A Combined Linkage and Exome Sequencing Analysis for Electrocardiogram Parameters in the Erasmus Rucphen Family Study.

Electrocardiogram (ECG) measurements play a key role in the diagnosis and prediction of cardiac arrhythmias and sudden cardiac death. ECG parameters, such as the PR, QRS, and QT intervals, are known to be heritable and genome-wide association studies of these phenotypes have been successful in identifying common variants; however, a large proportion of the genetic variability of these traits remains to be elucidated. The aim of this study was to discover loci potentially harboring rare variants utilizing variance component linkage analysis in 1547 individuals from a large family-based study, the Erasmus Rucphen Family Study (ERF). Linked regions were further explored using exome sequencing. Five suggestive linkage peaks were identified: two for QT interval (1q24, LOD = 2.63; 2q34, LOD = 2.05), one for QRS interval (1p35, LOD = 2.52) and two for PR interval (9p22, LOD = 2.20; 14q11, LOD = 2.29). Fine-mapping using exome sequence data identified a C > G missense variant (c.713C > G, p.Ser238Cys) in the FCRL2 gene associated with QT (rs74608430; P = 2.8 × 10-4, minor allele frequency = 0.019). Heritability analysis demonstrated that the SNP explained 2.42% of the trait's genetic variability in ERF (P = 0.02). Pathway analysis suggested that the gene is involved in cytosolic Ca2+ levels (P = 3.3 × 10-3) and AMPK stimulated fatty acid oxidation in muscle (P = 4.1 × 10-3). Look-ups in bioinformatics resources showed that expression of FCRL2 is associated with ARHGAP24 and SETBP1 expression. This finding was not replicated in the Rotterdam study. Combining the bioinformatics information with the association and linkage analyses, FCRL2 emerges as a strong candidate gene for QT interval.

Carotid Intima-Media Thickness and Arterial Stiffness and the Risk of Atrial Fibrillation: The Atherosclerosis Risk in Communities (ARIC) Study, Multi-Ethnic Study of Atherosclerosis (MESA), and the Rotterdam Study.

BACKGROUND: We evaluated the association of carotid intima-media thickness (cIMT), carotid plaque, carotid distensibility coefficient (DC), and aortic pulse wave velocity (PWV) with incident atrial fibrillation (AF) and their role in improving AF risk prediction beyond the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE)-AF risk score. METHODS AND RESULTS: We analyzed data from 3 population-based cohort studies: Atherosclerosis Risk in Communities (ARIC) Study (n=13 907); Multi-Ethnic Study of Atherosclerosis (MESA; n=6640), and the Rotterdam Study (RS; n=5220). We evaluated the association of arterial indices with incident AF and computed the C-statistic, category-based net reclassification improvement (NRI), and relative integrated discrimination improvement (IDI) of incorporating arterial indices into the CHARGE-AF risk score (age, race, height weight, systolic and diastolic blood pressure, antihypertensive medication use, smoking, diabetes, previous myocardial infarction, and previous heart failure). Higher cIMT (meta-analyzed hazard ratio [95% CI] per 1-SD increment, 1.12 [1.08-1.16]) and presence of carotid plaque (1.30 [1.19-1.42]) were associated with higher AF incidence after adjustment for CHARGE-AF risk-score variables. Lower DC and higher PWV were associated with higher AF incidence only after adjustment for the CHARGE-AF risk-score variables excepting height, weight, and systolic and diastolic blood pressure. Addition of cIMT or carotid plaque marginally improved CHARGE-AF score prediction as assessed by the relative IDI (estimates, 0.025-0.051), but not when assessed with the C-statistic and NRI. CONCLUSIONS: Higher cIMT, presence of carotid plaque, and greater arterial stiffness are associated with higher AF incidence, indicating that atherosclerosis and arterial stiffness play a role in AF etiopathogenesis. However, arterial indices only modestly improve AF risk prediction.

Genome-wide association studies identify genetic loci for low von Willebrand factor levels.

