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.

The cost-effectiveness of implementing a new guideline for cardiovascular risk management in primary care in the Netherlands.

BACKGROUND: A new Dutch guideline for cardiovascular disease management substantially extends the number of individuals for whom treatment with statins and/or antihypertensive agents is recommended. We estimated the cost-effectiveness of implementing the new guideline at the national level. METHODS: First, the number of currently untreated individuals who would become eligible for cholesterol-lowering or antihypertensive treatment under the new guideline was estimated using data from a recent population study. Cost-effectiveness of treating this group of patients was then assessed using a mathematical model. RESULTS: Implementing the guideline in the age category 30-69 years would lead to an additional 465,000 individuals requiring treatment. Over a period of 20 years, the cumulative incidence of acute myocardial infarction in the whole population would drop by 3.0%, that of stroke by 3.9%, and all-cause mortality would drop by 0.9%. The lifetime cost-effectiveness ratio was calculated to be 15,000 Euro per quality-adjusted life year gained. In the age categories 70-79 years and 80 years or above, an additional 600,000 and 450,000 persons, respectively, would need to be treated, resulting in corresponding reductions in cumulative incidences of 14 and 18% (acute myocardial infarction), 17 and 22% (stroke), and 1.2 and 0.6% (all-cause mortality) with cost-effectiveness ratios of 20,800 and 32,300 Euro, respectively, per quality-adjusted life year. CONCLUSION: Complete implementation of the new guideline would lead to a considerable increase in the number of individuals requiring treatment. This would be cost-effective up to the age of 70 years.

Economic evaluations of cholesterol-lowering drugs: a critical and systematic review.

The wide availability of economic evaluations and their increasing importance for decision making emphasises the need for economic evaluations that are methodologically sound. The aim of this review was to provide users of economic evaluations of cholesterol-lowering drugs with an insight into the quality of these evaluations. By focusing on the most relevant studies, the gap between research and policy making may be narrowed. A systematic review was conducted. All Dutch and English publications on economic evaluations of cholesterol-lowering drugs were identified by searching PubMed, the Centre for Reviews and Dissemination database (CRD), the NHS Economic Evaluation Database (NHS EED), the Health Technology Assessment database (HTA) and the Database of Abstracts of Reviews of Effects (DARE). A search strategy was set up to identify the articles to be included. The quality of these articles was assessed using Drummond's checklists. The scoring was performed by at least two reviewers. When necessary, disagreement between these reviewers was decided upon in a consensus meeting. We calculated an average quality score for the included articles. The search identified 1390 articles, of which 23 were included. Most studies measured the costs per life-year gained. The overall score per study was disappointing and varied between 2.7 and 7.7, with an average of 5.5. Most studies scored high on the measurement of costs and consequences, whereas the establishment of effectiveness left room for improvement. Only two studies included a well performed incremental analysis. This study noted an increase of quality of economic evaluations over time, suggesting the value of cost-effectiveness studies for policy decisions increases over time. In general, piggy-back evaluations tended to score higher on quality and may therefore be more valuable in decision making.

Earlier Age of Onset of Chronic Hypertension and Type 2 Diabetes Mellitus After a Hypertensive Disorder of Pregnancy or Gestational Diabetes Mellitus.

A prospective cohort study was conducted to assess the impact of a history of hypertensive disorder of pregnancy (HDP) or gestational diabetes mellitus (GDM) on the risk and age of onset of hypertension, type 2 diabetes mellitus (T2D), and cardiovascular disease (CVD) later in life, independent of hypertension and T2D. Between 1993 and 1997, 22 265 ever-pregnant women were included from the European Prospective Investigation into Cancer and Nutrition-NL study, aged 20 to 70 years at baseline. Details on complications of pregnancy and known hypertension were obtained by questionnaire. Blood pressure was measured at enrollment. Participants were followed for the occurrence of CVD events. Data were analyzed using ANCOVA, multivariable logistic regression, and Cox proportional hazard (with HDP and GDM as time-dependent variables for T2D and CVD) models. At enrollment, women with a HDP reported diagnosis of hypertension 7.7 years earlier (95% confidence interval [CI] 6.9-8.5) and women with GDM reported diagnosis of T2D 7.7 years earlier (95% CI 5.8-9.6) than women without pregnancy complications. After adjustment for potential confounders, HDP was associated with presence of hypertension at enrollment (odds ratio 2.12, 95% CI 1.98-2.28) and onset of CVD later in life (hazard ratio 1.21, 95% CI 1.10-1.32). After including the intermediates hypertension and T2D in the model, the risk of CVD later in life decreased (hazard ratio 1.09, 95% CI 1.00-1.20). GDM was associated with an increased risk of developing T2D later in life (hazard ratio 3.68, 95% CI 2.77-4.90), but not with risk of CVD. HDP and GDM have a substantial impact on the risk of CVD and are potentially important indicators for preventive cardiovascular risk management.

Gene-specific DNA methylation profiles and LINE-1 hypomethylation are associated with myocardial infarction risk.

