Relative-risk-estimate bias and loss of power in the mantel test for trend resulting from the use of magnetic-field point-in-time (“spot”) measurements in epidemiological studies based on an ordinal exposure scale

1992 ◽  
Vol 13 (5) ◽  
pp. 363-378 ◽  
Author(s):  
Vincent Delpizzo ◽  
Michael R. Salzberg
Keyword(s):  
Magnetic Field ◽  
Relative Risk ◽  
Epidemiological Studies ◽  
Mantel Test ◽  
Risk Estimate ◽  
Relative Risk Estimate ◽  
Field Point

scholarly journals Inference on Reported Vehicular Fatal Accidents in Nigeria Using a Bayesian Model

2021 ◽  
Vol 2 (1) ◽  
pp. 53-61
Author(s):  
Olalude Gbenga Adelekan ◽  
Mbata Ahamefula Ugochukwu ◽  
Amusan Ajitoni Simeon
Keyword(s):  
Relative Risk ◽  
Empirical Bayes ◽  
Risk Estimate ◽  
Relative Risk Estimate ◽  
Government Programs ◽  
Fatal Accidents ◽  
North Central ◽  
Bayes Model ◽  
Geopolitical Region ◽  
Special Case

The study introduced a special case of the Poisson-Generalized Gamma empirical Bayes model to survey states in Nigeria with a higher risk of fatal accidents. Monte Carlo error and stationary dynamic trace plots were used to validate model convergence and accuracy of the posterior estimates. The main results included the disease mappings that revealed Ebonyi had the highest risk of road vehicular fatal accidents in Nigeria with a relative risk estimate of 1.4120 while Abuja had the lowest risk with a relative risk estimate 0.5711. In terms of geopolitical region, the risk of road vehicular fatal accident is highest in South-South region with a relative risk estimate of 1.1850 while North-Central had the lowest risk with a relative risk estimate of 0.7846. The study is to aid planned government programs to ameliorate vehicular road carnage in Nigeria. 

scholarly journals The prevalence rate of hypopituitarism in patients with pituitary macroadenomas with various hormonal activities

2021 ◽  
Vol 49 ◽  
Author(s):  
Yu. G. Krivosheeva ◽  
I. A. Ilovayskaya
Keyword(s):  
Risk Factors ◽  
Relative Risk ◽  
Prevalence Rate ◽  
Pituitary Tumor ◽  
Pituitary Tumors ◽  
Epidemiological Studies ◽  
Newly Diagnosed ◽  
Chiasmal Compression ◽  
Secondary Hypothyroidism ◽  
Pituitary Macroadenomas

Rationale: According to the recent epidemiological studies, prevalence of pituitary tumors amounts to 1 per 865 to 2688 adults. The prevalence rates of hypopituitarism in pituitary macroadenomas are highly variable and comprise 37% to 85% among newly diagnosed non-functioning pituitary adenomas (NFPA). There is virtually no data on the prevalence of hypopituitarism in the cohort of newly diagnosed macroadenomas secreting prolactin and somatotropic hormone.Aim: To assess the prevalence of hypopituitarism in patients with pituitary macroadenomas with various hormonal activities and to identify its potential risk factors.Materials and methods: We analyzed data from 293 patients with pituitary macroadenomas with various hormonal activities: NFPA (n = 121), prolactinomas (n = 59), and somatotropinomas (n = 113). The patients had been examined before any treatment was commenced.Results: The prevalence rate of hypopituitarism was 59/121 (39.9%) among the patients with NFPA, 18/59 (27.3%) among those with prolactinomas, and 19/113 (14%) among those with somatotropinomas (р < 0.001). The symptoms of chiasmal compression and chiasmal syndrome were significantly more prevalent in the patients with hypopituitarism, than in those without it in all subgroups. The relative risk of hypopituitarism in the patients with chiasmal compression was 2.10 for NFPA (95% confidence interval (CI) 1.50–2.95, р = 0.003), 1.667 for prolactinomas (95% CI 1.29–2.18, р = 0.005), and 1.45 for somatotropinomas (95% CI 1.56–2.48, р = 0.001). The relative risk of hypopituitarism in the patients with chiasmal syndrome was 1.66 for NFPA (95% CI 1.26–2.18, р = 0.009), 2.08 for prolactinomas (95% CI 1.60– 2.69, р = 0.001), and 1.97 for somatotropinomas (95% CI 1.56–2.48, р = 0.005). The NFPA subgroup had the highest rate of hypothyroidism (36/59, 61.0%), whereas the prolactinoma subgroup had the highest rate of secondary hypogonadism (34/59, 57.6%); however, hypogonadism is one of the manifestations of persistent pathological hyperprolactinemia typical for prolactinomas. In the somatotropinoma subgroup, secondary hypothyroidism was found in 11/19 (57.9%) of the patients.Conclusion: Identification of hypopituitarism before any treatment depended on the type of hormonal activity of a pituitary tumor and was most frequent in NFPA. The risk factors for hypopituitarism were chiasmal compression, chiasmal syndrome, vertical diameter of the pituitary tumor, and its volume. Secondary adrenal insufficiency, being the most hazardous component of hypopituitarism, manifested most rarely.