Low von Willebrand factor (VWF) levels are associated with bleeding symptoms and are a diagnostic criterion for von Willebrand disease, the most common inherited bleeding disorder. To date, it is unclear which genetic loci are associated with reduced VWF levels. Therefore, we conducted a meta-analysis of genome-wide association studies to identify genetic loci associated with low VWF levels. For this meta-analysis, we included 31 149 participants of European ancestry from 11 community-based studies. From all participants, VWF antigen (VWF:Ag) measurements and genome-wide single-nucleotide polymorphism (SNP) scans were available. Each study conducted analyses using logistic regression of SNPs on dichotomized VWF:Ag measures (lowest 5% for blood group O and non-O) with an additive genetic model adjusted for age and sex. An inverse-variance weighted meta-analysis was performed for VWF:Ag levels. A total of 97 SNPs exceeded the genome-wide significance threshold of 5 × 10(-8) and comprised five loci on four different chromosomes: 6q24 (smallest P-value 5.8 × 10(-10)), 9q34 (2.4 × 10(-64)), 12p13 (5.3 × 10(-22)), 12q23 (1.2 × 10(-8)) and 13q13 (2.6 × 10(-8)). All loci were within or close to genes, including STXBP5 (Syntaxin Binding Protein 5) (6q24), STAB5 (stabilin-5) (12q23), ABO (9q34), VWF (12p13) and UFM1 (ubiquitin-fold modifier 1) (13q13). Of these, UFM1 has not been previously associated with VWF:Ag levels. Four genes that were previously associated with VWF levels (VWF, ABO, STXBP5 and STAB2) were also associated with low VWF levels, and, in addition, we identified a new gene, UFM1, that is associated with low VWF levels. These findings point to novel mechanisms for the occurrence of low VWF levels.

Heritabilities, proportions of heritabilities explained by GWAS findings, and implications of cross-phenotype effects on PR interval.

Electrocardiogram (ECG) measurements are a powerful tool for evaluating cardiac function and are widely used for the diagnosis and prediction of a variety of conditions, including myocardial infarction, cardiac arrhythmias, and sudden cardiac death. Recently, genome-wide association studies (GWASs) identified a large number of genes related to ECG parameter variability, specifically for the QT, QRS, and PR intervals. The aims of this study were to establish the heritability of ECG traits, including indices of left ventricular hypertrophy, and to directly assess the proportion of those heritabilities explained by GWAS variants. These analyses were conducted in a large, Dutch family-based cohort study, the Erasmus Rucphen Family study using variance component methods implemented in the SOLAR (Sequential Oligogenic Linkage Analysis Routines) software package. Heritability estimates ranged from 34% for QRS and Cornell voltage product to 49% for 12-lead sum. Trait-specific GWAS findings for each trait explained a fraction of their heritability (17% for QRS, 4% for QT, 2% for PR, 3% for Sokolow-Lyon index, and 4% for 12-lead sum). The inclusion of all ECG-associated single nucleotide polymorphisms explained an additional 6% of the heritability of PR. In conclusion, this study shows that, although GWAS explain a portion of ECG trait variability, a large amount of heritability remains to be explained. In addition, larger GWAS for PR are likely to detect loci already identified, particularly those observed for QRS and 12-lead sum.

Identifying genetic risk variants for coronary heart disease in familial hypercholesterolemia: an extreme genetics approach.

Mutations in the low-density lipoprotein receptor (LDLR) gene cause familial hypercholesterolemia (FH), a disorder characterized by coronary heart disease (CHD) at young age. We aimed to apply an extreme sampling method to enhance the statistical power to identify novel genetic risk variants for CHD in individuals with FH. We selected cases and controls with an extreme contrast in CHD risk from 17,000 FH patients from the Netherlands, whose functional LDLR mutation was unequivocally established. The genome-wide association (GWA) study was performed on 249 very young FH cases with CHD and 217 old FH controls without CHD (above 65 years for males and 70 years of age for females) using the Illumina HumanHap550K chip. In the next stage, two independent samples (one from the Netherlands and one from Italy, Norway, Spain, and the United Kingdom) of FH patients were used as replication samples. In the initial GWA analysis, we identified 29 independent single nucleotide polymorphisms (SNPs) with suggestive associations with premature CHD (P<1 × 10(-4)). We examined the association of these SNPs with CHD risk in the replication samples. After Bonferroni correction, none of the SNPs either replicated or reached genome-wide significance after combining the discovery and replication samples. Therefore, we conclude that the genetics of CHD risk in FH is complex and even applying an 'extreme genetics' approach we did not identify new genetic risk variants. Most likely, this method is not as effective in leveraging effect size as anticipated, and may, therefore, not lead to significant gains in statistical power.

