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1.  Genome-wide meta-analysis identifies 56 bone mineral density loci and reveals 14 loci associated with risk of fracture 
Estrada, Karol | Styrkarsdottir, Unnur | Evangelou, Evangelos | Hsu, Yi-Hsiang | Duncan, Emma L | Ntzani, Evangelia E | Oei, Ling | Albagha, Omar M E | Amin, Najaf | Kemp, John P | Koller, Daniel L | Li, Guo | Liu, Ching-Ti | Minster, Ryan L | Moayyeri, Alireza | Vandenput, Liesbeth | Willner, Dana | Xiao, Su-Mei | Yerges-Armstrong, Laura M | Zheng, Hou-Feng | Alonso, Nerea | Eriksson, Joel | Kammerer, Candace M | Kaptoge, Stephen K | Leo, Paul J | Thorleifsson, Gudmar | Wilson, Scott G | Wilson, James F | Aalto, Ville | Alen, Markku | Aragaki, Aaron K | Aspelund, Thor | Center, Jacqueline R | Dailiana, Zoe | Duggan, David J | Garcia, Melissa | Garcia-Giralt, Natàlia | Giroux, Sylvie | Hallmans, Göran | Hocking, Lynne J | Husted, Lise Bjerre | Jameson, Karen A | Khusainova, Rita | Kim, Ghi Su | Kooperberg, Charles | Koromila, Theodora | Kruk, Marcin | Laaksonen, Marika | Lacroix, Andrea Z | Lee, Seung Hun | Leung, Ping C | Lewis, Joshua R | Masi, Laura | Mencej-Bedrac, Simona | Nguyen, Tuan V | Nogues, Xavier | Patel, Millan S | Prezelj, Janez | Rose, Lynda M | Scollen, Serena | Siggeirsdottir, Kristin | Smith, Albert V | Svensson, Olle | Trompet, Stella | Trummer, Olivia | van Schoor, Natasja M | Woo, Jean | Zhu, Kun | Balcells, Susana | Brandi, Maria Luisa | Buckley, Brendan M | Cheng, Sulin | Christiansen, Claus | Cooper, Cyrus | Dedoussis, George | Ford, Ian | Frost, Morten | Goltzman, David | González-Macías, Jesús | Kähönen, Mika | Karlsson, Magnus | Khusnutdinova, Elza | Koh, Jung-Min | Kollia, Panagoula | Langdahl, Bente Lomholt | Leslie, William D | Lips, Paul | Ljunggren, Östen | Lorenc, Roman S | Marc, Janja | Mellström, Dan | Obermayer-Pietsch, Barbara | Olmos, José M | Pettersson-Kymmer, Ulrika | Reid, David M | Riancho, José A | Ridker, Paul M | Rousseau, François | Slagboom, P Eline | Tang, Nelson LS | Urreizti, Roser | Van Hul, Wim | Viikari, Jorma | Zarrabeitia, María T | Aulchenko, Yurii S | Castano-Betancourt, Martha | Grundberg, Elin | Herrera, Lizbeth | Ingvarsson, Thorvaldur | Johannsdottir, Hrefna | Kwan, Tony | Li, Rui | Luben, Robert | Medina-Gómez, Carolina | Palsson, Stefan Th | Reppe, Sjur | Rotter, Jerome I | Sigurdsson, Gunnar | van Meurs, Joyce B J | Verlaan, Dominique | Williams, Frances MK | Wood, Andrew R | Zhou, Yanhua | Gautvik, Kaare M | Pastinen, Tomi | Raychaudhuri, Soumya | Cauley, Jane A | Chasman, Daniel I | Clark, Graeme R | Cummings, Steven R | Danoy, Patrick | Dennison, Elaine M | Eastell, Richard | Eisman, John A | Gudnason, Vilmundur | Hofman, Albert | Jackson, Rebecca D | Jones, Graeme | Jukema, J Wouter | Khaw, Kay-Tee | Lehtimäki, Terho | Liu, Yongmei | Lorentzon, Mattias | McCloskey, Eugene | Mitchell, Braxton D | Nandakumar, Kannabiran | Nicholson, Geoffrey C | Oostra, Ben A | Peacock, Munro | Pols, Huibert A P | Prince, Richard L | Raitakari, Olli | Reid, Ian R | Robbins, John | Sambrook, Philip N | Sham, Pak Chung | Shuldiner, Alan R | Tylavsky, Frances A | van Duijn, Cornelia M | Wareham, Nick J | Cupples, L Adrienne | Econs, Michael J | Evans, David M | Harris, Tamara B | Kung, Annie Wai Chee | Psaty, Bruce M | Reeve, Jonathan | Spector, Timothy D | Streeten, Elizabeth A | Zillikens, M Carola | Thorsteinsdottir, Unnur | Ohlsson, Claes | Karasik, David | Richards, J Brent | Brown, Matthew A | Stefansson, Kari | Uitterlinden, André G | Ralston, Stuart H | Ioannidis, John P A | Kiel, Douglas P | Rivadeneira, Fernando
Nature genetics  2012;44(5):491-501.
