![]() If the incidence risk ratio is greater than 1, then exposure increases the outcome risk with greater departures from 1 indicative of a stronger effect. If the incidence risk ratio equals 1, then the risk of the outcome in both the exposed and non-exposed groups are equal. The incidence risk ratio provides an estimate of how many times more likely exposed individuals are to experience the outcome of interest, compared with non-exposed individuals. ![]() If both exposure and outcome are binary variables (yes or no) we can present the counts of subjects in each of the four exposure-disease categories in a 2 \(\times\) 2 table. At the start of the study period study subjects are classified according to exposure to a hypothesised risk factor. The EpiTools app for iPhone and Android devices provides easy access to many of the measures of association functions in epiR using a smart phone.Ĭonsider a study where subjects are disease free at the start of the study and all are monitored for disease occurrence for a specified time period. ![]() If this is not the case the argument outcome = "as.columns" (the default) can be changed to outcome = "as.rows". This vignette has been written assuming the reader routinely formats their 2 \(\times\) 2 table data with the outcome status as columns and exposure status as rows. Examples are provided to demonstrate how the package can be used to deal with exposure-outcome data presented in various formats. In this vignette we outline describe how epiR can be used to compute the various measures of association used in epidemiology notably the risk ratio, odds ratio, attributable risk in the exposed, attributable fraction in the exposed, attributable risk in the population and attributable fraction in the population. In human and animal health an ‘outcome-positive’ individual is an individual who has experienced a given disease of interest. The term ‘outcome’ is used to describe all the possible results that may arise from exposure to a causal factor or from preventive or therapeutic interventions (Porta, Greenland, and Last 2014). In this context the term ‘exposure’ is taken to mean a variable whose association with the outcome is to be estimated.Įxposures can be harmful, beneficial or both harmful and beneficial (e.g., if an immunisable disease is circulating, exposure to immunising agents helps most recipients but may harm those who experience adverse reactions). Measures of Association Measures of Association Mark Stevenson Ī common task in epidemiology is to quantify the strength of association between exposures (‘risk factors’) and disease outcomes.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |