mBAT-combo: A more powerful test to detect gene-trait associations from GWAS data.

Gene-based association tests aggregate multiple SNP-trait associations into sets defined by gene boundaries and are widely used in post-GWAS analysis. A common approach for gene-based tests is to combine SNPs associations by computing the sum of χ2 statistics. However, this strategy ignores the directions of SNP effects, which could result in a loss of power for SNPs with masking effects, e.g., when the product of two SNP effects and the linkage disequilibrium (LD) correlation is negative. Here, we introduce "mBAT-combo," a set-based test that is better powered than other methods to detect multi-SNP associations in the context of masking effects. We validate the method through simulations and applications to real data. We find that of 35 blood and urine biomarker traits in the UK Biobank, 34 traits show evidence for masking effects in a total of 4,273 gene-trait pairs, indicating that masking effects is common in complex traits. We further validate the improved power of our method in height, body mass index, and schizophrenia with different GWAS sample sizes and show that on average 95.7% of the genes detected only by mBAT-combo with smaller sample sizes can be identified by the single-SNP approach with a 1.7-fold increase in sample sizes. Eleven genes significant only in mBAT-combo for schizophrenia are confirmed by functionally informed fine-mapping or Mendelian randomization integrating gene expression data. The framework of mBAT-combo can be applied to any set of SNPs to refine trait-association signals hidden in genomic regions with complex LD structures.

Public willingness to participate in population DNA screening in Australia.

BACKGROUND: Population-based DNA screening for medically actionable conditions has the potential to improve public health by enabling early detection, treatment and/or prevention; however, public attitudes and willingness to participate in DNA screening have not been well investigated. METHODS: We presented a scenario to members of the Australian public, randomly selected from the electoral roll via the Australian Survey of Societal Attitudes, describing an adult population DNA screening programme currently under development, to detect risk of medically actionable cancers and heart disease. We asked questions regarding willingness to participate and pay, preferred delivery methods and concerns. RESULTS: We received 1060 completed questionnaires (response rate 23%, mean age 58 years). The vast majority (>92%) expressed willingness to undertake DNA screening. When asked about the optimal age of screening, most (56%) favoured early adulthood (aged 18-40 years) rather than at birth or childhood. Many respondents would prefer samples and data be kept for re-screening (36%) or research use (43%); some preferred samples to be destroyed (21%). Issues that decrease likelihood of participation included privacy (75%) and insurance (86%) implications. CONCLUSION: Our study demonstrates public willingness to participate in population DNA screening in Australia, and identifies barriers to participation, to be addressed in the design of screening programmes. Results are informing the development of a pilot national DNA screening programme.

Association of polygenic scores with chronic kidney disease phenotypes in a longitudinal study of older adults.

Risk of chronic kidney disease (CKD) is influenced by environmental and genetic factors and increases sharply in individuals 70 years and older. Polygenic scores (PGS) for kidney disease-related traits have shown promise but require validation in well-characterized cohorts. Here, we assessed the performance of recently developed PGSs for CKD-related traits in a longitudinal cohort of healthy older individuals enrolled in the Australian ASPREE randomized controlled trial of daily low-dose aspirin with CKD risk at baseline and longitudinally. Among 11,813 genotyped participants aged 70 years or more with baseline eGFR measures, we tested associations between PGSs and measured eGFR at baseline, clinical phenotype of CKD, and longitudinal rate of eGFR decline spanning up to six years of follow-up per participant. A PGS for eGFR was associated with baseline eGFR, with a significant decrease of 3.9 mL/min/1.73m2 (95% confidence interval -4.17 to -3.68) per standard deviation (SD) increase of the PGS. This PGS, as well as a PGS for CKD stage 3 were both associated with higher risk of baseline CKD stage 3 in cross-sectional analysis (Odds Ratio 1.75 per SD, 95% confidence interval 1.66-1.85, and Odds Ratio 1.51 per SD, 95% confidence interval 1.43-1.59, respectively). Longitudinally, two separate PGSs for eGFR slope were associated with significant kidney function decline during follow-up. Thus, our study demonstrates that kidney function has a considerable genetic component in older adults, and that new PGSs for kidney disease-related phenotypes may have potential utility for CKD risk prediction in advanced age.

