Adherence to dietary guidelines and risk of dementia: a prospective cohort study of 94 184 individuals.

AIMS: Recent estimates suggest that 40% of dementia cases could be avoided by treating recognised cardiovascular risk factors such as hypertension, diabetes, smoking and physical inactivity. Whether diet is associated with dementia remains largely unknown. We tested if low adherence to established dietary guidelines is associated with elevated lipids and lipoproteins and with increased risk of Alzheimer's disease and non-Alzheimer's dementia ­ a dementia subtype with a high frequency of cardiovascular risk factors. METHODS: We used the prospective Copenhagen General Population Study including 94 184 individuals with dietary information and free of dementia at baseline. Mean age at study entry was 58 years, and 55% (N = 51 720) were women and 45% (N = 42 464) were men. Adherence to dietary guidelines was grouped into low, intermediate and high adherence based on food frequency questionnaires. Main outcomes were non-Alzheimer's dementia and Alzheimer's disease. RESULTS: Low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol and plasma triglyceride levels were higher in individuals with intermediate and low adherence to dietary guidelines compared with individuals with high adherence (all p for trends <0.001). Age and sex-adjusted hazard ratios (HRs) for non-Alzheimer's dementia v. individuals with high adherence were 1.19 (95% confidence interval 0.97­1.46) for intermediate adherence, and 1.54 (1.18­2.00) for low adherence. Corresponding HRs in multivariable-adjusted models including APOE genotype were 1.14 (0.92­1.40) and 1.35 (1.03­1.79). These relationships were not observed in individuals on lipid-lowering therapy. CONCLUSIONS: Low adherence to national dietary guidelines is associated with an atherogenic lipid profile and with increased risk of non-Alzheimer's dementia ­ the subtype of dementia with a high frequency of vascular risk factors. This study suggests that implementation of dietary guidelines associated with an anti-atherogenic lipid profile could be important for prevention of non-Alzheimer's dementia.

Coffee intake protects against symptomatic gallstone disease in the general population: a Mendelian randomization study.

BACKGROUND AND OBJECTIVES: Coffee intake is associated with low risk of symptomatic gallstone disease (GSD). We tested the hypothesis that high coffee intake causally protects against symptomatic GSD using a Mendelian randomization design. METHODS: First, we tested whether high coffee intake was associated with low risk of GSD in 104 493 individuals from the general population. Mean follow-up was 8 years (range: <1-13 years). Secondly, we tested whether two genetic variants near CYP1A1/A2 (rs2472297) and AHR (rs4410790), combined as an allele score, were associated with higher coffee intake measured as a continuous variable. Thirdly, we tested whether the allele score was associated with lower risk of GSD in 114 220 individuals including 7294 gallstone events. Mean follow-up was 38 years (range: <1-40 years). RESULTS: In observational analysis, those with coffee intake of >6 cups daily had 23% lower risk of GSD compared to individuals without coffee intake [hazard ratio (HR) = 0.77 (95% confidence interval: 0.61-0.94)]. In genetic analysis, there was a stepwise higher coffee intake of up to 41% (caffeine per day) in individuals with 4 (highest) versus 0 (lowest) coffee intake alleles (P for trend = 3 x 10-178 ) and a corresponding stepwise lower risk of GSD up to 19%[HR = 0.81 (0.69-0.96)]. The estimated observational odds ratio for GSD for a one cup per day higher coffee intake was 0.97 (0.96-0.98), equal to 3% lower risk. The corresponding genetic odds ratio was 0.89 (0.83-0.95), equal to 11% lower risk. CONCLUSION: High coffee intake is associated observationally with low risk of GSD, and with genetic evidence to support a causal relationship.

Disminución de triglicéridos sin ayuno y reducción de mortalidad por cualquier causa: un estudio de randomización mendeliana / Low nonfasting triglycerides and reduced all-cause mortality: a mendelian randomization study

Antecedentes: El aumento de los triglicéridos plasmáticos sin ayuno, marcador del aumento de colesterol en lipoproteínas remanentes, es un importante factor de riesgo para enfermedad cardiovascular, pero se desconoce si la reducción en las concentraciones de triglicéridos, sobre una base genética, a lo largo de toda la vida en última instancia conduce a una menor mortalidad por cualquier causa. Pusimos a prueba esta hipótesis. Métodos: Estudiando individuos del Copenhagen City Heart Study en un diseño de randomización mendeliana, en primer lugar estudiamos si las menores concentraciones de triglicéridos sin ayuno se asociaron con una reducción de mortalidad por cualquier causa en un análisis observacional (n=13.957); segundo, si variantes genéticas en la enzima hidrolizante de triglicéridos lipoproteína lipasa, que resultan en reducción de los triglicéridos plasmáticos sin ayuno y del colesterol de remanentes, se asociaron con una reducción de mortalidad por cualquier causa (n=10.208). Resultados...

