Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Epidemiology and Biostatistics
Supervisor
Dr. Manuel Montero-Odasso
2nd Supervisor
Dr. Mark Speechley
Co-Supervisor
Abstract
Cognitive impairment and dementia are a multifactorial process involving several pathological mechanisms beyond neurodegeneration. Dementia is characterized by severe and progressive cognitive impairment affecting daily livings. In Canada, over 600,000 people live with dementia, and its consequences are catastrophic.
However, estimates suggest that 35% to 45% of dementia cases worldwide are attributable to 9 to 14 modifiable risk factors. The primary objective of this dissertation was to estimate the dementia prevention potential in Canada associated with well-established modifiable risk factors in Canada using the Canadian Longitudinal Study on Aging, a nation-wide longitudinal cohort of 30,097 adults. We found that 50% of dementia cases in Canada were attributable to 12 risk factors, with physical inactivity, obesity, hypertension, and hearing loss being the most prominent.
Recent lifestyle intervention trials showed that it is possible to improve cognition by combating combinations of risk factors. To help identify risk profiles of individuals most likely to benefit from these interventions, the second objective was to identify risk factor combinations that are both highly prevalent and strongly associated with low cognition. The dyadic combination of hearing loss and physical inactivity (Cohen’s effect size d = -0.21) was most strongly associated with low cognition, followed by adding hypertension for the triad (d = -0.25), and adding obesity for the tetrad (d = -0.27). The synergistic interaction effect observed between hypertension and physical inactivity supports the rationale of joint prevention efforts on both vascular and brain health.
The third objective was to identify combinations that are both highly prevalent and have the largest cognitive detrimental effect over 3 years. The combination of hearing loss with physical inactivity was the most prevalent dyad with the largest effect size (d = -0.28) and a synergistic effect. For the triad, the combination of hearing loss, physical inactivity, and hypertension had the greatest effect (d = -0.28), while the tetrad included hearing loss, physical inactivity, hypertension, and sleep disturbance (d = -0.20).
Altogether, this dissertation highlights, for the first time, that up to 50% of dementia cases in Canada could be prevented by targeting specific risk factors, with hearing loss and physical inactivity being those that would yield the largest effect size if addressed.
Summary for Lay Audience
Over 600,000 people are currently living with dementia in Canada, and this number is expected to rise to over 1.7 million by 2050. Cognitive impairment in aging is a multifactorial process involving several potentially modifiable risk factors. It has been suggested that 35% to 45% of dementia cases worldwide are attributable to 9 to 14 modifiable risk factors. However, their prevention potential in Canada was not known. Recent studies have suggested that it is possible to delay cognitive decline through lifestyle modifications that address combinations of risk factors including physical inactivity, vascular and metabolic risk factors, and sleep disturbance among others. However, it remains unclear which combinations of risk factors are most effective to target in order to prevent dementia and reduce its risk.
Using Canada’s largest study of aging, the Canadian Longitudinal Study on Aging, this dissertation aimed to: 1) estimate the dementia prevention potential associated with 12 modifiable risk factors in Canada, 2) identify the combinations of risk factors that are both highly prevalent and strongly associated with low cognition, and 3) identify the combinations of risk factors that are both highly prevalent and associated with the largest detrimental effect on cognitive changes in the Canadian population.
We found that nearly 50% of dementia cases in Canada could be prevented by addressing 12 modifiable risk factors across the life span, with physical inactivity, hearing loss, hypertension, and obesity as the prominent factors. The most prevalent two risk factor combination associated the lowest cognition and the largest detrimental effect on cognitive change was hearing loss and physical inactivity. For the combination of three risk factors, it was hearing loss, physical inactivity, and hypertension while for four factors, it was hearing loss, physical inactivity, hypertension, and obesity. The combination associated with the largest cognitive change was hearing loss, physical inactivity, hypertension, and sleep disturbance. These findings could help tailor Canada’s dementia prevention strategies and plan intervention studies to delay cognitive impairment and prevent dementia through lifestyle means.
Recommended Citation
Son, Surim, "Potentially Modifiable Risk Factors for Low Cognition and Dementia in Canada" (2025). Electronic Thesis and Dissertation Repository. 10759.
https://ir.lib.uwo.ca/etd/10759
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.