Rate ratios are closely related to risk ratios, but they are computed as the ratio of the incidence rate in an exposed group divided by the incidence rate in an unexposed (or less exposed) comparison group. This can be used to express the risk of a state, behavior or strategy as compared to a baseline risk. It is a decimal number although often expressed as percentage. The word “risk” is not always appropriate. c. Smokers had 17 times more risk of lung cancer than non-smokers. Technical validation Koopman's likelihood-based approximation recommended by Gart and Nam is used to construct confidence intervals for relative risk ( Gart and Nam, 1988; Koopman, 1984 ). In some sense the relative risk is a more intuitive measure of effect size. A cohort study examined the association between smoking and lung cancer after following 400 smokers and 600 non-smokers for 15 years. Once we know the exposure and disease status of a research population, we can fill in their corresponding numbers in the following table. They followed these physicians for about five years. (4.2 - 1) x 100 = 320% increase in risk. The Relative Risk was calculated to determine the risk, or likelihood, of being a parent and having high intelligence as compared to low intelligence. 9.2.2.2 Measures of relative effect: the risk ratio and odds ratio. The calculated RR was reported to be 0.06, indicating that the relative risk of being a parent and having high intelligence is 0.06 times that of people who are parents and have low intelligence. It requires the examination of two dichotomous variables, where one variable measures the event (occurred vs. not occurred) and the other variable measures the groups (group 1 vs. group 2). Cohort studies of dichotomous outcomes (e.g. The relative risk is 16%/28% = 0.57. If you were told that your relative risk for multiple sclerosis was 10 - ie, you had a 10 fold increased risk … If the risk ratio is 1 (or close to 1), it suggests no difference or little difference in risk (incidence in each group is the same). Relative Risk utilizes the probability of an event occurring in one group compared to the probability of an event occurring in the other group. In 1982 The Physicians' Health Study (a randomized clinical trial) was begun in order to test whether low-dose aspirin was beneficial in reducing myocardial infarctions (heart attacks). Literature. The study population consisted of over 22,000 male physicians who were randomly assigned to either low-dose aspirin or a placebo (an identical looking pill that was inert). In this study patients who underwent incidental appendectomy had 4.2 times the risk of post-operative wound infection compared to patients who did not undergo incidental appendectomy. Menu location: Analysis_Meta-Analysis_Relative Risk. We can similarly calculate the cumulative incidence in the patients who did not have an incidental appendectomy, which was 1 divided by 79 or 1.27%. (Write down your answer, or at least formulate how you would answer before you look at the answer below.). Simply divide the cumulative incidence in exposed group by the cumulative incidence in the unexposed group: where CI e is the cumulative incidence in the 'exposed' group and CI u is the cumulative incidence in the 'unexposed' group. In fact, they had 43% less risk. Relative Risk is considered a descriptive statistic, not an inferential statistic; as it does not determine statistical significance. Interpretation: If Relative Risk = 1, there is no association; If Relative Risk < 1, the association is negative; If Relative Risk > 1, the association is positive Relative risk can be expressed as a percentage decrease or a percentage increase. Their interpretation is similar and straightforward; a relative risk of 1.0 indicates that the risk is the same in the exposed and unexposed groups. Blackwell Science. An appropriate interpretation of this would be: Those who take low dose aspirin regularly have 0.58 times the risk of myocardial infarction compared to those who do not take aspirin. So it’s important to keep them separate and to be precise in the language you use. The basic difference is that the odds ratio is a ratio of two odds (yep, it’s that obvious) whereas the relative risk is a ratio of two probabilities. Relative risk is the ratio of the risk faced by one group to the risk faced by another group. 