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Objectives: The purpose of this study was to test whether the association of C-reactive protein (CRP) with increased risk of atrial fibrillation is a robust and perhaps even causal association. Background: Elevated levels of CRP previously have been associated with increased risk of atrial fibrillation. Methods: We studied 10,276 individuals from the prospective Copenhagen City Heart Study, including 771 individuals who had atrial fibrillation during follow-up, and another 36,600 persons from the cross-sectional Copenhagen General Population Study, including 1,340 cases with atrial fibrillation. Individuals were genotyped for 4 CRP gene polymorphisms and had high-sensitivity CRP levels measured. Results: A CRP level in the upper versus lower quintile associated with a 2.19-fold (95% confidence interval [CI]: 1.54- to 3.10-fold) increased risk of atrial fibrillation. Risk estimates attenuated slightly after multifactorial adjustment to 1.77 (95% CI: 1.22 to 2.55), and after additional adjustment for heart failure and plasma fibrinogen level to 1.47 (95% CI: 1.02 to 2.13) and 1.63 (95% CI: 1.21 to 2.20), respectively. Genotype combinations of the 4 CRP polymorphisms associated with up to a 63% increase in plasma CRP levels (p < 0.001), but not with increased risk of atrial fibrillation. The estimated causal odds ratio for atrial fibrillation by instrumental variable analysis for a doubling in genetically elevated CRP levels was lower than the odds ratio for atrial fibrillation observed for a doubling in plasma CRP on logistic regression (0.94 [95% CI: 0.70 to 1.27] vs. 1.36 [95% CI: 1.30 to 1.44]; p < 0.001). Conclusions: Elevated plasma CRP robustly associated with increased risk of atrial fibrillation; however, genetically elevated CRP levels did not. This suggests that elevated plasma CRP per se does not increase atrial fibrillation risk. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to examine the effect of PCSK9 R46L on low-density lipoprotein cholesterol (LDL-C), risk of ischemic heart disease (IHD), and mortality. Background: The 46L allele has been associated with reductions in LDL-C and risk of IHD, but results vary between studies. Methods: We determined the association of R46L genotype with LDL-C, risk of IHD, myocardial infarction (MI), and mortality in the prospective CCHS (Copenhagen City Heart Study) (n = 10,032) and validated the results in: 1) the cross-sectional CGPS (Copenhagen General Population Study) (n = 26,013); and 2) the case-control CIHDS (Copenhagen Ischemic Heart Disease Study) (n = 9,654). We also performed meta-analyses of present and previous studies (n = 66,698). Results: In carriers (2.6%) versus noncarriers, the 46L allele was associated with reductions in LDL-C of 0.35 to 0.55 mmol/l (11% to 16%) from 20 to 80+ years in the general population (CCHS and CGPS; p values <0.0001). Observed risk reductions for IHD in 46L allele carriers were: 6% in the CCHS study (hazard ratio [HR]: 0.94; 95% confidence interval [CI]: 0.68 to 1.31), 46% in the CGPS study (odds ratio [OR]: 0.54; 95% CI: 0.39 to 0.77), 18% in the CIHDS study (OR: 0.82; 95% CI: 0.55 to 1.21), and 30% in the studies combined (OR: 0.70; 95% CI: 0.58 to 0.86). In the CCHS study, HR for mortality was 1.18 (95% CI: 0.93 to 1.50). In meta-analyses, 46L allele carriers had a 12% (0.43 mmol/l) reduction in LDL-C and a 28% reduction in risk of IHD (HR: 0.72; 95% CI: 0.62 to 0.84), similar to results in the CCHS, CGPS, and CIHDS studies combined. However, the observed 12% (0.43 mmol/l) reduction in LDL-C theoretically predicted an only 5% reduction in risk of IHD (HR: 0.95; 95% CI: 0.92 to 0.97). Conclusions: The PCSK9 46L allele was associated with reductions in LDL-C from 20 to 80+ years in the general population. The reduction in risk of IHD was larger than predicted by the observed reduction in LDL-C alone. This could be because genotype is a better predictor of lifelong exposure to LDL-C than LDL-C measured in adult life. [Copyright &y& Elsevier]

