The NorMA cohort is a national cohort of inmates in Norwegian prisons that has formed the basis for a number of reports and scientific articles. But to what extent is the NorMA cohort representative of the Norwegian prison population? This question has been answered by a PhD candidate in the PriSUD project, Nicoline Toresen Lokdam, in a brand new article.
In the PriSUD project, we work with several types of data and data sources. One of the basic cohorts in the project is the one we call the NorMA cohort. An important question to ask when working with data from cohorts is how well the cohort represents the population one wants to investigate. In this new article, we have therefore investigated how well the NorMA cohort reflects the general Norwegian prison population
About the NorMA cohort
The NorMA cohort was established as part of the NorMA study in 2013-2014, in which almost 1,500 peopleanswered the comprehensive questionnaire on health and substance abuse among inmates in Norwegian prisons. About half also provided social security numbers, which gives the opportunity to follow these persons in Norwegian registers to see how they are doing after they were released. The other half, for which we do not have a person's number, answer to the same questionnaire, but cannot be followed up in the registers.
The article is based on questionnaire data from the NorMA study, combined with register data from the prison register (KOMPIS). The article has a methodological perspective that describes how data from registers can generally be used to assess whether data you work with is representative of the group you want to investigate. The article uses the NorMA cohort as an example, and thus also helps to shed light on how well the NorMA cohort represents the Norwegian prison population.
The study compared the NorMA cohort's 733 participants, who served all over the Norway in 2013-2014, with an average of the entire Norwegian prison population on a single day during the same period. "We can see that the NorMA cohort is largely representative of the part of the Norwegian prison population that we would normally investigate with register data, namely those that have a valid Norwegian person number. The groups are similar in relation to prison history, prison time, convictions and drug-related sentences (such as "use and possession"). On the other hand, part of the NorMA study consists of persons who did not have a valid Norwegian person number and who we cannot follow through studies on the NorMA cohort», says Nicoline.
«One of the strengths of the study is that we both have answers from the questionnaire survey of those who for various reasons did not provide a social security number, but also the prison's registrations of those without a social security number. Therefore, we have the opportunity to say something about how it affects our results if these people are not included. It is a great strength for further research on the NorMA cohort that one has knowledge of how the cohort represents the Norwegian prison population »says Nicoline.
The article is published in the medical methodological journal Research Methods in Medicine and Health Science and can be read here.