Androgen receptor enhancer amplification in matched patient-derived xenografts of primary and castrate-resistant prostate cancer.

Amplifications of the androgen receptor (AR) occur in up to 80% of men with castration-resistant prostate cancer (CRPC). Recent studies highlighted that these amplifications not only span the AR gene but usually encompass a distal enhancer. This represents a newly recognised, non-coding mechanism of resistance to AR-directed therapies, including enzalutamide. To study disease progression before and after AR amplification, we used tumour samples from a castrate-sensitive primary tumour and castrate-resistant metastasis of the same patient. For subsequent functional and genomic studies, we established serially transplantable patient-derived xenografts (PDXs). Whole genome sequencing showed that alterations associated with poor prognosis, such as TP53 and PTEN loss, existed before androgen deprivation therapy, followed by co-amplification of the AR gene and enhancer after the development of metastatic CRPC. The PDX of the primary tumour, without the AR amplification, was sensitive to AR-directed treatments, including castration, enzalutamide, and apalutamide. The PDX of the metastasis, with the AR amplification, had higher AR and AR-V7 expression in castrate conditions, and was resistant to castration, apalutamide, and enzalutamide in vivo. Treatment with a BET inhibitor outperformed the AR-directed therapies for the metastasis, resulting in tumour regression for some, but not all, grafts. Therefore, this study provides novel matched PDXs to test potential treatments that target the overabundance of AR in tumours with AR enhancer amplifications. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Predictive Performance of a Polygenic Risk Score for Incident Ischemic Stroke in a Healthy Older Population.

Background and Purpose: Polygenic risk scores (PRSs) can be used to predict ischemic stroke (IS). However, further validation of PRS performance is required in independent populations, particularly older adults in whom the majority of strokes occur. Methods: We predicted risk of incident IS events in a population of 12 792 healthy older individuals enrolled in the ASPREE trial (Aspirin in Reducing Events in the Elderly). The PRS was calculated using 3.6 million genetic variants. Participants had no previous history of cardiovascular events, dementia, or persistent physical disability at enrollment. The primary outcome was IS over 5 years, with stroke subtypes as secondary outcomes. A multivariable model including conventional risk factors was applied and reevaluated after adding PRS. Area under the curve and net reclassification were evaluated. Results: At baseline, mean population age was 75 years. In total, 173 incident IS events occurred over a median follow-up of 4.7 years. When PRS was added to the multivariable model as a continuous variable, it was independently associated with IS (hazard ratio, 1.41 [95% CI, 1.20­1.65] per SD of the PRS; P<0.001). The PRS alone was a better discriminator for IS events than most conventional risk factors. PRS as a categorical variable was a significant predictor in the highest tertile (hazard ratio, 1.74; P=0.004) compared with the lowest. The area under the curve of the conventional model was 66.6% (95% CI, 62.2­71.1) and after inclusion of the PRS, improved to 68.5 ([95% CI, 64.0­73.0] P=0.095). In subgroup analysis, the continuous PRS remained an independent predictor for large vessel and cardioembolic stroke subtypes but not for small vessel stroke. Reclassification was improved, as the continuous net reclassification index after adding PRS to the conventional model was 0.25 (95% CI, 0.17­0.43). Conclusions: PRS predicts incident IS in a healthy older population but only moderately improves prediction over conventional risk factors. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01038583.

The Genetic Architecture of Gene Expression in Peripheral Blood.

