A case-control study was performed early in the Nurses'...

A case-control study was performed early in the Nurses' Health Study (NHS) to assess the possible association between oral contraceptive (OC) use and ovarian cancer [50]. Forty seven ovarian cancer cases were identified at or before baseline (1976). For each case, 10 controls matched by year of birth and with intact ovaries at the time of the index woman's diagnosis were randomly chosen from questionnaire respondents free from ovarian cancer. The data in Table 13.58 were presented. Use logistic regression methods to assess whether there is an association between ovarian cancer risk and duration of OC use while controlling for age. Provide a two-sided $p$ -value. Assume that the average duration of use in the $<3$ years group $=1.5$ years and in the $3+$ years group $=4$ years. Also, provide an estimate of the OR relating ovarian cancer risk per year of use of $\mathrm{OCs}$ and a $95 \%$ Cl.

A case-control study was performed early in the Nurses' Health Study (NHS) to assess the possible association between oral contraceptive (OC) use and ovarian cancer [50]. Forty seven ovarian cancer cases were identified at or before baseline (1976). For each case, 10 controls matched by year of birth and with intact ovaries at the time of the index woman's diagnosis were randomly chosen from questionnaire respondents free from ovarian cancer. The data in Table 13.58 were presented.
Use logistic regression methods to assess whether there is an association between ovarian cancer risk and duration of OC use while controlling for age. Provide a two-sided $p$ -value. Assume that the average duration of use in the $<3$ years group $=1.5$ years and in the $3+$ years group $=4$ years. Also, provide an estimate of the OR relating ovarian cancer risk per year of use of $\mathrm{OCs}$ and a $95 \%$ Cl.

Key Concepts

Statistical Significance (p-value)

The p-value in statistical hypothesis testing quantifies the probability of observing the data, or something more extreme, under the null hypothesis that there is no effect or association. A two-sided p-value is used when deviations in either direction are considered significant, helping to decide whether the observed association might have occurred by chance.

Odds Ratio

The odds ratio is a measure of association used in case-control studies that quantifies how the odds of an outcome change with a unit change in exposure. In logistic regression, the odds ratio represents the factor by which the odds of the outcome increase (or decrease) for each one-unit increase in the predictor variable.

Confidence Interval

A confidence interval provides a range of values which is likely to contain the true measure of association, such as an odds ratio, with a specified level of confidence (commonly 95%). It offers insight into the precision and reliability of the estimated effect size from the study.

Matching in Study Design

Matching is used in case-control studies to control for confounding factors by ensuring that cases and controls are similar in certain characteristics (such as age or gender). This process helps isolate the effect of the exposure of interest by minimizing differences between groups that could influence the outcome.

Case-Control Study

A case-control study is an observational design in which participants are selected based on the presence (cases) or absence (controls) of a particular outcome. This design is useful for studying rare diseases and has an efficient time and resource profile, but it requires careful selection of controls and consideration of potential biases.

Logistic Regression Analysis

Logistic regression is a statistical method used to model the relationship between one or more independent variables and a binary outcome. It estimates the probability of the outcome as a function of predictors and is particularly useful for adjusting for confounders and quantifying the strength of association using odds ratios.

Transcript

00:01 Okay, so this question is asking about a study done where they found that users of oral contraceptives have higher rates of cervical cancer than non -users.

00:12 And it's, it concluded that basically the pill causes cervical cancer.

00:18 So part of it is asking if this is a observational study or a controlled experiment, and it is an observational study.

00:28 And the reason for this is because the investigators aren't actually putting any kind of treatment on subjects and looking at the effects.

00:39 They're just observing data that's already around them, and they're just analyzing data that they see around them.

00:45 They're not actually putting any kind of treatment on subjects and looking at their effects.

00:51 So it's definitely an observational study.

00:54 Part b is saying, why did the investigators adjust for age, education, marital status and that's to avoid what's known as confounding factors and confounding factors are essentially outside factors that may affect what you see they may affect your results and if they exist then you can't really be sure you they might have affected your results and you can't really be sure that in this case you couldn't really be sure that use of oral contraceptives has an effect on rate of cervical cancer if you don't adjust for age, education, neurocitis.

01:34 Because if you don't adjust for these, then these factors might really be the cause behind the rates of cervical cancer, not actually the use of oral contraceptives.

01:44 Parcée is asking, saying, women using the pill were likely to differ from non -users on another factor, which affects the risk of cervical cancer.

01:52 What factor is that? and that factor is going to be sexual activity.

02:00 Because women who use the pill are more likely to have more...

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