The science of aging: What 50,000 Canadians are teaching us

Canadians are aging…fast! In just 15 years, nearly one in four people will be 65 or older.

Fortunately, almost 15 years ago, researchers anticipated this demographic shift, and with funding from the Canadian Institutes of Health Research, a team set up one of the most ambitious studies of aging ever conducted in this country. The Canadian Longitudinal Study on Aging (CLSA) helps us better understand how we are aging, why we age differently and what we can do to age well.

In 2011, Dr. Parminder Raina (Lead Principal Investigator, McMaster University), Dr. Christina Wolfson (PI, McGill University), and Dr. Susan Kirkland (PI, Dalhousie University), along with researchers from across the country started collecting detailed data from more than 50,000 Canadians aged 45 to 85. They will continue to follow participants until 2031, conducting check-ins every three years.

“In order to truly understand the complexity of aging, you need a large sample size,” says Dr. Raina. “That’s where CLSA with its 50,000 participants becomes unique. And 20 years is a long enough time to give us the data points we need to understand the trajectories of aging.”

The researchers collect data through interviews, physical exams and biological samples. Participants are asked a wide range of questions, such as: Can you recall the list of words I just read you? Do you have difficulty getting in and out of bed? How many medications are you currently taking? How many close friends can you confide in? Do you feel safe in your neighbourhood?

Participants also undergo physical and biomedical tests including blood sampling, measurements of height, weight and waist circumference, grip strength and bone density. The CLSA includes more than 20 different modules that explore physical health, mental health, lifestyle, social factors and environmental influences.

“Many large studies like this in other parts of the world focused on a particular disease,” says Dr. Raina. “They look at dementia, heart disease or cancer. But we know that by the time people turn 70, they often have three or four chronic conditions. What we want to do is build a full picture of what it means to age in Canada to understand the process of aging.”

With a 96% retention rate at first follow-up, the CLSA fills a critical data gap that will provide evidence to inform health and social care policies for today and tomorrow’s seniors. However, Dr. Raina acknowledges that the study includes few participants from low-income groups and is largely composed of individuals of European origin. These limitations matter because aging does not look the same for everyone. To ensure future research and policies reflect the full range of aging experiences in Canada, Dr. Raina hopes there will be an opportunity to build on the legacy of the CLSA through parallel studies focused on diverse cultural and Indigenous populations whose experiences of aging may differ from those of the Canadian majority.

Just past the halfway point, the CLSA is already making a significant impact on aging research in Canada—shaping policy, informing practice and deepening public understanding. Its data has been shared with more than 600 research teams in Canada, the United States, Australia and Europe; used in over 700 scientific publications and reports; and supported more than 1,000 researchers and 250 training opportunities for students.

“I think it's a fascinating time to integrate science across diverse fields,” says Dr. Raina, “to bring biological sciences, population sciences and social sciences into focus to understand disease, disability and aging from an interdisciplinary lens. The CLSA has made that possible. That kind of integration wasn’t happening in this country before.”