Bone mineral density (BMD) is the most important predictor of fracture risk. We performed the largest meta-analysis to date on lumbar spine and femoral neck BMD, including 17 genome-wide association studies and 32,961 individuals of European and East Asian ancestry. We tested the top-associated BMD markers for replication in 50,933 independent subjects and for risk of low-trauma fracture in 31,016 cases and 102,444 controls. We identified 56 loci (32 novel)associated with BMD atgenome-wide significant level (P<5×10−8). Several of these factors cluster within the RANK-RANKL-OPG, mesenchymal-stem-cell differentiation, endochondral ossification and the Wnt signalling pathways. However, we also discovered loci containing genes not known to play a role in bone biology. Fourteen BMD loci were also associated with fracture risk (P<5×10−4, Bonferroni corrected), of which six reached P<5×10−8 including: 18p11.21 (C18orf19), 7q21.3 (SLC25A13), 11q13.2 (LRP5), 4q22.1 (MEPE), 2p16.2 (SPTBN1) and 10q21.1 (DKK1). These findings shed light on the genetic architecture and pathophysiological mechanisms underlying BMD variation and fracture susceptibility.
PMCID: PMC3338864  PMID: 22504420
2.  Endgame: engaging the tobacco industry in its own elimination 
A billion deaths from tobacco are expected by 2100. Many policy interventions such as increased taxation, restrictions on advertisement, smoking bans, as well as behavioral interventions, such as pharmacological and psychological treatments for smoking cessation, decrease tobacco use, but they reach their limits. Endgame scenarios focusing on tobacco supply rather than demand are increasingly discussed, but meet with resistance by the industry and even by many tobacco control experts. A main stumbling block that requires more attention is what to do with the tobacco industry in endgame scenarios. This industry has employed notoriously talented experts in law, business, organization, marketing, advertising, strategy, policy, and statistics and has tremendous lobbying power. Performance-based regulatory approaches can pose a legal obligation on manufacturers to decrease – and eventually – eliminate tobacco products according to specified schedules. Penalties and rewards can make such plans both beneficial for public health and attractive to the companies that do the job well. We discuss caveats and reality checks of engaging the tobacco industry to eliminate its current market and change focus. Brainstorming is warranted to entice the industry to abandon tobacco for other profit goals. To get the dialogue started, we propose the wild possibility of hiring former tobacco companies to reduce the costs of healthcare, thereby addressing concurrently two major challenges to public health.
PMCID: PMC4038649  PMID: 24117211
3.  How to Make More Published Research True 
PLoS Medicine  2014;11(10):e1001747.
In a 2005 paper that has been accessed more than a million times, John Ioannidis explained why most published research findings were false. Here he revisits the topic, this time to address how to improve matters.
Please see later in the article for the Editors' Summary
PMCID: PMC4204808  PMID: 25334033
4.  Association Between Pediatric Clinical Trials and Global Burden of Disease 
Pediatrics  2014;133(1):78-87.
The allocation of research resources should favor conditions responsible for the greatest disease burden. This is particularly important in pediatric populations, which have been underrepresented in clinical research. Our aim was to measure the association between the focus of pediatric clinical trials and burden of disease and to identify neglected clinical domains.
We performed a cross-sectional study of clinical trials by using trial records in All trials started in 2006 or after and studying patient-level interventions in pediatric populations were included. Age-specific measures of disease burden were obtained for 21 separate conditions for high-, middle-, and low-income countries. We measured the correlation between number of pediatric clinical trials and disease burden for each condition.
Neuropsychiatric conditions and infectious diseases were the most studied conditions globally in terms of number of trials (874 and 847 trials, respectively), while intentional injuries (5 trials) and maternal conditions (4 trials) were the least studied. Clinical trials were only moderately correlated with global disease burden (r = 0.58, P = .006). Correlations were also moderate within each of the country income levels, but lowest in low-income countries (r = .47, P = .03). Globally, the conditions most understudied relative to disease burden were injuries (–260 trials for unintentional injuries and –160 trials for intentional injuries), nutritional deficiencies (–175 trials), and respiratory infections (–171 trials).
Pediatric clinical trial activity is only moderately associated with pediatric burden of disease, and least associated in low-income countries. The mismatch between clinical trials and disease burden identifies key clinical areas for focus and investment.
PMCID: PMC3876184  PMID: 24344112
clinical trials; burden of disease; pediatric research
5.  The protective effect of LRRK2 p.R1398H on risk of Parkinson’s disease is independent of MAPT and SNCA variants 
Neurobiology of aging  2013;35(1):10.1016/j.neurobiolaging.2013.07.013.
The best validated susceptibility variants for Parkinson’s disease (PD) are located in the alpha-synuclein (SNCA) and microtubule-associated protein tau (MAPT) genes. Recently, a protective p.N551K-R1398H-K1423K haplotype in the leucine-rich repeat kinase 2 (LRRK2) gene was identified, with p.R1398H appearing to be the most likely functional variant. To date, the consistency of the protective effect of LRRK2 p.R1398H across MAPT and SNCA variant genotypes has not been assessed. To address this, we examined four SNCA variants (rs181489, rs356219, rs11931074, rs2583988), the MAPT H1-haplotype defining variant rs1052553, and LRRK2 p.R1398H (rs7133914) in Caucasian (N=10,322) and Asian (N=2,289) series. There was no evidence of an interaction of LRRK2 p.R1398H with MAPT or SNCA variants (all P≥0.10); the protective effect of p.R1398H was observed at similar magnitude across MAPT and SNCA genotypes, and the risk effects of MAPT and SNCA variants were observed consistently for LRRK2 p.R1398H genotypes. Our results indicate that the association of LRRK2 p.R1398H with PD is independent of SNCA and MAPT variants, and vice versa, in Caucasian and Asian populations.
