Estimating effects by combining instrumental variables with case-control designs: the role of principal stratification

The instrumental variable framework is commonly used in the estimation of causal effects from cohort samples. In the case of more efficient designs such as the case-control study, however, the combination of the instrumental variable and complex sampling designs requires new methodological consideration. As the prevalence of Mendelian randomization studies is increasing and the cost of genotyping and expression data can be high, the analysis of data gathered from more cost-effective sampling designs is of prime interest. We show that the standard instrumental variable analysis is not applicable to the case-control design and can lead to erroneous estimation and inference. We also propose a method based on principal stratification for the analysis of data arising from the combination of case-control sampling and instrumental variable design and illustrate it with a study in oncology

Prostate-specific antigen, sexual behavior, and sexually transmitted infections in US men 40–59 years old, 2001–2004: a cross – sectional study

<p>Abstract</p> <p>Background</p> <p>Sexually transmitted infections (STIs) are hypothesized to play a role in the development of prostate cancer, perhaps due to inflammation-induced oncogenesis. We assessed in a nationally representative population of middle-aged men whether sexual behavior indicators for an increased risk of genital infection were associated with serum prostate-specific antigen (PSA) concentration, a marker of prostatic disease and inflammation.</p> <p>Results</p> <p>The percentage of men between the ages of 40 and 59 with a PSA ≥ 4.0 ng/ml was 2.6% (95% confidence interval [CI], 1.8% – 3.8%). The percentage of men between the ages of 40 and 59 self-reporting a past diagnosis of genital warts or genital herpes, or a recent diagnosis of gonorrhea or chlamydia is estimated to be 7.3% (95% CI, 6.2% – 8.6%). Men self-reporting that they had had sex without using a condom in the past month had a lower PSA concentration and higher %fPSA than those who did not. There were no associations between any of the other sexual activity or laboratory measures and PSA or %fPSA.</p> <p>Conclusion</p> <p>In this nationally representative sample of middle-aged American men, we did not find consistent evidence for an association between sexual behavior or a history of STIs and PSA levels. Therefore, sexual factors are unlikely to lead to falsely elevated PSA tests in this population. We cannot rule out the role of these factors in causing false positive PSA tests in subgroups of the population that have a higher prevalence of high-risk sexual behavior, and more protracted or recent exposures to these agents.</p

Self-Empowerment Within the Woodside Juvenile Rehabilitation Center Population

Abstract: Intro Teens at the Woodside Juvenile Rehabilitation Center struggled with personal health and self-empowerment in the health care setting. Methods We spoke with both detention and treatment residents about their health. We constructed self-health surveys which were completed by 16 residents. Analysis of the results led to creation a self-health advocacy and activity booklet to be completed by current and future residents. Results Residents had health coverage but only sought dental care, feeling little control over doctor visits. Stress stemmed from family and friends and was coped with via exercise. Interest in learning about relaxation and long term health was expressed. Discussion Health information needed to be incorporated into patient-interactive teaching methods and self-analysis, focused on self-reflection and changing attitudes rather than raw health knowledge.https://scholarworks.uvm.edu/comphp_gallery/1020/thumbnail.jp

Urinary lignans and inflammatory markers in the US National Health and Nutrition Examination Survey (NHANES) 1999-2004 and 2005-2008

Purpose: Chronic inflammation has been implicated in the etiology of various chronic diseases. We previously found that certain urinary isoflavones are associated with markers of inflammation. In the present study, we examined the associations of serum C-reactive protein (CRP) and white blood cell (WBC) count with lignans, which are more frequent in the Western diet than isoflavones. Methods: Our analysis included 2,028 participants of NHANES 2005-2008 and 2,628 participants of NHANES 1999-2004 aged 18years and older. The exposures of interest were urinary mammalian lignans (enterodiol and enterolactone). Outcome variables were two inflammatory markers (CRP [≤10mg/L] and WBC [≥3.0 and ≤11.7 (1,000 cells/μL)]). Log-transformed CRP concentration and WBC count by log-transformed creatinine-standardized concentrations of mammalian lignans were used for linear regression. Results: Statistically significant inverse associations of urinary lignan, enterodiol, and enterolactone concentrations with circulating CRP and WBC counts were observed in the multivariate-adjusted models: In NHANES 2005-2008, per one-percent increase in lignan concentrations in the urine, CRP concentrations and WBC counts decreased by 8.1% (95% CI −11.5, −4.5) and 1.9% (95% CI −2.7; −1.2), respectively. Per one-percent increase in enterodiol and enterolactone, WBC counts decreased by 2.1% (95% CI −2.8, −1.3) and 1.3% (95% CI −1.9, −0.6), respectively. In NHANES 1999-2004, analogous results were 3.0% (95% CI −5.6, −0.3), 1.2% (95% CI −2.0; −0.4), 1.0% (95% CI −1.8, −0.2), and 0.8% (95% CI −1.4, 0.2). Conclusions: Mammalian lignans were inversely associated with markers of chronic inflammation. Due to the cross-sectional design, our findings require confirmation in prospective studies

