IJPDS International Journal of Population Data Science

Taking multiple medicines is common among people living with chronic pain. However, taking more medicines does not always mean facing greater risk.

In a study of 8,760 adults living with chronic pain in Quebec, Canada, researchers found that simply counting the number of pain-related medicines people used often told a different story from a score that also accounted for the types of medicines they were taking.

The team linked responses to Statistics Canada surveys conducted between 2007 and 2016 with provincial prescription records. They followed the medicines dispensed to people covered by Quebec’s public prescription drug plan over the two years after each survey.

For every month, they measured both the number of different pain-related medicines dispensed and a risk score (the MQS-4.0) reflecting the potential for adverse effects associated with those medicines. They then looked for groups of people whose patterns of use changed in similar ways over time.

PhD student Hermine Lore Nguena Nguefack carried out the statistical analyses and interpreted the findings, a substantial undertaking involving extensive programming of complex administrative data that were not originally designed for research. She also wrote the first draft of the paper.

“I’m passionate about turning health administrative data into a tool for action,” says Hermine. “This methodological project is a good example. I hope it will help future graduate students and research teams make more informed choices and produce findings with greater impact.”

Both measures (the prescribed medication count and risk score) revealed distinct patterns. However, the risk score, identified groups with clearer differences in pain, general and mental health, and use of healthcare services.

One group whose risk scores rose to a high level over time had more visits to doctors and emergency departments and more hospital stays than the other groups identified by the risk score.

Importantly, the two measures did not always identify the same people.

A total of 872 people fell into the higher-risk groups without falling into the groups using more medicines. Conversely, 2,441 people fell into the groups using more medicines without falling into the higher-risk groups.

These findings show why counting prescriptions alone can give an incomplete picture of potential medicines-related harm.

The findings apply to prescriptions captured by Quebec’s public drug plan, which does not record over-the-counter or hospital medicines. Even so, using both measures could give researchers a fuller picture of treatment burden and potential risk, and help inform future studies of medicine safety in chronic pain.

“A medication count tells us how many medicines someone uses, but it does not tell us the whole story about their potential risks”, says study lead author Anaïs Lacasse. “We demonstrated that looking at the kinds of medicines alongside the count may help us recognize people who would otherwise be missed.”

 

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Hermine Lore Nguena Nguefack (PhD student) and Professor Anaïs Lacasse, Université du Québec en Abitibi-Témiscamingue, Quebec, Canada

Nguena Nguefack HL, Ménard N, Beaudoin S, Pagé MG, Guénette L, Hudon C, et al. Medication Use Trajectories in Chronic Pain: Comparing Risk-Based and Count-Based Approaches Using Linked Prescription Claims Data. IJPDS [Internet]. 2026 Nov. 11(1). Available from: https://doi.org/10.23889/ijpds.v11i1.3350