PMCID: PMC3829604  PMID: 23962496
Parkinson disease; LRRK2; SNCA; MAPT; interaction; genetics
6.  Studying the Elusive Environment in Large Scale 
PMCID: PMC4110965  PMID: 24893084
7.  A Web-based database of genetic association studies in cutaneous melanoma enhanced with network-driven data exploration tools 
The publicly available online database MelGene provides a comprehensive, regularly updated, collection of data from genetic association studies in cutaneous melanoma (CM), including random-effects meta-analysis results of all eligible polymorphisms. The updated database version includes data from 192 publications with information on 1114 significantly associated polymorphisms across 280 genes, along with new front-end and back-end capabilities. Various types of relationships between data are calculated and visualized as networks. We constructed 13 different networks containing the polymorphisms and the genes included in MelGene. We explored the derived network representations under the following questions: (i) are there nodes that deserve consideration regarding their network connectivity characteristics? (ii) What is the relation of either the genome-wide or nominally significant CM polymorphisms/genes with the ones highlighted by the network representation? We show that our network approach using the MelGene data reveals connections between statistically significant genes/ polymorphisms and other genes/polymorphisms acting as ‘hubs’ in the reconstructed networks. To the best of our knowledge, this is the first database containing data from a comprehensive field synopsis and systematic meta-analyses of genetic polymorphisms in CM that provides user-friendly tools for in-depth molecular network visualization and exploration. The proposed network connections highlight potentially new loci requiring further investigation of their relation to melanoma risk.
Database URL:
PMCID: PMC4224266  PMID: 25380778
8.  A Nutrient-Wide Association Study on Blood Pressure 
Circulation  2012;126(21):2456-2464.
A nutrient-wide approach may be useful comprehensively to test and validate associations between nutrients (derived from foods and supplements) and blood pressure (BP) in an unbiased manner.
Methods and Results
Data from 4,680 participants ages 40–59 in the cross-sectional International Study of Macro/Micro-nutrients and Blood Pressure (INTERMAP) were stratified randomly into training and testing sets. NHANES cross-sectional cohorts of 1999–2000 to 2005–2006 were used for external validation. We performed multiple linear regression analyses associating each of 82 nutrients and 3 urine electrolytes with systolic and diastolic BP in the INTERMAP training set. Significant findings were validated in the INTERMAP testing set and further in the NHANES cohorts (False Discovery Rate <5% in training, p<0.05 for internal and external validation). Among the validated nutrients, alcohol and urinary sodium-to-potassium ratio were directly associated with systolic BP, and dietary phosphorus, magnesium, iron, thiamin, folacin, and riboflavin were inversely associated with systolic BP. In addition, dietary folacin, and riboflavin were inversely associated with diastolic BP. The absolute effect sizes in the validation data (NHANES) ranged from 0.97 mmHg lower systolic BP (phosphorus) to 0.39 mmHg lower systolic BP (thiamin) per 1SD difference in nutrient variable. Inclusion of nutrient intake from supplements in addition to foods gave similar results for some nutrients, though it attenuated the associations of folacin, thiamin and riboflavin intake with BP.
We identified significant inverse associations between B vitamins and BP, relationships hitherto poorly investigated. Our analyses represent a systematic unbiased approach to the evaluation and validation of nutrient-BP associations.
PMCID: PMC4105584  PMID: 23093587
lood pressure; diet; epidemiology; nutrition
9.  The diagnostic accuracy of the Patient Health Questionnaire-2 (PHQ-2), Patient Health Questionnaire-8 (PHQ-8), and Patient Health Questionnaire-9 (PHQ-9) for detecting major depression: protocol for a systematic review and individual patient data meta-analyses 
Systematic Reviews  2014;3:124.
Major depressive disorder (MDD) may be present in 10%–20% of patients in medical settings. Routine depression screening is sometimes recommended to improve depression management. However, studies of the diagnostic accuracy of depression screening tools have typically used data-driven, exploratory methods to select optimal cutoffs. Often, these studies report results from a small range of cutoff points around whatever cutoff score is most accurate in that given study. When published data are combined in meta-analyses, estimates of accuracy for different cutoff points may be based on data from different studies, rather than data from all studies for each possible cutoff point. As a result, traditional meta-analyses may generate exaggerated estimates of accuracy. Individual patient data (IPD) meta-analyses can address this problem by synthesizing data from all studies for each cutoff score to obtain diagnostic accuracy estimates. The nine-item Patient Health Questionnaire-9 (PHQ-9) and the shorter PHQ-2 and PHQ-8 are commonly recommended for depression screening. Thus, the primary objectives of our IPD meta-analyses are to determine the diagnostic accuracy of the PHQ-9, PHQ-8, and PHQ-2 to detect MDD among adults across all potentially relevant cutoff scores. Secondary analyses involve assessing accuracy accounting for patient factors that may influence accuracy (age, sex, medical comorbidity).
Data sources will include MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, PsycINFO, and Web of Science. We will include studies that included a Diagnostic and Statistical Manual or International Classification of Diseases diagnosis of MDD based on a validated structured or semi-structured clinical interview administered within 2 weeks of the administration of the PHQ. Two reviewers will independently screen titles and abstracts, perform full article review, and extract study data. Disagreements will be resolved by consensus. Risk of bias will be assessed with the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Bivariate random-effects meta-analysis will be conducted for the full range of plausible cutoff values.