Inflammation in benign prostate tissue and prostate cancer in the finasteride arm of the Prostate Cancer Prevention Trial

BACKGROUND: A previous analysis of the placebo arm of the Prostate Cancer Prevention Trial (PCPT) reported 82% overall prevalence of intraprostatic inflammation and identified a link between inflammation and higher-grade prostate cancer and serum PSA. Here we studied these associations in the PCPT finasteride arm. METHODS: Prostate cancer cases (N=197) detected either on a clinically indicated biopsy or on protocol-directed end-of-study biopsy, and frequency-matched controls (N=248) with no cancer on an end-of-study biopsy were sampled from the finasteride arm. Inflammation in benign prostate tissue was visually assessed using digital images of H&E stained sections. Logistic regression was used for statistical analysis. RESULTS: In the finasteride arm, 91.6% of prostate cancer cases and 92.4% of controls had at least one biopsy core with inflammation in benign areas; p < 0.001 for difference compared to placebo arm. Overall, the odds of prostate cancer did not differ by prevalence (OR=0.90, 95% CI 0.44-1.84) or extent (P-trend=0.68) of inflammation. Inflammation was not associated with higher-grade disease (prevalence: OR=1.07, 95% CI 0.43-2.69). Furthermore, mean PSA concentration did not differ by the prevalence or extent of inflammationin either cases or controls. CONCLUSION: The prevalence of intraprostatic inflammation was higher in the finasteride than placebo arm of the PCPT, with no association with higher-grade prostate cancer. IMPACT: Finasteride may attenuate the association between inflammation and higher-grade prostate cancer. Moreover, the missing link between intraprostatic inflammation and PSA suggests that finasteride may reduce inflammation-associated PSA elevation

Body fatness and sex steroid hormone concentrations in US men: results from NHANES III

Objective: Obesity is associated with a variety of chronic diseases, including cancer, which may partly be explained by its influence on sex steroid hormone concentrations. Whether different measures of obesity, i.e., body mass index (BMI), waist circumference, and percent body fat were differentially associated with circulating levels of sex steroid hormones was examined in 1,265 men, aged 20-90+years old, attending the morning examination session of the Third National Health and Nutrition Examination Survey (NHANES III). Materials and methods: Serum hormones were measured by immunoassay. Weight, height, and waist circumference were measured by trained staff. Percent body fat was estimated from bioelectrical impedance. Multivariate linear regression was used to estimate associations between body fatness measures and hormone levels. Results: Total and free testosterone and sex hormone binding globulin concentrations decreased, whereas total and free estradiol increased with increasing BMI, waist circumference, and percent body fat (all p trend<0.05). The magnitude of change in these hormones was similar for a one-quartile increase in each body fatness measure. Conclusion: Measured BMI, waist circumference, and percent body fat led to similar inferences about their association with hormone levels in me

Racial variation in vitamin D cord blood concentration in white and black male neonates

Aim: The aim of this study is to evaluate racial variation in umbilical cord blood concentration of vitamin D and to explore its correlation with markers of the insulin-like growth factor axis (IGFs) and sex steroid hormones in white and black male neonates. Methods: In 2004-2005, venous umbilical cord blood samples were collected from 75 black and 38 white male neonates, along with maternal and birth characteristics from two hospitals in Maryland, United States. 25-Hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] were measured by radioimmunoassay and testosterone, estradiol, and sex hormone-binding globulin (SHBG) by immunoassay and IGF-1, IGF-2, and IGF-binding protein-3 by ELISA. Crude and multivariable-adjusted geometric mean concentrations were computed. Results: Mean 25(OH)D levels were lower in black than in white neonates (11.44; 95% CI 10.10-12.95ng/mL vs. 18.24; 95% CI 15.32-21.72ng/mL; p<0.0001). Black neonates were at higher risk of suboptimal vitamin D levels [25(OH)D<20ng/mL] than whites (84 vs. 63%). 25(OH)D concentrations varied by season in whites but not in blacks and were significantly inversely correlated with mother's parity (number of live births) in blacks but not in whites. Mean concentration of 1,25(OH)2D did not differ by race. 25(OH)D and 1,25(OH)2D did not correlate with IGFs, sex steroid hormones, and SHBG. Conclusions: Suboptimal vitamin D levels were prevalent especially in blacks and influenced by mother's parity and by season. The observed vitamin D differences between black and white neonates warrant further evaluation of the etiology of the disparity in chronic diseases in adulthoo