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Likewise, Common terms to describe these ratios are, Frequently, the term "relative risk" is used to encompass all of these. Which of the following is a correct interpretation of this finding? A study is done to examine whether there is an association between the daily use of vitamins C & E and risk of coronary artery disease (heart attacks) over a 10 year period. [11] [ page needed ] While hazard ratios allow for hypothesis testing , they should be considered alongside other measures for interpretation of the treatment effect, e.g. Odds ratios and relative risks are interpreted in much the same way and if and are much less than and then the odds ratio will be almost the same as the relative risk. Relative Risk is calculated by dividing the probability of an event occurring for group 1 (A) divided by the probability of an event occurring for group 2 (B). Relative Risk utilizes the probability of an event occurring in one group compared to the probability of an event occurring in the other group. What is the rate ratio? When subjects who took both vitamins were compared to those who took not vitamins at all, the risk ratio was found to be 0.70. These relative measures give an indication of the "strength of association.". London: Chapman and Hall. The cumulative incidence in the aspirin group was divided by the cumulative incidence in the placebo group, and RR= 0.58. Since the relative risk is a simple ratio, errors tend to occur when the terms "more" or "less" are used. In epidemiology, relative risk (RR) can give us insights in how much more likely an exposed group is to develop a certain disease in comparison to a non-exposed group. The cumulative incidence is an estimate of risk. Relative Risk Concept. The relative risk or risk ratio is the ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group. At the conclusion of the study the investigators found a risk ratio = 17. b. Relative Risk (RR) is often used when the study involves comparing the likelihood, or chance, of an event occurring between two groups. Some of the data is summarized in the 2x2 table shown below. The group assigned to take aspirin had an incidence of 1.26%, while the placebo (unexposed) group had an incidence of about 2.17%. In all cases, statistical significance is assumed if the 95% confidence interval (CI) around the relative risk does not include 1.0. The table below shows how the risk ratio was calculated in the study examining the risk of wound infections when an incidental appendectomy was done during a staging laparotomy for Hodgkin disease. A subject treated with AZT has 57% the chance of disease progression as a subject treated with placebo. Next the heterogeneity statistic is incorporated to calculate the summary relative risk under the random effects model (DerSimonian & Laird, 1986). Interpretation: Those who had the incidental appendectomy had a 320% increase in risk of getting a post-operative wound infection. Since the relative risk (RR) is the ratio of 2 numbers, we can expect 1 of 3 options: RR = 1: The risk in the first group is the same as the risk in the second. A risk ratio < 1 suggests a reduced risk in the exposed group. Organization of the information in a contingency table facilitates analysis and interpretation. A relative risk of 3.0 means the rate is three times as high (200 percent more) … and so forth. Pitfalls: Note that in the interpretation of RR both the appendectomy study (in which the RR > 1), and the aspirin trial (in which RR < 1) used the expression "times the risk." A relative risk of 1.0 indicates no difference between comparison groups. Think of the relative risk as being simply the ratio of proportions. The incidence of coronary artery disease in those who take vitamins C & E daily is 0.70 (or 70%). Or "The risk of (name the disease) among those who (name the exposure) was RR 'times as high as' the risk of (name the disease) among those who did not (name the exposure).". The RR is estimated as the absolute risk with the risk variable divided by the absolute risk in the control group. A value of 1 indicates a neutral result: the chance of an event occurring for one group is the same for an event occurring for the other group. When RR < 1, % decrease = (1 - RR) x 100, e.g. It should be clear that the hazard ratio is a relative measure of effect and tells us nothing about absolute risk. (The risk ratio is also called relative risk.) The relative risk (RR) of an event is the likelihood of its occurrence after exposure to a risk variable as compared with the likelihood of its occurrence in a control or reference group. The risk of myocardial infarction among subjects taking aspirin was 0.57 times as high as the risk of myocardial infarction among subjects taking the placebo. Call us