We analyzed the mRNA levels for 36,778 transcript expression traits (probes) from 2,765 individuals to comprehensively investigate the genetic architecture and degree of missing heritability for gene expression in peripheral blood. We identified 11,204 cis and 3,791 trans independent expression quantitative trait loci (eQTL) by using linear mixed models to perform genome-wide association analyses. Furthermore, using information on both closely and distantly related individuals, heritability was estimated for all expression traits. Of the set of expressed probes (15,966), 10,580 (66%) had an estimated narrow-sense heritability (h2) greater than zero with a mean (median) value of 0.192 (0.142). Across these probes, on average the proportion of genetic variance explained by all eQTL (hCOJO2) was 31% (0.060/0.192), meaning that 69% is missing, with the sentinel SNP of the largest eQTL explaining 87% (0.052/0.060) of the variance attributed to all identified cis- and trans-eQTL. For the same set of probes, the genetic variance attributed to genome-wide common (MAF > 0.01) HapMap 3 SNPs (hg2) accounted for on average 48% (0.093/0.192) of h2. Taken together, the evidence suggests that approximately half the genetic variance for gene expression is not tagged by common SNPs, and of the variance that is tagged by common SNPs, a large proportion can be attributed to identifiable eQTL of large effect, typically in cis. Finally, we present evidence that, compared with a meta-analysis, using individual-level data results in an increase of approximately 50% in power to detect eQTL.

Genetic loci associated with coronary artery disease harbor evidence of selection and antagonistic pleiotropy.

Traditional genome-wide scans for positive selection have mainly uncovered selective sweeps associated with monogenic traits. While selection on quantitative traits is much more common, very few signals have been detected because of their polygenic nature. We searched for positive selection signals underlying coronary artery disease (CAD) in worldwide populations, using novel approaches to quantify relationships between polygenic selection signals and CAD genetic risk. We identified new candidate adaptive loci that appear to have been directly modified by disease pressures given their significant associations with CAD genetic risk. These candidates were all uniquely and consistently associated with many different male and female reproductive traits suggesting selection may have also targeted these because of their direct effects on fitness. We found that CAD loci are significantly enriched for lifetime reproductive success relative to the rest of the human genome, with evidence that the relationship between CAD and lifetime reproductive success is antagonistic. This supports the presence of antagonistic-pleiotropic tradeoffs on CAD loci and provides a novel explanation for the maintenance and high prevalence of CAD in modern humans. Lastly, we found that positive selection more often targeted CAD gene regulatory variants using HapMap3 lymphoblastoid cell lines, which further highlights the unique biological significance of candidate adaptive loci underlying CAD. Our study provides a novel approach for detecting selection on polygenic traits and evidence that modern human genomes have evolved in response to CAD-induced selection pressures and other early-life traits sharing pleiotropic links with CAD.

Genetic signatures of high-altitude adaptation in Tibetans.

Indigenous Tibetan people have lived on the Tibetan Plateau for millennia. There is a long-standing question about the genetic basis of high-altitude adaptation in Tibetans. We conduct a genome-wide study of 7.3 million genotyped and imputed SNPs of 3,008 Tibetans and 7,287 non-Tibetan individuals of Eastern Asian ancestry. Using this large dataset, we detect signals of high-altitude adaptation at nine genomic loci, of which seven are unique. The alleles under natural selection at two of these loci [methylenetetrahydrofolate reductase (MTHFR) and EPAS1] are strongly associated with blood-related phenotypes, such as hemoglobin, homocysteine, and folate in Tibetans. The folate-increasing allele of rs1801133 at the MTHFR locus has an increased frequency in Tibetans more than expected under a drift model, which is probably a consequence of adaptation to high UV radiation. These findings provide important insights into understanding the genomic consequences of high-altitude adaptation in Tibetans.

Establishing a cryopreservation protocol for patient-derived xenografts of prostate cancer.

BACKGROUND: Serially transplantable patient-derived xenografts (PDXs) are invaluable preclinical models for studying tumor biology and evaluating therapeutic agents. As these models are challenging to establish from prostate cancer specimens, the ability to preserve them through cryopreservation has several advantages for ongoing research. Despite this, there is still uncertainty about the ability to cryopreserve PDXs of prostate cancer. This study compared three different cryopreservation protocols to identify a method that can be used to reproducibly cryopreserve a diverse cohort of prostate cancer PDX models. METHODS: One serially transplantable prostate cancer PDX from the Melbourne Urological Research Alliance cohort was used to compare three cryopreservation protocols: slow freezing in fetal calf serum (FCS) with 10% dimethyl sulfoxide (DMSO), FCS with 10% DMSO supplemented with the Rho-associated kinase (ROCK) inhibitor Y-27632 and vitrification. The efficiency of the slow freezing protocols was then assessed in 17 additional prostate cancer PDXs. Following cryopreservation, PDXs were re-established in host mice that were either intact and supplemented with testosterone or castrated. Graft take rate, tumor growth, histological features, and transcriptome profiles before and after cryopreservation were compared. RESULTS: Slow freezing maintained the viability and histological features of prostate cancer PDXs, and the addition of a ROCK inhibitor increased their growth following cryopreservation. Using the slow freezing method, we re-established 100% of PDXs grown in either testosterone-supplemented or castrated host mice. Importantly, the long-term tumor growth rate and transcriptome profile were maintained following cryopreservation. CONCLUSION: This study has identified a protocol to reliably cryopreserve and re-establish a diverse cohort of serially transplantable PDXs of prostate cancer. This study has the potential to significantly improve the practicality of maintaining PDX models. Cryopreservation may also increase the accessibility of these important resources and provide new opportunities for preclinical studies on a broader spectrum of prostate tumors.

Dominance genetic variation contributes little to the missing heritability for human complex traits.

For human complex traits, non-additive genetic variation has been invoked to explain "missing heritability," but its discovery is often neglected in genome-wide association studies. Here we propose a method of using SNP data to partition and estimate the proportion of phenotypic variance attributed to additive and dominance genetic variation at all SNPs (hSNP(2) and δSNP(2)) in unrelated individuals based on an orthogonal model where the estimate of hSNP(2) is independent of that of δSNP(2). With this method, we analyzed 79 quantitative traits in 6,715 unrelated European Americans. The estimate of δSNP(2) averaged across all the 79 quantitative traits was 0.03, approximately a fifth of that for additive variation (average hSNP(2) = 0.15). There were a few traits that showed substantial estimates of δSNP(2), none of which were replicated in a larger sample of 11,965 individuals. We further performed genome-wide association analyses of the 79 quantitative traits and detected SNPs with genome-wide significant dominance effects only at the ABO locus for factor VIII and von Willebrand factor. All these results suggest that dominance variation at common SNPs explains only a small fraction of phenotypic variation for human complex traits and contributes little to the missing narrow-sense heritability problem.

Genome-wide genetic homogeneity between sexes and populations for human height and body mass index.

Sex-specific genetic effects have been proposed to be an important source of variation for human complex traits. Here we use two distinct genome-wide methods to estimate the autosomal genetic correlation (rg) between men and women for human height and body mass index (BMI), using individual-level (n = ∼44 000) and summary-level (n = ∼133 000) data from genome-wide association studies. Results are consistent and show that the between-sex genetic correlation is not significantly different from unity for both traits. In contrast, we find evidence of genetic heterogeneity between sexes for waist-hip ratio (rg = ∼0.7) and between populations for BMI (rg = ∼0.9 between Europe and the USA) but not for height. The lack of evidence for substantial genetic heterogeneity for body size is consistent with empirical findings across traits and species.

Monogenic and polygenic concepts in chronic kidney disease (CKD).