The proposed IPD meta-analyses will allow us to obtain estimates of the diagnostic accuracy of the PHQ-9, PHQ-8, and PHQ-2.
Systematic review registration
PROSPERO CRD42014010673
PMCID: PMC4218786  PMID: 25348422
Patient health questionnaire; PHQ-9; PHQ-8; PHQ-2; Depression; Screening; Diagnostic test accuracy; Systematic review; Individual patient data meta-analysis
Journal of psychiatric research  2013;47(10):1298-1303.
Mental disorders are associated with premature mortality, and the magnitudes of risk have commonly been estimated using hospital data. However, psychiatric patients who are hospitalized have more severe illness and do not adequately represent mental disorders in the general population. We conducted a national cohort study using outpatient and inpatient diagnoses for the entire Swedish adult population (N=7,253,516) to examine the extent to which mortality risks are overestimated using inpatient diagnoses only. Outcomes were all-cause and suicide mortality during 8 years of follow-up (2001–2008). There were 377,339 (5.2%) persons with any inpatient psychiatric diagnosis, vs. 680,596 (9.4%) with any inpatient or outpatient diagnosis, hence 44.6% of diagnoses were missed using inpatient data only. When including and accounting for prevalent psychiatric cases, all-cause mortality risk among persons with any mental disorder was overestimated by 15.3% using only inpatient diagnoses (adjusted hazard ratio [aHR], 5.89; 95% CI, 5.85–5.92) vs. both inpatient and outpatient diagnoses (aHR, 5.11; 95% CI, 5.08–5.14). Suicide risk was overestimated by 18.5% (aHRs, 23.91 vs. 20.18), but this varied widely by specific disorders, from 4.4% for substance use to 49.1% for anxiety disorders. The sole use of inpatient diagnoses resulted in even greater overestimation of all-cause or suicide mortality risks when prevalent cases were unidentified (~20–30%) or excluded (~25–40%). However, different methods for handling prevalent cases resulted in only modest variation in risk estimates when using both inpatient and outpatient diagnoses. These findings have important implications for the interpretation of hospital-based studies and the design of future studies.
PMCID: PMC3746500  PMID: 23806577
mental disorders; mortality; suicide
11.  Population-specific frequencies for LRRK2 susceptibility variants in the Genetic Epidemiology Of Parkinson’s Disease (GEO-PD) consortium 
Variants within the leucine-rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson’s disease. Leucine-rich repeat kinase 2 variation related to susceptibility to disease displays many features that reflect the nature of complex late-onset sporadic disorders, such as Parkinson’s disease. The Genetic Epidemiology of Parkinson’s disease consortium recently performed the largest genetic association study for variants in the leucine-rich repeat kinase 2 gene across 23 different sites in 15 countries. Herein we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K-R1398H-K1423K) reported in the original publication. Simple population allele frequencies can not only provide an insight into the clinical relevance of specific variants but also help genetically define patient groups. Establishing individual patient-based genomic susceptibility profiles incorporating both risk and protective factors will determine future diagnostic and treatment strategies.
PMCID: PMC4108155  PMID: 23913756
Parkinson disease; LRRK2; genetics; association study
12.  Simple, standardized incorporation of genetic risk into non-genetic risk prediction tools for complex traits: coronary heart disease as an example 
Frontiers in Genetics  2014;5:254.
Purpose: Genetic risk assessment is becoming an important component of clinical decision-making. Genetic Risk Scores (GRSs) allow the composite assessment of genetic risk in complex traits. A technically and clinically pertinent question is how to most easily and effectively combine a GRS with an assessment of clinical risk derived from established non-genetic risk factors as well as to clearly present this information to patient and health care providers.
Materials and Methods: We illustrate a means to combine a GRS with an independent assessment of clinical risk using a log-link function. We apply the method to the prediction of coronary heart disease (CHD) in the Atherosclerosis Risk in Communities (ARIC) cohort. We evaluate different constructions based on metrics of effect change, discrimination, and calibration.
Results: The addition of a GRS to a clinical risk score (CRS) improves both discrimination and calibration for CHD in ARIC. Results are similar regardless of whether external vs. internal coefficients are used for the CRS, risk factor single nucleotide polymorphisms (SNPs) are included in the GRS, or subjects with diabetes at baseline are excluded. We outline how to report the construction and the performance of a GRS using our method and illustrate a means to present genetic risk information to subjects and/or their health care provider.
Conclusion: The proposed method facilitates the standardized incorporation of a GRS in risk assessment.
PMCID: PMC4117937  PMID: 25136350
genetic risk scores; personalized medicine; coronary heart disease; electronic health records
13.  Estimates of the Continuously Publishing Core in the Scientific Workforce 
PLoS ONE  2014;9(7):e101698.
The ability of a scientist to maintain a continuous stream of publication may be important, because research requires continuity of effort. However, there is no data on what proportion of scientists manages to publish each and every year over long periods of time.
Methodology/Principal Findings
Using the entire Scopus database, we estimated that there are 15,153,100 publishing scientists (distinct author identifiers) in the period 1996–2011. However, only 150,608 (<1%) of them have published something in each and every year in this 16-year period (uninterrupted, continuous presence [UCP] in the literature). This small core of scientists with UCP are far more cited than others, and they account for 41.7% of all papers in the same period and 87.1% of all papers with >1000 citations in the same period. Skipping even a single year substantially affected the average citation impact. We also studied the birth and death dynamics of membership in this influential UCP core, by imputing and estimating UCP-births and UCP-deaths. We estimated that 16,877 scientists would qualify for UCP-birth in 1997 (no publication in 1996, UCP in 1997–2012) and 9,673 scientists had their UCP-death in 2010. The relative representation of authors with UCP was enriched in Medical Research, in the academic sector and in Europe/North America, while the relative representation of authors without UCP was enriched in the Social Sciences and Humanities, in industry, and in other continents.