Background: Increased nonfasting plasma triglycerides marking increased amounts of cholesterol in remnant lipoproteins are important risk factors for cardiovascular disease, but whether lifelong reduced concentrations of triglycerides on a genetic basis ultimately lead to reduced all-cause mortality is unknown. We tested this hypothesis. Methods: Using individuals from the Copenhagen City Heart Study in a mendelian randomization design, we first tested whether low concentrations of nonfasting triglycerides were associated with reduced all-cause mortality in observational analyses (n = 13 957); second, whether genetic variants in the triglyceride-degrading enzyme lipoprotein lipase, resulting in reduced nonfasting triglycerides and remnant cholesterol, were associated with reduced all-cause mortality (n = 10 208). Results...

Endogenous sex hormones and risk of venous thromboembolism in women and men.

BACKGROUND: Use of oral contraceptives with estrogen and hormone replacement therapy with estrogen or testosterone are associated with increased risk of venous thromboembolism (VTE). However, whether endogenous estradiol and testosterone concentrations are also associated with risk of VTE is unknown. OBJECTIVE: We tested the hypothesis that elevated endogenous total estradiol and total testosterone concentrations are associated with increased risk of VTE in the general population. METHODS: We studied 4658 women, not receiving exogenous estrogen, and 4673 men from the 1981-1983 Copenhagen City Heart Study, who had estradiol and testosterone concentrations measured. Of these, 636 developed VTE (deep venous thrombosis [DVT] and/or pulmonary embolism [PE]) during a follow-up of 21 years (range, 0.02-32 years). Associations between endogenous estradiol and testosterone concentrations and risk of VTE were estimated by Cox proportional hazards regression with time-dependent covariates and corrected for regression dilution bias. RESULTS: Multifactorially adjusted hazard ratios of VTE for individuals with estradiol levels >75th vs. ≤25th percentile were 0.84 (95%CI, 0.25-2.85), 1.05 (0.53-2.08) and 1.05 (0.03-35.13) for pre- and post-menopausal women and men, respectively. For testosterone, corresponding risk estimates were 0.64 (0.03-12.32), 1.11 (0.66-1.86) and 1.30 (0.62-2.73). In addition, no associations were observed between extreme hormone percentiles (>95th vs. ≤75th) and risk of DVT, PE or recurrent VTE. CONCLUSION: This prospective study suggests that high endogenous concentrations of estradiol and testosterone in women and men in the general population are not associated with increased risk of VTE, DVT or PE.

25-Hydroxyvitamin D concentrations and risk of venous thromboembolism in the general population with 18,791 participants.

BACKGROUND: Vitamin D has potential antithrombotic effects, suggesting that vitamin D analogs could be used as adjunctive antithrombotic agents. However, epidemiologic evidence of an association between reduced 25-hydroxyvitamin D concentrations and the risk of venous thromboembolism is lacking. OBJECTIVES: To test the hypothesis that reduced plasma 25-hydroxyvitamin D concentrations are associated with an increased risk of venous thromboembolism in the general population. METHODS: We prospectively studied 18 791 participants from the Copenhagen City Heart Study and the Copenhagen General Population Study. During up to 30 years of follow-up, 950 participants were diagnosed with venous thromboembolism. Plasma 25-hydroxyvitamin D concentrations were adjusted for seasonal variation. RESULTS: The cumulative incidence of venous thromboembolism as a function of age increased with decreasing tertiles of seasonally adjusted plasma 25-hydroxyvitamin D (log-rank trend: P = 4 × 10(-4) ). On comparison of participants in the lowest and the highest tertile of plasma 25-hydroxyvitamin D concentrations, the crude risk estimate in a model adjusted for age and sex was a 37% (95% confidence interval [CI] 15-64%) increased risk of venous thromboembolism. The corresponding risk increase in a model adjusted for age, sex, body mass index, smoking and cancer was 26% (95% CI 5-51%), and in a multivariable-adjusted model also including physical activity, hormone replacement therapy, menopausal status, oral contraception use and lipid-lowering therapy it was 28% (95% CI 6-53%). Furthermore, corresponding risk increases with attempts to correct for regression dilution bias were 103% (95% CI 37-202%), 70% (95% CI 14-155%) and 73% (95% CI 15-160%) in the three models, respectively. CONCLUSION: In these large general population studies, we observed a stepwise increasing risk of venous thromboembolism with decreasing tertiles of seasonally adjusted plasma 25-hydroxyvitamin D concentrations.