Kidney function is strongly influenced by genetic factors with both monogenic and polygenic factors contributing to kidney function. Monogenic disorders with primarily autosomal dominant inheritance patterns account for 10% of adult and 50% of paediatric kidney diseases. However, kidney function is also a complex trait with polygenic architecture, where genetic factors interact with environment and lifestyle factors. Family studies suggest that kidney function has significant heritability at 35-69%, capturing complexities of the genome with shared environmental factors. Genome-wide association studies estimate the single nucleotide polymorphism-based heritability of kidney function between 7.1 and 20.3%. These heritability estimates, measuring the extent to which genetic variation contributes to CKD risk, indicate a strong genetic contribution. Polygenic Risk Scores have recently been developed for chronic kidney disease and kidney function, and validated in large populations. Polygenic Risk Scores show correlation with kidney function but lack the specificity to predict individual-level changes in kidney function. Certain kidney diseases, such as membranous nephropathy and IgA nephropathy that have significant genetic components, may benefit most from polygenic risk scores for improved risk stratification. Genetic studies of kidney function also provide a potential avenue for the development of more targeted therapies and interventions. Understanding the development and validation of genomic scores is required to guide their implementation and identify the most appropriate potential implications in clinical practice. In this review, we provide an overview of the heritability of kidney function traits in population studies, explore both monogenic and polygenic concepts in kidney disease, with a focus on recently developed polygenic risk scores in kidney function and chronic kidney disease, and review specific diseases which are most amenable to incorporation of genomic scores.

Genome-wide association study identifies genetic regulation of oestrone concentrations and association with endometrial cancer risk in postmenopausal women.

BACKGROUND: Oestrone, predominantly made in fat, is the main circulating oestrogen and important for target tissue oestradiol production in women after menopause. The present study was undertaken to determine the genetic regulation of blood oestrone, measured with precision, in postmenopausal women and to explore associations between the identified genetic loci and endometrial cancer in a large, independent cohort. METHODS: A genome-wide association study (GWAS) was undertaken in women aged at least 70 years to identify genetic associations with blood oestrone concentrations measured by liquid chromatography and tandem mass spectrometry. The GWAS included participants from the Sex Hormones in Older Women (SHOW) study, a sub-study of the longitudinal ASPREE (ASPirin in Reducing Events in the Elderly) randomised trial. Of the 6358 women providing a biobank sample at enrolment, 4951 unrelated women of European ancestry, not taking sex hormones, anti-oestrogens, anti-androgens or systemic glucocorticoids were included in the GWAS. Single nucleotide polymorphisms (SNPs) from loci identified below the genome-wide significance threshold were then tested in an independent cohort (the UK Biobank) for association with endometrial cancer risk, using logistic regression and adjusting for age, body mass index (BMI) and the top 10 genetic principal components. FINDINGS: The median age of the 4951 women included in the GWAS was 75.9 years (range 70-94.8 years). The GWAS identified four independent SNPs associated with oestrone concentrations (p < 5 × 10-8). Among them, the effect (minor) alleles rs34670419-T, rs2846729-T and rs2414098-T were associated with lower oestrone concentrations. Carrying these effect alleles was associated with lower oestrone concentrations in a dose-dependent manner. The effect allele rs56400819-A was associated with higher oestrone concentrations. When applied to UK Biobank, carrier status for rs2414098-T associated with the CYP19A1 gene which encodes the aromatase enzyme required for oestrogen synthesis was significantly associated with lower endometrial cancer risk (adjusted odd ratio [aOR] 0.87 [95% CI 0.82-0.93]; p = 6.69 × 10-5 for women across all ages and aOR 0.89 [95% CI 0.83-0.96]; p = 0.003 for postmenopausal women). None of the models that included age, body mass index (BMI), the top 10 genetic principal components, parity and diabetes mellitus explained more than 7.6% of the variation in risk. INTERPRETATION: We have shown genetic regulation of oestrone concentrations in postmenopausal women, and that SNPs associated with oestrone were also associated with endometrial cancer risk, independent of BMI, parity and diabetes mellitus. Although the apparent contribution was modest, the biological influence of oestrone concentrations may be greater through conversion to oestradiol in endometrial tissue. FUNDING: The ASPREE trial was supported by the National Institute on Aging and the National Cancer Institute at the National Institutes of Health (Grant U01AG029824); the National Health and Medical Research Council (NHMRC) of Australia (Grant 34047, 1127060); Monash University (Australia); and the Victorian Cancer Agency (Australia). The ASPREE Healthy Ageing Biobank was funded by the CSIRO (Flagship Grant), the National Cancer Institute (Grant U01 AG029824) and Monash University. This analysis of sex hormones was funded by an NHMRC of Australia Project Grant (No. 1105305). SRD holds an NHMRC Investigator Grant (2016627). PL is supported by a National Heart Foundation Future Leader Fellowship (102604).