BACKGROUND: DNA methylation profiles are responsive to environmental stimuli and metabolic shifts. This makes DNA methylation a potential biomarker of environmental-related and lifestyle-driven diseases of adulthood. Therefore, we investigated if white blood cells' (WBCs) DNA methylation profiles are associated with myocardial infarction (MI) occurrence. Whole-genome DNA methylation was investigated by microarray analysis in 292 MI cases and 292 matched controls from the large prospective Italian European Prospective Investigation into Cancer and Nutrition (EPIC) cohort (EPICOR study). Significant signals (false discovery rate (FDR) adjusted P < 0.05) were replicated by mass spectrometry in 317 MI cases and 262 controls from the Dutch EPIC cohort (EPIC-NL). Long interspersed nuclear element-1 (LINE-1) methylation profiles were also evaluated in both groups. RESULTS: A differentially methylated region (DMR) within the zinc finger and BTB domain-containing protein 12 (ZBTB12) gene body and LINE-1 hypomethylation were identified in EPICOR MI cases and replicated in the EPIC-NL sample (ZBTB12-DMR meta-analysis: effect size ± se = -0.016 ± 0.003, 95 % CI = -0.021;-0.011, P = 7.54 × 10(-10); LINE-1 methylation meta-analysis: effect size ± se = -0.161 ± 0.040, 95 % CI = -0.239;-0.082, P = 6.01 × 10(-5)). Moreover, cases with shorter time to disease had more pronounced ZBTB12-DMR hypomethylation (meta-analysis, men: effect size ± se = -0.0059 ± 0.0017, P TREND = 5.0 × 10(-4); women: effect size ± se = -0.0053 ± 0.0019, P TREND = 6.5 × 10(-3)) and LINE-1 hypomethylation (meta-analysis, men: effect size ± se = -0.0010 ± 0.0003, P TREND = 1.6 × 10(-3); women: effect size ± se = -0.0008 ± 0.0004, P TREND = 0.026) than MI cases with longer time to disease. In the EPIC-NL replication panel, DNA methylation profiles improved case-control discrimination and reclassification when compared with traditional MI risk factors only (net reclassification improvement (95 % CI) between 0.23 (0.02-0.43), P = 0.034, and 0.89 (0.64-1.14), P < 1 × 10(-5)). CONCLUSIONS: Our data suggest that specific methylation profiles can be detected in WBCs, in a preclinical condition, several years before the occurrence of MI, providing an independent signature of cardiovascular risk. We showed that prediction accuracy can be improved when DNA methylation is taken into account together with traditional MI risk factors, although further confirmation on a larger sample is warranted. Our findings support the potential use of DNA methylation patterns in peripheral blood white cells as promising early biomarkers of MI.

Drug-gene interactions between genetic polymorphisms and antihypertensive therapy.

Genetic factors may influence the response to antihypertensive medication. A number of studies have investigated genetic polymorphisms as determinants of cardiovascular response to antihypertensive drug therapy. In most candidate gene studies, no such drug-gene interactions were found. However, there is observational evidence that hypertensive patients with the 460 W allele of the alpha-adducin gene have a lower risk of myocardial infarction and stroke when treated with diuretics compared with other antihypertensive therapies. With regard to blood pressure response, interactions were found between genetic polymorphisms for endothelial nitric oxide synthase and diuretics, the alpha-adducin gene and diuretics, the alpha-subunit of G protein and beta-adrenoceptor antagonists, and the ACE gene and angiotensin II type 1 (AT(1)) receptor antagonists. Other studies found an interaction between ACE inhibitors and the ACE insertion/deletion (I/D) polymorphism, which resulted in differences in AT(1) receptor mRNA expression, left ventricular hypertrophy and arterial stiffness between different genetic variants. Also, drug-gene interactions between calcium channel antagonists and ACE I/D polymorphism regarding arterial stiffness have been reported. Unfortunately, the quality of these studies is quite variable. Given the methodological problems, the results from the candidate gene studies are still inconclusive and further research is necessary.

Cigarette smoking and alcohol consumption in relation to cognitive performance in middle age.

In the elderly, cigarette smoking has been related to reduced cognitive performance and moderate alcohol consumption to increased cognitive performance. It is not clear whether these associations also exist in middle age. The authors examined these relations in a population-based cohort study of 1,927 randomly selected, predominantly middle-aged subjects aged 45-70 years at the time of cognitive testing and living in the Netherlands. From 1995 until 2000, an extensive cognitive battery was administered, and compound scores were calculated. Risk factors had been assessed approximately 5 years previously. Multiple linear regression analyses (in which one unit of the cognitive score = one standard deviation) showed that, after the authors adjusted for age, sex, education, alcohol consumption, and cardiovascular risk factors, current smokers had reduced psychomotor speed (beta = -0.159, 95% confidence interval: -0.071, -0.244; p = 0.0003) and reduced cognitive flexibility (beta = -0.133, 95% confidence interval: -0.035, -0.230; p = 0.008) compared with never smokers. This effect was similar to that of being approximately 4 years older. Alcohol consumption was related to increased speed and better flexibility, especially among women who drank 1-4 alcoholic beverages a day. In conclusion, among middle-aged subjects, current smoking was inversely and alcohol consumption positively related to psychomotor speed and cognitive flexibility. This finding suggests that actions to prevent cognitive decline can be taken in middle age.