calculated the net reclassification index (NRI), a measure for correct reclassification of subjects, to check improvement in risk prediction using 5 and 10% increments in absolute CVD risk.

RESULTS

A CVD event occurred in 280 men and 140 women. Obesity and maternal MI were positively and significantly related to total CVD after adjustment for classical risk factors (both hazard ratios ∼1.5). Adding obesity and parental MI to CVD risk prediction yielded a significant NRI of 4.5% in men and a non-significant NRI of 2.6% in women when 5% risk categories were used. For 10% categories, the NRIs were slightly larger (5.5% and 3.3%, respectively). The improvements in risk prediction were mainly due to obesity.

CONCLUSION

Modest improvements in CVD risk prediction can be obtained when obesity and, to a lesser extent, parental MI are added to the risk function.

Common variants in the type 2 diabetes KCNQ1 gene are associated with impairments in insulin secretion during hyperglycaemic glucose clamp

BACKGROUND

Genome-wide association studies in Japanese populations recently identified common variants in the KCNQ1 gene to be associated with type 2 diabetes. We examined the association of these variants within KCNQ1 with type 2 diabetes in a Dutch population, investigated their effects on insulin secretion and metabolic traits and on the risk of developing complications in type 2 diabetes patients.

METHODOLOGY

The KCNQ1 variants rs151290, rs2237892, and rs2237895 were genotyped in a total of 4620 type 2 diabetes patients and 5285 healthy controls from the Netherlands. Data on macrovascular complications, nephropathy and retinopathy were available in a subset of diabetic patients. Association between genotype and insulin secretion/action was assessed in the additional sample of 335 individuals who underwent a hyperglycaemic clamp.

PRINCIPAL FINDINGS

We found that all the genotyped KCNQ1 variants were significantly associated with type 2 diabetes in our Dutch population, and the association of rs151290 was the strongest (OR 1.20, 95% CI 1.07-1.35, p = 0.002). The risk C-allele of rs151290 was nominally associated with reduced first-phase glucose-stimulated insulin secretion, while the non-risk T-allele of rs2237892 was significantly correlated with increased second-phase glucose-stimulated insulin secretion (p = 0.025 and 0.0016, respectively). In addition, the risk C-allele of rs2237892 was associated with higher LDL and total cholesterol levels (p = 0.015 and 0.003, respectively). We found no evidence for an association of KCNQ1 with diabetic complications.

CONCLUSIONS

Common variants in the KCNQ1 gene are associated with type 2 diabetes in a Dutch population, which can be explained at least in part by an effect on insulin secretion. Furthermore, our data suggest that KCNQ1 is also associated with lipid metabolism.

Gamma-glutamyltransferase, cardiovascular disease and mortality in individuals with diabetes mellitus

BACKGROUND

Increased plasma activity of gamma-glutamyltransferase (GGT) is associated with cardiovascular diseases (CVD) and mortality in the general population. We investigated the association between GGT, CVD and mortality in individuals with diabetes mellitus.

METHODS

Data used were from 1280 participants, aged 35-70 years, with a confirmed diagnosis of diabetes mellitus in the European Prospective Investigation into Cancer and Nutrition in Potsdam (Germany), Bilthoven and Utrecht (the Netherlands). Multivariate hazard ratios (HR) and 95% confidence intervals (CI) for CVD (non-fatal and fatal events) and overall mortality were estimated using sex-specific quartiles of GGT.

RESULTS

After 8.2 years follow-up, 108 incident CVD cases and 84 deaths were observed. Participants with high GGT activity had an increased mortality risk: HR in the highest quartile was 3.96 (95% CI 1.74, 9.00). This association was in particular present in former and current smokers, younger persons and those with a higher waist-height ratio and alcohol consumption. No associations were observed for non-fatal CVD and non-fatal and fatal CVD events combined.

CONCLUSIONS

Higher GGT plasma activity is associated with increased all-cause mortality in individuals with diabetes.

Paternal and maternal history of myocardial infarction and cardiovascular diseases incidence in a Dutch cohort of middle-aged persons

BACKGROUND

A positive parental history of myocardial infarction (MI) is an independent risk factor for cardiovascular diseases (CVD). However, different definitions of parental history have been used. We evaluated the impact of parental gender and age of onset of MI on CVD incidence.

METHODS

Baseline data were collected between 1993 and 1997 in 10,524 respondents aged 40-65 years. CVD events were obtained from the National Hospital Discharge Register and Statistics Netherlands. We used proportional hazard models to calculate hazard ratios (HR) and 95% confidence intervals (CI) for CVD incidence and adjusted for lifestyle and biological risk factors.

RESULTS

At baseline, 36% had a parental history of MI. During 10-year follow-up, 914 CVD events occurred. The age and gender adjusted HR was 1.3 (95% CI 1.1-1.5) for those with a paternal MI, 1.5 (1.2-1.8) for those with a maternal MI and 1.6 (1.2-2.2) for those with both parents with an MI. With decreasing parental age of MI, HR increased from 1.2 (1.0-1.6) for age ≥70 years to 1.5 (1.2-1.8) for age <60 years for a paternal MI and from 1.1 (0.9-1.5) to 2.2 (1.6-3.0) for a maternal MI. The impact of having a mother with MI before age 60 significantly differed in women [(2.9 (1.8-4.6)] and men [1.5 (0.9-2.6)]. Adjustment only slightly influenced HRs for maternal MI.