Sex differences in lifetime risk and first manifestation of cardiovascular disease: prospective population based cohort study.

OBJECTIVE: To evaluate differences in first manifestations of cardiovascular disease between men and women in a competing risks framework. DESIGN: Prospective population based cohort study. SETTING: People living in the community in Rotterdam, the Netherlands. PARTICIPANTS: 8419 participants (60.9% women) aged ≥ 55 and free from cardiovascular disease at baseline. MAIN OUTCOME MEASURES: First diagnosis of coronary heart disease (myocardial infarction, revascularisation, and coronary death), cerebrovascular disease (stroke, transient ischaemic attack, and carotid revascularisation), heart failure, or other cardiovascular death; or death from non-cardiovascular causes. Data were used to calculate lifetime risks of cardiovascular disease and its first incident manifestations adjusted for competing non-cardiovascular death. RESULTS: During follow-up of up to 20.1 years, 2888 participants developed cardiovascular disease (826 coronary heart disease, 1198 cerebrovascular disease, 762 heart failure, and 102 other cardiovascular death). At age 55, overall lifetime risks of cardiovascular disease were 67.1% (95% confidence interval 64.7% to 69.5%) for men and 66.4% (64.2% to 68.7%) for women. Lifetime risks of first incident manifestations of cardiovascular disease in men were 27.2% (24.1% to 30.3%) for coronary heart disease, 22.8% (20.4% to 25.1%) for cerebrovascular disease, 14.9% (13.3% to 16.6%) for heart failure, and 2.3% (1.6% to 2.9%) for other deaths from cardiovascular disease. For women the figures were 16.9% (13.5% to 20.4%), 29.8% (27.7% to 31.9%), 17.5% (15.9% to 19.2%), and 2.1% (1.6% to 2.7%), respectively. Differences in the number of events that developed over the lifespan in women compared with men (per 1000) were -7 for any cardiovascular disease, -102 for coronary heart disease, 70 for cerebrovascular disease, 26 for heart failure, and -1 for other cardiovascular death; all outcomes manifested at a higher age in women. Patterns were similar when analyses were restricted to hard atherosclerotic cardiovascular disease outcomes, but absolute risk differences between men and women were attenuated for both coronary heart disease and stroke. CONCLUSIONS: At age 55, though men and women have similar lifetime risks of cardiovascular disease, there are considerable differences in the first manifestation. Men are more likely to develop coronary heart disease as a first event, while women are more likely to have cerebrovascular disease or heart failure as their first event, although these manifestations appear most often at older ages.

Normal values of the electrocardiogram for ages 16-90 years.

INTRODUCTION: To establish an up-to-date and comprehensive set of normal values for the clinically current measurements in the adult ECG, covering all ages for both sexes. METHODS: The study population included 13,354 individuals, taken from four population studies in The Netherlands, ranging in age from 16 to 90 years (55% men) and cardiologically healthy by commonly accepted criteria. Standard 12-lead ECGs were available for all participants. The ECGs were processed by a well-validated computer program. Normal limits were taken as the 2nd and 98th percentiles of the measurement distribution per age group. RESULTS: Our study corroborates many findings of previous studies, but also provides more differentiated results, in particular for the older age groups. Age trends were apparent for the QTc interval, QRS axis, and indices of left ventricular hypertrophy. Amplitudes in the left precordial leads showed a substantial increase in the older age groups for women, but not for men. Sex-dependent differences were apparent for most ECG parameters. All results are available on the Website www.normalecg.org, both in tabular and in graphical format. CONCLUSIONS: We determined age- and sex-dependent normal values of the adult ECG. Our study distinguishes itself from other studies by the large size of the study population, comprising both sexes, the broad range of ages, and the exhaustive set of measurements. Our results emphasize that most diagnostic ECG criteria should be age- and sex-specific.