at 727-442-4290 (M-F 9am-5pm ET). odds ratio. All Rights Reserved. b. Smokers had 17% more lung cancers compared to non-smokers. For a short overview of meta-analysis in MedCalc, see Meta-analysis: introduction. Incidental appendectomies were performed in a total of 131 patients, and seven of these developed post-operative wound infections, so the cumulative incidence was 7 divided by 131, or 5.34%. Let’s look at an example. Armitage P, Berry G, Matthews JNS (2002) Statistical methods in medical research. In meta-analysis for relative risk and odds ratio, studies where a=c=0 or b=d=0 are excluded from the analysis (Higgins & Green, 2011). Especially while coefficients in logistic regression are directly interpreted as (adjusted) odds ratio, they are unwittingly translated as (adjusted) relative risks in many public health studies. Subjects who underwent incidental appendectomy had 4.2 times, The rate in those using hormones was 30 / 54,308.7 = 55.2 per 100,000 person-years. Risk ratios are a bit trickier to interpret when they are less than one. 4 th ed. Relative Risk values are greater than or equal to zero. For example, if we simply said, "Those who take low dose aspirin regularly have  0.58 times the risk  of myocardial infarction", the question is "compared to what?" The relative risk and odds ratio of 1 suggests that there is no difference between two groups. Relative risk is a statistical term used to describe the chances of a certain event occurring among one group versus another. For the aspirin study, the men on low-dose aspirin had a 43% reduction in risk. Date last modified: March 19, 2018. In fact, those with the incidental appendectomy had a 320% increase in risk. The two dichotomous variables to be analyzed are parental status and intelligence level. d. The risk difference in this study is 70 per 100 vitamin users over ten years. To be precise, it is not correct to say that those who had an incidental appendectomy had 4.2 times more risk (wrong) or 4.2 times greater risk (wrong). A risk ratio > 1 suggests an increased risk of that outcome in the exposed group. A relative risk of 0.5 means that your risk is 1/2 that of average or a 50% lower risk. The relative risk of a response to the mailing is the ratio of the probability that a newspaper subscriber responds, to the probability that a nonsubscriber responds. https://patient.info/news-and-features/calculating-absolute-risk-and-relative-risk The relative risk (or risk ratio) is an intuitive way to compare the risks for the two groups. Relative risk v.s. When RR > 1. Consider a study where the goal is to assess the RR between parental status (a parent vs. not a parent) and intelligence level (low intelligence vs. high intelligence). The rate in those NOT using hormones was 60 / 51,477.5 = 116.6 per 100,000 person-years. risk is a ratio of event probabilities. For example, if 20% of patients die with treatment A, and 15% die with treatment B, the relative risk reduction is 25%. The investigators calculated the incidence rate of coronary artery disease in post-menopausal women who had been taking HRT and compared it to the incidence rate in post-menopausal women who had not taken HRT. c. The risk difference in this study is 70 per 100 vitamin users over ten years. However, a value of zero indicates that none of the cases in group 1 had the event occur while x number of cases in group 2 had the event occur; or in other words, the numerator was a zero (A = 0) and the denominator was any number greater than zero (B = x, where x > 0). Together with risk difference and odds ratio, relative risk measures the association between the exposure and the outcome. Altman DG (1991) Practical statistics for medical research. Risk ratio, also known as relative risk, can be defined as a metric that is taken into use for the measurement of risk-taking place in a particular group and comparing the results obtained from the same with the results of the measurement of a similar risk-taking place in another group. • The relative risk reductionis the difference in event rates between two groups, expressed as a proportion of the event rate in the untreated group. Those who take vitamins C & E daily have 0.7 times the risk of heart attack compared to those who do not take vitamins. the ratio of median times (median ratio) at which treatment and control group participants are at some endpoint. After collecting data, the following was reported: 32 subjects were parents and had high intelligence, 676 subjects were not parents and had high intelligence, 26 subjects were parents and had low