Can odds ratio predict risk?

The odds ratio can also be used to determine whether a particular exposure is a risk factor for a particular outcome, and to compare the magnitude of various risk factors for that outcome.

Can odds ratio determine risk?

RELATIVE RISK AND ODDS RATIO

An RR (or OR) more than 1.0 indicates an increase in risk (or odds) among the exposed compared to the unexposed, whereas a RR (or OR) <1.0 indicates a decrease in risk (or odds) in the exposed group.

Are odds ratios predictive?

The interpretation of the odds ratio depends on whether the predictor is categorical or continuous. Odds ratios that are greater than 1 indicate that the event is more likely to occur as the predictor increases. Odds ratios that are less than 1 indicate that the event is less likely to occur as the predictor increases.

What does odds ratio tell me?

The odds ratio tells us how much higher the odds of exposure are among case-patients than among controls. An odds ratio of • 1.0 (or close to 1.0) indicates that the odds of exposure among case-patients are the same as, or similar to, the odds of exposure among controls.

Why can odds ratios be misleading?

The discrepancy between a relative risk reduction and the equivalent relative odds reduction (100×(1−odds ratio)%) can be misleading. When event rates are high (commonly the case in trials and systematic reviews) the relative odds reduction can be many times larger than the equivalent relative risk reduction.

Odds Ratio Explained - Chocolate Consumption and Cardiovascular Disease

Is it better to use odds ratio OR relative risk?

When the outcome is not rare in the population, if the odds ratio is used to estimate the relative risk it will overstate the effect of the treatment on the outcome measure. The odds ratio will be greater than the relative risk if the relative risk is greater than one and less than the relative risk otherwise.

What is the advantage of odds ratio?

The great value of the odds ratio is that it is simple to calculate, very easy to interpret, and provides results upon which clinical decisions can be made. Furthermore, it is sometimes helpful in clinical situations to be able to provide the patient with information on the odds of one outcome versus another.

What does an odds ratio of 1.5 mean?

It means that the odds of a case having had exposure #1 are 1.5 times the odds of its having the baseline exposure. This is not the same as being 1.5 times as probable: odds are not the same as probability (odds of 2:1 against means a probability of 13).

How do you convert odds ratio to relative risk?

To convert an odds ratio to a risk ratio, you can use "RR = OR / (1 – p + (p x OR)), where p is the risk in the control group" (source: http://www.r-bloggers.com/how-to-convert-odds-ratios-to-relative-risks/).

Is odds ratio prospective OR retrospective?

The odds ratio ((a/c)/(b/d)) looks at the likelihood of an outcome in relation to a characteristic factor. In epidemiological terms, the odds ratio is used as a point estimate of the relative risk in retrospective studies. Odds ratio is the key statistic for most case-control studies.

What is the difference between predicted probabilities and odds ratio?

They differ in that the "odds [ratio] is the average number of success per failure. The probability is the average number of successes per trial." What is the more intuitive of the two will, of course, vary across people.

Does odds ratio always overestimate risk ratio?

However, in cohort studies and RCTs, odds ratios are often interpreted as risk ratios. This is problematic because an odds ratio always overestimates the risk ratio, and this overestimation becomes larger with increasing incidence of the outcome.

How do you calculate predicted odds ratio?

In a 2-by-2 table with cells a, b, c, and d (see figure), the odds ratio is odds of the event in the exposure group (a/b) divided by the odds of the event in the control or non-exposure group (c/d). Thus the odds ratio is (a/b) / (c/d) which simplifies to ad/bc.

What is the relationship between odds ratio and probability?

Odds are the probability of an event occurring divided by the probability of the event not occurring. An odds ratio is the odds of the event in one group, for example, those exposed to a drug, divided by the odds in another group not exposed. Odds ratios always exaggerate the true relative risk to some degree.

Should odds ratio and relative risk be the same?

The figures show that the odds ratio will always exaggerate the size of the effect compared with a relative risk. That is, if the odds ratio is less than one then it is always smaller than the relative risk. Conversely, if the odds ratio is greater than one then it is always bigger than the relative risk.

Why are odds better than probability?

A probability must lie between 0 and 1 (you cannot have more than a 100% chance of something). Odds are not so constrained. Odds can take any positive value (e.g. a ⅔ probability is the same as odds of 2/1). If instead we use odds (actually the log of odds, or logit), a linear model can be fit.

Is odds ratio a regression?

Logistic regression is used to obtain odds ratio in the presence of more than one explanatory variable. The procedure is quite similar to multiple linear regression, with the exception that the response variable is binomial. The result is the impact of each variable on the odds ratio of the observed event of interest.

Are odds ratios biased?

Bias in the risk ratio, rate ratio, or odds ratio can be produced even if measured errors are equal between exposed and unexposed or between study participants that have or do not have the health outcome.

How do you tell if a study is retrospective OR prospective?

What is the advantage of odds ratio?

The great value of the odds ratio is that it is simple to calculate, very easy to interpret, and provides results upon which clinical decisions can be made. Furthermore, it is sometimes helpful in clinical situations to be able to provide the patient with information on the odds of one outcome versus another.

Do odds reflect probabilities?

The odds on display never reflect the true probability or chance of an event occurring (or not occurring).

Why is odds ratio greater than relative risk?

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. (The relative risk is also called the risk ratio).

What is the rule of thumb for odds ratio?

But how big an effect is it? Epidemiologists use this very rough rule of thumb: An odds ratio of 4 or more is pretty strong and not likely to be able to be explained away by some unmeasured variables. An odds ratio bigger than 2 and less than 4 is possibly important and should be looked at very carefully.

When should I use odds ratio?

When is it used? Odds ratios are used to compare the relative odds of the occurrence of the outcome of interest (e.g. disease or disorder), given exposure to the variable of interest (e.g. health characteristic, aspect of medical history).

What does an odds ratio of 1.5 mean?

It means that the odds of a case having had exposure #1 are 1.5 times the odds of its having the baseline exposure. This is not the same as being 1.5 times as probable: odds are not the same as probability (odds of 2:1 against means a probability of 13).