1,721,146 research outputs found
Fibres, whole-grain foods and breast and other cancers
No full textThe possible relationship between fibre intake and breast cancer risk has been considered in several studies, but the issue is still unsettled. Epidemiological data are compatible with moderate protection from fibre-rich foods against the risk of breast cancer, but also with an absence of association. The apparently inconsistent results may be due to chance or bias, to different approaches to data analysis and interpretation, but may also reflect heterogeneity in the dietary sources of fibres (cereals or vegetables and fruit) in various populations, and different correlates of fibre intake
Diet and cancer prevention: A review of Italian studies
No full textCurrent scientific evidence suggests a protective role for fruits and vegetables in prevention of most common epithelial cancer including digestive and major non-digestive neoplasm. The relation between frequency of consumption of vegetables and fruit and cancer risk was analyzed using data from a series of case-control studies conducted in Northern Italy since 1983. For digestive tract cancer, population attributable risks for low intake of vegetables and fruit ranged between 15 and 40%. A selected number of anti-oxidants showed a significant inverse relation with breast and colorectal cancer risk. Red meat intake confirmed to be of specific relevance in nutritional etiology of human cancer with a relative risk (RR) far consistently above unity. Whole grain food intake was consistently related to reduced risk of several types of cancer, with a particular relevance for the upper digestive tract neoplasm. Epidemiological evidence on the relation between fiber intake and colorectal cancer have reported a moderate protection, but results are limited and inconsistent. Thus, we investigated the specific role of fibers on colorectal carcinogenesis in a case control study including 1,953 cases of colorectal cancer and 4,154 controls. Results provided further support for a protective and independent effect of fiber on colorectal cancer, particularly for cellulose and soluble non-cellulosic polysaccharides (NCP), and for fiber of vegetable or fruit origin. In contrast, refined grain intake has been associated to increased risk of different types of cancer. In conclusion, a low risk diet for cancer would imply increasing fruit and vegetables, avoiding increasing meat, but also refined carbohydrate consumption, and preferring olive oil and other unsaturated fats to saturated ones
Il test di ipotesi : hypothesis testing
No full textWhen we do research, we start with a hypothesis that is usually in narrative form: “Preliminary results of studies on a new antihypertensive drug (B) indicate that it can obtain a better pressure control than standard treatment (A)”. The null hypothesis is what is known or assumed from theory or previous research. When we test hypotheses, we always test the null hypothesis (A = B) against an alternative/research hypothesis (A B). Using a counterintuitive logic, we want to reject the null hypothesis in favor of the alternative.
After generating a representative sample of the study population, we randomise the subjects to either treatment A or B. We calculate the proportion of people with adequate pressure control in both treatment arms and the chi-square statistic (with its associated P value).
The formula for the test statistics is different for each type of test and data, but the basic concept is the same. We calculate how different the outcomes are in our groups, then decide whether to reject or fail to reject the null hypotesis of no difference between treatments.
We can make two errors: we can say that treatments are different when they are not (type I error or a), or we can say that they are not different, when they really are (type II error or b). Protection of test (1-a) is the probability of correctly fail to reject the null hypothesis when it is true. Statistical power (1-b) is the probability of rejecting a false null hypothesis.
The logic of hypothesis testing is counterintuitive (or backwards). We test whether there is no difference (the study treatment is equivalent to the standard treatment) in order to conclude that difference exists. When we fail to reject the null hypothesis, we need to provide
the statistical power, because we could not have enough statistical power in our study
Trends in asthma mortality in Italy and Spain, 1980-1996
No full textAsthma is a major public health problem, with variable trends in several countries. We analysed mortality trends from asthma in Italy and Spain between 1980 and 1996. Overall asthma-related mortality at all ages increased between 1980 and 1987 in both sexes in Italy, from 16.6 in 1980-1981 to 29.0 in 1986-1987 per million males, and from 8.0 in 1980-1981 to 13.8 in 1986-1987 per million females, but decreased thereafter to reach 14.6 per million in males and 8.7 in females in 1996. The downward trends after 1987 were consistent in middle age and elderly population, but asthma mortality tended to rise in children and young adults over the last few years. In Spain, overall age-standardized mortality rates from asthma declined in men from 37.8 in 1980-1981 to 10.1 in 1996, and from 19.5 in 1980-1981 to 13.2 per million females in 1996. In women, the fall in mortality rates was smaller, and overall mortality was higher than in males since early 1990s. Trends of asthma mortality in Italy and Spain were favourable over the last decade
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