Genetically elevated bilirubin and risk of ischaemic heart disease: three Mendelian randomization studies and a meta-analysis.

BACKGROUND: Elevated plasma levels of bilirubin, an endogenous antioxidant, have been associated with reduced risk of ischaemic heart disease (IHD) and myocardial infarction (MI). Whether this is a causal relationship remains unclear. OBJECTIVE: We tested the hypothesis that elevated plasma bilirubin is causally related to decreased risk of IHD and MI. DESIGN: We used a Mendelian randomization approach and three independent studies from Copenhagen, Denmark. We measured bilirubin in 43 708 white individuals from the general population, and genotyped rs6742078 G>T in the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene in 67 068 individuals, of whom 11 686 had IHD. RESULTS: Third versus first tertile of baseline bilirubin levels was associated with 134% increased bilirubin levels, with sex- and age-adjusted hazard ratios (HRs) of 0.86 [95% confidence interval (CI), 0.76-0.98; P = 0.02] for IHD and 0.81 (95% CI, 0.66-0.99; P = 0.04) for MI, but with corresponding multifactorially adjusted HRs of 0.93 (95% CI, 0.82-1.06; P = 0.29) and 0.90 (95% CI, 0.73-1.12; P = 0.35). UGT1A1 rs6742078 TT versus GG genotype was associated with 95% increased bilirubin levels (P < 0.001); TT versus GG genotype was associated with odds ratios (ORs) of 1.03 (95% CI, 0.96-1.11; P = 0.73) for IHD and 1.01 (95% CI, 0.92-1.12; P = 0.68) for MI. Finally, in a meta-analysis of the present three studies and eight previous studies including a total of 14 711 cases and 60 324 controls, the random effects OR for ischaemic cardiovascular disease for genotypes with approximately 100% increased bilirubin levels versus reference genotypes was 1.01 (95% CI, 0.88-1.16). CONCLUSION: These data suggest that plasma bilirubin is not causally associated with risk of IHD.

ß2-adrenergic receptor polymorphisms, asthma and COPD: two large population-based studies.

The ß(2)-adrenergic receptor (ADRB2) is an important regulator of airway smooth muscle tone. We tested the hypothesis that three functional polymorphisms in the ADRB2 gene (Thr164Ile, Gly16Arg and Gln27Glu) are associated with reduced lung function, asthma or chronic obstructive pulmonary disease (COPD). We first genotyped 8,971 individuals from the Copenhagen City Heart Study for all three polymorphisms. To validate our findings, we genotyped an additional 53,777 individuals from the Copenhagen General Population Study for the Thr164Ile polymorphism. We identified 60,910 Thr164Ile noncarriers, 1,822 heterozygotes and 16 homozygotes. In the Copenhagen City Heart Study, the Thr164Ile genotype was associated with reduced forced expiratory volume in 1 s (FEV(1)) % predicted (trend p = 0.01) and FEV(1)/forced vital capacity (FVC) (p = 0.001): Thr164Ile heterozygotes had 3% and 2% reduced FEV(1) % pred and FEV(1)/FVC, respectively, compared with noncarriers. The odds ratio for COPD in Thr164Ile heterozygotes was 1.46 (95% CI 1.05-2.02). In the Copenhagen General Population Study, the Thr164 genotype associated with reduced FEV(1) % pred (p = 0.04) and FEV(1)/FVC (p < 0.001): Thr164Ile homozygotes and heterozygotes had 7% and 1% reduced FEV(1) % pred and 6% and 1% reduced FEV(1)/FVC, respectively, compared with noncarriers. The odds ratios for COPD in Thr164Ile homozygotes and heterozygotes were 4.53 (95% CI 1.54-13.3) and 1.07 (95% CI 0.92-1.25), respectively. Our results suggest that ADRB2 Thr164Ile is associated with reduced lung function and increased risk of COPD in the general population.

ß2 -adrenergic receptor Thr164IIe polymorphism, blood pressure and ischaemic heart disease in 66 750 individuals.

