Cohort Studies

What is a cohort study?

An observational study that follows a group of similar people through time to record incident (new) cases of disease.

What is a cohort?

A group of similar people followed through time together.

What are prevalent cases?

Individuals who have the disease at a certain point in time.

What are incident cases?

New cases of disease that develop during the study period.

What is the purpose of baseline in cohort studies?

To determine the exposure and disease status of participants at the start of the study.

What is the follow-up assessment in cohort studies used for?

To determine the development of new (incident) diseases.

What is a prospective cohort study?

A study that follows participants into the future to measure incidence.

What is a retrospective cohort study?

A study that uses past records to determine exposure status and outcomes.

What is the key difference between prospective and retrospective cohort studies?

Calendar time; prospective studies identify exposure as it occurs, while retrospective studies ascertain from past data.

What does loss to follow-up mean?

The inability to continue tracking a participant due to various reasons such as dropping out or relocation.

What strategies can minimize loss to follow-up?

Offering incentives or sharing study findings with participants.

What is the difference between dropout and loss to follow-up?

Dropout is an explicit withdrawal from the study, while loss to follow-up involves participants becoming unreachable without clear communication.

How is relative risk (RR) interpreted when RR = 1?

There is no difference in the risk of the outcome between exposed and unexposed cohorts.

What does RR > 1 indicate?

The exposed cohort has a higher risk of developing the outcome compared to the unexposed cohort.

What does RR < 1 suggest?

The exposed cohort has a lower risk of developing the outcome, possibly indicating a protective effect.

What does a risk ratio of 5 indicate?

Smokers have five times the risk of developing lung cancer compared to non-smokers.

What type of studies allows evaluating multiple exposures simultaneously?

Case-Control studies.

What is a fixed (closed) population in longitudinal studies?

All participants start the study at the same time with no additional participants added.

What is a dynamic (open) population in longitudinal studies?

Participants can be added or dropped from the study after it begins.

What are the advantages of cohort studies?

They provide a clear temporal sequence, measure incidence, and are valuable for assessing rare exposures.

What are the limitations of cohort studies?

They can be expensive, time-consuming, and involve loss to follow-up.

What is the main focus of a case-control study?

To compare risk factor frequency between cases and controls.

What does the 95% confidence interval indicate in relative risk analysis?

If the entire interval is less than or greater than 1, it indicates statistical significance; if it overlaps 1, it is not significant.

What is a key feature of longitudinal studies?

They follow participants over a period to observe changes over time.

In cohort studies, when do researchers measure the incidence of disease?

After following the cohorts for a set period, usually several years.

What happens to participants labeled as ‘lost to follow-up’?

They become unreachable for further data collection, which complicates study results.

What is the outcome of cohort studies commonly measured against?

The incidence of disease among different exposure groups.

What is the significance of a risk ratio greater than 1 in public health?

It indicates a possible positive association between an exposure and a negative health outcome.

What can minimize participant loss in cohort studies?

Regular communication and engagement with participants.

What are two designs compared in the lecture regarding cohort studies?

Prospective and retrospective cohort designs.

What is the term used to define those who develop the disease in a cohort study?

Incident cases.

What defines a participant in a prospective cohort study?

Their exposure status is determined as they progress through the study.

What is the implication of a risk ratio less than 1?

There may be a protective effect associated with the exposure.

How many follow-up times are generally conducted in cohort studies?

At least two: one at baseline and one or more follow-ups.

What aspect of cohort studies does loss to follow-up significantly affect?

The validity of the study findings.

Why are case-control studies effective for rare diseases?

They allow for the simultaneous evaluation of multiple exposures and are typically less expensive.

Give an example of a situation that would indicate dropout.

A participant explicitly states they no longer wish to continue in the study.

What type of population design allows for recruiting new participants during the study?

Dynamic (open) population.

What would indicate that an exposure is risky in the study population based on relative risk?

When the entire 95% confidence interval is greater than 1.

Why is baseline measurement critical in cohort studies?

It serves as a benchmark for examining changes over time.

What does it mean when risk ratios between two groups are compared?

It assesses the relative risk of disease development associated with different exposures.

What does the term ‘incidence’ refer to in epidemiology?

The occurrence of new cases of a disease in a population over a specified period.

How can the results of cohort studies contribute to public health?

By identifying risk factors and preventive measures for certain diseases.