CONCLUSIONS

Respondents with a parental history of MI have an increased CVD incidence, in particular with parental onset of MI before age 70. A maternal history of MI before age 60 was the strongest predictor of CVD incidence.

Sleep duration and sleep quality in relation to 12-year cardiovascular disease incidence: the MORGEN study

STUDY OBJECTIVES

We studied sleep duration and sleep quality in relation to cardiovascular disease (CVD) incidence.

DESIGN/SETTING

Dutch population-based cohort study.

PARTICIPANTS

20,432 men and women aged 20-65 and with no history of CVD.

INTERVENTIONS

N/A.

MEASUREMENTS

Sleep duration and sleep quality were assessed by a self-administered questionnaire. Morbidity data, vital status, and causes of death were obtained through linkage with several national registries. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated using Cox proportional hazards models.

RESULTS

During 10-15 years of follow-up, 1,486 CVD and 1,148 coronary heart disease (CHD) events occurred. Short sleepers (≤ 6 h) had a 15% higher risk of total CVD (HR: 1.15; 95%CI: 1.00-1.32) and a 23% higher risk of CHD (HR: 1.23 [1.04-1.45]) compared to normal sleepers (7 h) after adjustment for all confounders. Additional adjustment for intermediate biological risk factors attenuated these relative risks to 1.11 (0.97-1.27) for total CVD and to 1.19 (1.00-1.40) for CHD. Short sleepers with poor sleep quality had a 63% higher risk of CVD (HR: 1.63 [1.21-2.19]) and a 79% higher risk of CHD incidence (HR: 1.79 [1.24-2.58]) compared to normal sleepers with good sleep quality, after adjustments for all confounders. We observed no associations between long sleep duration (≥ 9 h) and CVD or CHD incidence.

CONCLUSIONS

Short sleepers, especially those with poor sleep quality, have an increased risk of total CVD and CHD incidence. Future investigations should not only focus on sleep duration, but should also take sleep quality into account.

Mammographic density and breast cancer risk: the role of the fat surrounding the fibroglandular tissue

Introduction

Both the percent of mammographic density and absolute dense (fibroglandular) area are strong breast cancer risk factors. The role of non-dense (fat) breast tissue is not often investigated, but we hypothesize that this also influences risk. In this study we investigated the independent effects of dense and fat tissue, as well as their combined effect on postmenopausal breast cancer risk.

Methods

We performed a nested case-control study within the EPIC-NL cohort (358 postmenopausal breast cancer cases and 859 postmenopausal controls). We used multivariate logistic regression analyses to estimate breast cancer odds ratios adjusted for body mass index and other breast cancer risk factors.

Results

Large areas of dense (upper (Q5) vs lower quintile (Q1): OR 2.8 95% CI 1.7 to 4.8) and fat tissue (Q5 vs Q1: OR 2.4; 95% CI 1.3 to 4.2) were independently associated with higher breast cancer risk. The combined measure showed that the highest risk was found in women with both a large (above median) area of dense and fat tissue.

Conclusions

Fibroglandular and breast fat tissue have independent effects on breast cancer risk. The results indicate that the non-dense tissue, which represents the local breast fat, increases risk, even independent of body mass index (BMI). When studying dense breast tissue in relation to breast cancer risk, adjustment for non-dense tissue seems to change risk estimates to a larger extent than adjustment for BMI. This indicates that adjustment for non-dense tissue should be considered when studying associations between dense areas and breast cancer risk.

Low fertility and the risk of type 2 diabetes in women

BACKGROUND

Fertility problems are frequently followed by early menopause, and early menopause has been associated with increased risk of type 2 diabetes (T2D). Thus far, it is unknown whether low fertility is independently associated with future T2D risk.

METHODS

We assessed the association between measures of low fertility and T2D in the Prospect-European Prospective Investigation into Cancer and Nutrition (EPIC) cohort of 17,357 Dutch women, aged 49-70 years at baseline using Cox proportional hazards models, adjusted for various confounders. To investigate whether BMI and waist circumference influence the observed associations, analyses were additionally adjusted for these variables.

RESULTS

At baseline, 332 women had T2D. During a mean follow-up of 9.1 ± 3.6 years, 535 T2D cases occurred. Out of 15,707 Prospect-EPIC women who wanted to get pregnant, 1940 consulted a physician for fertility problems and 700 remained childless. No relation was found between consulting a physician for fertility problems or nulliparity and T2D risk. Of all women who wanted to get pregnant, 3946 (25.1%) had one or more miscarriages, with an average of 1.4 (± 0.9) miscarriages and a maximum of 10 miscarriages. Women who had one or more miscarriage showed the same risk for T2D as women who had no miscarriage. Also, none of the other measures of low fertility were associated with increased risk for T2D.

