Last update:
06-Jun-2005

The quantification of morbidity is realised with measures of occurrence (MO), while the study of relations between the characteristics of individuals (determinants) and the frequency of diseases is achieved with effect measures (EM). MO are distinguished into empirical and theoretical. Empirical MO are distinguished into incidence rates (incidence proportion and incidence density) and prevalence rates (point prevalence and period prevalence), while theoretical MO include incidence proportion, prevalence proportion, risk and odds of a probability. The greatest empirical EM are the rate difference of MO, the rate ratio of MO, the derivative effect measures (the relative excess rate of MO, the attributable fraction in the exposed and the population attributable fraction), the odds ratio and the coefficient of logistic regression (β). If all the confounders of the relation between the causal agent and the disease have been neutralised, then the attributable fraction (AF) in the exposed is a measure that quantifies the proportion of the disease burden among exposed people which is caused by the exposure. Population AF is a measure that quantifies the proportion of the disease burden among a population which is caused by the exposure. To obtain the overall AF for the total population, the fraction among the exposed should be multiplied by the proportion of all cases in the total population that is exposed. In the literature, one definition of population AF is the reduction in incidence that would be achieved if the population had been entirely unexposed, compared with its current (actual) exposure pattern.

Key words: Attributable fraction in exposed, Cause, Effect measures, Measures of occurrence, Population attributable fraction.