The relationship between lipoprotein A and other lipids with prostate cancer risk:A multivariable Mendelian randomisation study

BACKGROUND: Numerous epidemiological studies have investigated the role of blood lipids in prostate cancer (PCa) risk, though findings remain inconclusive to date. The ongoing research has mainly involved observational studies, which are often prone to confounding. This study aimed to identify the relationship between genetically predicted blood lipid concentrations and PCa. METHODS AND FINDINGS: Data for low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides (TG), apolipoprotein A (apoA) and B (apoB), lipoprotein A (Lp(a)), and PCa were acquired from genome-wide association studies in UK Biobank and the PRACTICAL consortium, respectively. We used a two-sample summary-level Mendelian randomisation (MR) approach with both univariable and multivariable (MVMR) models and utilised a variety of robust methods and sensitivity analyses to assess the possibility of MR assumptions violation. No association was observed between genetically predicted concentrations of HDL, TG, apoA and apoB, and PCa risk. Genetically predicted LDL concentration was positively associated with total PCa in the univariable analysis, but adjustment for HDL, TG, and Lp(a) led to a null association. Genetically predicted concentration of Lp(a) was associated with higher total PCa risk in the univariable (OR(weighted median) per standard deviation (SD) = 1.091; 95% CI 1.028 to 1.157; P = 0.004) and MVMR analyses after adjustment for the other lipid traits (OR(IVW) per SD = 1.068; 95% CI 1.005 to 1.134; P = 0.034). Genetically predicted Lp(a) was also associated with advanced (MVMR OR(IVW) per SD = 1.078; 95% CI 0.999 to 1.163; P = 0.055) and early age onset PCa (MVMR OR(IVW) per SD = 1.150; 95% CI 1.015,1.303; P = 0.028). Although multiple estimation methods were utilised to minimise the effect of pleiotropy, the presence of any unmeasured pleiotropy cannot be excluded and may limit our findings. CONCLUSIONS: We observed that genetically predicted Lp(a) concentrations were associated with an increased PCa risk. Future studies are required to understand the underlying biological pathways of this finding, as it may inform PCa prevention through Lp(a)-lowering strategies

Nationally Representative Estimates of Serum Testosterone Concentration in Never-Smoking, Lean Men Without Aging-Associated Comorbidities

Context Testosterone deficiency prevalence increases with age, comorbidities, and obesity. Objective To inform clinical guidelines for testosterone deficiency management and development of targets for nonpharmacologic intervention trials for these men, we determined serum testosterone in never-smoking, lean men without select comorbidities in nationally representative surveys. Design Setting Participants We used cross-sectional data for never-smoking, lean men ≥20 years without diabetes, myocardial infarction, congestive heart failure, stroke, or cancer, without use of hormone-influencing medications, and participated in morning sessions of National Health and Nutrition Examination Survey (NHANES) III (phase I 1988-1991) or continuous NHANES (1999-2004). By age, we determined median total testosterone (ng/mL) measured previously by a Food and Drug Administration-approved immunoassay and median estimated free testosterone concentration. Results In NHANES III, in never-smoking, lean men without comorbidities, median (25th, 75th percentile) testosterone was 4% to 9% higher than all men-20 to 39 years: 6.24 (5.16, 7.51), 40 to 59: 5.37 (3.83, 6.49), and ≥60: 4.61 (4.01, 5.18). In continuous NHANES, in never-smoking, lean men without comorbidities, levels were 13% to 24% higher than all men-20 to 39 years: 6.26 (5.32, 7.27), 40 to 59: 5.86 (4.91, 6.55), and ≥60: 4.22 (3.74, 5.73). In never-smoking, lean men without comorbidities, median estimated free testosterone was similar to (NHANES III) or slightly higher than (continuous NHANES) in all men. Conclusions These nationally representative data document testosterone levels (immunoassay) in never-smoking, lean men without select comorbidities 30 and 15 to 20 years ago. This information can be incorporated into guidelines for testosterone deficiency management and used to develop targets for nonpharmacologic intervention trials for testosterone deficiency