Association of renal function with vascular stiffness in older adults: the Rotterdam study.

BACKGROUND: arterial stiffening is a marker of vascular ageing and an independent risk factor for cardiovascular disease. A potential mechanism linking cardiovascular disease to chronic kidney disease might be the change in arterial elasticity. We aim to determine the association between renal function and arterial stiffness in older subjects. DESIGN: cross-sectional study. SETTING: Rotterdam study, a population-based cohort study. SUBJECTS: we included 3,279 subjects from 1997 to 1999 with a mean age of 71.9 years. METHODS: estimation of glomerular filtration rate (eGFR) was used to assess renal function. Aortic pulse wave velocity (PWV) and carotid distensibility coefficient were used as measures of arterial stiffness. RESULTS: each standard deviation increase in eGFR, adjusting for age and sex, was associated with 0.14 m/s lower PWV [95% confidence interval (CI): -0.23, -0.05]. Further adjustments for socio-demographic and cardiovascular risk factors did not change the association (ß: -0.16 m/s; 95% CI: -0.26, -0.06). There was a linear association between mean values of PWV and quartiles of glomerular filtration rate (P for trend = 0.006). There was no association between decreased renal function and carotid distensibility. There was no statistical difference in the strength of the association between renal function and PWV in subgroups of participants with and without cardiovascular risk factors. CONCLUSIONS: in this large population-based study of elderly subjects, our findings suggest that renal impairment is associated with aortic stiffness. This association is independent of cardiovascular risk factors.

Effects of long-term averaging of quantitative blood pressure traits on the detection of genetic associations.

Blood pressure (BP) is a heritable, quantitative trait with intraindividual variability and susceptibility to measurement error. Genetic studies of BP generally use single-visit measurements and thus cannot remove variability occurring over months or years. We leveraged the idea that averaging BP measured across time would improve phenotypic accuracy and thereby increase statistical power to detect genetic associations. We studied systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP) averaged over multiple years in 46,629 individuals of European ancestry. We identified 39 trait-variant associations across 19 independent loci (p < 5 × 10(-8)); five associations (in four loci) uniquely identified by our LTA analyses included those of SBP and MAP at 2p23 (rs1275988, near KCNK3), DBP at 2q11.2 (rs7599598, in FER1L5), and PP at 6p21 (rs10948071, near CRIP3) and 7p13 (rs2949837, near IGFBP3). Replication analyses conducted in cohorts with single-visit BP data showed positive replication of associations and a nominal association (p < 0.05). We estimated a 20% gain in statistical power with long-term average (LTA) as compared to single-visit BP association studies. Using LTA analysis, we identified genetic loci influencing BP. LTA might be one way of increasing the power of genetic associations for continuous traits in extant samples for other phenotypes that are measured serially over time.

Arterial stiffness and hypertension in a large population of untreated individuals: the Rotterdam Study.

OBJECTIVE: We studied whether arterial stiffness measured as aortic pulse wave velocity (aPWV) and carotid distensibility was associated with different subtypes of hypertension in a large population of untreated middle-aged and elderly men and women. METHODS: The study was conducted within the framework of the population-based Rotterdam Study. We included 4088 individuals with information on aPWV, with 3554 individuals with carotid distensibility measurements without use of antihypertensive medication. Isolated systolic hypertension (ISH) was defined as SBP at least 140 mmHg and DBP less than 90 mmHg. Combined systolic and diastolic hypertension (Sys/Dia hypertension) was defined as SBP at least 140 mmHg and DBP at least 90 mmHg. Analysis of covariance was used to compare means of arterial stiffness for the different subtypes of hypertension. Multinomial logistic regression analysis was performed to investigate the association of arterial stiffness and the subtypes of hypertension in models adjusted for age, sex, mean arterial pressure, heart rate and cardiovascular risk factors. RESULTS: The mean age of the individuals was 68 years: 45.3% were men, 1597 individuals had ISH and 441 individuals had Sys/Dia hypertension. aPWV was higher (13.2 vs. 12.9 m/s; P = 0.008) in individuals with ISH compared to those with Sys/Dia hypertension. Multivariate odds ratios and corresponding 95% confidence interval of aPWV for ISH were 1.53 (1.38-1.71) and 1.28 (1.09-1.53) for Sys/Dia hypertension. Corresponding odds ratios associated with carotid distensibility were 0.84 (0.75-0.94) and 0.66 (0.54-0.81), respectively. Age significantly modified the association of aPWV with subtypes of hypertension (P < 0.001). CONCLUSION: In a large untreated population, we found significant associations of both aPWV and carotid distensibility with ISH and Sys/Dia hypertension. individuals with ISH had higher values of aortic stiffness when compared to individuals with Sys/Dia hypertension, a difference that was most pronounced at older age. The results suggest that aortic stiffness contributes to ISH in older individuals without treatment for hypertension.

