#Retrospective cohort free#

Useful for tracking the progress of a disease with a long latency period.

Information or data is collected from past clinical records and the outcome of interest is investigated.

Cohorts are defined from a previous point in time, and are not followed up in the future.

Example: In a prospective cohort study researchers compared four different groups of women (two at-risk groups, two low-risk groups) to investigate which groups were more likely to develop PTSD symptoms after a birthing event.

The two groups of cohorts (exposed and un-exposed) are followed prospectively over time to track the development of new disease.

There are two types of cohort studies: Prospective and Retrospective.

#Retrospective cohort free#

The participants are divided into two groups – the first group is the ‘exposure’ group, the second group is free of the exposure.The participants must be identical, having common characteristics except for their exposure status.

A cohort study starts with the selection of a group of participants (known as a ‘cohort’) sourced from the same population, who must be free of the outcome under investigation but have the potential to develop that outcome.

Cohort Studies are a type of observational study. In Introduction to Study Designs, we learnt that there are many different study design types and that these are divided into two categories: Experimental and Observational. The study is now in its fifth decade and has produced over 1200 publications and reports, many of which have helped inform policy makers in New Zealand and overseas. This study is known as The Dunedin Study and it has followed the lives of 1037 babies born between 1 April 1972 and 31 March 1973 since their birth. These findings (and more) have come out of a large cohort study started in 1972 by researchers at the University of Otago in New Zealand. We always say the cross sectional is data for a point in time, but you can still ask about prior exposures.Did you know that the majority of people will develop a diagnosable mental illness whilst only a minority will experience enduring mental health? Or that groups of people at risk of having high blood pressure and other related health issues by the age of 38 can be identified in childhood? Or that a poor credit rating can be indicative of a person’s health status? You’re not recruiting people from Town A and Town B then comparing cancer rates. I could be wrong, but this seems like a cross sectional study to me.

In a cross sectional study, you recruit a sample population and ask about exposure and outcome at the same time. In a case-control study, you start with cases who have disease and controls who do not and ask about exposures. This is the simple version: In a cohort study you start have cases who were exposed and controls who weren’t and then follow up to ask about disease(it doesn’t matter whether you’re doing this prospectively or retrospectively). Think about how you design your study and gather data rather than the specific question. I feel like asking about where they lived years ago is still cross sectional.

Your second example is pretty clearly cross sectional. I initially wanted to say you were right but then I thought about it and disagree.