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Aims The association of plasma high-density lipoprotein (HDL) cholesterol with risk of dementia is unclear. We, therefore, tested the hypothesis that high levels of plasma HDL cholesterol are associated with increased risk of dementia and whether a potential association is of a causal nature. Methods and results In two prospective population-based studies, the Copenhagen General Population Study and the Copenhagen City Heart Study (N  = 111 984 individuals), we first tested whether high plasma HDL cholesterol is associated with increased risk of any dementia and its subtypes. These analyses in men and women separately were adjusted multifactorially for other risk factors including apolipoprotein E (APOE) genotype. Second, taking advantage of two-sample Mendelian randomization, we tested whether genetically elevated HDL cholesterol was causally associated with Alzheimer's disease using publicly available consortia data on 643 836 individuals. Observationally, multifactorially adjusted Cox regression restricted cubic spline models showed that both men and women with extreme high HDL cholesterol concentrations had increased risk of any dementia and of Alzheimer's disease. Men in the 96th–99th and 100th vs. the 41st–60th percentiles of HDL cholesterol had multifactorially including APOE genotype adjusted hazard ratios of 1.66 (95% confidence interval 1.30–2.11) and 2.00 (1.35–2.98) for any dementia and 1.59 (1.16–2.20) and 1.87 (1.11–3.16) for Alzheimer's disease. Corresponding estimates for women were 0.94 (0.74–1.18) and 1.45 (1.03–2.05) for any dementia and 0.94 (0.70–1.26) and 1.69 (1.13–2.53) for Alzheimer's disease. Genetically, the two-sample Mendelian randomization odds ratio for Alzheimer's disease per 1 SD increase in HDL cholesterol was 0.92 (0.74–1.10) in the IGAP2019 consortium and 0.98 (0.95–1.00) in the ADSP/IGAP/PGC-ALZ/UKB consortium. Similar estimates were observed in sex stratified analyses. Conclusion High plasma HDL cholesterol was observationally associated with increased risk of any dementia and Alzheimer's disease, suggesting that HDL cholesterol can be used as an easily accessible plasma biomarker for individual risk assessment. [ABSTRACT FROM AUTHOR]

Aims  Left ventricular (LV) myocardial crypts are considered a subtle marker of hypertrophic cardiomyopathy. However, crypts have also been observed in seemingly healthy individuals and it is unknown whether myocardial crypts are associated with adverse outcome. Methods and results  Myocardial crypts were defined as invaginations traversing >50% of the myocardial wall and assessed using contrast-enhanced cardiac computed tomography in 10 097 individuals from the Copenhagen General Population Study. Number of crypts, location, shape, penetrance, and volume were assessed. The endpoint was a composite of major adverse cardiovascular events and defined as death, myocardial infarction, heart failure, or stroke. Cox regression models were adjusted for clinical variables, medical history, electrocardiographic parameters, and cardiac chamber sizes. A total of 1199 LV myocardial crypts were identified in 915 (9.1%) individuals. Seven hundred (6.9%) had one crypt and 215 (2.1%) had multiple crypts. During a median follow-up of 4.0 years (interquartile range 1.5–6.7), major adverse cardiovascular events occurred in 619 individuals. Individuals with one or multiple crypts had a hazard ratio for major adverse cardiovascular events of 1.00 [95% confidence interval (CI): 0.72–1.40; P  = 0.98] and 0.90 (95% CI: 0.47–1.75; P  = 0.76), respectively, compared with those with no crypts. No specific pattern of crypt location, shape, penetrance, or volume was associated to an increased hazard ratio for major adverse cardiovascular events. Conclusion  LV myocardial crypts are frequent in the general population and are not associated with intermediate-term major adverse cardiovascular events. [ABSTRACT FROM AUTHOR]

Introduction: Observational studies have found lower concentrations of plasma bilirubin in current smokers compared with former and never smokers. However, whether there is a causal relationship between smoking and bilirubin is unknown. In a Mendelian randomization analysis, we tested the hypothesis that higher tobacco consumption is causally associated with lower concentrations of plasma bilirubin.Methods: We genotyped 103 557 individuals aged 20-100 years from the Copenhagen General Population Study for the CHRNA3 rs1051730 genotype, known to be associated with higher tobacco consumption. Tobacco consumption was defined as daily and cumulative tobacco consumption.Results: In observational multivariable-adjusted analyses, a 10 g/day higher daily tobacco consumption was associated with a 0.28 µmol/L (95% confidence interval = 0.20 to 0.35) lower concentration of plasma bilirubin in current smokers, and a 10 pack-year higher cumulative tobacco consumption was associated with a 0.19 µmol/L (0.17 to 0.21) lower concentration of plasma bilirubin in former and current smokers. Using the CHRNA3 rs1051730 genotype as a proxy for daily and cumulative tobacco consumption, the difference in plasma bilirubin per T-allele was -0.12 µmol/L (-0.23 to -0.002) in current smokers and -0.09 µmol/L (-0.15 to -0.01) in current and former smokers combined. Furthermore, observationally bilirubin concentrations increased with time from smoking cessation in former smokers.Conclusion: Higher daily and cumulative tobacco consumption were associated with lower concentrations of plasma bilirubin in observational and genetic analyses, suggesting that the association is causal.Implications: Our results are compatible with two possible interpretations of previous observational studies, either that bilirubin is a mediator of smoking-induced respiratory disease or that the association between plasma bilirubin and respiratory disease stems from residual confounding because of smoking. Future studies should examine whether bilirubin is a causal risk factor for respiratory disease, or merely a marker of smoking status. [ABSTRACT FROM AUTHOR]

Objective Gout is the most common form of inflammatory arthritis and is caused by hyperuricaemia. Some studies have found a reduction in plasma urate with vitamin C supplementation. We tested the hypothesis that high plasma vitamin C is causally associated with low plasma urate and low risk of hyperuricaemia, using a Mendelian randomization approach. Methods We measured plasma urate and genotyped for the SLC23A1 rs33972313 vitamin C variant in 106 147 individuals from the Copenhagen General Population Study, of which 24 099 had hyperuricaemia. We measured plasma vitamin C in 9234 individuals and genotyped for the SLC2A9 rs7442295 urate variant in 102 345 individuals. Results Each 10 µmol/l higher plasma vitamin C was associated with a −2.3(95%CI: −0.69 to −3.9) µmol/l lower plasma urate after multivariable adjustments. The SLC23A1 rs33972313 GG genotype was associated with a 9% (5.6%, 11.9%) higher plasma vitamin C compared with AA and AG combined but was not associated with plasma urate (P = 0.31). Likewise, for each 10 µmol/l higher plasma vitamin C the odds ratios for hyperuricaemia were 0.92 (0.86, 0.98) observationally after multivariable adjustments, but 1.01 (0.84, 1.23) genetically. Conclusion High plasma vitamin C was associated with low plasma urate and with low risk of hyperuricaemia. However, the SLC23A1 genetic variant causing lifelong high plasma vitamin C was not associated with plasma urate levels or with risk of hyperuricaemia. Thus, our data do not support a causal relationship between high plasma vitamin C and low plasma urate. [ABSTRACT FROM AUTHOR]