In 1906, Alois Alzheimer identified the first case of the disease that now bears his name. For over a century, his discovery remained a clinical mystery with no known prevention and, as of now, no cure.
Although a dementia cure remains elusive, researchers have learned a lot about the world of modifiable risks. In mid-March, a study in Neurology revealed that type 1 diabetes can triple dementia risk, and that type 2 diabetes doubles it. This report is one research milestone among three decades spent identifying lifestyle, metabolic, and environmental red flags.
The sheer volume of data has created a new challenge. For an aging global populace with limited time and resources, the hurdle is no longer a lack of information and life tips for reducing the chances of developing dementia. It is the difficulty of navigating a cluttered landscape of risk factors to find the preventive steps that actually move the needle.
Although a dementia cure remains elusive, researchers have learned a lot about the world of modifiable risks
The Institute for Health Metrics and Evaluation (IHME) used its burden-of-proof framework to rank the strength of evidence for 12 distinct risk factors for dementia. These risks include alcohol consumption, high body mass index, fewer years of education, elevated fasting plasma glucose levels, high systolic blood pressure, traumatic brain injury, depression, social isolation, hearing loss, smoking, low levels of physical activity, and air pollution.
The burden-of-proof method produces a score to rank the influence of different risk factors against each other. It combines how much a risk factor increases the likelihood of dementia and the consistency of available evidence among studies. If 50 research projects have assessed how smoking contributes to dementia, and only half have found that smoking indeed increases the risk of developing the disease, that inconsistency would be reflected in a lower score. By contrast, if all 50 studies showed that smoking increased dementia risk by only 2%, that would also have a lower score because the impact is consistent but very small.
The burden-of-proof method also shows how dementia risk changes with different levels of exposure to a hazard. For example, smoking an average of five cigarettes per day elevates risk by 16%, whereas smoking 15 cigarettes per day boosts the threat by 46%.
The study found that high blood sugar, hearing loss, low education, and air pollution ranked highest. The rankings for all risk factors are shown below, and the top four are described in more detail.
In adults, high fasting blood-sugar levels reflect the body's inability to produce or process insulin, leading to diabetes, damage to cells and vasculature in the brain, and higher production of the protein structures implicated in Alzheimer's disease. Global estimates find that more than 560 million adults live with diabetes, and that approximately 45% are unaware of their status. The IHME study's results suggest that at the diabetes threshold—a fasting blood-sugar level of 7.1 or higher—the risk of dementia increases by 35% to 55% compared to a normal range of 4.8 to 5.4. At higher levels above the diabetes threshold, risk can increase by 80%. These findings emphasize the importance of blood sugar checks and maintaining healthy levels.
Fewer years of formal education also increase dementia risk. Obtaining two years of education—versus the standard 18 years to pass through grade school, high school, college, and a master's program—increases dementia risk by more than 100%. Finishing 12 years of education—high school—elevates dementia risk by 23%. The reasons are complex and remain unclear. Education levels have been shown to correlate with poorer adult health status, including higher rates of hypertension and smoking. Higher education can also be linked to higher levels of cognitive stimulation in the workplace, and evidence suggests that more cognitively stimulating jobs lower dementia risk. Addressing education is not an individual problem; it requires a societal commitment to universal, high-quality education and policies that support retention in school and job readiness.
Hearing loss affects more than 1.5 billion adults, the majority of whom are older than 50, and less than 20% of individuals who would benefit from hearing aids have access. The IHME study found that moderate hearing loss increases dementia risk by 29% and that severe hearing loss increases dementia risk by 49% relative to normal hearing thresholds. A randomized controlled trial called ACHIEVE demonstrated that hearing-aid use decreased risk of further cognitive decline in adults already experiencing mild cognitive impairment or at higher risk of dementia. These results have contributed to concrete state-level policy changes. Multiple states have expanded Medicaid coverage for adult hearing aids, and in 2026 the state of Washington finalized a ruling for health plans to cover hearing instruments as an essential health benefit.
Exposure to air pollution in parts of the world is 10 to 20 times higher than World Health Organization recommended limits, particularly in large urban centers. More frequent wildfires are leading to transient spikes in air pollution that research increasingly links to long-term health consequences, such as asthma, chronic obstructive pulmonary disease, or ischemic events. Our results rank small particulate air pollution fourth for dementia risks. Exposure to levels to ambient air pollution defined by the U.S. Environmental Protection Agency as moderate increase dementia risk by 37%. Policy can impact air pollution levels; for example, the Clean Air Act Amendments in 1970 significantly decreased U.S. particulate pollution.
The risks analyzed in the IHME study are not exhaustive, and growing evidence positions other contributors such as vision loss, LDL cholesterol, menopause, or sleep. The growing list of risk factors for dementia is encouraging; by using methods such as the burden-of-proof approach to rank the importance of different risk factors based on the strength of evidence, policy and individuals have tools to decrease risk of dementia as the work toward a cure continues.