Mutations in apolipoprotein B (APOB) may reduce binding of low density lipoprotein (LDL) to the LDL receptor and cause hypercholesterolemia. We showed that heterozygotes for a new mutation in APOB have hypobetalipoproteinemia, despite a reduced binding of LDL to the LDL receptor. APOB R3480P heterozygotes were identified among 9,255 individuals from the general population and had reduced levels of apoB-containing lipoproteins. Most surprisingly, R3480P LDL bound with lower affinity to the LDL receptor than non-carrier LDL in vitro, and these results were confirmed by turnover studies of LDL in vivo. In very low density lipoprotein (VLDL) turnover studies, the amount of VLDL converted to LDL in R3480P heterozygotes was substantially reduced, suggesting that this was the explanation for the hypobetalipoproteinemia observed in these individuals. Our findings emphasized the importance of combining in vitro studies with both human in vivo and population-based studies, as in vitro studies often have focused on very limited aspects of complex mechanisms taken out of their natural context. [ABSTRACT FROM AUTHOR]

Background: Reduced low-density lipoprotein (LDL) cholesterol due to inhibition of proprotein convertase subtilisin/kexin 9 (PCSK9) reduces cardiovascular events and may therefore also reduce cardiovascular and all-cause mortality.Objectives: This study tested the hypothesis that genetically low LDL cholesterol due to PCSK9 variation is causally associated with low cardiovascular and all-cause mortality in the general population.Methods: A total of 109,566 individuals from the Copenhagen General Population Study and the Copenhagen City Heart Study were genotyped for PCSK9 R46L (rs11591147), R237W (rs148195424), I474V (rs562556), and E670G (rs505151). During a median follow-up of 10 years (range 0 to 42 years) and 1,247,225 person-years, there were 3,828 cardiovascular deaths and 16,373 deaths from any cause. Results were validated using data on 431,043 individuals from the UK Biobank.Results: An increasing number of weighted PCSK9 alleles were associated with stepwise lower LDL cholesterol of up to 0.61 mmol/l (24 mg/dl; 18.2%; p for trend <0.001) and with lower cardiovascular mortality (p = 0.001), but not with lower all-cause mortality (p = 0.11). In causal, genetic analyses, a 0.5-mmol/l (19.4-mg/dl) lower LDL cholesterol was associated with risk ratios for cardiovascular and all-cause mortality of 0.79 (95% confidence interval [CI]: 0.63 to 0.99; p = 0.04) and 1.02 (95% CI: 0.94 to 1.12; p = 0.63) in the Copenhagen studies, 0.79 (95% CI: 0.58 to 1.08; p = 0.14) and 0.98 (95% CI: 0.87 to 1.10; p = 0.75) in the UK Biobank, and of 0.79 (95% CI: 0.65 to 0.95; p = 0.01) and 1.01 (95% CI: 0.94 to 1.08; p = 0.85), respectively, in studies combined.Conclusions: Genetically low LDL cholesterol due to PCSK9 variation was causally associated with low risk of cardiovascular mortality, but not with low all-cause mortality in the general population. [ABSTRACT FROM AUTHOR]

Background: Familial hypercholesterolemia (FH) is a condition with very high concentrations of low-density lipoprotein (LDL) cholesterol and high risk of ischemic heart disease including myocardial infarction. However, there is limited and contradictory information on whether FH and high LDL cholesterol per se confer high risk of ischemic stroke. We tested the hypotheses that individuals in the general population with FH and/or high LDL cholesterol have higher risk of ischemic stroke.Methods: The associations of FH and high LDL cholesterol with ischemic stroke risk were tested in both causal, genetic, and observational analyses using 106 412 individuals from the CGPS (Copenhagen General Population Study; 2823 ischemic strokes and 3792 myocardial infarctions) and/or 10 372 individuals from the CCHS (Copenhagen City Heart Study; 945 ischemic strokes and 1142 myocardial infarctions). FH causative mutations were LDLR W23X(rs267607213), W66G(rs121908025) and W556S, and APOB R3500Q(rs5742904). A Mendelian randomization design tested whether high LDL cholesterol per se has a causal effect on ischemic stroke risk, using a combination of the FH causative mutations and common genetic variants associated with high LDL cholesterol.Results: The cumulative incidences in individuals in the CGPS with and without FH causative mutations were similar for ischemic stroke ( P=0.50) but not for myocardial infarction ( P<0.001): at age 80 years, 4% and 7% of these individuals developed ischemic stroke and 20% and 8% myocardial infarction, with similar results in the CCHS. There was no association between clinical FH and ischemic stroke, except if personal premature ischemic heart disease was included in the clinical FH criteria. Ischemic heart disease at baseline was associated with higher ischemic stroke risk, explaining the higher ischemic stroke risk in those with high LDL cholesterol. For a 1 mmol/L higher LDL cholesterol, the genetic causal risk ratio was 1.11 (0.62-2.02) for ischemic stroke and 1.45 (1.08-1.93) for myocardial infarction.Conclusions: FH and high LDL cholesterol did not confer an increased risk of ischemic stroke. A positive association with ischemic stroke observed for some clinical FH criteria and high LDL cholesterol appears to be due to previous ischemic heart disease, rather than to high LDL cholesterol per se. [ABSTRACT FROM AUTHOR]