Community concerns about genetic discrimination in life insurance persist in Australia: A survey of consumers offered genetic testing.

Fears of genetic discrimination in life insurance continue to deter some Australians from genetic testing. In July 2019, the life insurance industry introduced a partial, self-regulated moratorium restricting the use of genetic results in underwriting, applicable to policies up to certain limits (eg AUD$500,000 for death cover).We administered an online survey to consumers who had taken, or been offered, clinical genetic testing for adult-onset conditions, to gather views and experiences about the moratorium and the use of genetic results in life insurance, including its regulation.Most respondents (n = 367) had undertaken a genetic test (89%), and had a positive test result (76%; n = 243/321). Almost 30% (n = 94/326) reported testing after 1 July 2019. Relatively few respondents reported knowing about the moratorium (16%; n = 54/340) or that use of genetic results in life insurance underwriting is legal (17%; n = 60/348). Only 4% (n = 14/350) consider this practice should be allowed. Some respondents reported ongoing difficulties accessing life insurance products, even after the moratorium. Further, discrimination concerns continue to affect some consumers' decision-making about having clinical testing and applying for life insurance products, despite the Moratorium being in place. Most respondents (88%; n = 298/340) support the introduction of legislation by the Australian government to regulate this issue.Despite the introduction of a partial moratorium in Australia, fears of genetic discrimination persist, and continue to deter people from genetic testing. Consumers overwhelmingly consider life insurers should not be allowed to use genetic results in underwriting, and that federal legislation is required to regulate this area.

Genome-Wide Association Study of Cardiovascular Resilience Identifies Protective Variation in the CETP Gene.

Background The risk of atherosclerotic cardiovascular disease (ASCVD) increases sharply with age. Some older individuals, however, remain unaffected despite high predicted risk. These individuals may carry cardioprotective genetic variants that contribute to resilience. Our aim was to assess whether asymptomatic older individuals without prevalent ASCVD carry cardioprotective genetic variants that contribute to ASCVD resilience. Methods and Results We performed a genome-wide association study using a 10-year predicted ASCVD risk score as a quantitative trait, calculated only in asymptomatic older individuals aged ≥70 years without prevalent ASCVD. Our discovery genome-wide association study of N=12 031 ASCVD event-free individuals from the ASPREE (Aspirin in Reducing Events in the Elderly) trial identified 2 independent variants, rs9939224 (P<5×10-8) and rs56156922 (P<10-6), in the CETP (cholesteryl ester transfer protein) gene. The CETP gene is a regulator of plasma high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and lipoprotein(a) levels, and it is a therapeutic drug target. The associations were replicated in the UK Biobank (subpopulation of N=13 888 individuals aged ≥69 years without prevalent ASCVD). Carriers of the identified CETP variants (versus noncarriers) had higher plasma high-density lipoprotein cholesterol levels, lower plasma low-density lipoprotein cholesterol levels, and reduced risk of incident ASCVD events during follow-up. Expression quantitative trait loci analysis predicted the identified CETP variants reduce CETP gene expression across various tissues. Previously reported associations between genetic CETP inhibition and increased risk of age-related macular degeneration were not observed among the 3917 ASPREE trial participants with retinal imaging and genetic data available. Conclusions Common genetic variants in the CETP gene region are associated with cardiovascular resilience during aging. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01038583.