The proportion of the scientific workforce that maintains a continuous uninterrupted stream of publications each and every year over many years is very limited, but it accounts for the lion’s share of researchers with high citation impact. This finding may have implications for the structure, stability and vulnerability of the scientific workforce.
PMCID: PMC4090124  PMID: 25007173
14.  Concordance of effects of medical interventions on hospital admission and readmission rates with effects on mortality 
Many clinical trials examine a composite outcome of admission to hospital and death, or infer a relationship between hospital admission and survival benefit. This assumes concordance of the outcomes “hospital admission” and “death.” However, whether the effects of a treatment on hospital admissions and readmissions correlate to its effect on serious outcomes such as death is unknown. We aimed to assess the correlation and concordance of effects of medical interventions on admission rates and mortality.
We searched the Cochrane Database of Systematic Reviews from its inception to January 2012 (issue 1, 2012) for systematic reviews of treatment comparisons that included meta-analyses for both admission and mortality outcomes. For each meta-analysis, we synthesized treatment effects on admissions and death, from respective randomized trials reporting those outcomes, using random-effects models. We then measured the concordance of directions of effect sizes and the correlation of summary estimates for the 2 outcomes.
We identified 61 meta-analyses including 398 trials reporting mortality and 182 trials reporting admission rates; 125 trials reported both outcomes. In 27.9% of comparisons, the point estimates of treatment effects for the 2 outcomes were in opposite directions; in 8.2% of trials, the 95% confidence intervals did not overlap. We found no significant correlation between effect sizes for admission and death (Pearson r = 0.07, p = 0.6). Our results were similar when we limited our analysis to trials reporting both outcomes.
In this metaepidemiological study, admission and mortality outcomes did not correlate, and discordances occurred in about one-third of the treatment comparisons included in our analyses. Both outcomes convey useful information and should be reported separately, but extrapolating the benefits of admission to survival is unreliable and should be avoided.
PMCID: PMC3855143  PMID: 24144601
15.  The Power of Meta-Analysis in Genome Wide Association Studies 
Meta-analysis of multiple genome-wide association (GWA) studies has become common practice over the last few years. The main advantage of this technique is the maximization of power to detect the subtle genetic effects for common traits. Moreover, one can use meta-analysis to probe and identify heterogeneity in the effect sizes across the combined studies. In this review we systematically appraised and evaluated the characteristics of GWA meta-analyses with 10,000 or more subjects published until June 2012. We overview the current landscape of variants discovered by GWA meta-analyses and we discuss and assess with extrapolations from empirical data the value of larger meta-analyses for the discovery of additional genetic associations and new biology in the future. Finally, we discuss some emerging logistical and practical issues related to the conduct of meta-analysis of GWA studies.
PMCID: PMC4040957  PMID: 23724904
variance explained; gene discovery; sample size; common variants; rare variants; missing heritability; consortium
16.  Transforming Epidemiology for 21st Century Medicine and Public Health 
In 2012, the National Cancer Institute (NCI) engaged the scientific community to provide a vision for cancer epidemiology in the 21st century. Eight overarching thematic recommendations, with proposed corresponding actions for consideration by funding agencies, professional societies, and the research community emerged from the collective intellectual discourse. The themes are (i) extending the reach of epidemiology beyond discovery and etiologic research to include multilevel analysis, intervention evaluation, implementation, and outcomes research; (ii) transforming the practice of epidemiology by moving towards more access and sharing of protocols, data, metadata, and specimens to foster collaboration, to ensure reproducibility and replication, and accelerate translation; (iii) expanding cohort studies to collect exposure, clinical and other information across the life course and examining multiple health-related endpoints; (iv) developing and validating reliable methods and technologies to quantify exposures and outcomes on a massive scale, and to assess concomitantly the role of multiple factors in complex diseases; (v) integrating “big data” science into the practice of epidemiology; (vi) expanding knowledge integration to drive research, policy and practice; (vii) transforming training of 21st century epidemiologists to address interdisciplinary and translational research; and (viii) optimizing the use of resources and infrastructure for epidemiologic studies. These recommendations can transform cancer epidemiology and the field of epidemiology in general, by enhancing transparency, interdisciplinary collaboration, and strategic applications of new technologies. They should lay a strong scientific foundation for accelerated translation of scientific discoveries into individual and population health benefits.
PMCID: PMC3625652  PMID: 23462917
big data; clinical trials; cohort studies; epidemiology; genomics; medicine; public health; technologies; training; translational research
17.  Attention to Local Health Burden and the Global Disparity of Health Research 
PLoS ONE  2014;9(4):e90147.
