Barbra Dickerman

Background:Observational studies are used for estimating vaccine effectiveness under real-world conditions. The practical performance of two common approaches—cohort and test-negative designs—need to be compared for COVID-19 vaccines.Methods:

Background Prostate cancer is the most diagnosed cancer in African American men, yet prostate cancer screening regimens in this group are poorly guided by existing evidence, given underrepresentation of African American men in prostate cancer screening trials. It is critical to optimize prostate cancer screening and early detection in this high-risk group because underdiagnosis may lead to later-stage cancers at diagnosis and higher mortality while overdiagnosis may lead to unnecessary treatment. Methods We performed a review of the literature related to prostate cancer screening and early detection specific to African American men to summarize the existing evidence available to guide health-care practice. Results Limited evidence from observational and modeling studies suggests that African American men should be screened for prostate cancer …

Studies have reported that prior-season influenza vaccination is associated with higher risk of clinical influenza infection among vaccinees. This effect might arise from incomplete consideration of within-season waning and recent infection. Using data from the US Flu Vaccine Effectiveness (VE) Network (2011–2012 to 2018–2019 seasons), we found that repeat vaccinees were vaccinated earlier in a season by one week. After accounting for waning VE, repeat vaccinees were still more likely to test positive for A (H3N2)(OR= 1.11, 95% CI: 1.02–1.21) but not for influenza B or A (H1N1). We found that clinical infection influences individuals’ decision to vaccinate in the following season while protecting against clinical infection of the same (sub) type. However, adjusting for recent clinical infections did not strongly influence the estimated effect of prior-season vaccination. In contrast, we found that adjusting for subclinical …

Introduction: Social support is associated with improved cancer survivorship, but literature on its association with prostate cancer specific physical and psychosocial quality of life (QoL) is lacking. We investigated the associations of social support with physical and psychosocial QoL in individuals with prostate cancer in HPFS. Methods: We included 1,692 men (ages 61-95 years, mean: 71 years) diagnosed with non-metastatic prostate cancer between 2008 and 2016. Social support was measured by the Berkman-Syme Social Network Index (SNI) (a composite measure of marital status, sociability, membership in religious groups or other community organizations: socially isolated, moderately isolated, moderately integrated, socially integrated) and marital status (married, not married). Physical (measured by EPIC-CP: bowel function, urinary incontinence, urinary irritation/obstruction, sexual function, vitality/hormonal …

Introduction: Randomized trials have shown that physical activity can improve quality of life (QOL) among individuals with cancer. In the absence of a randomized trial of adequate size and follow-up to comprehensively evaluate this relationship for prostate cancer, we aim to emulate a target trial of guideline-based physical activity strategies and 6-year physical QOL. Methods: We will use observational data on individuals in the Health Professionals Follow-up Study diagnosed with nonmetastatic prostate cancer between 2010-2016 and free of conditions that could preclude following current physical activity recommendations at baseline (first post-diagnostic questionnaire). The physical activity strategies of interest are (1) engage in ≥150 minutes of moderate activity, or ≥75 minutes of vigorous activity per week, or an equivalent combination (i.e., ≥7.5 metabolic equivalent of task [MET]-hours/week of vigorous or …

Background: More than 60,000 U.S. adults are diagnosed with non-muscle invasive bladder cancer (NMIBC) each year. These patients are recommended to undergo surveillance via repeated cystoscopies. However, the ideal frequency of post-diagnostic cystoscopy surveillance remains unknown, and efforts are underway to de-escalate surveillance given uncertainty regarding its effect on mortality. We therefore aimed to compare the effectiveness of different post-diagnostic cystoscopy surveillance strategies on bladder cancer specific mortality. Methods: We used observational data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linkage to emulate a target trial, i.e., a hypothetical, pragmatic randomized trial that would answer our causal question. Eligible individuals were aged 66 years or older, diagnosed with NMIBC (Ta, Tis, or T1) classified as urothelial carcinoma between January 1 …

ImportanceObservational (nonexperimental) studies that aim to emulate a randomized trial (ie, the target trial) are increasingly informing medical and policy decision-making, but it is unclear how these studies are reported in the literature. Consistent reporting is essential for quality appraisal, evidence synthesis, and translation of evidence to policy and practice.ObjectiveTo assess the reporting of observational studies that explicitly aimed to emulate a target trial.Evidence ReviewWe searched Medline, Embase, PsycINFO, and Web of Science for observational studies published between March 2012 and October 2022 that explicitly aimed to emulate a target trial of a health or medical intervention. Two reviewers double-screened and -extracted data on study characteristics, key predefined components of the target trial protocol and its emulation (eligibility criteria, treatment strategies, treatment assignment, outcome[s …