Genomic Risk Score for Advanced Osteoarthritis in Older Adults.

OBJECTIVE: Prevention of osteoarthritis (OA) remains important, as there are no disease-modifying treatments. A personalized approach has the potential to better target prevention strategies. In the present study, we used recently identified genetic risk variants from genome-wide association analysis for advanced OA to calculate polygenic risk scores (PRS) for knee and hip OA and assessed PRS performance in an independent population of older community-dwelling adults. METHODS: PRS were calculated in 12,093 individuals of European genetic descent ages ≥70 years who were enrolled in the Aspirin in Reducing Events in the Elderly trial. The outcome measure was knee and hip replacement (hospitalizations during the trial and self-reported joint replacements before enrollment). PRS were considered as continuous (per SD) and categorical (low risk [0-20%], medium risk [21-80%], high risk [81-100%]) variables. Logistic regression was used to examine associations between PRS and risk of joint replacement, adjusted for age, sex, body mass index, and socioeconomic status. RESULTS: Among the participants, 1,422 (11.8%) had knee replacements and 1,297 (10.7%) had hip replacements. PRS (per SD) were associated with a risk of knee replacement (odds ratio [OR] 1.13 [95% confidence interval (95% CI) 1.07-1.20]) and hip replacement (OR 1.23 [95% CI 1.16-1.30]). Participants with high PRS had an increased risk of knee replacement (OR 1.44 [95% CI 1.20-1.73]) and hip replacement (OR 1.88 [95% CI 1.56-2.26]), compared to those with low PRS. Associations were stronger for PRS and hip replacement risk in women than in men. Associations were similar in sensitivity analyses that examined joint replacements before and during the trial separately. CONCLUSION: PRS have the potential to improve prevention of severe knee and hip OA by providing a personalized approach and identifying individuals who may benefit from early intervention.

Prognostic Value of a Polygenic Risk Score for Coronary Heart Disease in Individuals Aged 70 Years and Older.

BACKGROUND: The use of a polygenic risk score (PRS) to improve risk prediction of coronary heart disease (CHD) events has been demonstrated to have clinical utility in the general adult population. However, the prognostic value of a PRS for CHD has not been examined specifically in older populations of individuals aged ≥70 years, who comprise a distinct high-risk subgroup. The objective of this study was to evaluate the predictive value of a PRS for incident CHD events in a prospective cohort of older individuals without a history of cardiovascular events. METHODS: We used data from 12 792 genotyped, healthy older individuals enrolled into the ASPREE trial (Aspirin in Reducing Events in the Elderly), a randomized double-blind placebo-controlled clinical trial investigating the effect of daily 100 mg aspirin on disability-free survival. Participants had no previous history of diagnosed atherothrombotic cardiovascular events, dementia, or persistent physical disability at enrollment. We calculated a PRS (meta-genomic risk score) consisting of 1.7 million genetic variants. The primary outcome was a composite of incident myocardial infarction or CHD death over 5 years. RESULTS: At baseline, the median population age was 73.9 years, and 54.9% were female. In total, 254 incident CHD events occurred. When the PRS was added to conventional risk factors, it was independently associated with CHD (hazard ratio, 1.24 [95% CI, 1.08-1.42], P=0.002). The area under the curve of the conventional model was 70.53 (95% CI, 67.00-74.06), and after inclusion of the PRS increased to 71.78 (95% CI, 68.32-75.24, P=0.019), demonstrating improved prediction. Reclassification was also improved, as the continuous net reclassification index after adding PRS to the conventional model was 0.25 (95% CI, 0.15-0.28). CONCLUSION: A PRS for CHD performs well in older people and improves prediction over conventional cardiovascular risk factors. Our study provides evidence that genomic risk prediction for CHD has clinical utility in individuals aged 70 years and older. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01038583.

Aspirin for Primary Prevention of Cardiovascular Events in Relation to Lipoprotein(a) Genotypes.

