epidemiology community health and dentistry

community dentistry

1. EPIDEMIOLOGY

2. Estimation of Risk : Having calculated the incidence rates, the next step is to estimate the risk of outcome(e.g., disease or death) in the exposed and non-exposed cohorts. This is done in terms of two well known indices . two well-known indices:Of the above, periodic examination of eachmember of the cohort yields the greatestamount of information on the individualsexamined than would the use of any other  S  Relative risk (RR) or "risk ratio" procedure. %However, inspite of best efforts, a certainpercentage of losses to follow-up areinevitable due to death, change of residence,migration or withdrawal of occupation. Theselosses may bias the results. It is thereforenecessary to build into the study design asystem for obtaining basic information onoutcome for those who cannot be followedup in detail for the full duration of the study.The safest course recommended  is  to achieveas close to a 95 per cent follow-up aspossible.It  is  the ratio of the incidence of the disease (ordeath) among exposed and the incidenceamong non- exposed. RR  =Incidence of disease (or death) amongexposedIncidence of disease (or death) among non-exposed= 4^ = 90.5 5. Analysis The data are analysed in terms of:Risk factor(tobacco)Present(Chewers)Absent(Nonchewers)Developedoral cancer45Did notdevelop99559995Total 1000010000 (d^ Incidence rates of outcome amongexposed and non-exposed:In a cohort  study,  we can determine incidence KH This implies 9 times higher risk ofdevelopment of oral carcinoma in tobaccochewers compared to non-chewers.Estimation of relative risk (RR) is important inetiological enquiries. It is a direct measure (orindex) of the "strength" of the associationbetween suspected cause and effect. Arelative risk of one indicates no association;relative risk greater than one suggests"positive" association between exposure andthe disease under study. A relative risk of 2indicates that the incidence rate of disease is2 times higher in the exposed group ascompared with the unexposed. Equivalently,this represents a 100 percent increase in risk.A relative risk of 0.25 indicates a 75% c  ^ kofea—1  haJbH ,      Relative risk (RR) or “Risk ratio” Attributable risk (AR) of Risk difference

3. Relative Risk (RR) : Relative risk (RR) is the ratio of the incidence of the disease (or death) among exposed and the incidence among non-exposed .

4. Estimation of relative risk is important in etiological enquiries. It is a direct measure (or index) of the “strength” of the association between suspected cause and effect. A relative risk of 1 indicates no association ; relative risk greater than 1 suggests “positive” association between exposure and disease under study.

5. Attributable Risk : Attributable risk is the difference in incidence rates of disease (or death) between exposed group and non-exposed group . Attributable risk is often expressed as a percent . This is given by formula :

6. AR is to what extent the disease under study can be attributed to the exposure . The figure in our example indicates that the association between smoking and lung cancer is causal , 90 percent of the lung cancer among smokers was due to their smoking . This suggests the amount of disease that might be eliminated , if the factor under study could be controlled or eliminated .