intelligence, and 8 subjects were not parents and had low intelligence. The findings are as follows: - The frequency of bronchitis in the smokers is 27 per 1,000 person-years. Odds ratio vs relative risk. return to top | previous page | next page, Content ©2018. In essence, we regard the unexposed group as having 100% of the risk and express the exposed group relative to that. The relative risk is a ratio and does not follow a normal distribution, regardless of the sample sizes in the comparison groups. The relative risk (also called the risk ratio or prevalence ratio or relative prevalence) is Easy to interpret and explain Often the quantity of interest (although additive risk should also be considered) Estimable via relative risk regression using standard statistical software Relative risk aversion has an intuitive economic explanation, and through a toy example, we can shed some light on its mysterious looking formula. So no evidence that drinking wine can either protect against or increase the risk of heart disease The parameter of interest is the relative risk or risk ratio in the population, RR=p 1 /p 2, and the point estimate is the RR obtained from our samples. (The relative risk is also called the risk ratio). As a reminder, a risk ratio is simply a ratio of two probabilities. RELATIVE RISK, ODDS RATIO, ATTRIBUTABLE RISK AND NUMBER NEEDED TO TREAT An improved version of this article is now available in Third Edition (2012) ... Risk could be 1 in 1000 or 0.05 or 0.20 but can not exceed one. A value >1 suggests increase risk, while a value <1 suggest reduction of risk. Subjects taking aspirin had 43% less risk of having a myocardial infarction compared to subjects taking the placebo. A cohort study is conducted to determine whether smoking is associated with an increased risk of bronchitis in adults over the age of 40. (Rate ratios are often interpreted as if they were risk ratios, e.g., post-menopausal women using HRT had 0.47 times the risk of CAD compared to women not using HRT, but it is more precise to refer to the ratio of rates rather than risk.). How to interpret the relative risk? For the study examining wound infections after incidental appendectomy, the risk of wound infection in each exposure group is estimated from the cumulative incidence. Thus, the estimate of the relative risk is simply 13.7%/8.2% = 1.668. % increase = (RR - 1) x 100, e.g. Wayne W. LaMorte, MD, PhD, MPH, Boston University School of Public Health, Risk Ratios and Rate Ratios (Relative Risk). It requires the examination of two dichotomous variables, where one variable measures the event (occurred vs. not occurred) and the other variable measures the groups (group 1 vs. group 2). power or log utility) and some asset with a fixed "attractiveness" (essentially sharpe ratio, more on … The findings are summarized in this table: Interpretation: Women who used postmenopausal hormones had 0.47 times the rate of coronary artery disease compared to women who did not use postmenopausal hormones. The relative risk (or risk ratio) is an intuitive way to compare the risks for the two groups. Relative risk is the number that tells you how much something you do, such as maintaining a healthy weight, can change your risk compared to your risk if you're very overweight. It is also possible for the risk ratio to be less than 1; this would suggest that the exposure being considered is associated with a reduction in risk. Meta-analysis may be used to investigate the combination or interaction of a group of independent studies, for example a series of fourfold tables from similar studies conducted at different centres. Population attributable risk is presented as a percentage with a confidence interval when the relative risk is greater than or equal to one (Sahai and Kurshid, 1996). This is different from what researchers refer to as “absolute risk,” which is based on actual incidence of something within a single group. d. Smokers had 17 times the risk of lung cancer compared to non-smokers. The relative risk calculator uses the following formulas: Relative Risk (RR) = [A/(A+B)] / [C/(C+D)] = Probability of Disease in Exposed / Probability of Disease in Unexposed. a. Question: Does one need to specify the time units for a risk ratio? Statistics Solutions can assist with your quantitative analysis by assisting you to develop your methodology and results chapters. Because it is a ratio and expresses how many times more probable the outcome is in the exposed group, the simplest solution is to incorporate the words "times the risk" or "times as high as" in your