OBJECTIVES: The ß(2) -adrenergic receptor (ADRB2) is located on smooth muscle cells and is an important regulator of smooth muscle tone. The Thr164Ile polymorphism (rs1800888) in the ADRB2 gene is rare but has profound functional consequences on receptor function and could cause lifelong elevated smooth muscle tone. We tested the hypothesis that Thr164Ile is associated with increased blood pressure, increased frequency of hypertension and increased risk of cardiovascular disease (CVD). SUBJECTS: A total of 66 750 individuals from two large Danish general population studies were genotyped, and 1943 Thr164Ile heterozygotes and 16 homozygotes were identified. RESULTS: Thr164Ile genotype was associated with increased systolic and diastolic blood pressure in women (trend: P = 0.04 and 0.02): systolic and diastolic blood pressure increased by 5% and 2%, respectively, in female homozygotes compared with female noncarriers. All female Thr164Ile homozygotes had hypertension compared with 58% of female heterozygotes and 54% of female noncarriers (chi-square: P = 0.001). Female Thr164Ile homozygotes and heterozygotes had odds ratios for ischaemic heart disease (IHD) of 2.93 (0.56-15.5) and 1.28 (1.03-1.61), respectively, compared with female noncarriers (trend: P = 0.007). These differences were not observed in men. Furthermore, Gly16Arg (rs1042713) and Gln27Glu (rs1042714) in the ADRB2 gene were not associated with blood pressure, hypertension or CVD either in the population overall or in women and men separately. CONCLUSIONS: ADRB2 Thr164Ile is associated with increased blood pressure, increased frequency of hypertension and increased risk of IHD amongst women in the general population. These findings, particularly for homozygotes, are novel.

Risk of cancer by transferrin saturation levels and haemochromatosis genotype: population-based study and meta-analysis.

OBJECTIVE: Increased iron overload, whether or not owing to the presence of the haemochromatosis genotype C282Y/C282Y, may be associated with an increased risk of cancer. The aim of this study was to test the hypothesis that elevated transferrin saturation levels (as a proxy for iron overload) and haemochromatosis genotype C282Y/C282Y are associated with an increased risk of cancer. METHODS: We conducted a population-based study of 8763 individuals, of whom 1417 developed a first cancer during 15years of follow-up, and a meta-analysis. We stratified absolute 10-year risk of cancer by smoking status, an important risk factor. RESULTS: In women, transferrin saturation above 60% versus below 50% was associated with a hazard ratio of 3.6 (95% confidence interval (CI): 2.0-6.5; P<0.001) for any cancer; risk of liver cancer was increased in both women and men. In women, the corresponding absolute 10-year risk of any cancer was 34% and 30% in smokers and nonsmokers, respectively. In men, haemochromatosis genotype C282Y/C282Y versus wild type/wild type was associated with a hazard ratio of 3.7 (95% CI: 1.2-12; P=0.01) for any cancer, with a similar trend in women. In men, the corresponding absolute 10-year risk of cancer was 39% and 27% in smokers and nonsmokers, respectively. Other haemochromatosis genotypes were not associated with increased risk of cancer in women or men. From the meta-analysis, the odds ratio of any cancer for transferrin saturation ≥60% versus a reference group was 1.5 (95% CI: 1.2-1.8) for women and men combined. CONCLUSIONS: We have demonstrated that elevated transferrin saturation levels in women and haemochromatosis genotype C282Y/C282Y in men are associated with increased risk of cancer. Thus, our results support the implementation of cancer screening programmes in patients with iron overload or with C282Y/C282Y.

Mutation in APOA1 predicts increased risk of ischaemic heart disease and total mortality without low HDL cholesterol levels.