Net reclassification improvement: computation, interpretation, and controversies: a literature review and clinician's guide.

The net reclassification improvement (NRI) is an increasingly popular measure for evaluating improvements in risk predictions. This article details a review of 67 publications in high-impact general clinical journals that considered the NRI. Incomplete reporting of NRI methods, incorrect calculation, and common misinterpretations were found. To aid improved applications of the NRI, the article elaborates on several aspects of the computation and interpretation in various settings. Limitations and controversies are discussed, including the effect of miscalibration of prediction models, the use of the continuous NRI and "clinical NRI," and the relation with decision analytic measures. A systematic approach toward presenting NRI analysis is proposed: Detail and motivate the methods used for computation of the NRI, use clinically meaningful risk cutoffs for the category-based NRI, report both NRI components, address issues of calibration, and do not interpret the overall NRI as a percentage of the study population reclassified. Promising NRI findings need to be followed with decision analytic or formal cost-effectiveness evaluations.

Arterial stiffness is associated with carotid intraplaque hemorrhage in the general population: the Rotterdam study.

OBJECTIVE: The relation between arterial stiffness and atherosclerosis, and specifically the influence of arterial stiffness on plaque composition, is largely unknown. In a population-based study, we investigated the association between arterial stiffness and the presence and composition of carotid atherosclerotic plaques. APPROACH AND RESULTS: Arterial stiffness was measured in 6527 participants (67.0±8.6 years) using aortic pulse wave velocity (PWV). Presence of carotid atherosclerotic plaques was assessed with ultrasound. Subsequently, 1059 subjects with carotid plaques (>2.5 mm) underwent MRI to assess plaque composition (presence of intraplaque hemorrhage, lipid, and calcification). Generalized estimation equation analyses adjusted for age, sex, mean arterial pressure, heart rate, carotid wall thickening, pulse pressure, and traditional cardiovascular risk factors were used to study the association between PWV and the presence and composition of carotid atherosclerotic plaques. In multivariable analysis, higher PWV was independently related to higher prevalence of carotid atherosclerotic plaque on ultrasound (odds ratio for highest quartile of PWV compared with lowest quartile, 1.24 [95% confidence interval, 1.02-1.51]). Furthermore, higher PWV was associated with intraplaque hemorrhage (age- and sex-adjusted odds ratio per SD increase in PWV, 1.20 [1.04-1.38] and calcification, 1.18 [1.03-1.35]), but not with lipid. After adjustment for cardiovascular risk factors, PWV remained significantly associated with intraplaque hemorrhage (1.20 [1.01-1.43]). Additional adjustment for pulse pressure did not materially affect the effect estimate (1.19 [1.00-1.42]). CONCLUSIONS: Higher PWV is associated with presence and composition of carotid atherosclerotic plaques, in particular with intraplaque hemorrhage. These findings provide further clues for understanding the development of vulnerable atherosclerotic plaque.

Concordance for prognostic models with competing risks.

