How do you find the etiological fraction?
Etiologic fraction = [ a / ( a + b ) − c / ( c + d ) ] 1 − [ c / ( c + d ) ] (population attributable risk). The relative risk used by epidemiologists for prospective studies differs slightly from the odds ratio used in case–control studies and is defined as a/(ac)/b(bd).
How do you interpret population etiologic fractions?
PAF is defined as the fraction of all cases of a particular disease or other adverse condition in a population that is attributable to a specific exposure; PAF equals (O − E)/O, where O and E refer to the observed number of cases and the expected number of cases under no exposure, respectively.
How do you calculate population attributable risk fraction?
PAR is usually expressed as a percentage. The PAR% is calculated by dividing the population attributable risk (PAR) by the incidence in the total population and then multiplying the product by 100 to obtain a percentage.
What is the population etiologic fraction of lung cancer due to smoking?
The PAF of lung cancer was 85.3% (95% CI 80.0–89.2) for ever smoking.
How do you calculate relative risk?
Relative risk is calculated by dividing the death or disease risk in a specific population group (Group A) by the risk of people from all other groups. A relative risk that is greater than 1.0 shows that there is an increased risk among the people in Group A.
How do you calculate the proportion of a case exposed?
Attributable Proportion Among the Exposed It is calculated by taking the risk difference, dividing it by the incidence in the exposed group, and then multiplying it by 100 to convert it into a percentage.
Why population attributable fractions can sum to more than one?
PAFs can sum to more than 1 because some individuals with more than one risk factor can have disease prevented in more than one way, and the prevented cases of these individuals could be counted more than once.
How do you interpret relative risk?
A relative risk of one implies there is no difference of the event if the exposure has or has not occurred. If the relative risk is greater than 1, then the event is more likely to occur if there was exposure. If the relative risk is less than 1, then the event is less likely to occur if there was exposure.
How do you calculate population risk difference?
The risk difference is calculated by subtracting the cumulative incidence in the unexposed group (or least exposed group) from the cumulative incidence in the group with the exposure.
What does population attributable risk measure?
Population Attributable Risk (PAR) is the porportion of the incidence of a disease in the population (exposed and nonexposed) that is due to exposure. PAR is the difference between the risk in the total population and that in unexposed subjects.
What percentage of passive smokers get lung cancer?
The overall percentages of lung cancers attributable to passive smoking among never smokers were 15.5% (9.0–21.4%) for 9 population-based studies and 22.7% (16.6–28.3%) for 22 hospital-based studies.
What is one of the widely used sources of statistical data on cancer?
The primary source of data on cancer incidence is medical records.