OBJECTIVES: To determine whether mutations in APOA1 affect levels of high-density lipoprotein (HDL) cholesterol and to predict risk of ischaemic heart disease (IHD) and total mortality in the general population. BACKGROUND: Epidemiologically, risk of IHD is inversely related to HDL cholesterol levels. Mutations in apolipoprotein (apo) A-I, the major protein constituent of HDL, might be associated with low HDL cholesterol and predispose to IHD and early death. DESIGN: We resequenced APOA1 in 190 individuals and examined the effect of mutations on HDL cholesterol, risk of IHD, myocardial infarction (MI) and mortality in 10 440 individuals in the prospective Copenhagen City Heart Study followed for 31 years. Results were validated in an independent case-control study (n = 16 035). Additionally, we determined plasma ratios of mutant to wildtype (WT) apoA-I in human heterozygotes and functional effects of mutations in adenovirus-transfected mice. RESULTS: We identified a new mutation, A164S (1 : 500 in the general population), which predicted hazard ratios for IHD, MI and total mortality of 3.2 [95% confidence interval (CI): 1.6-6.5], 5.5 (95% CI: 2.6-11.7) and 2.5 (95% CI: 1.3-4.8), respectively, in heterozygotes compared with noncarriers. Mean reduction in survival time in heterozygotes was 10 years (P < 0.0001). Results for IHD and MI were confirmed in the case-control study. Furthermore, the ratio of mutant S164 to WT A164 apoA-I in plasma of heterozygotes was reduced. In addition, A164S heterozygotes had normal plasma lipid and lipoprotein levels, including HDL cholesterol and apoA-I, and this finding was confirmed in adenovirus-transfected mice. CONCLUSIONS: A164S is the first mutation in APOA1 to be described that predicts an increased risk of IHD, MI and total mortality without low HDL cholesterol levels.

Nonfasting cholesterol and triglycerides and association with risk of myocardial infarction and total mortality: the Copenhagen City Heart Study with 31 years of follow-up.

OBJECTIVES: We compared the ability of very high levels of nonfasting cholesterol and triglycerides to predict risk of myocardial infarction and total mortality. DESIGN: Prospective study from 1976 to 1978 until 2007. SETTING: Danish general population. PARTICIPANTS: Randomly selected population of 7581 women and 6391 men, of whom 768 and 1151 developed myocardial infarction and 4398 and 4416 died, respectively. Participation rate was 72%, and follow-up was 100% complete. Less than 2% of participants were taking lipid-lowering therapy. RESULTS: Compared to women with cholesterol <5 mmol L(-1) , multivariate-adjusted hazard ratios for myocardial infarction ranged from 1.3 [95% confidence interval (CI): 0.9-1.8] for a cholesterol level of 5.0-5.99 mmol L(-1) to 2.5 (95%CI: 1.6-4.0) for cholesterol ≥ 9 mmol L(-1) (trend: P < 0.0001). Compared with women with nonfasting triglycerides <1 mmol L(-1) , hazard ratios for myocardial infarction ranged from 1.5 (95%CI: 1.2-1.8) for triglycerides of 1.0-1.99 mmol L(-1) to 4.2 (95%CI: 2.5-7.2) for triglycerides ≥ 5 mmol L(-1) (p<0.0001). In men, corresponding hazard ratios ranged from 1.2 (95%CI: 1.0-1.5) to 5.3 (95%CI: 3.6-8.0) for cholesterol (P < 0.0001) and from 1.3 (95%CI: 1.0-1.6) to 2.1 (95%CI: 1.5-2.8) for triglycerides (P < 0.0001). Increasing cholesterol levels were not consistently associated with total mortality in women (trend: P = 0.39) or men (P = 0.02). By contrast, compared with women with triglycerides <1 mmol L(-1) , multivariate-adjusted hazard ratios for total mortality ranged from 1.1 (95%CI: 1.0-1.2) for triglycerides of 1.0-1.99 mmol L(-1) to 2.0 (95%CI: 1.5-2.9) for triglycerides ≥5 mmol L(-1) (trend: P < 0.0001); corresponding hazard ratios in men ranged from 1.1 (95%CI: 1.0-1.2) to 1.5 (95%CI: 1.2-1.7) (P < 0.0001). CONCLUSIONS: Stepwise increasing levels of nonfasting cholesterol and nonfasting triglycerides were similarly associated with stepwise increasing risk of myocardial infarction, with nonfasting triglycerides being the best predictor in women and nonfasting cholesterol the best predictor in men. Even more surprisingly, only increasing levels of nonfasting triglycerides were associated with total mortality, whereas increasing cholesterol levels were not.

Mutation analysis and evaluation of the cardiac localization of TMEM43 in arrhythmogenic right ventricular cardiomyopathy.