CONCLUSIONS

Generally, measures of low fertility were not independently associated with a risk of T2D in a cohort of 17 357 Dutch women.

Maternal and paternal transmission of type 2 diabetes: influence of diet, lifestyle and adiposity

OBJECTIVE

Transmission of family history of type 2 diabetes to the next generation is stronger for maternal than paternal diabetes in some populations. The aim of the present study was to investigate whether this difference is explained by diet, lifestyle factors and/or adiposity.

METHODS

We analysed 35174 participants from the Dutch contribution to the European Prospective Investigation into Cancer and Nutrition, a prospective population-based cohort (aged 20-70 years) with a median follow-up of 10.2 years. Parental history of diabetes was self-reported. Occurrence of diabetes was mainly identified by self-report and verified by medical records.

RESULTS

Amongst 35174 participants, 799 incident cases of diabetes were observed. In age- and sex-adjusted analyses, hazard ratio (HR) and 95% confidence intervals (CIs) for diabetes by maternal and paternal diabetes were 2.66 (2.26-3.14) and 2.40 (1.91-3.02), respectively. Maternal transmission of risk of diabetes was explained by diet (9.4%), lifestyle factors including smoking, alcohol consumption, physical activity and educational level (7.8%) and by adiposity, i.e. body mass index and waist and hip circumference (23.5%). For paternal transmission, the corresponding values were 2.9%, 0.0% and 9.6%. After adjustment for diet, lifestyle factors and adiposity, the HRs for maternal (2.20; 95% CI, 1.87-2.60) and paternal (2.23; 95% CI, 1.77-2.80) transmission of diabetes were comparable.

CONCLUSIONS

Both maternal and paternal diabetes are associated with increased risk of type 2 diabetes, independently of diet, lifestyle and adiposity. The slightly higher risk conferred by maternal compared to paternal diabetes was explained by a larger contribution of diet, lifestyle factors and adiposity.

Large-scale gene-centric analysis identifies novel variants for coronary artery disease

Coronary artery disease (CAD) has a significant genetic contribution that is incompletely characterized. To complement genome-wide association (GWA) studies, we conducted a large and systematic candidate gene study of CAD susceptibility, including analysis of many uncommon and functional variants. We examined 49,094 genetic variants in ∼2,100 genes of cardiovascular relevance, using a customised gene array in 15,596 CAD cases and 34,992 controls (11,202 cases and 30,733 controls of European descent; 4,394 cases and 4,259 controls of South Asian origin). We attempted to replicate putative novel associations in an additional 17,121 CAD cases and 40,473 controls. Potential mechanisms through which the novel variants could affect CAD risk were explored through association tests with vascular risk factors and gene expression. We confirmed associations of several previously known CAD susceptibility loci (eg, 9p21.3:p<10⁻³³; LPA:p<10⁻¹⁹; 1p13.3:p<10⁻¹⁷) as well as three recently discovered loci (COL4A1/COL4A2, ZC3HC1, CYP17A1:p<5×10⁻⁷). However, we found essentially null results for most previously suggested CAD candidate genes. In our replication study of 24 promising common variants, we identified novel associations of variants in or near LIPA, IL5, TRIB1, and ABCG5/ABCG8, with per-allele odds ratios for CAD risk with each of the novel variants ranging from 1.06–1.09. Associations with variants at LIPA, TRIB1, and ABCG5/ABCG8 were supported by gene expression data or effects on lipid levels. Apart from the previously reported variants in LPA, none of the other ∼4,500 low frequency and functional variants showed a strong effect. Associations in South Asians did not differ appreciably from those in Europeans, except for 9p21.3 (per-allele odds ratio: 1.14 versus 1.27 respectively; P for heterogeneity = 0.003). This large-scale gene-centric analysis has identified several novel genes for CAD that relate to diverse biochemical and cellular functions and clarified the literature with regard to many previously suggested genes.

Coronary artery disease (CAD) has a strong genetic basis that remains poorly characterised. Using a custom-designed array, we tested the association with CAD of almost 50,000 common and low frequency variants in ∼2,000 genes of known or suspected cardiovascular relevance. We genotyped the array in 15,596 CAD cases and 34,992 controls (11,202 cases and 30,733 controls of European descent; 4,394 cases and 4,259 controls of South Asian origin) and attempted to replicate putative novel associations in an additional 17,121 CAD cases and 40,473 controls. We report the novel association of variants in or near four genes with CAD and in additional studies identify potential mechanisms by which some of these novel variants affect CAD risk. Interestingly, we found that these variants, as well as the majority of previously reported CAD variants, have similar associations in Europeans and South Asians. Contrary to prior expectations, many previously suggested candidate genes did not show evidence of any effect on CAD risk, and neither did we identify any novel low frequency alleles with strong effects amongst the genes tested. Discovery of novel genes associated with heart disease may help to further understand the aetiology of cardiovascular disease and identify new targets for therapeutic interventions.