BackgroundObservational studies are increasingly used to inform health decision-making when randomised trials are not feasible, ethical or timely. The target trial approach provides a framework to help minimise common biases in observational studies that aim to estimate the causal effect of interventions. Incomplete reporting of studies using the target trial framework limits the ability for clinicians, researchers, patients and other decision-makers to appraise, synthesise and interpret findings to inform clinical and public health practice and policy. This paper describes the methods that we will use to develop the TrAnsparent ReportinG of observational studies Emulating a Target trial (TARGET) reporting guideline.Methods/designThe TARGET reporting guideline will be developed in five stages following recommended guidance. The first stage will identify target trial reporting practices by systematically reviewing …

Background:Metformin users appear to have a substantially lower risk of cancer than nonusers in many observational studies. These inverse associations may be explained by common flaws in observational analyses that can be avoided by explicitly emulating a target trial.Methods:We emulated target trials of metformin therapy and cancer risk using population-based linked electronic health records from the UK (2009–2016). We included individuals with diabetes, no history of cancer, no recent prescription for metformin or other glucose-lowering medication, and hemoglobin A1c (HbA1c)< 64 mmol/mol (< 8.0%). Outcomes included total cancer and 4 site-specific cancers (breast, colorectal, lung, and prostate). We estimated risks using pooled logistic regression with adjustment for risk factors via inverse-probability weighting. We emulated a second target trial among individuals regardless of diabetes status. We …

Vaccination against SARS-CoV-2 has been effective in reducing the burden of severe disease and death from COVID-19. Third doses of mRNA-based vaccines have provided a way to address waning immunity and broaden protection against emerging SARS-CoV-2 variants. However, their comparative effectiveness for a range of COVID-19 outcomes across diverse populations is unknown. We emulated a target trial using electronic health records of US veterans who received a third dose of either BNT162b2 or mRNA-1273 vaccines between 20 October 2021 and 8 February 2022, during a period that included Delta- and Omicron-variant waves. Eligible veterans had previously completed an mRNA vaccine primary series. We matched recipients of each vaccine in a 1:1 ratio according to recorded risk factors. Each vaccine group included 65,196 persons. The excess number of events over 16 weeks per 10,000 …

The accuracy of a prediction algorithm depends on contextual factors that may vary across deployment settings. To address this inherent limitation of prediction, we propose an approach to counterfactual prediction based on the g-formula to predict risk across populations that differ in their distribution of treatment strategies. We apply this to predict 5-year risk of mortality among persons receiving care for HIV in the U.S. Veterans Health Administration under different hypothetical treatment strategies. First, we implement a conventional approach to develop a prediction algorithm in the observed data and show how the algorithm may fail when transported to new populations with different treatment strategies. Second, we generate counterfactual data under different treatment strategies and use it to assess the robustness of the original algorithm’s performance to these differences and to develop counterfactual prediction …

Background The messenger RNA (mRNA)–based vaccines BNT162b2 and mRNA-1273 are more than 90% effective against coronavirus disease 2019 (Covid-19). However, their comparative effectiveness for a range of outcomes across diverse populations is unknown. Methods We emulated a target trial using the electronic health records of U.S. veterans who received a first dose of the BNT162b2 or mRNA-1273 vaccine between January 4 and May 14, 2021, during a period marked by predominance of the SARS-CoV-2 B.1.1.7 (alpha) variant. We matched recipients of each vaccine in a 1:1 ratio according to their risk factors. Outcomes included documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, symptomatic Covid-19, hospitalization for Covid-19, admission to an intensive care unit (ICU) for Covid-19, and death from Covid-19. We estimated risks using the Kaplan–Meier …

BackgroundAdiposity is consistently positively associated with postmenopausal breast cancer and inversely associated with premenopausal breast cancer risk, though the reasons for this difference remain unclear.MethodsIn this nested case–control study of 1649 breast cancer cases and 1649 matched controls from the Nurses’ Health Study (NHS) and the NHSII, we selected lipid and polar metabolites correlated with BMI, waist circumference, weight change since age 18, or derived fat mass, and developed a metabolomic score for each measure using LASSO regression. Logistic regression was used to investigate the association between this score and breast cancer risk, adjusted for risk factors and stratified by menopausal status at blood draw and diagnosis.ResultsMetabolite scores developed among only premenopausal or postmenopausal women were highly correlated with scores developed in all women …

Objective:To compare the risk of coronavirus disease 2019 (COVID-19) outcomes by antiretroviral therapy (ART) regimens among men with HIV.Design:We included men with HIV on ART in the Veterans Aging Cohort Study who, between February 2020 and October 2021, were 18 years or older and had adequate virological control, CD4+ cell count, and HIV viral load measured in the previous 12 months, and no previous COVID-19 diagnosis or vaccination.Methods:We compared the adjusted risks of documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, COVID-19-related hospitalization, and intensive care unit (ICU) admission by baseline ART regimen: tenofovir alafenamide (TAF)/emtricitabine (FTC), tenofovir disoproxil fumarate (TDF)/FTC, abacavir (ABC)/lamivudine (3TC), and other. We fit pooled logistic regressions to estimate the 18-month risks standardized by demographic …