A single report has associated mutations in TMEM43 (LUMA) with a distinctive form of arrhythmogenic right ventricular cardiomyopathy (ARVC). We aimed at performing mutational analysis of the gene and characterizing the associated immunohistochemical features. Sixty-five unrelated patients (55 fulfilling Task Force criteria and 10 borderline cases) were screened for mutations in TMEM43. Immunohistochemistry with anti-TMEM43, anti-plakoglobin, anti-plakophilin-2, anti-connexin-43, and anti-emerin antibodies was performed on myocardium from TMEM43-positive patients (n = 3) and healthy controls (n = 3). The genetic screening identified heterozygous variants in two families: one reported mutation (c.1073C> T; in two related patients) and one novel variant (c.705+ 7G> A; in one patient) of unknown significance. All three patients fulfilled Task Force criteria and did not carry mutations in any other ARVC-related gene. Immunostaining with TMEM43 antibody showed intense staining of the sarcolemma. The signal level was reduced in all the three TMEM43-positive patients. Immunostaining with plakoglobin-specific antibody also showed reduced signal levels in the three carriers. All patients displayed a similar immunoreactive signal for plakophilin-2, connexin-43, and emerin. In conclusion, two TMEM43 sequence variants were identified in this Danish ARVC cohort. Evaluation of the expression of TMEM43 showed a unique cardiac localization. The immunoreactive signal for the desmosomal protein plakoglobin was reduced in mutation carriers. The TMEM43 gene underlies a distinctive form of ARVC which may share a final common pathway with desmosome-associated ARVC.

Scavenger receptor AI/II truncation, lung function and COPD: a large population-based study.

OBJECTIVES: The scavenger receptor A-I/II (SRA-I/II) on alveolar macrophages is involved in recognition and clearance of modified lipids and inhaled particulates. A rare variant of the SRA-I/II gene, Arg293X, truncates the distal collagen-like domain, which is essential for ligand recognition. We tested whether the Arg293X variant is associated with reduced lung function and risk of chronic obstructive pulmonary disease (COPD) in the general population. METHODS: We genotyped 48,741 individuals from the adult Danish general population for Arg293X, and recorded lung function and spirometry-defined COPD. RESULTS: Arg293X homozygotes (n = 5) and heterozygotes (n = 587), compared with noncarriers (n = 48,149), had a 6% and 1% reduction in predicted percentage of forced vital capacity (FVC % predicted) (P = 0.05) and a nonsignificant 7% and 1% reduction in predicted percentage of forced expiratory volume in one second (FEV(1) % predicted) (P = 0.06), respectively. The Arg293X genotype interacted with gender (P = 0.004) and α(1) -antitrypsin MZ heterozygosity (P = 0.049), but not with superoxide dismutase-3 E1I1 heterozygosity (P = 0.11) in determining FEV(1) % predicted. Amongst men, FEV(1) % predicted and FVC % predicted were both reduced by 4% (P = 0.0004 and P = 0.0003, respectively) in Arg293X heterozygotes compared with noncarriers. Corresponding values were 14% (P = 0.03) and 11% (P = 0.04) amongst MZ heterozygotes, and 9% (P = 0.03) and 8% (P = 0.04) amongst E1I1 heterozygotes, compared with noncarriers. Lung function did not differ between Arg293X heterozygotes and noncarriers amongst females or individuals without MZ and E1I1. Arg293X heterozygosity was associated with spirometry-defined COPD amongst men [odds ratio (95% confidence interval): 1.7 (1.1-2.4)], but not with COPD in the whole cohort or in any other subgroup. CONCLUSIONS: SRAI/II Arg293X heterozygotes have reduced lung function and increased COPD risk amongst men. They also have reduced lung function amongst individuals heterozygous for the α(1)-antitrypsin MZ and superoxide dismutase-3 E1I1 genotypes.

C-reactive protein levels and body mass index: elucidating direction of causation through reciprocal Mendelian randomization.

CONTEXT: The assignment of direction and causality within networks of observational associations is problematic outside randomized control trials, and the presence of a causal relationship between body mass index (BMI) and C-reactive protein (CRP) is disputed. OBJECTIVE: Using reciprocal Mendelian randomization, we aim to assess the direction of causality in relationships between BMI and CRP and to demonstrate this as a promising analytical technique. PARTICIPANTS AND METHODS: The study was based on a large, cross-sectional European study from Copenhagen, Denmark. Genetic associates of BMI (FTO(rs9939609)) and circulating CRP (CRP(rs3091244)) have been used to reexamine observational associations between them. RESULTS: Observational analyses showed a strong, positive association between circulating CRP and BMI (change in BMI for a doubling in log CRP of 1.03 kg m(-2) (95% confidence interval (95% CI): 1.00, 1.07), P<0.0001). Analysis using CRP(rs3091244) to re-estimate the causal effect of circulating CRP on BMI yielded null effects (change in BMI for a doubling in log CRP of -0.24 kg m(-2) (95% CI: -0.58, 0.11), P=0.2). In contrast, analysis using FTO(rs9939609) to assess the causal effect of BMI on circulating CRP confirmed observational associations (ratio of geometric means of CRP per s.d. increase in BMI 1.41 (95% CI: 1.10, 1.80), P=0.006). CONCLUSIONS: Taken together, these data suggest that the observed association between circulating CRP and measured BMI is likely to be driven by BMI, with CRP being a marker of elevated adiposity. More generally, the method of reciprocal randomization has general applicability in determining the direction of causation within inter-correlated networks of metabolic components.

