Incidence Analysis (incidence + analysis)

Distribution by Scientific Domains


Selected Abstracts


Elaboration and Validation of a Diagrammatic Scale for Epidemiological Studies of Cercospora Leaf Spot of Castor Bean

JOURNAL OF PHYTOPATHOLOGY, Issue 6 2010
Wellington Freire Dos Santos
Abstract The castor bean cercospora leaf spot (Cercospora ricinella Sacc. & Berl.) is a common disease in castor bean crop (Ricinus communis L.), causing defoliation and losses. In spite of this, the evaluation of disease severity is an important decision support for adoption of strategies and tactics for disease control. Therefore the objective of this work was to elaborate and to validate a diagrammatic to evaluate cercospora leaf spot severity in the castor bean. The scale was developed based on six treatments with different irrigation depths plus the control treatment without irrigation. Based on disease incidence analysis, it was possible to select different severity levels per treatment, which were used to define the percentage intervals of foliar diseased area of the diagrammatic scale. In view of the inexistence of standardized methods for the quantification of cercospora leaf spot in the field, the levels of 0%, 0.1 to 1%, 1.1 to 10%, 10.1 to 20% and 20.1 to 45% of lesioned foliar area were established, pointing out the observation that in the interval of 20 to 45% leaf fall started to occur. The scale was tested according its accuracy, precision and reproducibility. For that, 40 leaves with different disease severity levels were appraised by 10 users, without and with the scale, with an interval of seven days between evaluations of the same users. The appraisers obtained better results under utilization of the scale. The scale proposed in this work presented appropriate applicability for cercospora leaf spot evaluation in castor bean. Higher disease intensity was observed in the control and in treatments with higher irrigation depth and lower irrigation frequency. [source]


Bayesian incidence analysis of animal tumorigenicity data

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 2 2001
D. B. Dunson
Statistical inference about tumorigenesis should focus on the tumour incidence rate. Unfortunately, in most animal carcinogenicity experiments, tumours are not observable in live animals and censoring of the tumour onset times is informative. In this paper, we propose a Bayesian method for analysing data from such studies. Our approach focuses on the incidence of tumours and accommodates occult tumours and censored onset times without restricting tumour lethality, relying on cause-of-death data, or requiring interim sacrifices. We represent the underlying state of nature by a multistate stochastic process and assume general probit models for the time-specific transition rates. These models allow the incorporation of covariates, historical control data and subjective prior information. The inherent flexibility of this approach facilitates the interpretation of results, particularly when the sample size is small or the data are sparse. We use a Gibbs sampler to estimate the relevant posterior distributions. The methods proposed are applied to data from a US National Toxicology Program carcinogenicity study. [source]


A new electromagnetic exposure metric: High frequency voltage transients associated with increased cancer incidence in teachers in a california school

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 8 2008
Samuel Milham MD
Abstract Background In 2003 the teachers at La Quinta, California middle school complained that they had more cancers than would be expected. A consultant for the school district denied that there was a problem. Objectives To investigate the cancer incidence in the teachers, and its cause. Method We conducted a retrospective study of cancer incidence in the teachers' cohort in relationship to the school's electrical environment. Results Sixteen school teachers in a cohort of 137 teachers hired in 1988 through 2005 were diagnosed with 18 cancers. The observed to expected (O/E) risk ratio for all cancers was 2.78 (P,=,0.000098), while the O/E risk ratio for malignant melanoma was 9.8 (P,=,0.0008). Thyroid cancer had a risk ratio of 13.3 (P,=,0.0098), and uterine cancer had a risk ratio of 9.2 (P,=,0.019). Sixty Hertz magnetic fields showed no association with cancer incidence. A new exposure metric, high frequency voltage transients, did show a positive correlation to cancer incidence. A cohort cancer incidence analysis of the teacher population showed a positive trend (P,=,7.1,×,10,10) of increasing cancer risk with increasing cumulative exposure to high frequency voltage transients on the classroom's electrical wiring measured with a Graham/Stetzer (G/S) meter. The attributable risk of cancer associated with this exposure was 64%. A single year of employment at this school increased a teacher's cancer risk by 21%. Conclusion The cancer incidence in the teachers at this school is unusually high and is strongly associated with high frequency voltage transients, which may be a universal carcinogen, similar to ionizing radiation. Am. J. Ind. Med. 51:579,586, 2008. © 2008 Wiley-Liss, Inc. [source]


Social Welfare in Vietnam: A Curse or Blessing for Poor Children?

ASIAN SOCIAL WORK AND POLICY REVIEW, Issue 2 2010
Keetie Roelen
Despite a rapid increase in economic growth accompanied by the rise of living standards over the last two decades in Vietnam, there is still a considerable proportion of the population that lives in poor and vulnerable conditions. Children in particular are disproportionately affected by poverty. The country employs a broad range of social protection programs that tend to be regressive in effect rather than supportive of the poor. The present paper evaluates the social welfare scheme in Vietnam in terms of child poverty. We use the Vietnam Household Living Standards Survey (VHLSS) 2006 and identify and quantify child poverty in monetary as well as multidimensional terms. We consider the link between social welfare receipt and poverty and evaluate coverage, exclusion, and inclusion errors. Furthermore, we use benefit incidence analysis to evaluate the impact of social welfare on monetary child poverty. Findings suggest that coverage of the social welfare scheme is limited and that the scheme suffers from considerable exclusion and inclusion errors. Furthermore, we find that social welfare only slightly reduces the incidence and depth of monetary poverty. [source]


Mortality after uveal and conjunctival melanoma: which tumour is more deadly?

