Relative risk (RR) or ratio refers to the ratio of the incidence of the exposed group to the unexposed group, which reflects the relative intensity of disease exposure.
RR = Incidence of exposed group/Incidence of non-exposed group.
Significance of RR: explain how many times the risk of exposed group is than that of non-exposed group.
Relative risk (RR) has no unit, and the known range is between 0 and ∝. RR = 1, indicating that there is no connection between exposure and disease. RR < 1, indicating that there is a negative correlation (suggesting that exposure is a protective factor. On the other hand, RR > 1 indicates that there is a positive correlation between them (suggesting that exposure is a risk factor). The greater the ratio, the stronger the connection.
Ratio ratio: also known as dominance ratio and cross product ratio. Refers to the ratio of exposed persons to unexposed persons in case group divided by the ratio of exposed persons to unexposed persons in control group.
Attributable risk (public health significance)
Attributable risk (AR) and ratio difference (RD) refer to the difference of incidence between exposed group and non-exposed group, which reflects the degree to which the incidence is attributed to exposure factors.
The importance of AR indicates the morbidity or mortality caused by exposure factors.
Attributable risk percentage (AR%) refers to the percentage of all cases caused by exposure factors in the exposed population.
The percentage of risk attributed to the population (PAR%%) indicates the proportion of the incidence caused by exposure in the whole population.
PAR%% not only considers the RR of exposure factors, but also relates to the exposure rate of a certain factor in the population.
Its public health significance is the extent to which the incidence (or mortality) of a disease in the population may decrease after the exposure factors are completely controlled.
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