Copy number variation in glutathione-S-transferase T1 and M1 predicts incidence and 5-year survival from prostate and bladder cancer, and incidence of corpus uteri cancer in the general population.

Glutathione-S-transferase T1 (GSTT1) and GSTM1 detoxify carcinogens and thus potentially contribute to inter-individual susceptibility to cancer. We determined the ability of GST copy number variation (CNV) to predict the risk of cancer in the general population. Exact copy numbers of GSTT1 and GSTM1 were measured by real-time PCR in 10 247 individuals, of whom 2090 had cancer. In men, the cumulative incidence of prostate cancer increased and the cumulative 5-year survival decreased with decreasing GSTT1 copy numbers (trends=0.02). The hazard ratios (HRs) (95% CIs) for prostate cancer and for death after prostate cancer diagnosis were, respectively, 1.2 (0.8-1.8) and 1.2 (0.6-2.1) for GSTT1*1/0, and 1.8 (1.1-3.0) and 2.2 (1.1-4.4) for GSTT1*0/0 versus GSTT1*1/1. In women, the cumulative incidence of corpus uteri cancer increased with decreasing GSTT1 copy numbers (trend=0.04). The HRs for corpus uteri cancer were, respectively, 1.8 (1.0-3.2) and 2.2 (1.0-4.6) for GSTT1*1/0 and GSTT1*0/0 versus GSTT1*1/1. Finally, the cumulative incidence of bladder cancer increased, and the cumulative 5-year survival decreased, with decreasing GSTM1 copy numbers (P=0.03-0.05). The HRs for bladder cancer were, respectively, 1.5 (0.7-3.2) and 2.0 (0.9-4.3) for GSTM1*1/0 and GSTM1*0/0 versus GSTM1*1/1. The HR for death after bladder cancer diagnosis was 1.9 (1.0-3.7) for GSTM1*0/0 versus GSTM1*1/0. In conclusion, exact CNV in GSTT1 and GSTM1 predict incidence and 5-year survival from prostate and bladder cancer, and incidence of corpus uteri cancer.

Wide spectrum of desmosomal mutations in Danish patients with arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a lethal condition characterised by ventricular tachyarrhythmias, right and/or left ventricular involvement and fibrofatty infiltrations in the myocardium. The disease has been associated with mutations in genes encoding desmosomal proteins. OBJECTIVE: To thoroughly evaluate an ARVC cohort for desmosomal mutations and large genomic rearrangements and characterise the phenotype associated with double-mutation carrier status. METHODS: 65 unrelated patients (55 fulfilling current criteria and 10 borderline cases) were screened for mutations in all known desmosome genes (desmocollin-2 (DSC2), desmoglein-2 (DSG2), desmoplakin (DSP), plakoglobin (JUP) and plakophilin-2 (PKP2)) and TGFb3. Presence of genomic rearrangements was assessed by multiplex ligation-dependent probe amplification. Results The screening identified 19 different mutations: two mutations in DSG2, four in DSC2, two in DSP (one heterozygous and one homozygous), four in JUP (one patient with compound heterozygous) and seven in PKP2. No genomic rearrangements or mutations in TGFb3 were identified. Ten of the mutations were novel. Seven families carried more than one mutation. Clinical evaluation of these families showed a variable phenotype associated with the double-mutation carrier status. The homozygous desmoplakin mutation (DSP p.G2056R+p.G2056R) carrier came from a consanguineous Danish family and had left ventricular involvement, palmar keratoderma and curly hair consistent with a Carvajal-like syndrome. CONCLUSIONS: 33% of patients in this Danish cohort with ARVC carried desmosomal mutations with a surprisingly wide mutation spectrum. A substantial proportion of patients carried more than one mutation. Our study supports comprehensive desmosomal mutation screening beyond the first encountered mutation, whereas routine screening for genomic rearrangements does not seem indicated.