scholarly journals Garlic consumption and colorectal cancer risk in man: a systematic review and meta-analysis

2015 ◽  
Vol 19 (2) ◽  
pp. 308-317 ◽  
Author(s):  
Manuela Chiavarini ◽  
Liliana Minelli ◽  
Roberto Fabiani
Keyword(s):  
Colorectal Cancer ◽  
Cancer Risk ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Pooled Analysis ◽  
Case Control ◽  
Dietary Factors ◽  
Colorectal Cancer Risk ◽  
Risk Estimate ◽  
Case Control Studies

AbstractObjectiveColorectal cancer shows large incidence variations worldwide that have been attributed to different dietary factors. We conducted a meta-analysis on the relationship between garlic consumption and colorectal cancer risk.DesignWe systematically reviewed publications obtained by searching ISI Web of Knowledge, MEDLINE and EMBASE literature databases. We extracted the risk estimate of the highest and the lowest reported categories of intake from each study and conducted meta-analysis using a random-effects model.ResultsThe pooled analysis of all fourteen studies, seven cohort and seven case–control, indicated that garlic consumption was not associated with colorectal cancer risk (OR=0·93; 95 % CI 0·82, 1·06, P=0·281; I2=83·6 %, P≤0·001). Separate analyses on the basis of cancer sites and sex also revealed no statistically significant effects on cancer risk. However, when separately analysed on the basis of study type, we found that garlic was associated with an approximately 37 % reduction in colorectal cancer risk in the case–control studies (combined risk estimate=0·63, 95 % CI 0·48, 0·82, P=0·001; I2=75·6 %, P≤0·001).ConclusionsOur results suggest that consumption of garlic is not associated with a reduced colorectal cancer risk. Further investigations are necessary to clarify the discrepancy between results obtained from different types of epidemiological studies.

scholarly journals The effects of 50 Hz magnetic field exposure on DNA damage and cellular functions in various neurogenic cells

2017 ◽  
Vol 58 (4) ◽  
pp. 474-486 ◽  
Author(s):  
Liling Su ◽  
Aziguli Yimaer ◽  
Xiaoxia Wei ◽  
Zhengping Xu ◽  
Guangdi Chen
Keyword(s):  
Magnetic Field ◽  
Dna Damage ◽  
Cortical Neurons ◽  
Cell Cycle Progression ◽  
Low Frequency ◽  
Epidemiological Studies ◽  
Neurogenic Tumor ◽  
Dna Double Strand Breaks ◽  
Cellular Functions ◽  
Field Exposure