The concordance probability is a widely used measure to assess discrimination of prognostic models with binary and survival endpoints. We formally define the concordance probability for a prognostic model of the absolute risk of an event of interest in the presence of competing risks and relate it to recently proposed time-dependent area under the receiver operating characteristic curve measures. For right-censored data, we investigate inverse probability of censoring weighted (IPCW) estimates of a truncated concordance index based on a working model for the censoring distribution. We demonstrate consistency and asymptotic normality of the IPCW estimate if the working model is correctly specified and derive an explicit formula for the asymptotic variance under independent censoring. The small sample properties of the estimator are assessed in a simulation study also against misspecification of the working model. We further illustrate the methods by computing the concordance probability for a prognostic model of coronary heart disease (CHD) events in the presence of the competing risk of non-CHD death.

Performance of Framingham cardiovascular disease (CVD) predictions in the Rotterdam Study taking into account competing risks and disentangling CVD into coronary heart disease (CHD) and stroke.

BACKGROUND: To evaluate the performance of Framingham predictions of cardiovascular disease (CVD) risk corrected for the competing risk of non-CVD death, in an independent European cohort of older individuals and subsequently extend the predictions by disentangling CVD into coronary heart disease (CHD) and stroke separately. METHODS: We used the Rotterdam Study data, a prospective cohort study of individuals aged 55 years and older (N=6004), to validate the Framingham predictions of CVD, defined as first occurrence of myocardial infarction, coronary death or stroke during 15 years of follow-up, corrected for the competing risk of non-CVD death. We subsequently estimated the risks of CHD and stroke separately, and used the sum as a predictor for the total CVD risk. Calibration plots and c-statistics were used to evaluate the performance of the models. RESULTS: Performance of the Framingham predictions was good in the low- to intermediate risk (≤30%, 15-year CVD risk) (17.5% observed vs. 16.6% expected) but poorer in the higher risk (>30%) categories (36.3% observed vs. 44.1% expected). The c-statistic increased from 0.66 to 0.69 after refitting. Separately estimating CHD and stroke revealed considerable heterogeneity with regard to the contribution of CHD and stroke to total CVD risk. CONCLUSIONS: Framingham CVD risk predictions perform well in the low- to intermediate risk categories in the Rotterdam Study. Disentangling CVD into CHD and stroke separately provides additional information about the individual contribution of CHD and stroke to total individual CVD risk.

Comparison of prognosis in unrecognized versus recognized myocardial infarction in men versus women >55 years of age (from the Rotterdam Study).

Unrecognized myocardial infarction (MI) is frequent in the general population. Its prognosis is reported to be at least as unpropitious as that of recognized MI, particularly in men. However, contemporary data with long follow-up are lacking. The aims of this study were to investigate the long-term prognosis of unrecognized MI with respect to all-cause and cause-specific mortality and to investigate possible differences in prognosis by gender. In the population-based Rotterdam Study (2,672 men and 3,862 women), the presence of unrecognized MI and recognized MI was determined at baseline (1990 to 1993). The cohort was followed for nearly 2 decades for all-cause and cause-specific mortality. During 82,268 patient-years of follow-up (median 15.6 years) 3,412 patients died (1,300 from cardiovascular causes). Men and women with recognized and unrecognized MIs had increased total mortality rates compared with those without MIs. Hazard ratios (HRs) for men and women were 1.57 (95% confidence interval [CI] 1.36 to 1.81) and 1.89 (95% CI 1.56 to 2.30) for recognized MI and 1.72 (95% CI 1.43 to 2.07) and 1.36 (95% CI 1.14 to 1.61) for unrecognized MI. Unrecognized MI was associated with increased risks for cardiovascular mortality (men: HR 2.19, 95% CI 1.66 to 2.91; women: HR 1.36, 95% CI 1.03 to 1.81) and noncardiovascular mortality (men: HR 1.47, 95% CI 1.14 to 1.89; women: HR 1.39, 95% CI 1.10 to 1.75). In conclusion, the long-term prognosis of patients with unrecognized MIs is worse compared with those without MIs and applies not only to cardiovascular mortality but also to noncardiovascular mortality. In men, the prognosis is as unfavorable as that of patients with recognized MIs.

No evidence for genome-wide interactions on plasma fibrinogen by smoking, alcohol consumption and body mass index: results from meta-analyses of 80,607 subjects.