Novel mutations in leukotriene C4 synthase and risk of cardiovascular disease based on genotypes from 50,000 individuals.

BACKGROUND: Atherosclerosis is an inflammatory condition where cysteinyl leukotrienes have been identified to play an important role. Furthermore, cysteinyl leukotrienes may also affect thrombus formation. Using prospective, cross-sectional and case-control designs, we tested the hypothesis that hitherto unknown genetic variation, likely to affect the function of leukotriene C(4) synthase, is associated with risk of venous thromboembolism, ischemic stroke and myocardial infarction. METHODS AND RESULTS: Resequencing the gene coding for leukotriene C(4) synthase in an extreme risk population with more than 1500 individuals revealed 17 new mutations, of which four are likely to change protein function (211G>A (minor allele frequency, 0.0001), IVS3 + 1G>A (0.002), 374G>A (0.0006) and 451_453+10del (0.0007)). Based on genotyping 50,000 individuals, age and sex adjusted odds ratios for venous thromboembolism were 2.0 (95% CI, 1.3-3.5) for IVS3+1G>A heterozygotes vs. wild type, and 1.9 (1.5-2.7) for any mutation heterozygote vs. wild type. Corresponding values were 2.0 (1.3-3.2) and 1.5 (1.1-2.1) for ischemic stroke, and 1.0 (0.8-1.3) and 1.2 (1.0-1.4) for myocardial infarction. CONCLUSIONS: Four novel mutations that are likely to change the function of leukotriene C(4) synthase were associated with increased risk of venous thromboembolism and ischemic stroke. These findings need confirmation in other independent studies. In addition, the mechanism behind these findings deserves further investigation.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables.

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

Haemochromatosis genotype and iron overload: association with hypertension and left ventricular hypertrophy.

OBJECTIVE: We hypothesized that there is an association between haemochromatosis genotype C282Y/C282Y and/or iron overload and risk of hypertension and/or left ventricular hypertrophy (LVH). METHODS: We analysed data from a cross-sectional study of the general population including 8992 individuals from the Copenhagen City Heart Study (CCHS), a follow-up study of 36,480 individuals from the Copenhagen General Population Study (CGPS), and a case-only study of 3815 Scandinavians from the Losartan Intervention For End-point Reduction in Hypertension Genetic Substudy (LIFEGEN) with LVH and hypertension. RESULTS: In the CCHS, individuals with C282Y/C282Y versus wild type/wild type had an odds ratio for antihypertensive medication use of 4.8 (1.8-13; P = 0.003). In the CGPS, the corresponding hazard ratio was 1.7 (1.0-2.3; P = 0.003). Also, hazard ratios for antihypertensive medication use in the CGPS were 1.6 (1.0-2.6; P = 0.05) for transferrin saturation > or =80% vs. <50%, and 2.3 (1.3-4.2; P = 0.005) for C282Y/C282Y + transferrin saturation > or =80% vs. wild type/wild type + transferrin saturation <50%. These results were most pronounced in men above 55 years of age. We did not find any association between C282Y/C282Y or iron overload and LVH or hypertension (measured as blood pressure at a single occasion or continuous blood pressure), or LVH with hypertension in the CCHS or with severity of LVH in LIFEGEN. CONCLUSIONS: We found that haemochromatosis genotype C282Y/C282Y and extremely elevated transferrin saturation either separately or combined were associated with increased risk of antihypertensive medication use. Therefore, testing for haemochromatosis genotype C282Y/C282Y and extreme transferrin saturation could be considered in patients with essential hypertension.

Systematically missing confounders in individual participant data meta-analysis of observational cohort studies.

One difficulty in performing meta-analyses of observational cohort studies is that the availability of confounders may vary between cohorts, so that some cohorts provide fully adjusted analyses while others only provide partially adjusted analyses. Commonly, analyses of the association between an exposure and disease either are restricted to cohorts with full confounder information, or use all cohorts but do not fully adjust for confounding. We propose using a bivariate random-effects meta-analysis model to use information from all available cohorts while still adjusting for all the potential confounders. Our method uses both the fully adjusted and the partially adjusted estimated effects in the cohorts with full confounder information, together with an estimate of their within-cohort correlation. The method is applied to estimate the association between fibrinogen level and coronary heart disease incidence using data from 154,012 participants in 31 cohorts