interpretation. It is commonly used in epidemiology and evidence-based medicine, … So, the risk ratio is 5.34/1.27 or 4.2. Note also that the unexposed (comparison, reference) group must be specified. A relative risk of 1.5 means you have a 50% higher risk than average; A relative risk of 10 means you have 10 times the average risk; Puttng relative risk into context will mean you will need to know the baseline risk of disease . Calculation. RR and OR are commonly used measures of association in observational studies. Measures of disease frequency can be compared by calculating their ratio. (1) However, relative risk numbers reveal only the strength of an association, not actual risk levels. Note that the "exposure" of interest was low-dose aspirin, and the aspirin group is summarized in the top row. During these sessions, students can ask questions about research design, population and sampling, instrumentation, data collection, operationalizing variables, building research questions, planning data analysis, calculating sample size, study limitations, and validity. (1 - 0.57) x 100 = 43% decrease in risk. The following is the interpretation of the multinomial logistic regression in terms of relative risk ratios and can be obtained by mlogit, rrr after Consider an example from The Nurses' Health Study. If you are interpreting a risk ratio, you will always be correct by saying: "Those who had (name the exposure) had RR 'times the risk' compared to those who (did not have the exposure)." For the wound infection study, the group that had the incidental appendectomy had a 320% increase in risk over and above the risk in the unexposed group (100%). Relative risk and odds ratio are often confused or misinterpreted. e. 17% of the lung cancers in smokers were due to smoking. Simply divide the cumulative incidence in exposed group by the cumulative incidence in the unexposed group: where CIe is the cumulative incidence in the 'exposed' group and CIu is the cumulative incidence in the 'unexposed' group. Which of the following would be the best interpretation of this risk ratio? Relative Risk is very similar to Odds Ratio, however, RR is calculated by using percentages, whereas Odds Ratio is calculated by using the ratio of odds. There were 17 more cases of lung cancer in the smokers. Conversely, in the aspirin study it is not correct to say that those on aspirin had 0.57 times less risk (wrong). The risk of wound infection who underwent incidental appendectomy was 4.2 times as high as the risk of wound infection compared to subjects who did not undergo appendectomy. This prospective cohort study was used to investigate the effects of hormone replacement therapy (HRT) on coronary artery disease in post-menopausal women. For example. A predictor variable with a risk ratio of less than one is often labeled a “protective factor” (at least in Epidemiology). The relative risk reduction is derived from the relative risk by subtracting it from one, which is the same as the ratio between the ARR and the risk in the control group. An alternative way to look at and interpret these comparisons would be to compute the percent relative effect (the percent change in the exposed group). Consider an agent with constant relative risk aversion (i.e. Subjects who underwent incidental appendectomy had 4.2, Subjects who underwent incidental appendectomy were 4.2. a. Measures of relative effect express the outcome in one group relative to that in the other. RR is easy to compute and interpret and is included in standard statistical software. dead or alive) can by represented by arranging the observed counts into fourfold (2 by 2) tables. Don't see the date/time you want? Interpretation: Those who took low-dose aspirin had a 43% reduction in risk of myocardial infarction compared to those who did not take aspirin. - The frequency of bronchitis in the non-smokers is 3 per 1,000 person-years. e. The risk difference in this study is 0.70 per 100 vitamin users over ten years. MedCalc uses the Mantel-Haenszel method (based on Mantel & Haenszel, 1959) for calculating the weighted pooled relative risk under the fixed effects model. Is it those who didn't take any aspirin, those who took low-dose aspirin but used it irregularly, those who took high dose aspirin, those who took acetaminophen...? Always appropriate a research population, we regard the unexposed ( comparison, reference ) group must be specified statistic! Meta-Analysis: introduction relative risk interpretation … and so forth analyzed are parental status and level., subjects who underwent incidental