Most studies on global health inequality consider unequal health care and socio-economic conditions but neglect inequality in the production of health knowledge relevant to addressing disease burden. We demonstrate this inequality and identify likely causes. Using disability-adjusted life years (DALYs) for 111 prominent medical conditions, assessed globally and nationally by the World Health Organization, we linked DALYs with MEDLINE articles for each condition to assess the influence of DALY-based global disease burden, compared to the global market for treatment, on the production of relevant MEDLINE articles, systematic reviews, clinical trials and research using animal models vs. humans. We then explored how DALYs, wealth, and the production of research within countries correlate with this global pattern. We show that global DALYs for each condition had a small, significant negative relationship with the production of each type of MEDLINE articles for that condition. Local processes of health research appear to be behind this. Clinical trials and animal studies but not systematic reviews produced within countries were strongly guided by local DALYs. More and less developed countries had very different disease profiles and rich countries publish much more than poor countries. Accordingly, conditions common to developed countries garnered more clinical research than those common to less developed countries. Many of the health needs in less developed countries do not attract attention among developed country researchers who produce the vast majority of global health knowledge—including clinical trials—in response to their own local needs. This raises concern about the amount of knowledge relevant to poor populations deficient in their own research infrastructure. We recommend measures to address this critical dimension of global health inequality.
PMCID: PMC3972174  PMID: 24691431
18.  Opportunities and Challenges for Selected Emerging Technologies in Cancer Epidemiology: Mitochondrial, Epigenomic, Metabolomic, and Telomerase Profiling 
Remarkable progress has been made in the last decade in new methods for biological measurements using sophisticated technologies that go beyond the established genome, proteome, and gene expression platforms. These methods and technologies create opportunities to enhance cancer epidemiologic studies. In this article, we describe several emerging technologies and evaluate their potential in epidemiologic studies. We review the background, assays, methods, and challenges, and offer examples of the use of mitochondrial DNA and copy number assessments, epigenomic profiling (including methylation, histone modification, microRNAs (miRNAs), and chromatin condensation), metabolite profiling (metabolomics), and telomere measurements. We map the volume of literature referring to each one of these measurement tools and the extent to which efforts have been made at knowledge integration (e.g. systematic reviews and meta-analyses). We also clarify strengths and weaknesses of the existing platforms and the range of type of samples that can be tested with each of them. These measurement tools can be used in identifying at-risk populations and providing novel markers of survival and treatment response. Rigorous analytical and validation standards, transparent availability of massive data, and integration in large-scale evidence are essential in fulfilling the potential of these technologies.
PMCID: PMC3565041  PMID: 23242141
Epigenetics; methylation; mitochondria; risk assessment; telomerase
19.  Heritability and Genome-wide Association Study To Assess Genetic Differences Between Advanced Age-Related Macular Degeneration Subtypes  
Ophthalmology  2012;119(9):1874-1885.
To investigate whether the two subtypes of advanced age-related macular degeneration (AMD), choroidal neovascularization (CNV) and geographic atrophy (GA), segregate separately in families and to identify which genetic variants are associated with these two subtypes.
Sibling correlation study and genome-wide association study (GWAS)
For the sibling correlation study, we included 209 sibling pairs with advanced AMD. For the GWAS, we included 2594 participants with advanced AMD subtypes and 4134 controls. Replication cohorts included 5383 advanced AMD participants and 15,240 controls.
Participants had AMD grade assigned based on fundus photography and/or examination. To determine heritability of advanced AMD subtypes, we performed a sibling correlation study. For the GWAS, we conducted genome-wide genotyping and imputed 6,036,699 single nucleotide polymorphism (SNPs). We then analyzed SNPs with a generalized linear model controlling for genotyping platform and genetic ancestry. The most significant associations were evaluated in independent cohorts.
Main Outcome Measures
Concordance of advanced AMD subtypes in sibling pairs and associations between SNPs with GA and CNV advanced AMD subtypes.
The difference between the observed and expected proportion of siblings concordant for the same subtype of advanced AMD was different to a statistically significant degree (P=4.2 x 10−5) meaning that siblings of probands with CNV or GA are more likely to develop CNV or GA, respectively. In the analysis comparing participants with CNV to those with GA, we observed a statistically significant association at the ARMS2/HTRA1 locus [rs10490924, odds ratio (OR)=1.47, P=4.3 ×10−9] which was confirmed in the replication samples (OR=1.38, P=7.4 x 10−14 for combined discovery and replication analysis).
Whether a patient with AMD develops CNV vs. GA is determined in part by genetic variation. In this large GWAS meta-analysis and replication analysis, the ARMS2/HTRA1 locus confers increased risk for both advanced AMD subtypes but imparts greater risk for CNV than for GA. This locus explains a small proportion of the excess sibling correlation for advanced AMD subtype. Other loci were detected with suggestive associations which differ for advanced AMD subtypes and deserve follow-up in additional studies.
PMCID: PMC3899891  PMID: 22705344
20.  Clinical Outcome Prediction by MicroRNAs in Human Cancer: A Systematic Review 
MicroRNA (miR) expression may have prognostic value for many types of cancers. However, the miR literature comprises many small studies. We systematically reviewed and synthesized the evidence.
Using MEDLINE (last update December 2010), we identified English language studies that examined associations between miRs and cancer prognosis using tumor specimens for more than 10 patients during classifier development. We included studies that assessed a major clinical outcome (nodal disease, disease progression, response to therapy, metastasis, recurrence, or overall survival) in an agnostic fashion using either polymerase chain reaction or hybridized oligonucleotide microarrays.