Plasma fibrinogen is an acute phase protein playing an important role in the blood coagulation cascade having strong associations with smoking, alcohol consumption and body mass index (BMI). Genome-wide association studies (GWAS) have identified a variety of gene regions associated with elevated plasma fibrinogen concentrations. However, little is yet known about how associations between environmental factors and fibrinogen might be modified by genetic variation. Therefore, we conducted large-scale meta-analyses of genome-wide interaction studies to identify possible interactions of genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentration. The present study included 80,607 subjects of European ancestry from 22 studies. Genome-wide interaction analyses were performed separately in each study for about 2.6 million single nucleotide polymorphisms (SNPs) across the 22 autosomal chromosomes. For each SNP and risk factor, we performed a linear regression under an additive genetic model including an interaction term between SNP and risk factor. Interaction estimates were meta-analysed using a fixed-effects model. No genome-wide significant interaction with smoking status, alcohol consumption or BMI was observed in the meta-analyses. The most suggestive interaction was found for smoking and rs10519203, located in the LOC123688 region on chromosome 15, with a p value of 6.2 × 10(-8). This large genome-wide interaction study including 80,607 participants found no strong evidence of interaction between genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentrations. Further studies are needed to yield deeper insight in the interplay between environmental factors and gene variants on the regulation of fibrinogen concentrations.

Serum uric acid and chronic kidney disease: the role of hypertension.

BACKGROUND: There are inconsistent findings on the role of hyperuricemia as an independent risk factor for chronic kidney disease (CKD). Hypertension has been implicated as a factor influencing the association between serum uric acid and CKD. In this population-based study we investigated the association between serum uric acid and decline in renal function and tested whether hypertension moderates this association. METHODS: We included 2601 subjects aged 55 years and over from the Rotterdam Study. Serum uric acid and estimated glomerular filtration rate (eGFR) were assessed at baseline. After average 6.5 years of follow-up, second eGFR was assessed. CKD was defined as eGFR<60 ml/min/1.73 m(2). All associations were corrected for socio-demographic and cardiovascular factors. RESULTS: Each unit (mg/dL) increase in serum uric acid was associated with 0.19 ml/min per 1.73 m(2) faster annual decline in eGFR. While the association between serum uric acid and incidence of CKD was not significant in our study population (Hazard Ratio: 1.12, 95% confidence interval [CI]: 0.98-1.28), incorporating our results in a meta-analysis with eleven published studies revealed a significant association (Relative Risk: 1.18, 95%CI: 1.15-1.22). In the stratified analyses, we observed that the associations of serum uric acid with eGFR decline and incident CKD were stronger in hypertensive subjects (P for interaction = 0.046 and 0.024, respectively). CONCLUSIONS: Our findings suggest that hyperuricemia is independently associated with a decline in renal function. Stronger association in hypertensive individuals may indicate that hypertension mediates the association between serum uric acid and CKD.

Serum potassium levels and the risk of atrial fibrillation: the Rotterdam Study.

BACKGROUND: Atrial fibrillation is the most common sustained arrhythmia in the elderly. Serum potassium is associated with ventricular arrhythmias and cardiac arrest. Little is known about the association of serum potassium with atrial fibrillation. The objective of this study was to investigate the association of serum potassium and the risk of atrial fibrillation in a population based setting. METHODS: The study was performed within the prospective population-based Rotterdam Study. The study population consisted of 4059 participants without atrial fibrillation at baseline for whom baseline levels of serum potassium were measured. Atrial fibrillation was ascertained from centre visit ECG assessments as well as medical records. RESULTS: During a mean follow up of 11.8 years (SD=5.2 yr), 474 participants developed atrial fibrillation. Participants with hypokalemia (<3.5 mmol/l) had a higher risk of atrial fibrillation (HR: 1.63, 95%CI: 1.03-2.56) than those with normokalemia (3.5-5.0 mmol/l). This association was independent of age, sex, serum magnesium, and other potential confounders. Especially in participants with a history of myocardial infarction, those with hypokalemia had a higher risk of atrial fibrillation than those with normokalemia (HR: 3.81, 95%-CI: 1.51-9.61). CONCLUSIONS: In this study low serum levels of potassium were associated with a higher risk of atrial fibrillation.