It is unclear whether elevated low-density lipoprotein (LDL) triglycerides are associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). This study tested the hypothesis that elevated LDL triglycerides are associated with an increased risk of ASCVD and of each ASCVD component individually. The study investigators used the Copenhagen General Population Study, which measured LDL triglycerides in 38,081 individuals with a direct automated assay (direct LDL triglycerides) and in another 30,208 individuals with nuclear magnetic resonance (NMR) spectroscopy (NMR LDL triglycerides). Meta-analyses aggregated the present findings with previously reported results. During a median follow-up of 3.0 and 9.2 years, respectively, 872 and 5,766 individuals in the 2 cohorts received a diagnosis of ASCVD. Per 0.1 mmol/L (9 mg/dL) higher direct LDL triglycerides, HRs were 1.26 (95% CI: 1.17-1.35) for ASCVD, 1.27 (95% CI: 1.16-1.39) for ischemic heart disease, 1.28 (95% CI: 1.11-1.48) for myocardial infarction, 1.22 (95% CI: 1.08-1.38) for ischemic stroke, and 1.38 (95% CI: 1.21-1.58) for peripheral artery disease. Corresponding HRs for NMR LDL triglycerides were 1.26 (95% CI: 1.20-1.33), 1.33 (95% CI: 1.25-1.41), 1.41 (95% CI: 1.31-1.52), 1.13 (95% CI: 1.05-1.23), and 1.26 (95% CI: 1.10-1.43), respectively. The foregoing results were not entirely statistically explained by apolipoprotein B levels. In meta-analyses for the highest quartile vs the lowest quartile of LDL triglycerides, random-effects risk ratios were 1.50 (95% CI: 1.35-1.66) for ASCVD (4 studies; 71,526 individuals; 8,576 events), 1.62 (95% CI: 1.37-1.93) for ischemic heart disease (6 studies; 107,538 individuals; 9,734 events), 1.30 (95% CI: 1.13-1.49) for ischemic stroke (4 studies; 78,026 individuals; 4,273 events), and 1.53 (95% CI: 1.29-1.81) for peripheral artery disease (4 studies; 107,511 individuals; 1,848 events). Elevated LDL triglycerides were robustly associated with an increased risk of ASCVD and of each ASCVD component individually in 2 prospective cohort studies and in meta-analyses of previous and present studies combined. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Plasma apolipoprotein B (apoB) is a composite measure of all apoB-containing lipoproteins causing atherosclerotic cardiovascular disease; however, it is unclear which fraction of risk is explained by cholesterol and triglycerides, respectively, in very low-density lipoproteins (VLDLs).Objectives: The authors tested the hypothesis that VLDL cholesterol and triglycerides each explain part of the myocardial infarction risk from apoB-containing lipoproteins.Methods: Nested within 109,751 individuals from the Copenhagen General Population Study, the authors examined 25,480 subjects free of lipid-lowering therapy and myocardial infarction at study entry. All had measurements of plasma apoB (quantitating number of apoB-containing lipoproteins) and cholesterol and triglyceride content of VLDL, intermediate-density lipoproteins (IDLs), and low-density lipoproteins (LDLs).Results: During a median 11 years of follow-up, 1,816 were diagnosed with myocardial infarction. Per 1-mmol/l higher levels, multivariable-adjusted hazard ratios for myocardial infarction were 2.07 (95% confidence interval [CI]: 1.81 to 2.36) for VLDL cholesterol, 1.19 (95% CI: 1.14 to 1.25) for VLDL triglycerides, 5.38 (95% CI: 3.73 to 7.75) for IDL cholesterol, and 1.86 (95% CI: 1.62 to 2.14) for LDL cholesterol. Per 1-g/l higher plasma apoB, the corresponding value was 2.21 (95% CI: 1.90 to 2.58). In a step-up Cox regression, risk factors for myocardial infarction entered by importance as VLDL cholesterol, systolic blood pressure, smoking, and IDL + LDL cholesterol, whereas VLDL triglycerides did not enter the model. VLDL cholesterol explained 50% and IDL + LDL cholesterol 29% of the risk of myocardial infarction from apoB-containing lipoproteins, whereas VLDL triglycerides did not explain risk.Conclusions: VLDL cholesterol explained one-half of the myocardial infarction risk from elevated apoB-containing lipoproteins, whereas VLDL triglycerides did not explain risk. [ABSTRACT FROM AUTHOR]