Forty-six articles presenting results on 43 studies pertaining to 20 different types of malignancy were eligible for inclusion in this review. The median study size was 65 patients (interquartile range [IQR] = 34–129), the median number of miRs assayed was 328 (IQR = 250–470), and overall survival or recurrence were the most commonly measured outcomes (30 and 19 studies, respectively). External validation was performed in 21 studies, 20 of which reported at least one nominally statistically significant result for a miR classifier. The median hazard ratio for poor outcome in externally validated studies was 2.52 (IQR = 2.26–5.40). For all classifier miRs in studies that evaluated overall survival across diverse malignancies, the miRs most frequently associated with poor outcome after accounting for differences in miR assessment due to platform type were let-7 (decreased expression in patients with cancer) and miR 21 (increased expression).
MiR classifiers show promising prognostic associations with major cancer outcomes and specific miRs are consistently identified across diverse studies and platforms. These types of classifiers require careful external validation in large groups of cancer patients that have adequate protection from bias. –
PMCID: PMC3317879  PMID: 22395642
22.  Assessment of Gene-by-Sex Interaction Effect on Bone Mineral Density 
Liu, Ching-Ti | Estrada, Karol | Yerges-Armstrong, Laura M. | Amin, Najaf | Evangelou, Evangelos | Li, Guo | Minster, Ryan L. | Carless, Melanie A. | Kammerer, Candace M. | Oei, Ling | Zhou, Yanhua | Alonso, Nerea | Dailiana, Zoe | Eriksson, Joel | García-Giralt, Natalia | Giroux, Sylvie | Husted, Lise Bjerre | Khusainova, Rita I. | Koromila, Theodora | Kung, Annie WaiChee | Lewis, Joshua R. | Masi, Laura | Mencej-Bedrac, Simona | Nogues, Xavier | Patel, Millan S. | Prezelj, Janez | Richards, J Brent | Sham, Pak Chung | Spector, Timothy | Vandenput, Liesbeth | Xiao, Su-Mei | Zheng, Hou-Feng | Zhu, Kun | Balcells, Susana | Brandi, Maria Luisa | Frost, Morten | Goltzman, David | González-Macías, Jesús | Karlsson, Magnus | Khusnutdinova, Elza K. | Kollia, Panagoula | Langdahl, Bente Lomholt | Ljunggren, Östen | Lorentzon, Mattias | Marc, Janja | Mellström, Dan | Ohlsson, Claes | Olmos, José M. | Ralston, Stuart H. | Riancho, José A. | Rousseau, François | Urreizti, Roser | Van Hul, Wim | Zarrabeitia, María T. | Castano-Betancourt, Martha | Demissie, Serkalem | Grundberg, Elin | Herrera, Lizbeth | Kwan, Tony | Medina-Gómez, Carolina | Pastinen, Tomi | Sigurdsson, Gunnar | Thorleifsson, Gudmar | vanMeurs, Joyce B.J. | Blangero, John | Hofman, Albert | Liu, Yongmei | Mitchell, Braxton D. | O’Connell, Jeffrey R. | Oostra, Ben A. | Rotter, Jerome I | Stefansson, Kari | Streeten, Elizabeth A. | Styrkarsdottir, Unnur | Thorsteinsdottir, Unnur | Tylavsky, Frances A. | Uitterlinden, Andre | Cauley, Jane A. | Harris, Tamara B. | Ioannidis, John P.A. | Psaty, Bruce M. | Robbins, John A | Zillikens, M. Carola | vanDuijn, Cornelia M. | Prince, Richard L. | Karasik, David | Rivadeneira, Fernando | Kiel, Douglas P. | Cupples, L. Adrienne | Hsu, Yi-Hsiang
Sexual dimorphism in various bone phenotypes, including bone mineral density (BMD), is widely observed; however the extent to which genes explain these sex differences is unclear. To identify variants with different effects by sex, we examined gene-by-sex autosomal interactions genome-wide, and performed eQTL analysis and bioinformatics network analysis.
We conducted an autosomal genome-wide meta-analysis of gene-by-sex interaction on lumbar spine (LS-) and femoral neck (FN-) BMD, in 25,353 individuals from eight cohorts. In a second stage, we followed up the 12 top SNPs (P<1×10−5) in an additional set of 24,763 individuals. Gene-by-sex interaction and sex-specific effects were examined in these 12 SNPs.
We detected one novel genome-wide significant interaction associated with LS-BMD at the Chr3p26.1-p25.1 locus, near the GRM7 gene (male effect = 0.02 & p-value = 3.0×10−5; female effect = −0.007 & p-value=3.3×10−2) and eleven suggestive loci associated with either FN- or LS-BMD in discovery cohorts. However, there was no evidence for genome-wide significant (P<5×10−8) gene-by-sex interaction in the joint analysis of discovery and replication cohorts.
Despite the large collaborative effort, no genome-wide significant evidence for gene-by-sex interaction was found influencing BMD variation in this screen of autosomal markers. If they exist, gene-by-sex interactions for BMD probably have weak effects, accounting for less than 0.08% of the variation in these traits per implicated SNP.
PMCID: PMC3447125  PMID: 22692763
gene-by-sex; interaction; BMD; association; aging
23.  Pediatric Versus Adult Drug Trials for Conditions With High Pediatric Disease Burden 
Pediatrics  2012;130(2):285-292.
Optimal treatment decisions in children require sufficient evidence on the safety and efficacy of pharmaceuticals in pediatric patients. However, there is concern that not enough trials are conducted in children and that pediatric trials differ from those performed in adults. Our objective was to measure the prevalence of pediatric studies among clinical drug trials and compare trial characteristics and quality indicators between pediatric and adult drug trials.
