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Understanding what it means to run a “cohort”

The term “cohort” is one that has been used a lot recently. You may have read the MS Update, news release, or the blog about the team that will establish the Canadian Proactive Cohort Study for People Living with MS (CanProCo). This initiative was made possible by funding partners, the MS Society of Canada, Biogen, and Brain Canada, who are collectively contributing more than $7 million to study the progression of multiple sclerosis (MS) in Canada. But what does the term “cohort” mean; how does it differ from a clinical trial study; and what is the goal of this multi-million-dollar initiative?

When the term cohort is used, it refers to a group of people who are linked in some way. For example, a birth cohort refers to people who were born during a certain period such as a year.  For our interests, when we say cohort, we are referring to a group of individuals that have MS.  A cohort study is observational, where researchers dig deep into the disease and explore many aspects that affect the defined population, such as risk factors, treatments, interventions etc.

This is where the differences between a cohort study and clinical study lie. A clinical study is investigational meaning the researchers have a pre-determined treatment protocol to treat the condition, hoping that the treatment will be effective (such as a clinical trial for a new drug). Whereas a cohort study gathers information on the method of treatment, environmental factors, physical and biological attributes to provide a holistic picture of factors that contribute to the condition. Most clinical studies tend to focus on the outcomes of specific agents on the disease, such as relapse rates, disability progression and MRI activity and are generally shorter in duration than a cohort study. A cohort study will capture outcomes from MS treatments as well as details from disease onset up to the patient’s current health status. For instance, we know that many individuals diagnosed with relapsing-remitting MS will progress to secondary-progressive MS after approximately 10-15 years of disease onset. A better understanding of what causes this progression to occur is needed to identify treatments to manage MS and ultimately identify information that will lead to a cure.

Current MS cohort studies have provided fundamental information to shape the research of tomorrow. This includes a range of information like prevalence and incidence of MS, demographic data as well as clinical data. However, factors that differ among cohorts include geographical location, recruitment criteria, and types of data collected.

The CanProCo research team will observe a large group of people living with MS from across Canada over a period of time, collect specific information that will allow them to identify features of progression in MS, and understand why and how progression occurs. While researchers will collect and analyze new information over time, they will also look at existing health data making this cohort both a retrospective and prospective study. The research team has developed a set of questions related to progression pertaining to the three pillars of the cohort: neuroimaging, neuroimmunology, and epidemiology/health outcomes. These questions include:: mechanisms of progression (e.g. how does progression occur at the cellular level and what biological markers can be used to track progression?), treatments/real-world evidence (e.g. how do existing treatments for MS impact progression and what role does early diagnosis and self-management play?) and impact (what is the impact of progression on the health system, society, the economy, and the person’s quality of life?). To answer these and other questions, the researchers will collect different types of information, biological samples, imaging data, clinical data such as symptoms and treatment responses, information about lifestyle, disability, healthcare costs, and other aspects of daily living and quality of life. By collecting this information, we will have a comprehensive picture of how progression affects an individual with MS physically, emotionally, economically and socially.

The results of this study could potentially impact how we treat MS, how we diagnose MS, how people live with MS, and how we talk about MS progression altogether – this is a significant pursuit of knowledge, one that could dramatically change the landscape about what we know about MS, and MS progression.

For more information on the MS Progression Cohort Study, visit the website here. Also, check out the published paper on MS cohorts that I co-authored.


Bebo B et al. (2017) Landscape of MS patients cohorts and registries: Recommendations for maximizing impact. Mult Scler. [Epub ahead of print].  

Gliklich, R. E., & Dreyer, N. A. (2014). Registries for evaluating patient outcomes: a user’s guide. Rockville, MD: U.S. Department of Health and Human Services, Agency for Healthcare Research and Quality.

  1. Phyllis taylor says:

    I hope you do some research in nova Scotia it’s the top province in Canada for MS ….i have two cousin with MS …plus I had a 4 cousin that had it …all female on my mom’s side ….

  2. Jane Parnell says:

    I hope you include historic health of patient from birth to current. My daughter aged 30 has MS. Diagnosed at age 25. Atypical issues include blood types. Mother (me) A- (received RhoGAM shot after first live birth (my son), father B+, daughter AB-. Atypical circumstance at birth. Mother (me) had undiagnosed chicken pox at daughter’s birth (known because my son had diagnosed chicken pox about two weeks before my daughter’s birth and my rash occured when my daughter was 4 days old). I have mentioned this to doctors but no reaction or statement from them. I just feel that if a root cause of MS is found or at least explored, there is a stronger likelihood of a cure.

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