ACTA OPHTHALMOLOGICA, Issue 2 2009
Emma Kujala
Abstract. Purpose:, We aimed to model and compare mortality rates for uveal melanoma (UM) and conjunctival melanoma (CM) by adjusting for differences in tumour size and local recurrence. Methods:, Population-based mortality data for 240 and 85 patients with primary UM and CM and 91 and 23 patients with disseminated UM and CM, respectively, were compared with cumulative incidence analysis. Cox proportional hazards multivariate regression with time-dependent variables was used to adjust for differences in tumour diameter, thickness and recurrence rates. Results:, The 10-year cumulative incidences of metastatic death from UM and CM were 39% (95% confidence interval [CI] 33,45) and 32% (95% CI 21,44), respectively. After adjusting for tumour size, risk of death from CM was higher than from UM (hazard ratio [HR] 1.9; p = 0.039). Additional adjustment for more frequent local recurrence of CM diminished the difference (HR 1.5; p = 0.25). Survival periods after systemic metastasis of UM and CM were comparable (median 8 months). Conclusions:, Clinical observations show longer survival after primary CM than after primary UM. This reflects the smaller average size of CM. However, a primary CM of a given size is more deadly than a UM of equivalent size because primary CM tends to recur after treatment and, possibly, because additional lymphatic dissemination occurs with CM. [source]


Cumulative incidence analysis and relative survival

ACTA OPHTHALMOLOGICA, Issue 2008
T KIVELÄ
Purpose To highlight concepts related to competing events in time-to-event data sets. Methods Introduction to cumulative incidence and relative survival analyses and competing risks proportional hazards regression with examples from recent literature. Results Kaplan-Meier and Cox regression analysis were designed to study mortality. They return biased estimates in the presence of competing events that render subjects immune to the event of interest (e.g. one is no longer at risk of vision loss, bleb failure or graft rejection after dying). Kaplan-Meier can then be supplemented with cumulative incidence analysis and Cox with competing risks regression. The data needed are time-to-event or last follow-up, last status (e.g. experienced an event, under follow-up, lost to follow-up) and explanatory or confounding variables. Subjects who experienced a competing event are treated as such and subjects who did not experience any event are "censored" at last follow-up. A set of stepped curves is produced which show the cumulative incidence of each event as a function of time by study group; groups can be compared using dedicated tests. Competing risks regression provides a hazard ratio, adjusted for the effect of other variables in the model. Relative survival is an alternative to cumulative incidence method when analyzing mortality. It does not require that the status at last follow-up be known. Survival of the study group is compared with that of the underlying population. The difference is equivalent to the cumulative incidence of disease-specific death, but cumulative incidences of competing events are not available. Conclusion After this talk, participants should be able to recognize competing events, assess whether Kaplan-Meier and Cox regression were appropriate methods and know alternatives to them. [source]


Increased death risk and altered cancer incidence pattern in patients with isolated or combined autoimmune primary adrenocortical insufficiency

CLINICAL ENDOCRINOLOGY, Issue 5 2008
Sophie Bensing
Summary Objectives, Primary adrenocortical insufficiency is mostly caused by an autoimmune destruction of the adrenal cortex. The disease may appear isolated or as a part of an autoimmune polyendocrine syndrome (APS). APS1 is a rare hereditary disorder with a broad spectrum of clinical manifestations. In APS2, primary adrenocortical insufficiency is often combined with autoimmune thyroid disease and/or type 1 diabetes. We analysed mortality and cancer incidence in primary adrenocortical insufficiency patients during 40 years. Data were compared with the general Swedish population. Design and patients, A population based cohort study including all patients with autoimmune primary adrenocortical insufficiency (3299) admitted to Swedish hospitals 1964,2004. Measurements, Mortality risk was calculated as the standardized mortality ratio (SMR) and cancer incidence as the standardized incidence ratio (SIR). Results, A more than 2-fold increased mortality risk was observed in both women (SMR 2·9, 95% CI 2·7,3·0) and men (SMR 2·5, 95% CI 2·3,2·7). Highest risks were observed in patients diagnosed in childhood. SMR was higher in APS1 patients (SMR 4·6, 95% CI 3·5,6·0) compared with patients with APS2 (SMR 2·1, 95% CI 1·9,2·4). Cancer incidence was increased (SIR 1·3, 95% CI 1·2,1·5). When tumours observed during the first year of follow-up were excluded, only the cancer risk among APS1 patients remained increased. Cause-specific cancer incidence analysis revealed significantly higher incidences of oral cancer, nonmelanoma skin cancer, and male genital system cancer among patients. Breast cancer incidence was lower than in the general population. Conclusions, Our study shows a reduced life expectancy and altered cancer incidence pattern in patients with autoimmune primary adrenocortical insufficiency. [source]