Background: Despite the greater prevalence of familial hypercholesterolemia (FH) in subjects with ischemic heart disease (IHD), premature IHD, and severe hypercholesterolemia (low-density lipoprotein ≥190 mg/dl), overall prevalence estimates are not available.Objectives: The aim of this study was to provide worldwide estimates of FH prevalence in subjects with IHD, premature IHD, and severe hypercholesterolemia compared with those in the general population.Methods: In this systematic review and meta-analyses, Embase, PubMed, and the Web of Science were searched until June 3, 2019, for peer-reviewed papers and conference abstracts reporting heterozygous FH prevalence in nonfounder populations, revealing 104 studies eligible for inclusion.Results: Estimates of FH prevalence were pooled using random-effects meta-analyses and were 0.32% (95% confidence interval [CI]: 0.26% to 0.39% [corresponding to 1:313]) among 10,921,310 unique subjects in the general population (33,036 patients with FH) on the basis of 44 studies, 3.2% (95% CI: 2.2% to 4.3% [1:31]) among 84,479 unique subjects with IHD (2,103 patients with FH) on the basis of 28 studies, 6.7% (95% CI: 4.9% to 8.7% [1:15]) among 31,316 unique subjects with premature IHD (1,471 patients with FH) on the basis of 32 studies, and 7.2% (95% CI: 4.6% to 10.8% [1:14]) among 17,728 unique subjects with severe hypercholesterolemia (920 patients with FH) on the basis of 7 studies. FH prevalence in the general population was similar using genetic versus clinical diagnoses. Seventeen of 195 countries (9%) in the world have reported FH prevalence for the general population, leaving 178 (91%) countries in the world with unknown prevalence.Conclusions: Compared with 1:313 among subjects in the general population, FH prevalence is 10-fold higher among those with IHD, 20-fold higher among those with premature IHD, and 23-fold higher among those with severe hypercholesterolemia. The prevalence of FH is unknown in 90% of countries in the world. [ABSTRACT FROM AUTHOR]

Background: Results from randomized controlled trials (RCTs) have raised concern that the cholesterol-lowering drug ezetimibe might increase the risk of cancer. We tested the hypothesis that genetic variation in NPC1L1, mimicking treatment with ezetimibe, was associated with an increased risk of cancer.Methods: We included 67 257 individuals from the general population. Of these, 8333 developed cancer and 2057 died of cancer from 1968 to 2011. To mimic the effect of ezetimibe, we calculated weighted allele scores based on the low-density lipoprotein (LDL) cholesterol-lowering(= NPC1L1-inhibitory) effect of each variant. We tested the associations of the NPC1L1 allele scores with LDL cholesterol and with risk of any cancer, death from any cancer and 27 site-specific cancers. As a positive control, we tested the association of the NPC1L1 allele scores with risk of ischaemic vascular disease (IVD).Results: The NPC1L1 allele scores did not associate with risk of any cancer, death from any cancer or with any of 27 site-specific cancers. Hazard ratios (HRs) for a 1-unit increase in internally weighted allele scores were 1.00 (95% confidence interval: 0.98-1.02) for any cancer, and 1.02 (0.98-1.06) for cancer death. The corresponding HR for IVD was 0.97 (0.94-0.99). Results were similar for an externally weighted allele score and for a simple allele count. Finally, the null association with cancer was robust in sensitivity analyses.Conclusions: Lifelong, genetic inhibition of NPC1L1, mimicking treatment with ezetimibe, does not associate with risk of cancer. These results suggest that long-term treatment with ezetimibe is unlikely to increase the risk of cancer, in agreement with the overall evidence from ezetimibe RCTs. [ABSTRACT FROM AUTHOR]