ImportanceThe risk of adverse events has been found to be low for participants receiving the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna Inc) vaccines in randomized trials. However, a head-to-head comparison of their safety for a broader range of potential adverse events over longer follow-up and in larger and more diverse populations is lacking, to our knowledge.ObjectiveTo compare the head-to-head safety in terms of risk of adverse events of the BNT162b2 and mRNA-1273 vaccines in the national health care databases of the US Department of Veterans Affairs, the largest integrated health care system in the US.Design, Setting, and ParticipantsIn this cohort study, the electronic health records of US veterans who received a first dose of the BNT162b2 or mRNA-1273 vaccine between January 4 and September 20, 2021, were used. Recipients of each vaccine were matched in a 1:1 ratio according …

BackgroundBecause randomized trials of sustained dietary changes are sometimes impractical for long-term outcomes, the explicit emulation of a (hypothetical) target trial using observational data may be an important tool for nutritional epidemiology.ObjectivesWe describe a methodological approach that aims to emulate a target trial of dietary interventions sustained over many years using data from observational cohort studies.MethodsWe estimated the 20-y risk of all-cause mortality under the sustained implementation of the food-based goals of the American Heart Association (AHA) 2020 using data from 3 prospective observational studies of US men [Health Professionals Follow-up Study (HPFS)] and women [Nurses’ Health Study (NHS) and Nurses’ Health Study II (NHS II)]. We applied the parametric g-formula to estimate the 20-y mortality risk under a dietary intervention and under no dietary intervention …

Background Previous case-control studies have reported a strong association between statin use and lower cancer risk. It is unclear whether this association reflects a benefit of statins or is the result of design decisions that cannot be mapped to a (hypothetical) target trial (that would answer the question of interest). Methods We outlined the protocol of a target trial to estimate the effect of statins on colorectal cancer incidence among adults with low-density lipoprotein (LDL) cholesterol below 5 mmol/L. We then emulated the target trial using linked electronic health records of 752 469 eligible UK adults (CALIBER 1999–2016) under both a cohort design and a case-control sampling of the cohort. We used pooled logistic regression to estimate intention-to-treat and per-protocol effects of statins on colorectal cancer, with adjustment for baseline and time-varying risk factors via …

BackgroundEvidence for androgen deprivation therapy (ADT) and risk of dementia is both limited and mixed. We aimed to assess the association between ADT and risk of dementia among men with localized and locally advanced prostate cancer (PCa).MethodsWe conducted a retrospective cohort study using SEER-Medicare-linked data among 100,414 men aged ≥ 66 years and diagnosed with localized and locally advanced PCa (cT1–cT4) between 1992 and 2009. We excluded men with a history of stroke, dementia, or use of psychiatric services. Men were followed until death or administrative end of follow-up at 36 months. Inverse-probability weighted Fine-Gray models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for Alzheimer’s, all-cause dementia, and use of psychiatric services by duration of pharmacologic ADT (0, 1–6, and ≥ 7 months).ResultsAmong 100,414 men …

Clinical researchers generate and analyze health data for three classes of tasks: description, prediction, and counterfactual prediction [1]. Description uses data to provide a quantitative summary of certain features of the world. Prediction uses data to map some features of the world (the inputs) to other features of the world (the outputs). Counterfactual prediction uses data to predict certain features of the world if the world had been different. Causal inference is a common goal of counterfactual prediction. Indeed, causal inference can be viewed as the prediction of the distribution of an outcome under two (or more) hypothetical interventions followed by a comparison of those outcome distributions. This contrast of outcome distributions may be the basis of subsequent decision-making: we often choose to implement the hypothetical intervention that, according to our analyses, leads to the most favorable outcome.But …

Obesity is associated with a higher risk of advanced prostate cancer, but men with the same body mass index (BMI) may differ in their underlying metabolic health. Using metabolomics data from nested case-control studies in the Health Professionals Follow-Up Study, we calculated Pearson correlations between 165 circulating metabolites and three adiposity measures (BMI, waist circumference, and derived fat mass from a validated prediction equation) to identify adiposity-associated metabolites. We used Lasso to further select metabolites for prediction models of adiposity measures, which we used to calculate metabolic scores representing metabolic obesity. In an independent set of 212 advanced prostate cancer cases (T3b/T4/N1/M1 or lethal during follow-up) and 212 controls, we used logistic regression to evaluate the associations between adiposity measures and metabolic scores with risk of advanced disease. All adiposity measures were associated with higher blood levels of carnitines (Pearson r range, 0.16 to 0.18) and lower levels of glutamine (r = −0.19) and glycine (r, −0.29 to −0.20), in addition to alterations in various lipids. No adiposity measure or metabolic score was associated with risk of advanced prostate cancer (e.g., odds ratio for a 5 kg/m2 increase in BMI 0.96 (95% CI: 0.73, 1.27) and BMI metabolic score 1.18 (95% CI: 0.57, 2.48)). BMI, waist circumference, and derived fat mass were associated with a broad range of metabolic alterations. Neither adiposity nor metabolic scores were associated with risk of advanced prostate cancer.