BACKGROUND: The role of aspirin in reducing lipoprotein(a)-mediated atherothrombotic events in primary prevention is not established. OBJECTIVES: This study sought to assess whether low-dose aspirin benefits individuals with elevated plasma lipoprotein(a)-associated genotypes in the setting of primary prevention. METHODS: The study analyzed 12,815 genotyped individuals ≥70 years of age of European ancestry and without prior cardiovascular disease events enrolled in the ASPREE (ASPirin in Reducing Events in the Elderly) randomized controlled trial of 100 mg/d aspirin. We defined lipoprotein(a)-associated genotypes using rs3798220-C carrier status and quintiles of a lipoprotein(a) genomic risk score (LPA-GRS). We tested for interaction between genotypes and aspirin allocation in Cox proportional hazards models for incidence of major adverse cardiovascular events (MACE) and clinically significant bleeding. We also examined associations in the aspirin and placebo arms of the trial separately. RESULTS: During a median 4.7 years (IQR: 3.6-5.7 years) of follow-up, 435 MACE occurred, with an interaction observed between rs3798220-C and aspirin allocation (P = 0.049). rs3798220-C carrier status was associated with increased MACE risk in the placebo group (HR: 1.90; 95% CI: 1.11-3.24) but not in the aspirin group (HR: 0.54; 95% CI: 0.17-1.70). High LPA-GRS (vs low) was associated with increased MACE risk in the placebo group (HR: 1.70; 95% CI: 1.14-2.55), with risk attenuated in the aspirin group (HR: 1.41; 95% CI: 0.90-2.23), but the interaction was not statistically significant. In all participants, aspirin reduced MACE by 1.7 events per 1,000 person-years and increased clinically significant bleeding by 1.7 events per 1,000 person-years. However, in the rs3798220-C and high LPA-GRS subgroups, aspirin reduced MACE by 11.4 and 3.3 events per 1,000 person-years respectively, without significantly increased bleeding risk. CONCLUSIONS: Aspirin may benefit older individuals with elevated lipoprotein(a) genotypes in primary prevention.

Aspirin and the Risk of Colorectal Cancer According to Genetic Susceptibility among Older Individuals.

Although aspirin has been considered a promising agent for prevention of colorectal cancer, recent data suggest a lack of benefit among older individuals. Whether some individuals with higher risk of colorectal cancer may benefit from aspirin remains unknown. We used a 95-variant colorectal cancer polygenic risk score (PRS) to explore the association between genetic susceptibility to colorectal cancer and aspirin use in a prospective study of 12,609 individuals of European descent ages ≥70 years, enrolled in the ASPirin in Reducing Events in the Elderly (ASPREE) double-blinded, placebo-controlled randomized trial (randomized controlled trial; RCT). Cox proportional hazards models were used to assess the association of aspirin use on colorectal cancer, as well as the interaction between the PRS and aspirin treatment on colorectal cancer. Over a median of 4.7 years follow-up, 143 participants were diagnosed with incident colorectal cancer. Aspirin assignment was not associated with incidence of colorectal cancer overall [HR = 0.94; 95% confidence interval (CI), 0.68-1.30] or within strata of PRS (P for interaction = 0.97). However, the PRS was associated with an increased risk of colorectal cancer (HR = 1.28 per SD; 95% CI, 1.09-1.51). Individuals in the top quintile of the PRS distribution had an 85% higher risk compared with individuals in the bottom quintile (HR = 1.85; 95% CI, 1.08-3.15). In a prospective RCT of older individuals, a PRS is associated with incident colorectal cancer risk, but aspirin use was not associated with a reduction of incident colorectal cancer, regardless of baseline genetic risk. PREVENTION RELEVANCE: There is strong evidence to support prophylactic aspirin use for the prevention of colorectal cancer. However recent recommendations suggest the risk of bleeding in older individuals outweighs the benefit. We sought to determine whether some older individuals might still benefit from aspirin based on their genetic susceptibility.