Background--Elevated nonfasting remnant cholesterol and low-density lipoprotein (LDL) cholesterol are causally associated with ischemic heart disease (IHD), but whether elevated nonfasting remnant cholesterol and LDL cholesterol both cause low-grade inflammation is currently unknown. Methods and Results--We studied 60 608 individuals from the Copenhagen General Population Study, the Copenhagen City Heart Study, and the Copenhagen Ischemic Heart Disease study, of whom 10 668 had IHD diagnosed between 1977 and 2011. We genotyped for variants affecting levels of nonfasting remnant cholesterol, LDL cholesterol, C-reactive protein by CRP alleles, and C-reactive protein by IL6R alleles. Using a multidirectional mendelian randomization design, we investigated possible causal associations between the lipoproteins and C-reactive protein and between the lipoproteins and IHD. A 1-mmol/L(39 mg/dL) higher level of nonfasting remnant cholesterol was associated observationally with a 37% (95% confidence interval, 35-39) higher C-reactive protein level and causally with a 28% (95% confidence interval, 10-48) higher level. For LDL cholesterol, a 1-mmol/L (39-mg/dL) higher level was associated observationally with a 7% (95% confidence interval, 6-7) higher C-reactive protein level, but we found no causal association. Likewise, higher levels of C-reactive protein did not associate causally with elevated nonfasting remnant cholesterol or LDL cholesterol. Finally, the causal risk ratio for IHD for a 1-mmol/L (39-mg/dL) higher level was 3.3 (95% confidence interval, 2.1-5.2) for nonfasting remnant cholesterol and 1.8 (95% confidence interval, 1.5-2.2) for LDL cholesterol. The causal associations for remnant cholesterol were present even in those without diabetes mellitus and obesity. Conclusions--Elevated nonfasting remnant cholesterol is causally associated with low-grade inflammation and with IHD, whereas elevated LDL cholesterol is associated causally with IHD without inflammation. [ABSTRACT FROM AUTHOR]

Background Low plasma levels of low-density lipoprotein (LDL) cholesterol are associated with an increased risk of cancer, but whether this association is causal is unclear. Methods We studied 10 613 participants in the Copenhagen City Heart Study (CCHS) and 59 566 participants in the Copenhagen General Population Study, 6816 of whom had developed cancer by May 2009. Individuals were genotyped for PCSK9 R46L (rs11591147), ABCG8 D19H (rs11887534), and APOE R112C (rs429358) and R158C (rs7412) polymorphisms, all of which are associated with lifelong reduced plasma LDL cholesterol levels. Plasma LDL cholesterol was calculated using the Friedewald equation in samples in which the triglyceride level was less than 354 mg/dL and measured directly by colorimetry for samples with higher triglyceride levels. Risk of cancer was estimated prospectively using Cox proportional hazards regression analyses and cross-sectionally by logistic regression analyses. Causality was studied using instrumental variable analysis. All statistical tests were two-sided. Results In the CCHS, compared with plasma LDL cholesterol levels greater than the 66th percentile (>158 mg/dL), those lower than the 10th percentile (<87 mg/dL) were associated with a 43% increase (95% confidence interval [CI] = 15% to 79% increase) in the risk of cancer. The polymorphisms were associated with up to a 38% reduction (95% CI = 36% to 41% reduction) in LDL cholesterol levels but not with increased risk of cancer. The causal odds ratio for cancer for a 50% reduction in plasma LDL cholesterol level due to all the genotypes in both studies combined was 0.96 (95% CI = 0.87 to 1.05), whereas the hazard ratio of cancer for a 50% reduction in plasma LDL cholesterol level in the CCHS was 1.10 (95% CI = 1.01 to 1.21) (P for causal odds ratio vs observed hazard ratio = .03). Conclusion Low plasma LDL cholesterol levels were robustly associated with an increased risk of cancer, but genetically decreased LDL cholesterol was not. This finding suggests that low LDL cholesterol levels per se do not cause cancer. [ABSTRACT FROM PUBLISHER]

A response by Anette Varbo, Marianne Benn and colleagues to letters to the editor about their paper "Elevated Remnant Cholesterol Causes Both Low-Grade Inflammation and Ischemic Heart Disease, Whereas Elevated Low-Density Lipoprotein Cholesterol Causes Ischemic Heart Disease Without Inflammation" published in "Circulation" is presented.