Abstract Epidemiological studies have indicated a possible association between extremely low–frequency magnetic field (ELF-MF) exposure and the risk of nervous system diseases. However, laboratory studies have not provided consistent results for clarifying this association, despite many years of studies. In this study, we have systematically investigated the effects of 50 Hz MF exposure on DNA damage and cellular functions in both neurogenic tumor cell lines (U251, A172, SH-SY5Y) and primary cultured neurogenic cells from rats (astrocytes, microglia, cortical neurons). The results showed that exposure to a 50 Hz MF at 2.0 mT for up to 24 h did not influence γH2AX foci formation (an early marker of DNA double-strand breaks) in any of six different neurogenic cells. Exposure to a 50 Hz MF did not affect cell cycle progression, cell proliferation or cell viability in neurogenic tumor U251, A172 or SH-SY5Y cells. Furthermore, the MF exposure for 24 h did not significantly affect the secretion of cytokines (TNF-α, IL-6 or IL-1β) in astrocytes or microglia, or the phagocytic activity of microglia. In addition, MF exposure for 1 h per day did not significantly influence expression levels of microtubule-associated protein tau, microtubule-associated protein 2, postsynaptic density 95 or gephyrin in cortical neurons, indicating an absence of effects of MF exposure on the development of cortical neurons. In conclusion, our data suggest that exposure to a 50 Hz MF at 2.0 mT did not elicit DNA damage effects or abnormal cellular functions in the neurogenic cells studied.

scholarly journals Physical Activity and the Risk of Gallbladder Disease: A Systematic Review and Meta-Analysis of Cohort Studies

2016 ◽  
Vol 13 (7) ◽  
pp. 788-795 ◽  
Author(s):  
Dagfinn Aune ◽  
Michael Leitzmann ◽  
Lars Johan Vatten
Keyword(s):  
Physical Activity ◽  
Systematic Review ◽  
Relative Risk ◽  
Disease Risk ◽  
Leisure Time Physical Activity ◽  
Meta Analysis ◽  
Vigorous Physical Activity ◽  
Gallbladder Disease ◽  
Epidemiological Studies ◽  
Response Analysis

Background:Physical activity has been hypothesized to reduce the risk of gallbladder disease (gallstones, cholecystitis, cholecystectomy); however, results from epidemiological studies have not always shown statistically significant associations. We conducted a systematic review and meta-analysis to clarify the presence and strength of an association between physical activity and gallbladder disease risk.Methods:PubMed and Embase databases were searched for studies of physical activity and gallbladder disease up to 9th of January 2015. Prospective studies reporting relative risk (RR) estimates and 95% confidence intervals (CIs) of gallbladder disease associated with physical activity were included. Summary RRs were estimated using a random effects model.Results:Eight studies including 6958 cases and 218,204 participants were included. The summary RR for the highest versus the lowest level of physical activity was 0.75 (95% CI: 0.69–0.81, n = 8) and there was no evidence of heterogeneity, I2 = 0%). In the dose-response analysis the summary relative risk per 20 MET-hours of activity was 0.85 (95% CI: 0.80–0.90, I2 = 0%, n = 2) for leisure-time physical activity, 0.83 (95% CI: 0.76–0.90, I2 = 0%, n = 2) for vigorous physical activity, and 0.86 (95% CI: 0.76–0.98, I2 = 0%, n = 2) for nonvigorous physical activity.Conclusion:Our analysis confirms a protective effect of physical activity on risk of gallbladder disease.

What Does an Observed Relative Risk Convey about Possible Misclassification?

1984 ◽  
Vol 23 (01) ◽  
pp. 37-40 ◽  
Author(s):  
M. Blettner ◽  
J. Wahrendorf
Keyword(s):  
Relative Risk ◽  
Epidemiological Study ◽  
Epidemiological Studies ◽  
Quantitative Information ◽  
Relative Risks ◽  
Order Of Magnitude

SummaryMisclassification of exposure in epidemiological studies has the effect of distorting the results in various directions. We give quantitative information about the possible order of magnitude of misclassification and of “true” effects given the observations of an epidemiological study. It will be demonstrated that misclassification can also distort trends in relative risks. Real examples from the epidemiological literature are used for illustration.

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