For conditions representing a high burden of pediatric disease, we identified all drug trials registered in with start dates between 2006 and 2011 and tracked the resulting publications. We measured the proportion of pediatric trials and subjects for each condition and compared pediatric and adult trial characteristics and quality indicators.
For the conditions selected, 59.9% of the disease burden was attributable to children, but only 12.0% (292/2440) of trials were pediatric (P < .001). Among pediatric trials, 58.6% were conducted without industry funding compared with 35.0% of adult trials (P < .001).
Fewer pediatric compared with adult randomized trials examined safety outcomes (10.1% vs 16.9%, P = .008). Pediatric randomized trials were slightly more likely to be appropriately registered before study start (46.9% vs 39.3%, P = .04) and had a modestly higher probability of publication in the examined time frame (32.8% vs 23.2%, P = .04).
There is substantial discrepancy between pediatric burden of disease and the amount of clinical trial research devoted to pediatric populations. This may be related in part to trial funding, with pediatric trials relying primarily on government and nonprofit organizations.
PMCID: PMC3408692  PMID: 22826574
clinical trials; evidence-based medicine; pediatrics; medication use; research subjects
24.  Potential Reporting Bias in fMRI Studies of the Brain 
PLoS ONE  2013;8(7):e70104.
Functional magnetic resonance imaging (fMRI) studies have reported multiple activation foci associated with a variety of conditions, stimuli or tasks. However, most of these studies used fewer than 40 participants.
After extracting data (number of subjects, condition studied, number of foci identified and threshold) from 94 brain fMRI meta-analyses (k = 1,788 unique datasets) published through December of 2011, we analyzed the correlation between individual study sample sizes and number of significant foci reported. We also performed an analysis where we evaluated each meta-analysis to test whether there was a correlation between the sample size of the meta-analysis and the number of foci that it had identified. Correlation coefficients were then combined across all meta-analyses to obtain a summary correlation coefficient with a fixed effects model and we combine correlation coefficients, using a Fisher’s z transformation.
Principal Findings
There was no correlation between sample size and the number of foci reported in single studies (r = 0.0050) but there was a strong correlation between sample size and number of foci in meta-analyses (r = 0.62, p<0.001). Only studies with sample sizes <45 identified larger (>40) numbers of foci and claimed as many discovered foci as studies with sample sizes ≥45, whereas meta-analyses yielded a limited number of foci relative to the yield that would be anticipated from smaller single studies.
These results are consistent with possible reporting biases affecting small fMRI studies and suggest the need to promote standardized large-scale evidence in this field. It may also be that small studies may be analyzed and reported in ways that may generate a larger number of claimed foci or that small fMRI studies with inconclusive, null, or not very promising results may not be published at all.
PMCID: PMC3723634  PMID: 23936149
25.  Evaluation of Excess Significance Bias in Animal Studies of Neurological Diseases 
PLoS Biology  2013;11(7):e1001609.
The evaluation of 160 meta-analyses of animal studies on potential treatments for neurological disorders reveals that the number of statistically significant results was too large to be true, suggesting biases.
Animal studies generate valuable hypotheses that lead to the conduct of preventive or therapeutic clinical trials. We assessed whether there is evidence for excess statistical significance in results of animal studies on neurological disorders, suggesting biases. We used data from meta-analyses of interventions deposited in Collaborative Approach to Meta-Analysis and Review of Animal Data in Experimental Studies (CAMARADES). The number of observed studies with statistically significant results (O) was compared with the expected number (E), based on the statistical power of each study under different assumptions for the plausible effect size. We assessed 4,445 datasets synthesized in 160 meta-analyses on Alzheimer disease (n = 2), experimental autoimmune encephalomyelitis (n = 34), focal ischemia (n = 16), intracerebral hemorrhage (n = 61), Parkinson disease (n = 45), and spinal cord injury (n = 2). 112 meta-analyses (70%) found nominally (p≤0.05) statistically significant summary fixed effects. Assuming the effect size in the most precise study to be a plausible effect, 919 out of 4,445 nominally significant results were expected versus 1,719 observed (p<10−9). Excess significance was present across all neurological disorders, in all subgroups defined by methodological characteristics, and also according to alternative plausible effects. Asymmetry tests also showed evidence of small-study effects in 74 (46%) meta-analyses. Significantly effective interventions with more than 500 animals, and no hints of bias were seen in eight (5%) meta-analyses. Overall, there are too many animal studies with statistically significant results in the literature of neurological disorders. This observation suggests strong biases, with selective analysis and outcome reporting biases being plausible explanations, and provides novel evidence on how these biases might influence the whole research domain of neurological animal literature.
Author Summary
Studies have shown that the results of animal biomedical experiments fail to translate into human clinical trials; this could be attributed either to real differences in the underlying biology between humans and animals, to shortcomings in the experimental design, or to bias in the reporting of results from the animal studies. We use a statistical technique to evaluate whether the number of published animal studies with “positive” (statistically significant) results is too large to be true. We assess 4,445 animal studies for 160 candidate treatments of neurological disorders, and observe that 1,719 of them have a “positive” result, whereas only 919 studies would a priori be expected to have such a result. According to our methodology, only eight of the 160 evaluated treatments should have been subsequently tested in humans. In summary, we judge that there are too many animal studies with “positive” results in the neurological disorder literature, and we discuss the reasons and potential remedies for this phenomenon.
PMCID: PMC3712913  PMID: 23874156

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