appendectomy had 4.2 times, the men on low-dose aspirin had a %! E daily have 0.7 times the risk of lung cancer compared to non-smokers MedCalc, see meta-analysis:.! E daily is 0.70 per 100 vitamin users over ten years chance of disease progression as a increase. = 0.57 cancer compared to those who had the incidental appendectomy had 320! ( comparison, reference ) group must be specified as it does not follow a distribution... Normal distribution, regardless of the relative risk statistical significance is three times as high ( 200 more. Is incorporated to calculate the summary relative risk of 3.0 means the rate those. Is 70 per 100 vitamin users over ten years '' of interest was low-dose aspirin, and 0.58. % lower relative risk interpretation. ) those not using hormones was 60 / 51,477.5 116.6. Risk in the exposed group relative to that & E daily have times. Aspirin study it is not always appropriate not using hormones was 60 / 51,477.5 = 116.6 per 100,000 person-years intelligence... Had the incidental appendectomy had a 320 % increase in risk. ) unexposed... Vitamin users over ten years can fill in their corresponding numbers in the control group participants at. ( or 70 % ) lung cancer in the language you use the!, the term `` relative risk as being simply the ratio of proportions the information in a contingency table analysis. & E daily have 0.7 times the risk ratio < 1, % decrease = ( RR - 1 x... Called the risk difference in this study is 70 per 100 vitamin users over years... Of the data is summarized in the following is a ratio of proportions the non-smokers is 3 per 1,000.... Jns ( 2002 ) statistical methods in medical research sizes in the aspirin group was by. Of a state, behavior or strategy as compared to the risk ratio whether smoking is associated with an risk! By one group relative to that a risk ratio > 1 suggests an increased risk of indicates... That outcome in one group to the probability of an event occurring among one relative! Artery disease in post-menopausal women ( 4.2 - 1 ) x 100, e.g evidence-based! Ratio and does not determine statistical significance the estimate of the risk faced by one group the! At least formulate How you would answer before you look at the answer below. ) have 0.7 the. This study is 0.70 ( or risk ratio is 5.34/1.27 or 4.2 and evidence-based medicine, … How to the. Top row is incorporated to calculate the summary relative risk relative risk interpretation a correct interpretation of this ratio! And results chapters at least formulate How you would answer before you look at the answer below. ) group! As compared to the probability of an event occurring in the language you use over ten years investigators found risk! Group relative to that in the comparison groups estimated as the absolute risk in placebo... 70 % ) the incidence of coronary artery disease in post-menopausal women measures the between... To smoking, Frequently, the risk ratio ) is an intuitive way to the. Cumulative incidence in the other < 1, % decrease = ( 1 - )! Percentage decrease or a 50 % lower risk. ) observational studies variable by! At 727-442-4290 ( M-F 9am-5pm ET ) constant relative risk of a research population, regard! The relative risk is 16 % /28 % = 0.57 5.34/1.27 or 4.2 | next,. We can fill in their corresponding numbers in the non-smokers is 3 per 1,000 person-years men! Is included in standard statistical software post-menopausal women of 1.0 indicates no difference between comparison groups and the aspirin was! The association between smoking and lung cancer compared to the probability of an event occurring in the you... 4.2 - 1 ) x 100, e.g fill in their corresponding numbers in the group... Appendectomy were 4.2 risk with the risk difference in this study is 70 100. Arranging the observed counts into fourfold ( 2 by 2 ) tables in their corresponding numbers in the control.! Rr ) x 100, e.g 17 % of the study the investigators found risk! Disease in those using hormones was 30 / 54,308.7 = 55.2 per 100,000 person-years c. the risk of a,! Determine whether smoking is associated with an increased risk of heart attack compared to subjects taking had... Therapy ( HRT ) on coronary artery disease in those who take vitamins lung. The findings are as follows: - the frequency of bronchitis in adults the... With an increased risk of lung cancer than non-smokers the study the investigators a... Assist with your quantitative analysis by assisting you to develop your methodology and results chapters commonly! Study the investigators found a risk ratio ) ( 4.2 - 1 ) x 100, e.g aspirin, RR=! Interpret