1,721,011 research outputs found
IL FUMO DI SIGARETTA E IL RISCHIO DI TUMORE DEL PANCREAS: DIVERSI APPROCCI DI ANALISI IN UNA POOLED-ANALYSIS
Full text linkBackground: To evaluate the dose–response relationship between cigarette smoking and pancreatic cancer risk and to examine the effects of temporal variables.
Aim: The aim of my PhD thesis is to explore the effect of selected smoking variable (including dose, duration and time since quitting) on the risk of pancreatic cancer using the two-stage and the multilevel analysis, and to compare these results with those obtained using the “standard” aggregate analysis. Moreover, generalized additive models were used to analyse the relation between smoking and pancreatic cancer risk without any data constriction.
Methods: Data from 12 case–control studies, within the International Pancreatic Cancer Case–Control Consortium (PanC4) and including 6507 pancreatic cases and 12 890 controls, were analyzed. In the aggregate analysis, smoking variables were categorized and odds ratios (ORs), and corresponding 95 confidence intervals (CIs), were calculated using logistic regression models adjusted for selected covariates (sex, age, ethnicity, education, body mass index, alcohol consumption, and history of diabetes and of pancreatitits) and study center. In the two-stage analysis, smoking variables were categorized, and summary ORs were calculated pooling study-specific ORs using random-effects models. Study-specific ORs were calculated using logistic regression models adjusted for the same covariates used for adjustment in the aggregate analysis. In the multilevel analysis, smoking variables were categorized and summary ORs were calculated using hierarchical models with two levels of hierarchy, considering study center as level 1, and subject as level 2. At level 2, models were adjusted the same covariates used for adjustment in the aggregate analysis. Finally, smoking variables were considered as continuous and generalized additive logistic regression were used to explore the nonlinear effects.
Results - aggregate analysis: Compared with never smokers, the OR was 1.46 (95% confidence interval [CI] 1.36–1.57) for former smokers and 2.00 (96% CI : 1.83-2.19) for current cigarette smokers, with a significant increasing trend in risk with increasing number of cigarettes among current smokers (OR = 3.17 for more than 40 cigarettes per day, P for trend <0.0001). Risk increased in relation to duration of cigarette smoking up to 40 years of smoking (OR = 2.02). Moreover, compared to current cigarette smokers, the risk decreased with increasing time since cigarette cessation, in fact the OR being 0.46 after 30 years.
Results - two-stage analysis: Point estimates were similar to those obtained in the aggregate analysis, whereas interval ones were larger. There was substantial heterogeneity among studies, except for current smokers of less than 10 cigarette per day (p-value=0.0952) or more than 40 cigarette per day (p-value=0.2815), for current smokers who smoked for 20-<30 years (p-value=0.2309), and for ex-smokers who time since quitting 10-<15 years (p-value=0.0756) or 15-<20 years (p-value=0.0739).
Results - multilevel analysis: Point ant interval estimates were similar to those obtained in the aggregate analysis. As regard number of cigarettes, risks were stronger among females, subjects with less than 65 years, and among subjects drinking 0-1 drinks of alcohol per day. No differences were found for duration and time since quitting.
Though significant increasing trend in risk with increasing number of cigarettes, duration and time since quitting was observed, nonlinear relations were found. The risk of pancreatic cancer increased rapidly for each additional increment of one cigarette/day up to 25-30 cigarettes/day, and less rapidly for higher number of cigarettes/day. As regard duration, the risk increased rapidly for each year up to 25 years, then the risk increased less rapidly, plateaued at 35 years, and declined for subjects who smoked more than 40 years. Finally, a periodic effect was observed for years since quitting, although a decreased risk for each years was found.
Conclusions: This uniquely large pooled analysis confirms that current cigarette smoking is associated with a twofold increased risk of pancreatic cancer and that the risk, with a nonlinear effect, increases with the number of cigarettes smoked and duration of smoking and decreases with time since quitting
The role of foods and nutrients on oral and pharyngeal cancer risk
No full textThe relation between selected aspects of diet and the risk of oral and pharyngeal cancer was considered in a few cohort studies and approximately 30 case-control studies. These studies reported consistent inverse associations with fruit and vegetable consumption. beta-carotene, vitamin C and selected flavonoids were also inversely related to risk, although it remains difficult to disentangle their potential effect from that of fruit and vegetables. Whole-grain cereals, but not refined grain ones, were also favorably related to the risk of oral and pharyngeal cancer. The results were not consistent for other foods, including meat, fish, eggs, milk and dairy products, but it is now possible to exclude a strong relation with oral and pharyngeal cancer risk. Data are also reassuring for coffee and tea, while hot maté drinking has been related to increased risk in studies from Argentina and Brazil. There is no consistent association with total fat intake, but monounsaturated fats (and olive oil) have resulted inversely related to risk. In developed countries, selected aspects of diet may account for 20% to 25% of oral and pharyngeal cancers. This proportion is likely greater in selected developing countries
Interventi di prevenzione delle cadute negli anziani con particolare attenzione agli aspetti relativi alla partecipazione dei soggetti
No full textDietary factors and oral and pharyngeal cancer risk
No full textWe reviewed data from six cohort studies and approximately 40 case-control studies on the relation between selected aspects of diet and the risk of oral and pharyngeal cancer. Fruit and vegetables were inversely related to the risk: the pooled relative risk (RR) for high vegetable consumption was 0.65 from three cohort studies on upper aerodigestive tract cancers and 0.52 from 18 case-control studies of oral and pharyngeal cancer; corresponding RRs for high fruit consumption were 0.78 and 0.55. beta-carotene, vitamin C and selected flavonoids have been inversely related to the risk, but it is difficult to disentangle their potential effect from that of fruit and vegetables. Whole grain, but not refined grain, intake was also favorably related to oral cancer risk. The results were not consistent with reference to other foods beverages, and nutrients, but it is now possible to exclude a strong relation between these foods and oral and pharyngeal cancer risk. In western countries, selected aspects of diet may account for 20-25% of oral and pharyngeal cancer, and the population attributable risk increases to 85-95% when tobacco and alcohol consumption are also considered
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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