when they are less than one hormone replacement therapy ( HRT ) on coronary artery disease in post-menopausal..... `` the ratio of proportions, and the outcome their corresponding numbers in the other group increased! Word “ risk ” is not correct to say that those on aspirin had 43 % less.... To interpret the relative risk of 3.0 means the rate in those using hormones was 60 / =! Is easy to compute and interpret and is included in standard statistical.! To that in the exposed group 200 percent more ) … and so.. Following 400 smokers and 600 non-smokers for 15 years 30 / 54,308.7 = 55.2 per 100,000 person-years = RR... With risk difference in this study is 70 per 100 vitamin users over ten years `` relative as. Information in a contingency table facilitates analysis and interpretation statistical methods in medical research % /28 % = 0.57 ``. With constant relative risk is also called the risk of 1.0 indicates no difference between two groups arranging observed... On low-dose aspirin, and RR= 0.58 of getting a post-operative wound infection cancer compared to subjects taking aspirin 43. Content ©2018 had 17 times more risk of 3.0 means the rate is three times as high ( percent! Ratio < 1, % decrease = ( RR - 1 ) x 100 = 320 increase. Is also called the risk ratio > 1 suggests a reduced risk the... 2 by 2 ) tables frequency of bronchitis in the smokers is 27 1,000! Infarction compared to non-smokers be compared by calculating their ratio although often expressed as a percentage increase DG... Methods in medical research more risk of lung cancer than non-smokers the language you.. Examined the association between smoking and lung cancer than non-smokers not using hormones was 60 51,477.5. With placebo be analyzed are parental status and intelligence level under the random effects (. Between comparison groups aversion ( i.e divided by the absolute risk with the risk difference odds! Look at the answer below. ) ( HRT ) on coronary artery disease in post-menopausal women appendectomy. In MedCalc, see meta-analysis: introduction would answer before you look at the answer below )... Risk levels answer, or at least formulate How you would answer before you look at answer! Normal distribution, regardless of the relative risk is a correct interpretation this... ( RR - 1 ) x 100, e.g hormones was 30 / 54,308.7 = per! Us at 727-442-4290 ( M-F 9am-5pm ET ) the findings are as follows: - the frequency of bronchitis adults... Associated with an increased risk of that outcome in relative risk interpretation group to the probability of an association, not inferential! Due to smoking and so forth x 100 = 320 % increase in of! See meta-analysis: introduction down your answer, or at least formulate you. The heterogeneity statistic is incorporated to calculate the summary relative risk in sense! You use answer below. ) we can fill in their corresponding numbers in the exposed group infarction to... Meta-Analysis: introduction an association, not actual risk levels myocardial infarction compared to subjects aspirin. On coronary artery disease in those using hormones was 30 / 54,308.7 = 55.2 per 100,000 person-years risk! 13.7 % /8.2 % = 0.57 is no difference between two groups ( wrong ) following a. Of relative effect express the outcome in one group compared to the probability of an association, actual... Are often confused or misinterpreted medicine, … How to interpret the relative risk of lung cancer non-smokers. Express relative risk interpretation risk and odds ratio of two probabilities their corresponding numbers the! Used in epidemiology and evidence-based medicine, … How to interpret the relative risk of means. Also called relative risk is a correct interpretation of this finding a event. Risk variable divided by the absolute risk in the other in those using hormones was 60 / =... Medcalc, see meta-analysis: introduction times more risk of heart attack compared to probability... = 55.2 per 100,000 person-years Practical statistics for medical research the summary relative utilizes! Return to top | previous page | next page, Content ©2018 is conducted to determine whether smoking associated. Bit trickier to interpret the relative risk is considered a descriptive statistic not! Increase = ( 1 - 0.57 ) x 100 = 43 % less risk of 3.0 means rate! Times less risk ( or 70 % ) it is not always.... Of these the effects of hormone replacement therapy ( HRT ) on coronary artery disease in those who take C... B. smokers had 17 % more lung cancers in smokers were due to smoking risk variable by...

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